Supercharging Versus Turbo Charging

I have a choice. Both will net me that same boost both will take about the same amount of fab work to install.

So lets here it.

What would you do.

Likes and dislikes for either choice.

Ohya this is for my 924s

The supercharger will give you more torque at low RPM, but will become inefficient at higher RPM due to heat. The turbo will shine at higher RPM, and not offer as much at low RPM. So the right answer depends on what you're going to do with the car, and how you're going to drive it.

Personally, I like superchargers for the low rpm grunt.

If anyone cares the supercharger is a hybrid unit I put together from a 230 Kompressor M62 (back housing) and an M62 from an early Buick Riv (snout and impellers). The turbo is from a Mazda Speed 3 2.2. Since it was for a 2.2 and I am putting it on a 2.5 but want relatively low boost it should be good. At least that what the maps for it say. It is a KO4

Either will net me 10PSI of boost with no issue. The supercharger will be harder to up the boost. The turbo should be easy to up it to about 16 PSI if I want but that would probably do bad things to my motor with out adding dish pistons to lower the static compression.

Since the turbo come from a 2.2 my 2,5 should spool it rather quickley. The supercharger is sized perfectly for my car with the stock crank pulley. The c230 obviously uses a 2.3L motor and the riv uses a 3.8 my car is a 2.5 so again it is in the sweet spot in terms of efficiency. Typically I don't get over about 4500 rpm so I have been leaning towards the supercharger but there is the little kid in me that keeps saying turbo it. LOL

What is it going in? What kind of power are you looking for?

Turbo. A proper turbo setup will give the same low end power or more than a supercharger setup, without the heatsoak issues.

More power under the curve > any theoretical low end "spike" you might think you might get.

JtspellS wrote: What is it going in? What kind of power are you looking for?

dean1484 wrote: Ohya this is for my 924s

In reply to dean1484:

Slow me is slow, Turbo gives you the head room for later growth but the S/C will give you the power right stat now!!

dean1484 wrote: Either will net me 10PSI of boost with no issue. The supercharger will be harder to up the boost. The turbo should be easy to up it to about 16 PSI if I want but that would probably do bad things to my motor with out adding dish pistons to lower the static compression.

That's the real answer. Boost is addictive, and that supercharger is limited to about 240-250 whp before the bearings become a liability. Will's answer is the knee-jerk assumption about the two methods, but it's really not accurate. I've tested superchargers with more top end than turbos and turbos with more low end than superchargers. It's all about sizing and implementation.

The turbo is going to be easier to install as well - a good belt drive is a lot harder to accomplish than you think.

No one has said "both." Shame on you guys. Seriously.

poopshovel wrote: No one has said "both." Shame on you guys. Seriously.

He he he he Ther is a guy with a subi that tried it.. . Or was that with two supperchargers.

The super is less efficient at pumping air than a turbo.
So it takes more energy to make the same amount of boost.
The super takes that energy directly from the crankshaft.
The turbo takes that energy from heat and gas velocity of exhaust gas that would othewise be wasted anyway.

Bottom line, super makes less HP at rear wheels than turbo for same amount of boost.

From a packaging sandpoint the supercharger is an easier install unless I want to make the turbo a rear mount.

The supercharger will mount where the air compressor use to be. I have made up he plate that bolts to the block I just have to make up the adapted for the supercharger for the plumbing. Belt alignment is not that bad. I have actually done it before. The key is to measure things and get references so you can keep things square / parallel with each other. Yes it is a nuisance but not that bad

The turbo can be installed up close to the engine but I will probably have to make a hybrid log / shorty manifold and even at that it is going to be tight to keep it higher than the oil pan. Then there is the issue of the piping back up front to the IC and to the air filter box. All doable but it will require some very precise tubing work. If I mount it by the motor I have to keep it high so I can drain the oil it back to the pan. And that leads to the problem of drilling a hole in the pan. I could probably just go through the pan gasket as it is a shim gasket that is about 3/8" thick. I could take a 1/2 inch piece of copper pipe and crush fit it through the gasket. This would make a good seal and keep metal shavings out of the pan. Otherwise I have to drop the crossmember to take the pan off.

erohslc wrote: The turbo takes that energy from heat and gas velocity of exhaust gas that would othewise be wasted anyway.

I agree and disagree. The turbo saps energy from the crankshaft as well, just not as much. Turbos add significant exhaust backpressure which takes its toll on the crank via the exhaust stroke needing to work that much harder. Many of those super-high-hp diesel sled trucks you have seen can frequently see 100-140 psi of pressure in the exhaust manifold. That definitely saps power from the crank.

I vote for turbo. SCs work off the crank's RPM. Regardless of your need for boost, the SC offers boost based on RPM. Turbos work off your right foot. A turbo (for the most part) doesn't affect anything until you pass a certain point with your right foot. It is a truly load-based input.

Centrifugal superchargers offer boost based on RPM - they're basically a turbo compressor driven by the crank.

Positive displacement superchargers (like the one here) offer boost based directly on the relationship between crank speed and blower speed. Assuming a 100% efficient blower, that would mean peak boost is available at idle. Of course, that's not really what happens.

One thing to note from the Colorado point of view: supercharged cars are affected by altitude like naturally aspirated cars are. As the air density drops, so does the power. Heck, they typically are affected worse as their efficiency drops out of the sweet spot. Turbos are still affected, but nowhere near as badly.

dean1484 wrote:

poopshovel wrote: No one has said "both." Shame on you guys. Seriously.

