Does our Miata need individual throttle bodies? | Garage Rescue Miata

David S.
Update by David S. Wallens to the Mazda Miata project car
Oct 20, 2021

Can we share a secret with you? When we originally built our 1992 Mazda Miata back in 1999 or so, part of the wish list included individual throttle bodies.

We already had the Flyin' Miata/Link ECU and cylinder headwork, so why not go all the way? Figure in the expense and complexity, however, and let’s just say that things didn’t pan out that way.

Instead we went with a Jackson Racing cold-air intake, a very popular setup at the time, yet running the Link meant that we could ditch the mass airflow meter. So call it a unique take on a popular setup.

Ed Senf pulled everything together, including managing the headwork and performing all the tuning. At the time, Ed ran his own dyno shop just north of Atlanta. Since then, he’s become a go-to tuner in the pro ranks: IMSA, SRO World Challenge, MX-5 Cup and even Le Mans. He also did the tuning on BimmerWorld’s famed Bergsteiger Pikes Peak racer.

[Meet the Bergsteiger, BimmerWorld´s 1000-Plus Horsepower E36-Chassis BMW M3 Pikes Peak Racer]

Now that our Miata is back on the road, we’ve been returning to that question: Does our Miata need individual throttle bodies?

It’s a question for the ages, right? We’ve been talking to Ed about it and even took the time to write down some pros and cons:

Pros:

  • Looks rad.
  • Sounds rad.
  • Did we mention that it looks and sounds rad?
  • Likely potential for more power.
  • Theoretically improved throttle response.
  • Looks rad.
  • Sounds rad.

Cons:

  • Still costs a few bucks and likely not the best ROI regarding horsepower per dollar.
  • Do we even think about street legality?
  • Do we need new cams, too?
  • Do we need to upgrade our 20-year-old ECU, too?
  • How much shop and dyno time will this take?
  • The Jackson Racing intake now carries a cool, period-correct vibe.

What will drivability look like? Ed’s original setup still runs so well. Even when cold, the car comes to life on the first turn of the key and instantly sets into a stable idle. It doesn’t stall, bobble or act up–yet at the same time delivers 20 more horsepower at the wheels than the stock setup.

So, for the peanut gallery (that’s you) what would you do–and what would you like to see us do? (Paging Keith Tanner….)

 

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maschinenbau
maschinenbau GRM+ Memberand UltraDork
10/19/21 8:41 a.m.

Does the pope E36 M3 in the woods?

gumby
gumby GRM+ Memberand Dork
10/19/21 8:43 a.m.
maschinenbau said:

Does the pope E36 M3 in the woods?

Do bears wear funny hats?

JAdams
JAdams Reader
10/19/21 8:50 a.m.

Yes! Yes! Yes!

 

I'd love to do ITBs on my NA and would love if you guys led the way so I could follow. 

alfadriver
alfadriver GRM+ Memberand MegaDork
10/19/21 8:51 a.m.

Need or want?  

I honestly think you don't NEED it.  But 100% on the want thing.  Go for it.

mmcvay
mmcvay New Reader
10/19/21 9:16 a.m.

Putting itbs on my 92 was probably the best thing I did to it. They made the B6 feel like a real sports car motor unlike stock. It's worth it just for the intake noise.

Colin Wood
Colin Wood Associate Editor
10/19/21 9:35 a.m.

I think ITBs are one of those things that won't always add power, but they can add fun–and isn't that why we play with cars in the first place?

frenchyd
frenchyd UltimaDork
10/19/21 9:39 a.m.

In reply to David S. Wallens :

You are aware that air has mass?  That an object in motion tends to stay in motion and an object at rest tends to remain at rest. 
 Individual throttle bodies will need to start and stop intake air  4 times per revolution more often than air inducted through one  throttle body.  It's far easier to divert air already in motion than to start and stop air. 
   You can make up for that loss by increasing duration on the camshaft at the expense of low end  power. 
 OK 4 injector stacks look sexy. But cost you power.   What is your priority ? 
 

ps I don't see Ferrari, Aston Martin etc. using individual stacks. 

APEowner
APEowner GRM+ Memberand SuperDork
10/19/21 9:46 a.m.

I think it's a bad idea and not worth the time and money.  I totally think you should do it and I'd be thrilled to be proven wrong.

maschinenbau
maschinenbau GRM+ Memberand UltraDork
10/19/21 9:55 a.m.

In reply to frenchyd :

You may not be aware, but they're used in plenty of modern exotic and sports cars. Mclaren F1, Ferrari 355, many Lotuses, BMW M N/A engines, RB26 (which was turbo AND ITB), and my favorite, the Lexus LFA. Not a magic bullet, but there is power potential there.

Junghole
Junghole SuperDork
10/19/21 10:00 a.m.

Does the hp gain outweigh the torque loss? 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 10:14 a.m.

I've been offline for a couple of weeks, did not expect one of my videos to get posted here :) 

Frenchy, I have repeated dyno charts on several Miata engines that show they do not cost you power but provide some gains. Proper A-B tests. The airflow you're imagining is the same regardless of where the throttle body is.

My BMW M5 also has 8 individual throttles and does okay on power. 

ITBs are fun but most aftermarket implementations are not great street options. They work much better if you run a plenum like the BMW or like I did on one of my Miatas. On a high compression engine, they make quite the hammering noise. But they do sound good when you're in the mood and have the ability to play. They're also a great magazine project because people love the idea.

The Link ECU that's in the Miata in question can run ITBs -BTDT - but it's definitely not ideal as it can't use anything but MAP. Worked well enough on my Locost but you accept certain compromises on a car like that :)

I will admit that I have a set stashed away that I'm thinking of putting on one of my Miatas just because. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 10:22 a.m.

