CyCloNe!

I know this topic has been beat to death and I have some many of the threads but here's my question. First the supercharger would be of roots sytle and either would be utilized on our engines. If both forced induction methods utilize the same boost level lets say a moderate 15psi and both at 15psi project the same CFM, lets just say 600CFM. What would be the differences in drivability be? I assume the turbo would each 15psi sooner and charger would start boost sooner? Would power output be the same since both are flowing the same amount of air?

Any insight would be appreciated, please lets keep the bashing to a min.

eman930

Well, You'd loose HP running the supercharger, and probably wouldn't have a lot of top end HP, and have more down low power, Now with the turbo you don't have as much parasitic draw, and you'd have good mid-high HP

TurboTommy

Actually, with a positive displacement type supercharger, the boost will be all in alot sooner than the turbo engine.
The supercharger makes less power than a turbo because there is a significant parasitic draw directly from the crankshaft. I think it even takes a higher percentage of power from the crank as boost goes up (It might only take 10% from the crank to make, let's say 4 - 5 psi boost; but maybe 20% power from the crank to make 15 - 20 psi boost) Something like that.
A supercharger also puts more heat into the air, so that's a negative.
Pumping losses are less than a turbo engine, so that's a positive.
You can't cam a supercharged engine quite as aggressively, or the exhaust needs to be a little bit restrictive; either way a slight loss in VE
Turbo also experiences losses of VE because of the exhaust restriction of the turbine. But, you have the option at least (if you want to tollerate a more sluggish boost rise) to dramatically increase VE and diminish pumping losses to zero with the appropriate hotside of the turbo. This can, in turn, increase power above what even the achievable boost suggests. This manipulation of efficiency is the biggest advantage of a turbo engine.

So, you might lose 20% power from the crank at higher boost levels with a supercharged engine (I think that's roughly what it is; others can chime in)
With a turbo engine, it can be achieved that there's almost zero parasitic loss (takes some doing, though)
That would be the difference in power.

Dubai944

You made some good points but not sure I agree with these ones. Any Exhaust restriction is never a good thing and isn't needed specifically for supercharged engines, and appropriate cam timing is dependant on matching the rest of engine. If everything else works together you can run just as aggresive cam timing on a supercharged engine as on any other. I run very aggressive cams on my supercharged engine and it works very well.

I'm not claiming to be an engine expert, but this is consistent with everything I've seen written on supercharged engines and experienced myself. I would have thought a turbo would be more sensitive to aggresive cam timing than a supercharged engine?

CyCloNe!

Thanks for into gentlemen. So imagine my 951 would it be more beneficial to keep the turbo or could i put like an m90 eaton on there and be just as satisfied at the same cfm. I'm debating removing the turbo go supercharger, looking for a realistic 325whp. I know a turbo can achieve this easily but i wonder how about a supercharger on these motors?

86 951 Driver

I wouldn't use a M90. It would run out of steam I would think. I know you could run it with an aftercooler, but it would make less power than a turbo.

I thought you recently upgraded your turbo?

Dougs951

I would stay turbo, unless a paxton has fallen in your lap.

Black51

I say go for it!

Of course, just like selecting the right turbo, finding the right supercharger for your application will be key.

odb812

Why? There are plenty of tried and true ways to get 325whp out of your car and I see a lot of the equipment needed already in your signature. Nobody here will be able to help you debug supercharger issues.

333pg333

Question: 2.5L motor or bigger? If it is bigger then you should be able to circumvent some of the 'lag' with displacement.

drift a 944

Why not have both?

Reimu

A k27/6 could get you there with minimal lag

I can't see how you could justify all of the supercharging stuff in the end...

TurboTommy

With your aggressive cams, how do you keep your hard earned (crankshaft power) boost pressure from flowing right out through a free-flowing exhaust (I agree it's silly to purposely have a restrictive exhaust).
It must be alot of trial and error to get it right. Most engineered supercharged systems don't bother and just use conservative cams.
I listed the cam issue , earlier, really only as being noteworthy and not necessarily a potential major detriment.
On the opposing end, I just think there's greater gains to be had with aggressive cams on a turbo engine (which has good exhaust management)

CyCloNe!

Lol don't tempt me....

Honestly I'm probably around 300+whp as is but I'm just throwing out ideas. I've also been considering a gt3076 wheel being installed in my to4e and machining the housing for it.

blown 944

After doing both I can say that for anything over 10 psi the turbo is the way to go.

Many valid points have been made already.

The supercharger definitely has a little more I initial grunt but if you used a small dbb turbo you probably wouldn't nOtice much difference.


The disadvantages that I recall are belt slip and noise overall.


I did enjoy it though, and if I weren't going for high power I may consider it again. However, this time would be far more refined.