Does boost lag add character?

Colin Wood said:
 

Is the nearly instant boost of modern setups an improvement? Or do the old-school turbo systems that need time to spool up add a certain charm to some cars?

Yes.

I prefer the newer stuff. The big hit of power may feel exciting, but it makes the car more of a PITA to drive. 

My six cylinder twin turbo XC90 doesn't feel fast, but it can certainly get you where you need to go quite quickly, with no perceptible lag.  The same vehicle with the single turbo five is slower, but has that ever so enjoyable rush of acceleration when the turbo spools.  I kinda like the five better.

Driven5 said:

Colin Wood said:
 

Is the nearly instant boost of modern setups an improvement? Or do the old-school turbo systems that need time to spool up add a certain charm to some cars?

Yes.

Yes, there is something absolutely intoxicating about driving something laggy. Also modern cars are so fast and easy to drive it's a riot. 

Lag sucks. Give me throttle response over horsepower in that case. Best of all is throttle response WITH horsepower.

Who doesn't like non-linear throttle response with hammer-like qualities, especially at the apex in the wet?

Me, for one.

In reply to Driven5 :

I couldn't agree more. Modern cars are really good because they have almost no flaws, but, as I've gotten older, those flaws are what give a lot of older cars character.

In reply to Colin Wood :

"It's better, because it's worse." - Jeremy Clarkson in some old Top Gear episode, I think

"character" is the things that a car does that are less than perfect, so sure.

OTOH, the downside to modern "zero lag" turbos is that one of the ways they achieve this is by being undersized.  Most modern turbos are there so that they can sell you a 2.0L I4 with the same power specs as the 3.0L V6 they used to have, while getting better EPA fuel mileage.  This is a recipe for a boring engine that spools up quickly and peters out above 4000 RPM.  Whether it be a modern turbo engine, an old-school V8 with crappy heads that don't flow, or a diesel, I'm not a fan of that kind of torque curve in a sport-ish car.  (diesels are great for tow vehicles, OTOH)

There's also something really entertaining about a car where the torque triples between 3000 and 4000 RPM. :)

But there are good character traits and bad character traits. A big laggy turbo is a bad character trait. An engine that takes a bit of time to warm up before it runs perfectly is a better one. 

Modern engines are able to take advantage of much more sophisticated engine management, so you don't need to run an 8:1 compression ratio to keep the engine from detonating. If you can run a 13:1 static compression ratio and vary the effective compression ratio with VVT and then toss in complete control over the throttle plate, you've got lots of energy to spin up a big turbo. The BBR turbo kit for the ND Miata fits that description - it spools faster than the supercharger available for the platform but has enough headroom for 400 hp on a 2.0. So it's not just as simple as "use a small turbo, it'll spool faster".

My old 323 GTX had character out the wazoo. It was a cute little hatchback that thought it was a rally car. But the laggy turbo was the exact opposite of endearing, it was annoying.

Many, many years ago, I had an MR2 Turbo while out in L.A. and, of course, I took it up to Mulholland Drive. Riding the lag through the turns felt like surfing. 

Character isn't better, it's just character

Lag is fine if the car isn't meant to turn

I get to play engineer with my V12. I tried to use the turbo charts to figure out what would be best but got bogged down between drag racing , autocross and road racing.  I spent hours watching UTube, reading books and magazines. 
    Just when I thought I had the answers I'd ask around to confirm only to find out that little information applied and I couldn't figure out which.   
        On advise from a friend I'm putting a pair of T3's  on and he's got all sorts of bits and pieces I can trade him for.  Since mine are new if we got the housing wrong it's just unbolt the hot or cold side and trade a pair from him.   
      He says that the size he selected is what he doesn't have so he's happy to trade.  I'm actually comfortable with this approach.  Try and adjust,  

     We'll make passes at the drag strip,  runs at the autocross and then go to Elkhart  Lake.  If I blow a head gasket or something. So what, I've got spares. 
    Ive watched Calvin Nelson on the dyno and drag strip so hopefully my approach is going to  result in decent reliable performance. 
  I don't know how much dyno time I'll buy, I'm sure not as much as the Nelsons do. But I'll concede his superiority  and maybe stay under 14 psi .  The first time maybe stay under 6 psi. 

If you don't have to wait for boost, is it even there?

Isn't boost lag the time it takes to downshift a gear or too? 

I'm with Keith on this one. Years ago I drove a first year 911 turbo and the lag was indeed annoying and that was on a track. I can ony imagine how annoying it would be on the road. It wasn't as pronounced as the early 80s turbo Capri but it was still annoying.

Keith Tanner said:

Lag sucks. Give me throttle response over horsepower in that case. Best of all is throttle response WITH horsepower.

Quoted for truth. 

I had a chance to drive a big turbo FD. Below 4500 it had all the power of a lawnmower. Above 4500 it had all the power of a carrier launch. The transition was violently horrible. It was a hateful car to drive. 

I would not want to confuse powerband with lag.  A turbo that hits late and hard is just sized that way.  Laggy turbos accelerate slower than the engine does - they lag behind the engine.

Ever drive a car that built no boost in 1st gear because the engine accelerated too quickly?

I like my tiny turbo spooled up hella early. Feels more linear.

In reply to Pete. (l33t FS) :

Agreed, there's a difference between spool time and lag. Spool time can be a little entertaining - it's like an engine coming on cam. Lag sucks. It's like having a rubber band for a throttle cable.

Character is how you describe something you know is wrong 

In reply to mke :

Doesn't mean it can't be endearing. 
 

I do love a healthy bit of turbo lag and so do pencil thin connecting rods. 

The funny thing is, the turbo in the S60R feels like a big-block rush of torque at any RPM... on the street. 

When I rallycrossed it, the little bit of delay was maddening.

I suspect that 2-3 decades, the idea of any kind of internal combustion engine in a car will be regarded as "character".

Lag is giving your opponent a gentlemanly head start.

My modded cars run properly sized ball bearing turbos, I don't get lag.

In reply to Honsch :

It's wonderful if you can afford the good stuff. Choosing to build for the challenge means the budget for turbo's has to be tiny. 
 But with knowledge much can be done on a tiny budget look at the Nelsons. They are impressive. 

Ball bearing turbos have been on production cars for more than two decades. They're not necessarily the big money choice :) Properly sized doesn't cost extra. 