Don't have the before/after charts for one engine handy (I'm 2000 miles from home) but it went from 134 to 146 rwhp with throttle bodies. Should have gone higher, I realized years later that I never ran it all the way to redline on the dyno for some reason.

Here's an A-B of a ported intake manifold vs a set of throttle bodies on a high compression stroked Miata engine. Yes, I know about the torque dip in the middle - but the point is the before/after. Shortly after, I failed sound at Laguna due to intake noise :)

http://targamiata.com/images_lrg/targa%20IRTB.pdf

ah, found a dyno video. I have some driving videos somewhere as well.

 

DeadSkunk  (Warren)
DeadSkunk (Warren) UltimaDork
10/19/21 10:34 a.m.

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........I've seen it on an NA and everybody was freaking out because they failed to notice the injectors sitting right behind each SU. I'll bet somewhere someone has hidden injectors inside the SUs for giggles, too.

z31maniac
z31maniac MegaDork
10/19/21 10:50 a.m.
frenchyd said:

In reply to David S. Wallens :

You are aware that air has mass?  That an object in motion tends to stay in motion and an object at rest tends to remain at rest. 
 Individual throttle bodies will need to start and stop intake air  4 times per revolution more often than air inducted through one  throttle body.  It's far easier to divert air already in motion than to start and stop air. 
   You can make up for that loss by increasing duration on the camshaft at the expense of low end  power. 
 OK 4 injector stacks look sexy. But cost you power.   What is your priority ? 
 

ps I don't see Ferrari, Aston Martin etc. using individual stacks. 

Many vehicles still use ITB's, but are fed by a common plenum. 
 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 10:58 a.m.
DeadSkunk (Warren) said:

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........I've seen it on an NA and everybody was freaking out because they failed to notice the injectors sitting right behind each SU. I'll bet somewhere someone has hidden injectors inside the SUs for giggles, too.

Jenvey makes a range of stealth throttle bodies that look like carbs with hidden injectors and throttle position sensors. The current owner of my Locost plans to install a set at some point. 
https://store.jenvey.co.uk/heritage

Rodan
Rodan SuperDork
10/19/21 11:01 a.m.

The juice isn't worth the squeeze... but it will sound spectacular! wink

alfadriver
alfadriver GRM+ Memberand MegaDork
10/19/21 11:05 a.m.
DeadSkunk (Warren) said:

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........I've seen it on an NA and everybody was freaking out because they failed to notice the injectors sitting right behind each SU. I'll bet somewhere someone has hidden injectors inside the SUs for giggles, too.

The other idea is to put EFI on cars that already have ported mechanical injection.  With ITBs.  I know you can get Weber like EFI systems, but for some cars, that's kind of a step backwards. (not in terms of performance, in terms of looking original)

alfadriver
alfadriver GRM+ Memberand MegaDork
10/19/21 11:06 a.m.

In reply to Keith Tanner :

Makes a Miata sound more like an Alfa.  :)

californiamilleghia
californiamilleghia UltraDork
10/19/21 11:07 a.m.

i love the idea of using  throttle bodies off a production car or motorbike , 

but the "brain" is a problem and  I  think beyond most of us :(

if there was an cheap Arduino type board  that could run it  maybe it be more popular , 

Even something that replaced a stock single 'smog' carb that is worn out......

I know.....dream on  !

DeadSkunk  (Warren)
DeadSkunk (Warren) UltimaDork
10/19/21 11:08 a.m.
alfadriver said:

In reply to Keith Tanner :

Makes a Miata sound more like an Alfa.  :)

This made me chuckle.

alfadriver
alfadriver GRM+ Memberand MegaDork
10/19/21 11:23 a.m.
californiamilleghia said:

i love the idea of using  throttle bodies off a production car or motorbike , 

but the "brain" is a problem and  I  think beyond most of us :(

if there was an cheap Arduino type board  that could run it  maybe it be more popular , 

Even something that replaced a stock single 'smog' carb that is worn out......

I know.....dream on  !

While Keith figured out a speed-density solution, an alpha - N solution does a good job, which can be done with even a microsquirt.  It's a little harder to calibrate, but with air temp, water temp, and BP corrections, it can run really well.  Heck, my Alfa is Alpha-N but with a mechanical computer.  I would imagine that it's an option for Speeduino.

(but I will 100% admit to being nervous about doing it, too.  I've never pulled the trigger)

frenchyd
frenchyd UltimaDork
10/19/21 11:43 a.m.
maschinenbau said:

In reply to frenchyd :

You may not be aware, but they're used in plenty of modern exotic and sports cars. Mclaren F1, Ferrari 355, many Lotuses, BMW M N/A engines, RB26 (which was turbo AND ITB), and my favorite, the Lexus LFA. Not a magic bullet, but there is power potential there.

Well technically most EFI  injectors  turn the cylinders into individual throttle bodies with a common plenum.  Most use one throttle plate ( per side) rather than individual throttle plates. 
      The individual throttle plates will create severe headaches. Placement is critical, the potential for a lot of air leaks, binding in one or more throttles caused by vibration, misalignment, wear.  Then the throttle linkage itself!  The weight of all those throttle plates. Plus the added turbulence of individual throttle plates.  
     Finally every time the intake is removed the potential is there  to bend, warp,  or damage something. And thus the need for once reassembled to synchronize the whole assembly. 

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) MegaDork
10/19/21 12:08 p.m.

Secondary emissions, manufacturering cost and maintenance are the main reasons manufacturers aren't too interested in them. It has nothing to do with performance potential. 

