Agent911

This must be one of the oldest arguments around. However, I wanted some expert opinion.

which one gives your more Hp per engine liter displacement? and why?

Philbertt

My understanding is that turbos produdce more Hp. Generally speaking, superchargers are driven directly off the crankshaft and thus produce boost immediately. Turbos are driven off exhaust pressure which is why there is a lag before the turbine of the turbo gets spinning. The turbo is more efficient and can withstand higher boost levels. However, there are many factors at work, and some engines work better with superchargers. For example, if the compression ratio gets too high, a turbo charger will not work as well. I don't know the mechanics of why this is the way it is. Another factor is air tempature, and most turbos are used in conjunction with an intercooler. Few if any superchargers use a cooling device, and thus the intake air tempature is higher in supercharged cars, which produces less power.

I don't know if any of this helped, or if I'm just going over the basic differences between the two forms of forced induction.

-Phil

Skydive69

My last ride was SC equipped, and I sure miss that immediate, powerful surge!

Bluto

The car was American and the overall build quality, and handling sucked!

Great engine and powertrain though.

That supercharger was there from the moment you stepped on the gas!

Haywood Jablome

If turbos made more power wouldn't the drag-racers (top fuelers) use them?

There is more to road driving than ulitmate power, with electronic management turbo power is quite nice.

(Supercharged and loving it.)

Skydive69

escaping that with German engineering, and discovered that the grass was not necessarily greener on the non-American side.

Bluto

at least in the interior of the car.

I had a 97 Grand Prix GTP. I literally had the door panels falling off the car. And that cheap s*** used on the interior sucked!

Have not had any, (knocking on wood) build quality issues yet w/the TT.

GTP was great for get-up and go, but that was about it!

Skydive69

Fit (if not finish) is certainly vastly superior to anything American that I have driven. My Pontiac TA Convertible was a joke re the way the body panels were misfit. The TT has wonderful fit, but I have a left rocker panel that has two spots with darkened paint (silver), and another spot where it is lighter than it should be.

Parshall

Simplified overview

First the Misconceptions:
For starters, both are 'superchargers.' A turbo charger is really a 'turbine supercharger.' What people call a supercharger is usually a positive displacement 'roots supercharger'.

Superchargers do use intercoolers and Eaton style roots superchargers need them even more than the turbo for the same boost pressure.

Eaton superchargers are not as efficient compressors as a good turbo. This means they heat up the air more and rob more power for the same compression.

There are positive displacement and turbine superchagers that are belt driven. The belt driven turbine supercharger is 1/2 of an exhaust driven supercharger but without the lag.

The turbo lag. Turbine compressors designed for maximum power are not very efficient at low RPMs. So when an american driver used to a V8 steps on the gas at 1500 rpm and nothing happens, it is NOT turbo lag. It is the fact that the turbine is not designed to be efficient at 1500 rpm. Most designs take until 3000 to 4000 rpm before the turbine is spinning fast enough for good boost. Then you hang on. Again, this boost difference/waiting/lack of relative power from 1500rpm to 3000rpm is not turbo lag. Turbo lag is the time it takes a turbo to go from the boost pressure of a motor at 3-4000rpm with a closed throttle and so slow exhaust gases to 3-4000rpm open throttle and fast exhaust gases.

Pros and cons?
Turbos will generally give better fuel economy due to higher efficiencies. Hence turbos on european cars where fuel efficiency is a bigger concern than in the US.

Turbos work better at high rpms and high compression ratios. Torque is proportional to compression ratio. Power is proportional to torwue times rpm. A high compression turbo in a high rpm motor will be able to give higher peak power than a roots supercharger. A high rpm racing engine would benefit more from a turbo than roots blower.

A racing series with fuel mileage limits will benefit better from a turbine than a roots. The turbine charged motor would get better mileage and so require fewer pit stops. This is why you see turbo charged motors winning LeMans and not roots charged motors. The turbos are more efficient.

For car manufacturers trying to cater to american tastes for low end torque. The roots is much better. A roots charged 4 cylinder will feel more like a V8 than a turbine charged 4 cylinder. The roots 4 will get worse mileage than the turbo version but better mileage and emissions than a V8. This is a compromise manufacturers are willing to make due to the better marketability of the roots style motor in America.

Drag racers need torque torque torque and instant low end response. This is a roots superchargers forte.

Conclusion:
If all you care about is instant response and 0-60 times, then you want a roots style supercharger.

If you want to out race another car over a period of time and want peak power and efficiency, you probably want a turbo.

Edwin

Good post. Thanks for the good info.