With 70s turbo tech in the garage i definitely enjoy some lag and the following rush to the red line. It makes the car feel 50% faster than it really is. It feels much faster than a modern car with the same kind of performance, for me feeling faster is much more important than what the stop watch says, since im in it for the fun. But of course if it's way to much lag it starts getting annoying instead. 

I always thaught it would be fun to built a compressed air assist in to a turbo system. Adding it to the hot side would cool the exhaust gasses effectively removing energy so this got me thinking could you add it to the cold side?  A servo controlled air jet of compressed air on the cold side controlled by software the senses throttle change over a given period of time with a time delay to control its cut off as well as monitor monafold pressure to limit over boost?  

dean1484 said:

I always thaught it would be fun to built a compressed air assist in to a turbo system. Adding it to the hot side would cool the exhaust gasses effectively removing energy so this got me thinking could you add it to the cold side?  A servo controlled air jet of compressed air on the cold side controlled by software the senses throttle change over a given period of time with a time delay to control its cut off as well as monitor monafold pressure to limit over boost?  

I'd need to dig, but I could have sworn I read in a magazine AGES ago about some drag racing import (I can't remember what it was supra, s14, civic possibly) had an obnoxiously large turbo on it and they ran nitrous on the intake side to help spool when staging. No idea if it worked as intended or how successful it was. I want to say it was a blurb in super street? Like 15+ years ago now. 

So compressed air should function, would be less 'possibly explode things' as well.

Excessive turbo lag is not endearing it is annoying. The choice of the BMW pictured is an apt one. A friend used to race a 2002 turbo and he had to floor the gas pedal at the apex of a turn in order to get boost by the time he was exiting that turn. He said a miscalculation could be ...exciting (or boring, depending on whether he miscalculated for early or late).

One thing I do not understand is why people used to NA engines complain about lag with a turbo car.  What do they think the slow acceleration low down in the rpm band on an NA engine is? Cam lag?

Closest thing you get to an immediate boot in the back comes with supercharged cars, but then they run out of whoof earlier than the turbo does.

You want instant good acceleration?  Pony up the big bucks for a twin charged system using a supercharger down low and a turbo higher up.  The best is probably the Volvo T6 and T8 installations.

Another problem is that while manufacturers tend to opt for reasonably small turbos for fast action, people that want more power often go to a too large turbo and end up with excessive lag and then bitch about it even though they caused it.

I run a 2.0 in my daily driver that came with 260 bhp stock. I had the sense when modding it to stop with a larger impeller that gave very good performance lower down, and have 375 bhp/375 Tq. Others, hungry for power, use a much larger turbo that results in 450+ higher up but has significant lag down low. Of course then they complain about the lag, having caused it themselves.

wspohn said:

One thing I do not understand is why people used to NA engines complain about lag with a turbo car.  What do they think the slow acceleration low down in the rpm band on an NA engine is? Cam lag?

Shape of the power curve and turbo lag aren't the same.  Any engine needs to be in its powerband (however wide or narrow that may be) to make good power.  But with a laggy turbo, just getting the revs up isn't the whole picture.  You still get a delay in power production as you come back into the throttle from closed throttle even though you've downshifted to get into a good part of the power curve.  An NA engine doesn't have that problem. 

Pete. (l33t FS) said:

I would not want to confuse powerband with lag.  A turbo that hits late and hard is just sized that way.  Laggy turbos accelerate slower than the engine does - they lag behind the engine.

Ever drive a car that built no boost in 1st gear because the engine accelerated too quickly?

That's a big point. A turbo that only makes boost over a particular RPM, but does so as soon as you reach that point is something I'd call character, while one that takes a notable lag to start delivering boost when it hits that point is more of an undesirable flaw.

MadScientistMatt said:

That's a big point. A turbo that only makes boost over a particular RPM, but does so as soon as you reach that point is something I'd call character, while one that takes a notable lag to start delivering boost when it hits that point is more of an undesirable flaw.

The current prices for 930 turbos would seem to argue against the undesirability. :)

And yes, boost threshold (minimum RPM for boost) and lag are different things, but they are correlated.  All else being equal, a larger turbo means a higher boost threshold, a higher power potential, and yes, more lag.  Improved tech like ball bearings, fancy lightweight exotic material wheels, twin-spool inlets -- they all improve things, but that tradeoff between size and response is still present, just shifted a bit.

I stand by my assertion that most modern turbo cars are undersized and that the engine package would be better if they accepted a minor amount more lag in order to allow it to make full boost all the way to redline.  To be clear I'm not saying I want a car with a response like a 930, but the minor amount more lag that's present it the relatively few modern performance-oriented turbo cars is completely acceptable to me.  

 This is also why I'm disappointed that F1 is abandoning the MGU-H part of their hybrid system.  Using an electric motor to spin up the turbo has the potential to really change that inherent tradeoff.  I suspect it doesn't really matter in the end though, EVs will probably get rid of turbocharged ICEs before we'd get an MGU-H in a street car anyway.

dean1484 said:

I always thaught it would be fun to built a compressed air assist in to a turbo system. Adding it to the hot side would cool the exhaust gasses effectively removing energy so this got me thinking could you add it to the cold side?  A servo controlled air jet of compressed air on the cold side controlled by software the senses throttle change over a given period of time with a time delay to control its cut off as well as monitor monafold pressure to limit over boost?  

Ford did it in a WRC Focus a couple decades ago.

Titanium pressure tank in the rear bumper, stored pressurized air from the turbo and released it to the intake as desired.

I forget if it was banned or Ford agreed to stop using it or if it simply was not worth the complication, but technically all air entering the engine did come through the restrictor, just not all at the same time.

DjGreggieP said:

dean1484 said:

I always thaught it would be fun to built a compressed air assist in to a turbo system. Adding it to the hot side would cool the exhaust gasses effectively removing energy so this got me thinking could you add it to the cold side?  A servo controlled air jet of compressed air on the cold side controlled by software the senses throttle change over a given period of time with a time delay to control its cut off as well as monitor monafold pressure to limit over boost?  

I'd need to dig, but I could have sworn I read in a magazine AGES ago about some drag racing import (I can't remember what it was supra, s14, civic possibly) had an obnoxiously large turbo on it and they ran nitrous on the intake side to help spool when staging. No idea if it worked as intended or how successful it was. I want to say it was a blurb in super street? Like 15+ years ago now. 