 

I'd be very curious about an E85 setup on a stock intake, versus a skunk 2 plenum intake, versus itbs. 

David S. Wallens
David S. Wallens Editorial Director
10/19/21 12:29 p.m.

Good chatter. Thanks, everyone, for the interest. 

Some follow-up comments:

Need it? Who needs any of this stuff? I'm thinking pure emotion (and editorial, of course).

Keith, good point about the Link needing a MAP. Hadn't even gotten that far, but Ed and I figured we'd need to replace the ECU anyway. (And please tell me more about that set that you have stashed away. laugh) And what do you think about the Jenvey setups? Is that a turnkey solution? 

We've discussed bike IRTBs but Ed noted that he could feel the drivability issues from his house. (Which is not near my house as he was making a funny.)

That's the "problem" with the current setup. The engine is totally cold right now. If I turned the key, it would fire right up and then immediately set to a nice idle. No weirdness, no drivability issues--and that's with the Link, the cam gears, the lightened pulley, the aluminum flywheel, the bolt-ons, the headwork, etc., etc. Side note: The engine used to sometimes stall when returning to idle, but replacing the throttle damper seems to have totally solved that issue.

The Skunk2 intake sounds very cool but, sadly, they don't offer it for the 1.6L. Sad face. 

Stefan (Forum Supporter)
Stefan (Forum Supporter) GRM+ Memberand MegaDork
10/19/21 12:45 p.m.
californiamilleghia said:

i love the idea of using  throttle bodies off a production car or motorbike , 

but the "brain" is a problem and  I  think beyond most of us :(

if there was an cheap Arduino type board  that could run it  maybe it be more popular , 

Even something that replaced a stock single 'smog' carb that is worn out......

I know.....dream on  !

I did it on my 924.  Used DCOE-style throttle bodies from TWM Induction and an MegaSquirt 1 w/the Extra code to also control the Ford EDIS distributorless ignition.  Used Alpha-N for tuning (leveraging TPS/RPM instead of MAP/RPM).  Worked well enough to pass emissions tests (the acceleration enrichment was a mess though, so it was a PITA to drive because I was just learning about tuning so I had a ways to go).

Its down right now because I wanted to upgrade to MegaSquirt 2 which adds more processing power and the ability to run Alpha-N blended mode where you could tune using the MAP sensor at lower engine speeds/loads, then switch to Alpha-N for higher speeds/loads.  I haven't gotten back to it in several years due to having kids and losing space in the garage to work on the car.

A buddy, Derek (he had the lambo, viper and corvette builds here), converted his 924 to ITBs off a motorcycle and was more successful out of the box due to using MS2 and having the injectors in the head.

So its completely possible.

jwagner (Forum Supporter)
jwagner (Forum Supporter) Reader
10/19/21 12:49 p.m.

Gonna be the turd in the punchbowl -

ITBs are cool, but just dropping in a later 1.8 will get you the same horsepower and you can tweak that for another twenty or so.  (add ITBs?)  The time and $$ you spend on ITBs just are not worth it for the horsepower.  Not sure how much the "cool" is worth.

ebay has ITBs for LS motors...

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 1:15 p.m.
alfadriver said:

In reply to Keith Tanner :

Makes a Miata sound more like an Alfa.  :)

I see no problem with this :)

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 1:27 p.m.
David S. Wallens said:

Good chatter. Thanks, everyone, for the interest. 

Some follow-up comments:

Need it? Who needs any of this stuff? I'm thinking pure emotion (and editorial, of course).

Keith, good point about the Link needing a MAP. Hadn't even gotten that far, but Ed and I figured we'd need to replace the ECU anyway. (And please tell me more about that set that you have stashed away. laugh) And what do you think about the Jenvey setups? Is that a turnkey solution? 

We've discussed bike IRTBs but Ed noted that he could feel the drivability issues from his house. (Which is not near my house as he was making a funny.)

That's the "problem" with the current setup. The engine is totally cold right now. If I turned the key, it would fire right up and then immediately set to a nice idle. No weirdness, no drivability issues--and that's with the Link, the cam gears, the lightened pulley, the aluminum flywheel, the bolt-ons, the headwork, etc., etc. Side note: The engine used to sometimes stall when returning to idle, but replacing the throttle damper seems to have totally solved that issue.

The Skunk2 intake sounds very cool but, sadly, they don't offer it for the 1.6L. Sad face. 

The Link works far better than its specifications would imply because it is coded from the ground up to be a Miata ECU. It's baked into the OS, and it makes full use of that meager hardware. But that also means a lack of flexibility to do anything weird, so it can't manage alpha-N. The problem is has with ITBs is that they run in a very narrow vacuum range and the Link has limited resolution in MAP, so it can't really distinguish between cruise and WOT. The Targa Miata ran a Hydra which is far more flexible and was able to handle the ITBs better. 

I think the Jenveys would be great on a Miata. You get the vintage look of carbs, it's really different but you can retain modern management and fuel delivery. You'd probably need a Weber adapter from Pierce and then just bolt them on. They're not turnkey because they don't include engine management. Switch to a modern Megasquirt (hello DIY Autotune!) and it could be a great solution with just the right kind of obstacles to be interesting editorially. This would also work very well for CM content, I think.

For idle, cold start, etc, just get Tom to machine a little plenum block to mount the IAC somewhere hidden and feed it vacuum lines from all four runners. Makes a world of difference in real-world driveability and that also gives you a good MAP signal.

Most of the UK crowd are using bike throttles these days, because really they're just butterflies at the end of the day. But they are also willing to accept crap driveability for character, so you do need to filter for that when looking for info.

