Turbo and Supercharger Output Temps
Turbo Mini Forums

Imagine you have a Roots type blower and a T2 (running in the 65 or 70% efficiency envelope). Both are the correct size for the engine and both are creating 8 or 10 psi.

What is the theoretical output temerature of both? assuming a starting air temperature of 20.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Use this:



Use absolute pressures and temperatures. N = 1.4 ish.

That gives you the theoretical temperature rise at 100% efficiency.

Divide the temperature rise by the efficiency, add to the inlet temp and bob's your uncle.

Edited by Paul S on 2nd Jan, 2008.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Ok.

So assuming a turbo has 70% efficiency, what is an average efficiency to take for a supercharger 55%?

Also, is the increase in temperature caused by the heat of the turbine taken into account in the efficiency
rating? If it is then the output temp of supercharger will always be higher I guess.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

I would take 60% as an average for a supercharger, assuming a roots type with a helical rotor such as the Eaton M45.

I doubt that the eficiency includes any external heat factors. But then it is being continuously cooled by the incoming air.

I've yet to see the compressor map for a supercharger that is more efficient than a turbo, at the sizes we are interested in.

I get 87 degrees C at 10 psi on 70% efficiency.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Thanks very much Paul. I had managed to get this formula off the net.



Which after a bit of fannying around, turns out to be what you said in one nice formula. But could I get it to give a real answer? no. It turns out the important fact is to use ABSOLUTE values for temperature, fucking Kelvins!!!!.

I still wonder if there is a significant increase in temperature caused by the heat transfer from the turbine though. I mean it's not designed to transfer heat to the air, like a car radiator for instance, but it must transfer something.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Interesting one this.....

I was a sceptic about VMax's suck through as suck throughs aren't the deal in a lot of ways and then I had a think about it. It's quite a good idea as it will improve the efficiency of the blower in 2 ways.

1. The fuel coated rotors will seal better.

2. The more finely divided fuel will have a greater surface area, which will allow more evaporation and charge cooling.

The maths required to figure this out is way more complicated than is to bore a hole in manifolds and whack some thermometers in.

If you're after a comparison about what welly you can get out of both. Ask yourself, what is the blower drawing at those revs?

Answer:- A fair bit.

Bugger off, I'm getting there.

The theory is that you cannot run an intercooler with a suck through setup, so you will never get the same power as with a blow through with an intercooler.

Furthermore, fuel evaporation is a bad thing as it takes up far more space and displaces the air you need for combustion.

I think that although the blower will draw some power from the crank, I think that this is offset by the low pressure on the exhaust side and the potential to benefit from longer duration cams.

I'm hoping to put my Eaton M24 on a 998 some time this year, so i will have a direct comparison with my 998 turbo.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I'm 'doing a Vegard', although this resurrection of an old post is not really that old.

Anyway, this link has some nice comprssor maps for various turbos (no GT17) and some supercharger figures.

Interestingly for the superchargers it shows the Delta T and power consumption.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

this is too deep for me,

but i can tell you out of my T25 running 12psi and a day when the ambiant temp was 25 my turbo was putting out 112 degrees straight out of the turbo.
this is why i put the cooler on and now on a same temp day it is in the mid to high 30 degrees.

179hp on 12psi 1293cc of pure A series
14.0et @101 mph