So compressed air should function, would be less 'possibly explode things' as well.

Nitrous to get the turbo party started is fairly old, I remember reading about it in the 80s.  A lot of standalone engine controllers that can do nitrous control have an option for it, too.

Exhaust energy spins the turbo, making the engine make more power gives the exhaust more energy.

In reply to codrus (Forum Supporter) :

I agree about modern turbos being undersized. Most modern turbo cars Ive driven, have a tiny turbo that run out of steam too early, but are also hampered by horrible boost control components or tune. I get production costs and a tune that has a wide margin for safety, but still. A tune on a 1.4T ecotec or a diverter valve on a fiat 124 feels like a completely different car.

In reply to codrus (Forum Supporter) :

It's considerably more efficient to use the electrical power to directly drive the wheels vs engine boost. The end goal is the same- wheel torque. 

In reply to alfadriver :

Is it? I would think 30-40hp of turbo energy could create hundreds more horsepower.

What interests me is the history of turbocompound engines, and the idea that one could generate a sizeable amount of power that way.

Pete. (l33t FS) said:

In reply to alfadriver :

Is it? I would think 30-40hp of turbo energy could create hundreds more horsepower.

What interests me is the history of turbocompound engines, and the idea that one could generate a sizeable amount of power that way.

But making that additional horsepower means more fuel used.  From a pure mechanical efficiency standpoint, it's better to put 20hp directly to the wheels vs into the turbo.  That doesn't necessarily work out the same from a "produce maximum power and do it as quickly as possible" perspective. 

In reply to rslifkin :

I see what you mean there.  I suppose it ends up being what the end goal is: power production or minimal fuel used for a given maintenance power level.

rslifkin said:

Pete. (l33t FS) said:

In reply to alfadriver :

Is it? I would think 30-40hp of turbo energy could create hundreds more horsepower.

What interests me is the history of turbocompound engines, and the idea that one could generate a sizeable amount of power that way.

But making that additional horsepower means more fuel used.  From a pure mechanical efficiency standpoint, it's better to put 20hp directly to the wheels vs into the turbo.  That doesn't necessarily work out the same from a "produce maximum power and do it as quickly as possible" perspective. 

The comparison is kind of nonsensical.  Yes, making less power and going slower is usually more efficient than making more power and going faster, but that doesn't really seem relevant to the thread.  If you're looking for pure efficiency, you probably want to dump the ICE entirely and go with a straight EV.

The reasons F1 dropped the MGU-H have to do with inter-team politics and R&D costs, nobody there really cares about efficiency.

I've had three different setups on my 87 Supra with a 1jz swap. Stock twins with a downpipe upgrade had fantastic response, but was limited to about 350whp before compressor wheels are at "might shatter" levels of boost.

Went with a mid sized Comp 6265 DBB 0.70 housing. Out on the open road, it was phenomenal. Response was acceptable, lag was minimal if you had the rpm's above 4k. Good turbo if you remain engaged and drive spirited. Pulled hard through 8k ish. However... at lower speeds, like autocross, below 4k happens a lot, especially if you're on a course large enough to need 2nd gear, which is a lot of them. It had to go. Max potential of this turbo was somewhere in the 650-ish hp range.

Put a Garrett G25-660 0.92 on it, and the response is more like the stock twins, but it can be pushed a LOT harder. On paper, it's down about 120whp versus the Comp, but you wouldn't know it from driving the thing. Transient response is amazing, at pretty much any engine speed, and it no longer has that dead spot that the larger turbo had when autocrossing. No regrets here, apart from misunderstanding fitment potential for the reverse rotation version, combined with my manifold. Oops. Test fit before coating parts, folks!

Point I'm trying to make, is it all depends on your desired use.

alfadriver said:

In reply to codrus (Forum Supporter) :

It's considerably more efficient to use the electrical power to directly drive the wheels vs engine boost. The end goal is the same- wheel torque. 

Plus you can get at least some of that electrical power from deceleration, which is energy that's normally thrown away. 

In reply to te72 :

That is exactly the path I don't want to follow.  Replacing turbo's to achieve my goal. 
 I've gone conservative trying to avoid that process.  I don't need power down below about 3500 rpm I don't want to go over 7000 rpm. I'd like to. Stay around 9-10 Psi would be comfortable. But 14 is still in my comfort zone 

codrus (Forum Supporter) said:

 

The comparison is kind of nonsensical.  Yes, making less power and going slower is usually more efficient than making more power and going faster, but that doesn't really seem relevant to the thread.  If you're looking for pure efficiency, you probably want to dump the ICE entirely and go with a straight EV.

The reasons F1 dropped the MGU-H have to do with inter-team politics and R&D costs, nobody there really cares about efficiency.

 

It does matter.  The MGU-H costs a TON of money and adds very little.  Nowhere close to it's cost and complexity.  The goal is to put torque to the wheels, and using the less efficient path does not shorten lap times.  It's faster and more efficient to just drive the wheels.  Remember, there's a time delay from when you compress the intake air until you see it at the wheels, whereas putting that energy to the wheels does not have a delay.

If it were as useful as the basic hybrid system- which costs more- it would stay.

Pete. (l33t FS) said:

In reply to alfadriver :

Is it? I would think 30-40hp of turbo energy could create hundreds more horsepower.

What interests me is the history of turbocompound engines, and the idea that one could generate a sizeable amount of power that way.

So we don't need to start the discussion that using exhaust waste energy to turn the turbo is more efficient than electrical energy, do we?  It it were, everyone would be using belt driven superchargers instead of exhaust driven.  And remember, this is a boost limited system- so just adding more boost via electrical energy isn't an option.

The whole point of the e-boost systems is to reduce the boost lag, which is another way of saying a faster delivery to the wheels based on the driver input.  Given the delay of the spin turbine-increase intake pressure-combust more energy vs. just putting that same energy directly to the wheels- e-boost vs. more hybrid drive does not make sense- especially when one factors in cost and complexity.

alfadriver said:

So we don't need to start the discussion that using exhaust waste energy to turn the turbo is more efficient than electrical energy, do we?  It it were, everyone would be using belt driven superchargers instead of exhaust driven.