He he he he Ther is a guy with a subi that tried it.. . Or was that with two supperchargers.

Google "twincharge" It's not just for scoobies! Seriously, why pick one or the other? I road in Clemson's twincharged civic. That car was badass.

I'll trade you that M62 hybrid for the Thuderbird M90 I have... :) I need something shorter for my application...

My opinion depends a lot on what you plan to do with the car... I have found positive displacement SC cars tend to have a more linear power band... You don't really feel the boost kick in... This can be good if you are looking for a very flat torque curve... little more boring on the streets daily driving..

Turbo cars can have the same affect with the right set up... But generally home built junk yard set ups have a little more peeky kind of feel to them... You end up feeling the surge of power as the turbo builds boost... This can be fun daily driving..

it really all depends on the usage.

I have driven a number of Turbo and Supercharged vehicles. For a commercial truck, I will take a Turbo Diesel everyday and twice on sunday.

For a car.. I never cared for the way a turbo kicks in. For day to day driving, I would stick with a supercharger. If it was for racing, I would go Turbo.

Superchargers are just nicer to drive on the street. Not faster, not as powerful, but nicer. It is more akin to having a larger displacement engine under the hood

Actually, one of the things I like about a turbo on the street is the way you can't tell it's there unless you ask for it. Supercharged (aftermarket) cars tend to have a bit more noise and vibration as well as poor idle behavior. A supercharger on a new intake manifold avoids the idle problems, but that's tough to do in a one-off. Turbos are also really nice and smooth on the highway.

One of my favorite tricks to do when taking people for rides in turbo cars is to drive normally and get them chatting. They forget about the turbo - then I slap open the throttle and pull through the gears and they forget about chatting. The lack of indicators before makes the after so much more fun.

Supercharged cars really do just feel bigger displacement, that's true.

That's the right answer. It all comes down to installation ease, and end use (drivability).Power is not the issue.

curtis73 wrote:

erohslc wrote: The turbo takes that energy from heat and gas velocity of exhaust gas that would othewise be wasted anyway.

I agree and disagree. The turbo saps energy from the crankshaft as well, just not as much. Turbos add significant exhaust backpressure which takes its toll on the crank via the exhaust stroke needing to work that much harder. Many of those super-high-hp diesel sled trucks you have seen can frequently see 100-140 psi of pressure in the exhaust manifold. That definitely saps power from the crank.

The backpressure from the turbine is certainly an issue, but I'm sure it's not sapping nearly as much power as a supercharger. Even at ~10 psi manifold pressure, and air flow rates sufficient to get ~300 bhp, it can take 50 hp, just to spin a roots-type supercharger. That means the power increase from boosting the car has to be way more than 50 hp to get any appreciable net increase.

As someone who loves the roots-type blowers, I gotta admit that the tradeoff is usually a substantial hit in hp (for the same amount of boost in a well designed turbo vs supercharger), but it's easier/cheaper to get good throttle response and increased power pretty much everywhere in the powerband (again if everything is designed/sized well).

Will wrote: The supercharger will give you more torque at low RPM, but will become inefficient at higher RPM due to heat. The turbo will shine at higher RPM, and not offer as much at low RPM. So the right answer depends on what you're going to do with the car, and how you're going to drive it. Personally, I like superchargers for the low rpm grunt.

really?

No low end grunt there at all.

Given the packaging issues of a turbo in the 924s and issues with cooked engine mounts and all that that the factory cars where notorious for (yeah, I know that the 924 turbo used a different engine) I would think the supercharger install would be much easier to accomplish ini a satisfactory manner.

If you can mount the supercharger close to the intake manifold you should also be able to work around the issues that you tend to get with hotside s/c installs on Miatas, for example.

If you want to be technical a turbocharger is form of supercharger, so the question is wrong

Turbos are cooler and better in just about every way you just have to set them up right. If you are ever going to want more a lot power from your car then turbo. Or if you can match the turbo size to your engine and the power you want then a turbo is the best answer at the end of the day.

Superchargers are the lame redneck answer. If you can't do your own fab work or have some fancy N/A style exhaust you don't want to remake and you just want to make your car a little more fun, then supercharger. What I don't like most about these things is half of them just force non intercooled (ie hot) air into the intake. This is just a waste of easy power

jere wrote: If you want to be technical a turbocharger is form of supercharger, so the question is wrong Turbos are cooler and better in just about every way you just have to set them up right. If you are ever going to want more a lot power from your car then turbo. Or if you can match the turbo size to your engine and the power you want then a turbo is the best answer at the end of the day. Superchargers are the lame redneck answer. If you can't do your own fab work or have some fancy N/A style exhaust you don't want to remake and you just want to make your car a little more fun, then supercharger. What I don't like most about these things is half of them just force non intercooled (ie hot) air into the intake. This is just a waste of easy power

let's not jump all over the turbocharge bandwagon like a fanboi. Superchagers have their place or car makers would not still be putting them in cars.

Thing to remember about non-intercooled superchaged air. Most S/Cs don't put out more than 8psi.. 12 at those levels, heating the air is nowhere near as bad as on a turbocharged car

And I would not call Superchargers "redneck" MB used them quite successfully for a long time