forward facing turbo

[90ggsx]

Completely makes sense. That's pretty much what we have the rules set up for on idahomotorsports

 

[Barnes]

If my math is right, a forward facing turbo gains at absolute max (stagnation) ~0.5psig @ 150mph.

So you basically gain nothing. What you *do* gain is an intake that is not restrictive. But as discussed already, a correctly setup intake is not restrictive. I would think perhaps the best gain to a forward facing turbo with an inlet open to the front is the coolest air possible.

 

[prove_it]

^that's pretty much the reasoning for a forward facing turbo. Typically it's pointless until your going after 700+ in a drag car.

 

[thecman02]

The extra pressure at that inlet is then multiplied by the pressure ratio the engine is running. So with high pressure ratios you gain about 2 psi. It really only helps in compressor limited situations.

 

[Barnes]

Uh? That doesn't make any sense to me. If the airflow stagnation pressure is 0.5psig (gauge pressure), how is it possible the intake charge see more than that pressure?

EDIT: Thinking about this a bit more I think what you are saying is that if I take atmposheric pressure of 14.7psia (just for arguments sake, don't nit-pick the value), then add 0.5psig, I get an *effective* atmospheric pressure of 15.2psia. Is that what you are saying? So in that case running a pressure ratio of 2, I'd get 15.2psig vs. 14.7psig. And at a PR of 3, I'd get 30.4psig, vs. 29.4psig?

 

[prove_it]

Ram air effect at higher speeds creates a minor "boost". Turbos work off of the difference between inlet and outlet, higher inlet means more output.

I doubt you'll see 2psi below 100mph though.

 

[Barnes]

See my edit. Just keep in mind that the 0.5psig @ 150mph is *stagnation* pressure. I.E. The max pressure that could be generated. Since the air is in fact *not* stagnating, it's certainly less.

 

[prove_it]

See your math backs up my claim that a FF turbo is useless unless your hitting 150mph or higher. As a drag car you'd be planning on 9's for it to be worth the money.

Just use a normal set-up and add 2 lbs of boost and your already making more power than if it was a FF turbo. I think too many get all excited over the "ram" air concept. It doesn't do much until your past 130mph anyways. You make a bigger gain from pulling in fresh cold air than the effect itself.

Thanks to barnes for mathematically proving it.

 

[thecman02]

EDIT: Thinking about this a bit more I think what you are saying is that if I take atmposheric pressure of 14.7psia (just for arguments sake, don't nit-pick the value), then add 0.5psig, I get an *effective* atmospheric pressure of 15.2psia. Is that what you are saying? So in that case running a pressure ratio of 2, I'd get 15.2psig vs. 14.7psig. And at a PR of 3, I'd get 30.4psig, vs. 29.4psig?

That's exactly what I meant. Although I would argue that if you place the inlet at the leading edge of the car you will get a pressure increase equal to stagnation pressure. Most setups aren't in the optimal location so .5 boost at the inlet is definitely a best case scenario. A nice well rounded inlet/bellmouth will net you a similiar gain to by reducing the minor loss of the entry.

Prove it, I would definitely agree that it makes no sense except in a full out race car looking to get every little advantage possible. As far as the OP is concerned he should buy a nice FP manifold/turbo setup.

 

[Spyke169]

So are we only focusing on the benefits of the turbo inlet facing towards the front of the vehicle and that is all? When looking at most forward facing manifolds, they are long runner, the advantages of this go much further than what has been discussed here...

 

[prove_it]

Yea, but still not worth over 1k for the manifold + costs of building all the piping, ETC.

 

[LIV4PSI]

Unless you are a badass like theCman02, and also have friends who fabricate. Paying retail for a stranger to do it, would cost much more.