In a street car context you would only need to spin the turbo up when there isn't enough exhaust energy to spin it otherwise.  Once the exhaust gas is flowing and the turbo is spooled you shut the electric motor back off -- this is not an electric supercharger.

Also unlike the classic "electric supercharger", you don't need to power it with the alternator because this presupposes a hybrid car with a lithium/etc battery.  You charge that battery using an MGU-H in generator mode instead of a wastegate, recovering more of that wasted exhaust energy than you could get otherwise.

Incidentally, I suspect that if any OEMs were actually trying to build them these days, pure electric superchargers probably would be more efficient than belt-driven ones.  We're seeing an ongoing trend away from belt-driven accessories (electric power steering, electric water pumps, electric AC compressor) because the efficiency losses of turning that pulley when you don't need the accessory are higher than the efficiency losses of making and storing electricity.  You don't see it though because basically everyone has given up on superchargers (other than turbos) at this point.

The whole point of the e-boost systems is to reduce the boost lag, which is another way of saying a faster delivery to the wheels based on the driver input.  Given the delay of the spin turbine-increase intake pressure-combust more energy vs. just putting that same energy directly to the wheels- e-boost vs. more hybrid drive does not make sense- especially when one factors in cost and complexity.

Putting electric power to the wheels is not going to deliver the same degree lag mitigation as spinning up the turbo.  A turbo can easily double the power output of the motor, so we're talking about a need for over 100 hp to deliver the same kind of response. 

In reply to codrus (Forum Supporter) :

The problem with direct driven supercharging is that you use the mechanical power to make boost- which takes off some of the energy that can go down the driveshaft.  Whereas the whole point of exhaust energy is that you try to use as much as the waste heat going down the exhaust to recover some of it.  That's why exhaust supercharging is more popular than direct drive.

Still- this is a boost limited system- so the entire point of the e-boost system is to get to that limit faster.  And the whole point of that issue is to make wheel torque faster.  And direct drive of the wheels is the fastest path of using your electrical energy.

E-boost does not make more power in a boost limited system, it just makes it quicker.

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

I think a lot of the reason for things like electric water pumps, electric power steering, and even electric A/C compressors is that it divorces the pumping device from engine speed.  If you size a belt driven accessory so that it can be most useful at idle (like, say, power steering and A/C that need to be strongest when stopped) then it is vastly oversized when driving down the road and possibly dangerously oversized at the engine's redline.

I strongly suspect this is why BMW went to electric water pumps.  Their newer engines could generate huge heat loads at near idle speeds, but a belt driven water pump sized to work well down there would cavitate at high engine speeds.  Electric water pump solves that issue.

codrus (Forum Supporter) said:

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

But if you can dump a burst of power to the wheels from another source while the turbo spools to provide smoother power delivery, is that not just as good as spooling the turbo faster?  In either case you're getting a smoother, faster power delivery so it doesn't feel laggy. 

codrus (Forum Supporter) said:

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

 

You pointed out F1's decision to get rid of the MGU-H.  I'm pointing out why I think they did.  And the same does apply to real cars- but moreso since cost is a bigger issue with real cars.

And the current solution for turbo lag vs. boost limits is variable vane turbos are making a comeback.  

Pete. (l33t FS) said:

I think a lot of the reason for things like electric water pumps, electric power steering, and even electric A/C compressors is that it divorces the pumping device from engine speed.  If you size a belt driven accessory so that it can be most useful at idle (like, say, power steering and A/C that need to be strongest when stopped) then it is vastly oversized when driving down the road and possibly dangerously oversized at the engine's redline.

I strongly suspect this is why BMW went to electric water pumps.  Their newer engines could generate huge heat loads at near idle speeds, but a belt driven water pump sized to work well down there would cavitate at high engine speeds.  Electric water pump solves that issue.

Given all of the compromises involved, I would say that is very accurate.  Especially for higher revving engines.

rslifkin said:

codrus (Forum Supporter) said:

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

But if you can dump a burst of power to the wheels from another source while the turbo spools to provide smoother power delivery, is that not just as good as spooling the turbo faster?  In either case you're getting a smoother, faster power delivery so it doesn't feel laggy. 

No, because of the multiplication effect of the turbo.  Making up numbers, putting 20 hp into that compressor wheel might give you 100 hp from getting the boost sooner, and that's a smaller/lighter motor than putting 100 hp to the wheels directly.  You'd also need to dump power to the wheels for longer, because simply accelerating the car isn't bringing the turbo RPMs up.  If you've got a mechanical system with 500 ms of lag, putting extra power to the wheels doesn't reduce that lag, whereas spooling up the turbo directly does.

alfadriver said:

You pointed out F1's decision to get rid of the MGU-H.  I'm pointing out why I think they did.  And the same does apply to real cars- but moreso since cost is a bigger issue with real cars.

Fundamentally F1 dumped it because Mercedes did such a better job of it than everyone else that they felt it was the only way to stop them from winning all of the championships.  That's not really relevant to street cars. :)

I have never driven a turbo anything on the street that I liked more than a similar hp non-turbo version....lag is the devil.  I've never driven a turbo out on a road course but I'm pretty sure it would be hard to beat in that space, on the street though where you change you mind often and can't always plan the rpm not so much.

I'll diverge a bit and talk no lag superchargers.  I've done a few of those on street car over the years and they drive nice...but Im not sure I'd build another one of these again either, at least not with the near flat boost curve the roots and screw blowers kick out.  The engineer in me loves this setup but personally just something about the way they drove I didn't love.....fast and responsive yes, but the way they drove, once I got over the euphoria of the hp no. 

When I first got my 308 I remember I called my father, who'd tried to talk me out of the idea,  from the car to say how amazing it felt.  It wasn't fast, but the sound, the vibration maybe, don't know but it very much reminder me of my motorcycle racing days.  It was a claimed but tired 235hp@6800 and in town I would shift about 4500 or so.  Then engine rebuild and blower 1 bumper it like 400hp so much faster but I noticed I was now shifting at about 3500rpm.  Blower 2 bumped it to 600ish hp and I was now shifting at 2500rpm and it now reminded me of a bigblock corvette, it would just kind of shake and go.  I t still had most of the magic when driven to redline in anger but in normal driving it was a completely different car in normal driving. Hopefully the 14 year v12 conversion restores all the magic.