The set on my shelf is the set that was in the dyno and talky video - some TWMs. Very nicely made with a single casting.  Not sure if you can stilll get them, I think Weber owns the brand now.

Driven5
Driven5 UltraDork
10/19/21 1:32 p.m.
David S. Wallens said:

We've discussed bike IRTBs but Ed noted that he could feel the drivability issues from his house.

I always figured that was more a shortcoming of the tuner than the hardware.

David S. Wallens
David S. Wallens Editorial Director
10/19/21 1:42 p.m.

In reply to Keith Tanner :

Thanks for the extra info. Thanks. 

Correct me if I'm wrong, but I believe Borla now owns TWM. We knew Gary at TWM. He once partied at JG's place. Did TWM made a manifold for the 1.6L?

What about the complete Jenvey kit with the intake maniold? Is it still missing anything? Still need to deal with the IAC?

And will this work with stock cams, or do we also have to go cam shopping?

Thanks. 

David S. Wallens
David S. Wallens Editorial Director
10/19/21 1:43 p.m.
Driven5 said:
David S. Wallens said:

We've discussed bike IRTBs but Ed noted that he could feel the drivability issues from his house.

I always figured that was more a shortcoming of the tuner than the hardware.

He was seeing some hardware issues that he didn't like. I admit this was a few months back, so I'll have to find that conversation. 

JAdams
JAdams Reader
10/19/21 1:53 p.m.

I've already commented earlier but never been so happy to see an article asking for interest. I hope you guys land on a Jenvey kit and document it well. I'd love to add some pretty ITBs to my rotrex'd car.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 2:05 p.m.

My mistake, I posted earlier about the Jenvey "heritage series" bodies that are the carburetor cosplayers. I forgot they also have a bolt-on TB kit for the Miata that I believe is pretty good but more expensive than grabbing parts off a crashed bike so you don't see it as often. Still, if I were doing this I'd give it a good look. I'd still like to use the Heritage setup because it would make me laugh to have fake carbs. 

I'd recommend adapting the IAC for any application. It's something that people don't always do because it's more stuff in the engine bay (for the wire tuck crowd) or because it involves complexity/cost. But it's the right way to do it. 

Right, TWM is now Borla. And I think Pierce is under the same umbrella which may make things easier. My TWM setup has a very nice mechanism for the throttles.

Do the cams need to be tuned for ITBs? That sounds like a great story idea :) My ITB 1.6 had Web Camshaft 505s which I loved - streetable but operatic at the top end. Throw in some valve springs, a bit of compression and rev it to 8000 or so :)

asphalt_gundam
asphalt_gundam Reader
10/19/21 2:13 p.m.

I'd be interested in a thorough article. Specifically setup, tuning,  dyno and tune comparison between open stacks and common plenum, and of course all the problems along the way.

alfadriver
alfadriver GRM+ Memberand MegaDork
10/19/21 2:17 p.m.

In reply to Keith Tanner :

WRT cams, w/o a real plenum, you could increase overlap to help midrange, too- and not hurt idle as much.  Kind of the other direction of increasing the engine speed.  And also differentiating whether this is for a street car to increase the sound/feel vs. going for power.  That would be an interesting comparison that can be done on a dyno with adjustable cams.

David S. Wallens
David S. Wallens Editorial Director
10/19/21 2:30 p.m.

In reply to Keith Tanner :

I do hear you on fake carbs. Hmmm, more info to digest. And, yes, lots of potential editorial fodder. 

I had a Web camshaft in my Rabbit GTI. Sadly, you can no longer simply Google "Web cam" these days....

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
10/19/21 3:31 p.m.
alfadriver said:

In reply to Keith Tanner :

WRT cams, w/o a real plenum, you could increase overlap to help midrange, too- and not hurt idle as much.  Kind of the other direction of increasing the engine speed.  And also differentiating whether this is for a street car to increase the sound/feel vs. going for power.  That would be an interesting comparison that can be done on a dyno with adjustable cams.

This can do some weird stuff at idle, as the fuel can come flying out of the stacks and all over the place at idle (and I have seen this). We ended up having to dial it back out, so the engine bay didn't get covered. 

I have seen ITB both make and lose power and torque compared to plenum/single throttle. Generally the ones with the best mids were on the small-ish side and had great response but lost some top end. The ones that made the best top end seemed a bit lazy in the mids to drive but looked good on the dyno. The guys making big power in the drag setups are using pretty big throttles and an airbox fwiw.

Stefan (Forum Supporter)
Stefan (Forum Supporter) GRM+ Memberand MegaDork
10/19/21 3:31 p.m.
David S. Wallens said:

In reply to Keith Tanner :

Thanks for the extra info. Thanks. 

Correct me if I'm wrong, but I believe Borla now owns TWM. We knew Gary at TWM. He once partied at JG's place. Did TWM made a manifold for the 1.6L?

What about the complete Jenvey kit with the intake maniold? Is it still missing anything? Still need to deal with the IAC?

And will this work with stock cams, or do we also have to go cam shopping?

Thanks. 

TWM makes/made DCOE, DCNF and similar IrTB replacements.  That's what I used on my 924.  The only issue I had was that once they were warmed up they liked to stick slightly just above idle so they wouldn't always idle down.  This was a common problem with some of them apparently.

I used a poor-man's variable cam timing pulley (Franco automatically adjusting cam gear) along with a slightly higher lift cam and longer trumpets to help retain some midrange power.  Ultimately, the 44mm bores were just too big for my engine due to the lack of decent compression ratio.  With IrTB's you can get away with slightly smaller sizes than the carbs due to the lack of chokes.

Hard to believe these pics are from 2010!

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/21 3:51 p.m.

One other thing for editorial: you can tune the powerband by varying the length of the bolt-on velocity stacks. Not hugely, but you can see it on the dyno. It's pretty cool to see. That's why the 787B rotary had an adjustable length intake.

infernosg
infernosg Reader
10/19/21 4:02 p.m.

In short, yes. It wants individual throttle bodies. That being said, you're still going to want some kind of plenum. For all the reasons above but also intake air temperature unless you plan on having the air horns sticking through the hood. My RX7 runs an IDA-style throttle body (not quite "individual throttle bodies) and before I made my plenum I could easily see 140F and higher intake air temperatures and since it was pulling in hot air from under the hood going faster didn't really improve things. After adding the air box and running a tube to a filter located in the airstream my IATs are never much more than 10F above ambient. Maybe it's a rotary thing but I also haven't really had any issues using MAP-based tuning. I'll admit my car's tune isn't 100% but I'm not sure alpha-N will fix that. Going to play around with it this Fall/Winter to see if there's any improvement.

EDIT: Pictures. Because posts are worthless without them.

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
10/19/21 4:53 p.m.

Oh pics. Hard to argue. 

californiamilleghia
californiamilleghia UltraDork
10/19/21 5:12 p.m.

How do you deal with no accelerator pumps ?

My old vw bug did not have one and it had a BIG flat spot off idle.......

j_tso
j_tso GRM+ Memberand HalfDork
10/19/21 5:19 p.m.
noddaz
noddaz GRM+ Memberand UberDork
10/19/21 5:41 p.m.

Yes, it does.

When do you start?

 

Stefan (Forum Supporter)
Stefan (Forum Supporter) GRM+ Memberand MegaDork
10/19/21 5:54 p.m.
californiamilleghia said:

How do you deal with no accelerator pumps ?

My old vw bug did not have one and it had a BIG flat spot off idle.......

They are created by the software, its called Acceleration Enrichment and its actually kinda fun to tune.  Once you get the hang of it.  After tuning cold start and the general fuel table, accel enrichment is a bit of dark art but it is where the engine really comes alive.

alfadriver
alfadriver GRM+ Memberand MegaDork
10/19/21 6:01 p.m.

David, 

If you want to confuse some viewer, see if you can find a SPICA airbox.  Then you will have to find a cool air source, but heads would tilt a little in confusion seeing that.  There are some Alfa people near you that probably has a spare or two.

secretariata (Forum Supporter)
secretariata (Forum Supporter) GRM+ Memberand UltraDork
10/19/21 6:20 p.m.

In reply to frenchyd :

So the guy constantly selling the V-12 love is complaining about added complexity?  cheeky

secretariata (Forum Supporter)
secretariata (Forum Supporter) GRM+ Memberand UltraDork
10/19/21 6:21 p.m.

Do it!

Tom1200
Tom1200 UltraDork
10/19/21 8:58 p.m.

Ooooo I'm really going to throw gasoline on the fire, yes to ITBs but only if you use a slide valve  throttle rather than butterfly type.

The flat slide carbs on my Datsun make a glorious intake roar.

thatsnowinnebago
thatsnowinnebago GRM+ Memberand UltraDork
10/19/21 10:25 p.m.

You guys like to party, right?

frenchyd
frenchyd UltimaDork
10/19/21 10:36 p.m.
secretariata (Forum Supporter) said:

In reply to frenchyd :

So the guy constantly selling the V-12 love is complaining about added complexity?  cheeky

If you think a V12 is complex, you've never taken one apart. They are simpler than a Chevy V8. If you know what you're doing you can change both camshafts in half the time  you can change a Chevy camshaft.   
     Yes the fuel injection is complex compared to modern. But so was anything from the 1970's including Chevy's. 

Stampie
Stampie GRM+ Memberand MegaDork
10/20/21 6:18 a.m.

In reply to frenchyd :

Again you are ignoring how much stuff on top of the engine you have to remove to get to the camshafts.  Do you just copy and paste the same false claims over and over?

alfadriver
alfadriver GRM+ Memberand MegaDork
10/20/21 7:27 a.m.

In reply to Stampie :

It's a lot easier to just ignore him.   And in the end, we should be supporting GRM's "should we do this project" question- especially since this is such a great want for fun thought.  Heck, it can even be turned into a project to find the right sound to feel faster.

maschinenbau
maschinenbau GRM+ Memberand UltraDork
10/20/21 7:41 a.m.

But for real, please do this project. Very high chance I put ITB's on a 2JZ in the next year, so I'd love to work in parallel

David S. Wallens
David S. Wallens Editorial Director
10/20/21 8:39 a.m.
thatsnowinnebago said:

You guys like to party, right?

Yes, we do.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/20/21 10:21 a.m.

Must just be me, but it seems that a V12 should be approximately 50% more complicated than a V8 based on parts count. 

noddaz
noddaz GRM+ Memberand UberDork
10/20/21 11:44 a.m.

David S. Wallens
David S. Wallens Editorial Director
10/20/21 11:57 a.m.

In reply to noddaz :

Yup, the Jenvey kit looks very cool. 

JoeTR6
JoeTR6 Dork
10/20/21 11:57 a.m.

Yes.  Yes it does.

MadScientistMatt
MadScientistMatt UltimaDork
10/20/21 12:42 p.m.

The last time we dynoed ITBs on a 1.6, the car only picked up less than 10 hp at the wheels. One wag on MiataTurbo.net's reaction was "Yes, they look and sound cool, but for $2000, I can buy a pimp suit and a guitar, and look and sound cooler."