Turboson the street though are magic free imho 

In reply to codrus (Forum Supporter) :

As I see it, F1 dropped the MGU-H because no other engine makers were willing to spend the money for such a minor gain.  Especially since it was faster to just put the same energy to the wheels.

codrus (Forum Supporter) said:

 

No, because of the multiplication effect of the turbo.  Making up numbers, putting 20 hp into that compressor wheel might give you 100 hp from getting the boost sooner, and that's a smaller/lighter motor than putting 100 hp to the wheels directly.  You'd also need to dump power to the wheels for longer, because simply accelerating the car isn't bringing the turbo RPMs up.  If you've got a mechanical system with 500 ms of lag, putting extra power to the wheels doesn't reduce that lag, whereas spooling up the turbo directly does.

You do realize that the time lag to apply electrical power to the wheels and the turbo is exactly the same, right?  And the boost then has to be generated and then combusted before it turns into wheel torque.  Whereas the electrical energy just goes to the wheels.   (and since all engines are boost limited, there are limits to how much boost can be generated)

In terms of reality- there are multiple mild hybrid systems out there that use the alternator as a motor to drive the engine, but there are no e-boost systems out there.  Cost-benefit is on the side of the direct drive motor.  It's pretty cheap to turn an alternator into a motor compared to adding an electric motor into a turbo system.  It's just a more efficient (cost, timing, etc) way of filling that lag hole.

My FD RX7 was so smooth with it's power delivery and I think it was one of the first modern turbocharged cars to really reduce lag with it's sequential setup. That said, I was coming from a Precision 66 mm Galant VR-4 with 7.8 to 1 compression. The FD was a better overall car in almost every way except it never left me and passengers giggling and pushed into the back seat.  Had I kept the FD longer, I probably would have put a big single on it. A stock Galant with a 14b wasn't particularly laggy but purposefully making it laggier in exchange for a bigger payoff was a sacrifice I wanted to make. If people want turbocharged cars that don't *feel* turbocharged and have zero lag I could see why but as for me, I like the drama. Street cars aren't competing so it's not about being the fastest but what is more fun to you.

In reply to crankwalk (Forum Supporter) :

Love the pic...and that is why 80s turbos had a bad habit of ending up in guard rails.  

This is what I was saying...its fine on the boost, its fine off the boost but when you change your mind there is no "medium".  You get the on ramp and start rolling in throttle for a little fun then find its now accelerating hard without adding throttle until the its spinning if you don't get out of the throttle quick enough.  Its an unstable system in engineer speak because it requires active input to control.

I had 1990zx6 motorcycle that from the factory the power dropped between 9000-9500 then the climbed steeply to 12500.  On the track you had to keep it above 9500, miss a down shift and mid-corner the you'd find the back walking out  as 9500 throttle was WAY too much 2-300 rpm later..really dangerous.  Lag is like that...bam! the car is spinning.  Nothing charming about it.

mke said:

In reply to crankwalk (Forum Supporter) :

 

I had 1990zx6 motorcycle that from the factory the power dropped between 9000-9500 then the climbed steeply to 12500.  On the track you had to keep it above 9500, miss a down shift and mid-corner the you'd find the back walking out  as 9500 throttle was WAY too much 2-300 rpm later..really dangerous.  Lag is like that...bam! the car is spinning.  Nothing charming about it.

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it.

But what about blow through carburetors and old school turbo tech (the worst of the worst to some)? My 82 Seca Turbo does nothing until 5k then boost hits and stretches your arms straight out. On a 120 tire. From an engineering perspective this would all be trash and leave room for improvement and you wouldn't be wrong in a sense.

But I LOVE a turbo rush that makes you E36 M3 yourself occasionally.The question is does it add character and some people like it. When you are familiar with it's characteristics and can control it by respecting and anticipating an imperfect power delivery, it's really enjoyable to me.  Different strokes for different folks.

I've driven turbo cars that 'came on' so hard if you floored it from lower rpm that they would break the rear wheels loose.  I really like the modern twin scroll turbos (a Borg Warner invention, IIRC). as they minimize that sort of behaviour and smooth out the transitions, minimizing lag as long as you don't go too big with them.

In reply to wspohn :

Mazda had twin scroll Hitachi (?) turbos on RX-7s in the 80s.

I think it might have been Garrett or Schwitzer that pioneered it, although given how B-W hoovered up a lot of turbo companies, maybe technically they did 

The tiny twin scroll TD04 on my S40 (dates back to 1996, mine was an 02) may as well have had the boost gauge attached to the throttle pedal. 9psi at quarter-third throttle, any more than that just told the trans what gear to be in.  Fun ride.

crankwalk (Forum Supporter) said:

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it......

That's a bit different.  There is nothing very dangerous a about an engine coming onto its power band and nothing really dangerous about rapid changes in power if you're going straight. 

The problem is rapid changes in power mid-corner and even worse is what I described where there was a significant power drop for 500 rpm followed by a rapid increase....it was very dangerous out on the track but almost unnoticeable on the street where you're not normally managing mid-corner wheel slip.

Turbo lag is the same issue.  As long as you're going straight its fine and to you're point can be quite a rush.  Mid corner that rush often becomes a crash.  We had a 2010 FWD VW tiguan....hit the gas to pull out and start the turn then the turbo came on, the front wheels start slipping and the car heads for the ditch until you back off the throttle...just horrible to drive.  Our 2018 GLC is much better for sure but that has a lot to do with the 9spd? trans and better ECU mapping, but its got nothing on our non-turbo 2014 glk so I'll be sad when it dies as its the last on the nonturbos.

On the ferrari I spent a ton of time on the simulator trying to get the power curve looking decent and once its ready for the dyno I'll do what I usually do and play with the tuning to force the curve smooth (pull out a little timing to remove the peak before the dip) so I don't need to worry about who's driving it...more throttle, more rpm = more power as it should be.

In reply to mke :

The best description of driving a 3 liter 930 was that if you were not on the power, you understeered into the weeds. If you got on the power, the turbo would hit late and you would go backwards into the weeds when the tires spun. And if you lifted after the turbo hit, you would snap around and then back into the weeds. 

But if you could time it just right and lift a little just as the turbo woke up, it was seamless. "And if you were very, very good, it would let you do it again"

I am sure a lot of that is the really low compression ratios used on the early turbo cars.  IIRC the 930 had 6:1 at first.  No power off boost.  For one reason or another, higher compression also seems to make a turbo happier.  The most linear, instant-boost car I ever experienced was a 4.5l BGN with 10:1 compression and a 76mm turbo.

mke said:

crankwalk (Forum Supporter) said:

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it......

That's a bit different.  There is nothing very dangerous a about an engine coming onto its power band and nothing really dangerous about rapid changes in power if you're going straight. 

The problem is rapid changes in power mid-corner and even worse is what I described where there was a significant power drop for 500 rpm followed by a rapid increase....it was very dangerous out on the track but almost unnoticeable on the street where you're not normally managing mid-corner wheel slip.

Turbo lag is the same issue.  As long as you're going straight its fine and to you're point can be quite a rush.  Mid corner that rush often becomes a crash.  

 

I understand exactly what you're talking about I just disagree. Even vehicles that I would consider laggy could be predictable  in corners with throttle modulation and being comfortable with that vehicle. A lifetime Corvette driver hopping directly in 930 with no frame of reference may have a higher likelihood of losing it mid turn when boost comes on unexpectedly (to them). Some say that's a deadly flaw but to somebody with lots of seat time in a 930, it is viewed as part of the dynamics and can be mastered. Just part of its character. I appreciate laggy, journal bearing 70s and 80s tech for what it is and don't try to "engineer out" its quirks. I think a period correct early turbo tech hot rod is charming and If I wanted no lag and seamless delivery, I'd just buy something new.

I guess I'll say the market voted and turbos were the exception and generally sold poorly until they could be about as smooth as non-turbos.  A modern turbo is at least as smooth and responsive as an 80s/90s non-turbo....and now they're everywhere.

mke said:

I guess I'll say the market voted and turbos were the exception and generally sold poorly until they could be about as smooth as non-turbos.  A modern turbo is at least as smooth and responsive as an 80s/90s non-turbo....and now they're everywhere.

The question isn't "What's better, faster, and more practical?" the question is "does boost lag add character?" and I say yes it absolutely can. It has nothing to do what the market has spoken about. The market has spoken that automatics are better. Infotainment systems are better. Airbags are better. What sells better doesn't have anything to do with character to me. Turbo lag in a early turbo vehicle is like anything else that has since been made "better". Character is a nostalgic part of the experience for better or worse. 

Turbo lag adds character to a car like lead paint adds character to a house 

In reply to mke :

I think the turbo lag character thing is kind of like piston port vs reed valve two strokes. The piston port motor has that drama to it but its drama most people would happily be rid of.

I think it adds character to certain cars. I think I would feel a lot better about the character/lag on a 930 while out for a Sunday drive than I would about the lag on my 2002 WRX wagon while getting groceries. The 2015 GTI handles the latter with aplomb, and manages to be engaging on the former, while admittedly not having much 'character' from an engine standpoint. 

Lots of confusion here between Lag and Boost Threshold.
 

If you can shift into boost, it's a boost threshold issue. If you need to keep your foot down for X time to make boost, reguardless of RPM, that's lag.

While the two are linked, they are fundamentally different things.

mr2peak said:

While the two are linked, they are fundamentally different things.

Different but both dangerous in a similar way.  A steep torque rise is an unstable characteristic and lag means without looking at the tach you can't be sure what's coming next...but you never want the engine output to change with no change in driver input.

The VW I had was even worse because the ECU was lagging the throttle I guess for emissions but leaving a stop sign 100% pedal got me 18% at the engine, until the ECU decided to open the throttle more so the big issue wasn't even real turbo lag, it was simulated lag some jackass programmed into the ECU 

The tach isn't going to be related to lag, though.  A laggy turbo is laggy no matter the engine speed.  Obviously it is going to be better at higher RPM because things just plain happen faster at higher speeds (Deep Thought of the day ) but it is still going to be there.

In the Group B era, Audi had little idea what they were doing and mostly had the laurels to rest on of being first with all wheel drive.  When everyone else did that too, they focused on making more power at the expense of drivability and handling, which is kind of backwards for the kind of roads driven on.  Anyway, toward the end, they had hotsides so large that the turbos would not build full boost until 4000-5000rpm and the turbos had so much mass that the lag was absurd, so Audi basically invented the first recirculation antilag to keep the turbo spinning when off throttle.  They also invented DSG transmissions so the drivers did not have to lift to upshift.

In reply to Pete. (l33t FS) :

yes of course, I was saying without looking at the tach you don't know if you are above or below the boost threshold so you don't know it you have all there is or you're about to be clobbered.

In reply to mke :

Watch an average person drive and notice how twitchy their foot is on the throttle.  It's no wonder manufacturers have had to add lag to make things feel smoother and/or keep emissions down at times. 

In reply to rslifkin :

that and how slowly they take action I guess.  My wife never noticed the throttle lag thing that made me just hate the car.....I usually get the hand-me-downs but I told her I wouldn't take that one, I hated it.

Am I wrong?  Isn't it just a matter of selecting the right combination of sizes to eliminate lag? Lots of power requires a big turbo. But gives you lag. Smaller turbo gives you quicker reaction / lack of lag but you trade off peak power.  ( power only useful on the race track) 

    A turbo can be cheap if you aren't concerned about the latest high tech stuff. Or originality. 
     I can understand bragging rights.  Making that extra 100 hp over a properly sized turbo. But if lag bothers you get a smaller turbo.  Your Porsche/ BMW/ Nissan etc.  won't care. And if you're not all out racing it will feel better. 

frenchyd said:

Am I wrong?  Isn't it just a matter of selecting the right combination of sizes to eliminate lag? Lots of power requires a big turbo. But gives you lag. Smaller turbo gives you quicker reaction / lack of lag but you trade off peak power.  ( power only useful on the race track) 

Do you like engines that fall on their face at 4500 RPM?  That's what you get if you aim for a "zero lag" turbo.

Well, sure. But we want power, that's why it has a turbo. It also needs to be sized large enough to handle the flow at high RPM, or you will choke the motor and will need to heavily rely on large wastegates.

EFRs use a lighter alloy wheel than other manufacturers, giving them better response than anything else on the market in a comparable size. The tradeoff is turbine geometry (due to the shaping ability of the alloy) that leaves a little efficiency on the table, compared to say a new Garrett G-Series. Once you get sizing as perfect as possible, there is still a trade-off between power and response, that's just the way it is.