Perhaps a good question to explore would be what sort of engine can really use these ITBs to their full potential. When would they make sense, and when would the money better go towards a turbo kit?

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) MegaDork
10/20/21 1:01 p.m.

I think 3 pages of discussion in less than 2 days means that it has the interest of the people and thusly from an article standpoint, it should be done. 

 

 

*Please note that I'm not a publisher, nor an editor nor do I pretend to be one on the internet, so the feelings expressed or merely one man's highly questionable opinion* 

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
10/20/21 1:44 p.m.
MadScientistMatt said:

Perhaps a good question to explore would be what sort of engine can really use these ITBs to their full potential. When would they make sense, and when would the money better go towards a turbo kit?

Start with the kind that "can't" use a turbo kit (rules, strong personal preference, etc) otherwise boost it and call it a day.

z31maniac
z31maniac MegaDork
10/20/21 2:55 p.m.
alfadriver said:

In reply to Stampie :

It's a lot easier to just ignore him.   And in the end, we should be supporting GRM's "should we do this project" question- especially since this is such a great want for fun thought.  Heck, it can even be turned into a project to find the right sound to feel faster.

I know I'm big contributor to the "shut up frenchy" stuff. And I should ignore him, but I don't like seeing blatantly false, misleading, or incorrect misinformation being shared on a forum that is known for having a good signal-to-noise ratio. 

David S. Wallens
David S. Wallens Editorial Director
10/20/21 4:38 p.m.

In reply to JoeTR6 :

So, how has the experience with the company been? 

JoeTR6
JoeTR6 Dork
10/20/21 5:11 p.m.
David S. Wallens said:

In reply to JoeTR6 :

So, how has the experience with the company been? 

I bought my throttles (DCOE-style) through a US distributor that I wouldn't recommend.  But then again, Jenvey also no longer does so.   So I do not have any experience dealing with Jenvey directly, and can only speak about the product.  I'm very satisfied.  The quality compares well with TWM/Borla (with another set of TR6 throttles).  My only issue was with some machining swarf keeping one of the fuel rail o-rings from seating, and that was easily removed once identified.  So far, they are working great.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/20/21 5:13 p.m.
Junghole said:

Does the hp gain outweigh the torque loss? 

Usually, ITBs make the low load/low speed areas much more crisp, because there is a lot less reversion.  Vacuum dies quickly in the short space between the throttle plate and intake valves, so exhaust tends not to backfeed into the intake on intake valve opening.

It was definitely the best thing I did to the RX-7.

 

Peak power will actually be higher with a well sorted plenum manifold, but the overall powerband, and part throttle drivability, tend to be better with ITB.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/20/21 5:21 p.m.
MadScientistMatt said:

The last time we dynoed ITBs on a 1.6, the car only picked up less than 10 hp at the wheels. One wag on MiataTurbo.net's reaction was "Yes, they look and sound cool, but for $2000, I can buy a pimp suit and a guitar, and look and sound cooler."

Perhaps a good question to explore would be what sort of engine can really use these ITBs to their full potential. When would they make sense, and when would the money better go towards a turbo kit?

Big cams installed with a tight lobe center will love ITBs.  Or vice-versa?

David S. Wallens
David S. Wallens Editorial Director
10/20/21 5:24 p.m.

In reply to JoeTR6 :

Thanks for the feedback. I stopped by the Jenvey booth at SEMA or PRI, but this was years ago. Color me intrigued about the whole thing. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/20/21 5:31 p.m.

Boy, if only there was a SEMA show in a few weeks :)

At one point I had a turbo 1.6 and a tricked out 2.0 Miata in the garage. Peak power was pretty darn similar, investment on the 2.0 was probably 4-5x as much. You don't do it for the bulk hp/$ ratio, that's for sure. But that 2.0 was a very, very fun engine. And there clearly is interest. 

David S. Wallens
David S. Wallens Editorial Director
10/20/21 6:03 p.m.

In reply to Keith Tanner :

And if only I knew someone who's already been down this road before. laugh

thatsnowinnebago
thatsnowinnebago GRM+ Memberand UltraDork
10/20/21 6:09 p.m.
David S. Wallens said:
thatsnowinnebago said:

You guys like to party, right?

Yes, we do.

Sounds like you know what to do then. 

mke
mke Dork
10/22/21 8:55 a.m.

Come on in, the water's fine!

It looks like all the issues have been touched on.   There is no 1 thing that makes ITBs hard to get right, but there are a lot of little things ...how to get a good MAP signal (or how to get alpha-n working well at low power), how to get IAC working right, how to get and keep them sync'd, how to install an air filter, how to get it to come off idle smoothly....you just have a lot more opportunities to get something not quite right and have a frustrating experience.   

All that said, its not that hard, especially on the 4 cyl where there is only 1 bank to deal with.  Every sport bike made is setup this way these days....because it makes the most HP which means there is no other option right?  

I'll add this, unlike with carbs there is very little downside to a TB that is bigger than needed.  The bigger the TB the harder is it to get a smooth off idle transition and it theory it could cost HP because there is more air mass in the intake track to accelerate so velocity should in theory decreases.  In practice though the stuff I've tried or seen tried what happens is the hp goes up as TB size goes up until a bigger TB no longer helps....I've never seen the hp start coming back down, not to say it couldn't, but I've not seen it.  The easiest way to pick the right size TB is when the head is still on the flowbench....you up size the TB until the flow stops going up and that result will match the dyno test result without needing to pay for dyno time or burn your hands swapping hot parts.

When I was picking TBs for the frankenferrari I tried a couple sport bike options, a couple more junkyard options, its only 1 cylinder so any TB will do, it doesn't have to be a viable real setup, you're just checking sizing then you go shopping for parts that will work on a real engine.