Or just use a supercharger

mr2peak said:

Or just use a supercharger

indeed.  24psi as fast as you can slam the throttle to the floor at any rpm.  It doesn't make as much power as a similar boost turbo but its instant, smooth and predicable.

Still no replacement for displacement though 

codrus (Forum Supporter) said:

frenchyd said:

Am I wrong?  Isn't it just a matter of selecting the right combination of sizes to eliminate lag? Lots of power requires a big turbo. But gives you lag. Smaller turbo gives you quicker reaction / lack of lag but you trade off peak power.  ( power only useful on the race track) 

Do you like engines that fall on their face at 4500 RPM?  That's what you get if you aim for a "zero lag" turbo.

That BGN engine I mentioned made power to 7000+. 810 at the wheels on E85.

The guy had a blowoff valve for whatever reason (on a Buick!) and cruising at 35mph, the turbo was spooled up enough to make the valve chitter.  High compression, high flowing heads, good intake and exhaust, well sorted camshaft, the works. Not a bolt on and pray setup.

Definitely a wild ride, but too rich for my blood.  Plus totally unusable except on a prepared dragstrip.

The guys in "stock appearing" classes (iron heads, stock manifolds, stock appearing turbo) could make similar power but at the expense of response. Need 90-100psi in the exhaust manifolds to make 30psi boost.  That 4.5 made the power at only 23-25psi boost.

codrus (Forum Supporter) said:

frenchyd said:

Am I wrong?  Isn't it just a matter of selecting the right combination of sizes to eliminate lag? Lots of power requires a big turbo. But gives you lag. Smaller turbo gives you quicker reaction / lack of lag but you trade off peak power.  ( power only useful on the race track) 

Do you like engines that fall on their face at 4500 RPM?  That's what you get if you aim for a "zero lag" turbo.

 Most guys with those silly power numbers make a pass or two at the drag strip and then use the car for bragging rights until the engine dies or everybody catches up. Forget about practicality. 
      
I had a junkyard Jaguar with a pair of T2 turbo's from Junkyard Saabs.   It would smoke the tires. But made short of 500 hp. It was designed for Chump Car racing because I built it for $500 ( early days rules)  

 When they threatened penalty laps and possibly crushing the car   I decided not to race with them and sold it.  It still shows up once in a while so I guess it's pretty durable. 
      Factory red line is 6500, but stock the camshaft is so mild it runs out of breath at 5500 so it's not all the size of the turbo.   
   
   Road racing rewards different than drag racing. But I suspect part of the reason the Nelsons don't do as well in the autocross 

mke said:

mr2peak said:

Or just use a supercharger

indeed.  24psi as fast as you can slam the throttle to the floor at any rpm.  It doesn't make as much power as a similar boost turbo but its instant, smooth and predicable.

Still no replacement for displacement though 

Superchargers don't make the silly chassis twisting  numbers the Big Turbo's can but they make a much more responsive and fun car to enjoy.  
 My only objection to superchargers is visibility. Front engine and your blind to the front.  Rear engine You're blind to the rear. 
   You can crank drive  a supercharger. They don't add that much weight to the front.   Mine weighs 45 pounds and pumps 250 cu in per rotation. But you loose a little boost with the plumbing.  

Yes, it adds character.  But not the good kind.

Some people with a lot of character are shiny happy people.

I still think that twin charging is the answer.  Yes, a suitably small turbo gives close to instant response but it also limits top end power.

Look at the Volvo Polestar - with a small supercharger for bottom range and a large turbo for top end they were pushing 362 bhp and 347 Tq out of a 2.0 engine with bottom to top flexibility.. It just adds cost of course.

In reply to wspohn :

That's why I used 2 smallish turbo's. ( T3's)  rather than one big turbo.  Basically turned it into 2  2&1/2 liter six cylinders.  Using low boost at rpm below 4500 rpm and building up to a comfortable 12+psi at peak RPM.  At least if I'm reading the Turbo charts right.   Yes I know the really big silly numbers come up in that 30 psi  range. 
    But the smaller  cheap turbo's are not difficult to swap out for the next size. 

Seems like, to me, depends what you are trying to do and what you like personally. 

I will use my most laggy car as an example, 1995 Mitsubishi Lancer Evolution III. I just love that when I am driving that car it is a time machine. It isn't the fastest car around, it isn't the best handling car around.. back in 1995 Japan it was but times have changed. It is very engaging to drive, gives you great feedback, very sharp, direct. 

If I wanted a car that is super capable, fast out of the box just buy a new Corvette and you're done. I am not the type to fundamentally change a car to try and make the car into something it was never intended to be. But, I did do some things to help improve spool, ported the exhaust manifold, removed some volume on charge pipe system, full exhaust. 

So yeah, I like it, it adds a level of engagement, another level of thing to think about while you're driving but that car I have for driving. My evo 7 is my daily now, smaller twin scroll turbo, probably 400-500 sooner rpm spool (that then falls off at the top). I like that better for that car. 

So, depends what you want, what you like. Certainly adds character to me, character being a quality. 

crankwalk (Forum Supporter) said:

mke said:

In reply to crankwalk (Forum Supporter) :

 

I had 1990zx6 motorcycle that from the factory the power dropped between 9000-9500 then the climbed steeply to 12500.  On the track you had to keep it above 9500, miss a down shift and mid-corner the you'd find the back walking out  as 9500 throttle was WAY too much 2-300 rpm later..really dangerous.  Lag is like that...bam! the car is spinning.  Nothing charming about it.

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it.

But what about blow through carburetors and old school turbo tech (the worst of the worst to some)? My 82 Seca Turbo does nothing until 5k then boost hits and stretches your arms straight out. On a 120 tire. From an engineering perspective this would all be trash and leave room for improvement and you wouldn't be wrong in a sense.

 

But I LOVE a turbo rush that makes you E36 M3 yourself occasionally.The question is does it add character and some people like it. When you are familiar with it's characteristics and can control it by respecting and anticipating an imperfect power delivery, it's really enjoyable to me.  Different strokes for different folks.

I think for me it depends on if it's possible to keep in the boost once you've decided that you want to do boosty things.  The Seca Turbos that Crankwalk and I have are a great example. They have all kinds of turbo lag.  They're completely gutless off the boost.  I mean they're low compression 650cc engines with a restriction built into the exhaust until the boost comes up.  On the boost they're capable of running sub 11 second quarter mile times, although I suspect you have to abuse the heck out of the clutch to do that.

On a twisty back road though it's possible with some practice to keep them in the boost all the time and the throttle is fairly linear even under boost.  I have lots of practice with mine.  I've owned it since new.

The original Pontiac Sunbird Turbo was terrible.  It was also laggy and gutless off boost and fairly powerful under boost but the power was either all on or all off.  It also had terrible torque steer and was a crummy car on top of that.  Off boost it was a boring econobox and on boost it would be trying to turn you into oncoming traffic unless you were shifting in which case it would head for the ditch.

So, predictable and controllable I'm fine with it and it adds character. Otherwise, it's just annoying.

frenchyd said:

In reply to te72 :

That is exactly the path I don't want to follow.  Replacing turbo's to achieve my goal. 
 I've gone conservative trying to avoid that process.  I don't need power down below about 3500 rpm I don't want to go over 7000 rpm. I'd like to. Stay around 9-10 Psi would be comfortable. But 14 is still in my comfort zone 

Knowing what you intend to do with the car is #1 priority here. I didn't really have any interest in autocross since my nearest events were 3+ hours (one way!) to enter. When some local guys started putting events together, I realized how much fun it was. If not for autocross, I'd have left that old turbo on there, plenty of fun and pulled HARD from 4k+ in 1st and 2nd, 3rd or higher and it was happy to pull from 3k or so, all the way to 8k+.

Despite the experiences of others in the thread, I never really found it to be uncontrollable, but I have my Supra set up quite well, it's really well behaved for a car that goes from no torque to all the torque in a 500-ish rpm window. With the G25-660 though, it's far smoother of a ramp up and WAY easier to drive. Almost boring, in a way that's weird to say about a car like this.

My experience with turbo pretty much starts and stops at a '95 Eclipse GS-T and a 2020 X3. In the Mitsu it was fun in a childish kind of character way. Starts were undramatic (boring and slow) but in 2nd it got fun, esp with a mild turbo upgrade.

Then I drove a Terminator Cobra and instant torque stole my heart. IMO supercharging is akin to the feel of all motor, which is just a better driving experience. 
 

When I drove that twin turbo X3 last year it made me hate lag (or whatever it's technically called) all over again. Compared to the published power, dead starts were pathetically slow (when else are you really wanting to use your power on a daily basis --besides the occasional overtaking?) and I despised it. They've eliminated the "suddenly fast" feel that was present in the GS-T and so there wasn't even that to look forward to. 
 

So I guess to answer the original question: yes, the sudden boost was fun on the street, which is where FWD cars like that Eclipse happen to belong anyway... but character isn't necessarily the kind of thing you want in a DD. 

In reply to P3PPY :

You should drive a Super Coupe.  The supercharger was laggy.  Modern turbo cars are much more responsive.  Heck even my 16 year old Volvo with its old-tech turbo engine (low compression, port injection, large turbo) is more responsive.

I could also detect lag in Buick supercharged V6s.  Not nearly as bad as those T-birds with six feet of plumbing between the fixed-speed blower and the engine, but it is noticable.

In reply to Pete. (l33t FS) :

I hadn't thought about the plumbing part. IIRC in the Mustang the blower is right above the water intercooler, but Id forgotten about piping

In reply to P3PPY :

There will always be a SMALL amount of lag because of the way the blower runs at a fixed ratio to the engine, and how it is not a compressor.

What is enlightening is running both a manifold pressure gauge and a Dash Control in my Volvo. Volvo does not use a MAP sensor but it does use a charge pressure sensor pre throttle body, which is what the Dash Control reads.  I will see vacuum in the manifold and 4-6psi in the charge pipe, because the turbo is generating pressure, the throttle plate is holding it back.  Open the throttle and instant boost, as long as the turbo is already awake.

Then something from a GRM article about driving 930s on track made even more sense: holding maintenance throttle before the corner-out not only ensures the rear end is loaded, it also prespools the turbo.

codrus (Forum Supporter) said:

frenchyd said:

Am I wrong?  Isn't it just a matter of selecting the right combination of sizes to eliminate lag? Lots of power requires a big turbo. But gives you lag. Smaller turbo gives you quicker reaction / lack of lag but you trade off peak power.  ( power only useful on the race track) 

Do you like engines that fall on their face at 4500 RPM?  That's what you get if you aim for a "zero lag" turbo.

That simply isn't true.

The GM LNF uses an EFR dual scroll turbo well sized to the 2.0 engine and has little lag plus it peaks power at 5300 but continues up to 6200 and a mild tune gives a higher peak rpm with little or nothing lost down low.

In reply to wspohn :

For racing  if I select the right size turbo's  I don't care if power falls off at red line.  I can gear for the track I'm racing at. I not only have a transmission that allows me to select the sets of gears that work best.  Changing  them between sessions only requires a little time.   I can also change the diameter of the final drive by altering tire sizes. Between different final drive ratio's  and transmission gear ratio choices, plus  tires.  I can exit each corner at peak power  

   OK, I give up a broad power band.  I don't need or even want it.    I'm not being stupid on a public street. Where that matters. 

In reply to Pete. (l33t FS) :

Pop off valves can be set to bypass boost at a given point either mechanically by dialing it in  or electronically. And when it's bypassed it can either be wasted or sent back around  behind the MAP sensor and before the throttle body. Helping to keep the turbine spooled up. Thus eliminating  lag in shifting. 
    OK it eliminates some of the cool turbo sounds.   Seems like a good trade off.  

In reply to frenchyd :

The thing is, though, it does take power to drive the compressor, which comes from exhaust energy via the turbine.  With nothing driving the turbine off throttle, the compressor slows down.  Turbo speed is boost, not so much actual flow (within limits: see the speed lines on a compressor chart)

An RX-7club member logged turbo speed with and without a blowoff valve.  The turbo actually slowed down a little faster with a blowoff valve, because the turbo is under more load if it is compressing air vs. if flow is stalled.  Stick your hand over a hair drier and hear the motor spin faster because you've removed the load...

Blowoff valves? Wastegates?

You guys are turbo'ing wrong. =P