A 150hp 4 cyl is a large sport bike and those TB sets are pretty cheap on ebay if you have the ability to get them on the engine.  

I did this intake conversion for a guy who then added sportbike TBs.  It's a stock manifold with the plenum sawed off and adapters welded on.   It used the OEM injectors and fuel rails as well. Then you can see the spacers he added between them to get the spacing to match the new engine cylonder spacing.  This was a 12 so I think he needed 4 sets to get the right combination of inner and outer TBs but on a 4cyl you just need 1 set...$100 + $20 of aluminum tubing and maybe 8-20 hours total work....very inexpensive conversion, but just because its inexpensive doesn't mean it can't look and work well.

So I'd say the more throttlebodies the better :)

 

Driven5
Driven5 UltraDork
10/22/21 12:39 p.m.
z31maniac said:

I know I'm big contributor to the "shut up frenchy" stuff. And I should ignore him, but I don't like seeing blatantly false, misleading, or incorrect misinformation being shared on a forum that is known for having a good signal-to-noise ratio. 

While using noise to cancel noise may work in the audio world, that part doesn't actually translate into metaphoric usage. It just makes the signal-to-noise ratio even worse.

 

Speaking of noise... I think mke may be on to something!

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/23/21 6:42 a.m.
mke said:

I'll add this, unlike with carbs there is very little downside to a TB that is bigger than needed.  The bigger the TB the harder is it to get a smooth off idle transition and it theory it could cost HP because there is more air mass in the intake track to accelerate so velocity should in theory decreases.  In practice though the stuff I've tried or seen tried what happens is the hp goes up as TB size goes up until a bigger TB no longer helps....I've never seen the hp start coming back down, not to say it couldn't, but I've not seen it. 

The part where my brain exploded was when I was reading about a dogbone Escort in California that had an Esslinger 3.3l "Lima" based engine, making about 400hp.  That is still an eight valve head.  He described the intake as having "only" 55mm throttle bodies. 

That is, 55mm per cylinder.

Yoicks!

He also described walking away from YBB (Sierra/Escort Cossie) swapped Escorts at Laguna Seca, with half the valves and none of the turbos.

 

Teh RX-7 has 4x42mm throttle plates, which is actually restrictive per datalogs.  Ignoring the 1.3l BS, each chamber is like a 2.6l four's chamber, each chamber pulls from two throttle plates, so two 42mm throttle plates per "cylinder" is too small.  Have a proper DCOE manifold on the shelf, was considering 45mm throttles, but maybe 50mm would be better.

Not that it needs all that much top end charge, but once you get locked into a serious horsepower collection, the tendency is to push it as far as you can.

mke
mke Dork
10/23/21 8:30 a.m.
Pete. (l33t FS) said:
mke said:

I'll add this, unlike with carbs there is very little downside to a TB that is bigger than needed.  The bigger the TB the harder is it to get a smooth off idle transition and it theory it could cost HP because there is more air mass in the intake track to accelerate so velocity should in theory decreases.  In practice though the stuff I've tried or seen tried what happens is the hp goes up as TB size goes up until a bigger TB no longer helps....I've never seen the hp start coming back down, not to say it couldn't, but I've not seen it. 

  That is still an eight valve head.  He described the intake as having "only" 55mm throttle bodies. 

That is, 55mm per cylinder.

I'm not familar with that application but  mine are 54mm because they were the biggest I could get for relatively little money ($50 each) and are costing about 0.5-1% on the flow bench so 55 or 56 would have been my preference if available. There is a company doing a 58mm conversion on them I saw...for another 300 each!  so that is not happening sad  I did cut the side of the shafts flat which added about 2% or so iirc to get me to were I am.

Mine are off a ducati 749/999 (well 6 actually) so 375-500cc per TB from the factory and I'm at about 450cc and that sizing seems about spot on with big valves and a high flowing port....its really hp/cyl whic is really flow/cyl that you're trying to match, no idea how that translates to a roary though?  Anyway,  the stock 308 or TR head flow about 60% of what I have now and on those 44mm from a zx14 or hayabusa seemed about right and I helped a couple guys install them on their 308s, one a 4V, one a 2V, both heads flow exactly the same stock btw, the 4v just needs less cam for the same hp numbers so better for pollution regs I guess.  Anyway, these are 3 liter V8s making a little south of 300hp so pretty much the same as a 1.6 or 1.8liter 4 making up to about 150hp and 150hp is right about what those bikes made stock so again everything kind of matches up to the expectation.  A smaller but higher output engine is generally more sensitive to small flow changes so something that works well on a big V8 making 50hp/cylinder is probably too small on a little 4 banger making the same 50hp/cyl. So were it me, I'd be looking for an option right around 44mm for an application like this (miata) I think.

Last thought is a TB flows better and a carb of the same size...a TB is an empty tube, a carb has stuff mucking up the air flow so when you see people switch from carbs to efi and pick up hp its usually that they had carbs that were too small and replaced with the same size TB, which is effectively bigger so they added the flow they needed, at least this is true for race engine.  On street engines you really don't have a choice but to run the carbs a bit smaller than optimal hp wise as that is the only way to keep the bottom and midrange working well and that is were street engine live 99% of the time so you just have to get that working right.  With EFI and TBs, that is basically a non-issue so I err on the large size if unsure and use a nice progressive throttle pedal linkage to give good throttle position control at small openings where a small change in throttle position makes a big airflow change so its easy to drive around town. 

With DBW so common getting a progression you like just means changing numbers in a table, not not reworking linkages.  This is how the table I use on the frankenferrari...you see the lower left the pedal move a lot for small changes in the TBs then on the upper right the TBs are moving much quick where there is a much smaller % flow change from a % position change.  at idle with the pedal full up the TBs are at 6%...this was high idle on a not well running engine so real idle will probably be say 4% but 6 for now....then when the pedal is at 20% the tbs are at 10%, so only a 4% change and that seemed about right playing with it in the garage...very progressive because that small position change will more than double air flow into the engine.  As I said in my 1st post, its the small things like this that can be really frustrating about ITB setups when you get them wrong.  ITBs are wonderful when they are right, but getting them right, especially on a street car, often takes a bit of patience.

 

 

accordionfolder
accordionfolder SuperDork
10/24/21 9:26 a.m.

You guys want a great deal on my Wossner 12:1 1.6 pistons and REALLY make it scream? These came with an engine I bought and I'm probably never going to use them...

David S. Wallens
David S. Wallens Editorial Director
10/24/21 9:33 a.m.

In reply to accordionfolder :

Please show yourself out. I mean, What more can you tell us about them? smiley

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) MegaDork
10/24/21 10:02 a.m.

12:1, cams,  E85 and ITBs would make for a properly spicy fun setup. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/24/21 11:15 a.m.

In reply to mke :

Ever look under the hood of a 2.3l OHC powered Ford?  That, on steroids.

Esslinger made quite a name for themselves building fast Lima based engines.  I say "based" because they make their own heads and blocks, including tall deck blocks for the 3l+ engines.  Bring a styrofoam cooler full of money. 

 

Not all that different from what guys who rally Volvos do with redblock engines where class rules limit them to stock engine architecture and number of valves.

accordionfolder
accordionfolder SuperDork
10/24/21 4:50 p.m.
David S. Wallens said:

In reply to accordionfolder :

Please show yourself out. I mean, What more can you tell us about them? smiley

Lol, not much to say! I was hoping for 150obo + shipping. They're 500 new, and these are bnib. I think they'd make a super neat build especially with the availability of e85, just not enough time!

 

**Edit, apparently 650 new.

https://www.vividracing.com/wossner-16l-785mm-121-pistons-mazda-miata-19901993-p-132253.html

 

 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/25/21 8:46 a.m.

"while you're in there...."

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/25/21 8:58 a.m.

In reply to Keith Tanner :

2 years and $30,000 later, the car is so upgraded that it is sold at a huge loss and a bone stock NA is purchased because it's more pleasant to drive, look forward to spending time behind the wheel instead of dreading it.

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
10/25/21 9:42 a.m.
Pete. (l33t FS) said:

In reply to Keith Tanner :

2 years and $30,000 later, the car is so upgraded that it is sold at a huge loss and a bone stock NA is purchased because it's more pleasant to drive, look forward to spending time behind the wheel instead of dreading it.

Every project.

accordionfolder
accordionfolder SuperDork
10/25/21 9:50 a.m.
Pete. (l33t FS) said:

In reply to Keith Tanner :

2 years and $30,000 later, the car is so upgraded that it is sold at a huge loss and a bone stock NA is purchased because it's more pleasant to drive, look forward to spending time behind the wheel instead of dreading it.

Stock 1.6 cars are fantastic for the road, but on track or autoX ... Man they're incredibly slow. Good character, but literally ~6 seconds a lap to a stock VVT engine at NCM, same tires and setup. I drove one for a whole season in 2020 and loved it, but even 141 whp from my VVT car might as well be a rocket ship compared to it.

Rodan
Rodan SuperDork
10/25/21 9:07 p.m.

In reply to accordionfolder :

I can vouch for this.  Compared to a worn out 1.6, a stock VVT 1.8 at ~140hp is a LOT of fun.  But it's still not really fast... wink

wspohn
wspohn SuperDork
10/26/21 9:55 a.m.
DeadSkunk (Warren) said:

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........

SU sort of did that themselves (I owned a pair of these).

David S. Wallens
David S. Wallens Editorial Director
10/27/21 11:18 a.m.

One thing I do like about the Miata's current setup: It uses pump fuel and, as a result, I can fuel up anywhere. It doesn't have a huge tank, and on the highway the engine turns about 4500 rpm. Being able to fill up anywhere has been nice. (I know, think about the editorial....)

californiamilleghia
californiamilleghia UltraDork
10/27/21 12:00 p.m.

In reply to wspohn :

the 2 barrels are cool , how rare are they and what did they come on ?

Thanks

wspohn
wspohn SuperDork
10/28/21 11:48 a.m.
californiamilleghia said:

In reply to wspohn :

the 2 barrels are cool , how rare are they and what did they come on ?

Thanks

The DU6 carbs were very rare back in the day. They used them on the Lotus FPF engines (used in F1 cars), Cooper Monacos, briefly experimentally in MGA Twin Cam factory racers, and the Triumph TRS Le Mans cars.

Very, very rare for many years, they are now being reproduced for Jaguars etc. at pretty eye-watering prices.  I played around with them a bit as I was setting up an MGA Twin Cam for racing, but I decided (wisely, I think) to go with the more easily tunable 45 DCOE Webers, just as the factory had done.  

Should have hung them on the wall as garage trophies but sold them to someone who was restoring one of the TRS cars.

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) MegaDork
10/30/21 10:53 a.m.

ITBs and bear wheels so that the induction noise from the ITBs can be referenced as the growl of the bear. Or you can go panda with it and turn a bamboo shift knob. There is 3D printing filament that is made from bamboo as well for some questionable theme ideas. Such as a bamboo printed pi dash surround, bamboo spoiler risers, etc. 

Sponsored by

GRM Ad Dept

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