ChrisD

Doh, I've completely forgotten about that. I suppose you can just chuck it next time you get a chance. I seriously doubt my car will ever make it back to stock. Thanks for hanging on to it for me.

MacGyver

You got the 720 crank hp part right, but not the resulting (if perfect) wheel hp...for a 17% tranny loss, that equates to 598 wheel hp, not 650 hp. Rarely are things linear, but you should still be reasonably close. Is this 2 bar right into the TB, or 2 bar between the compressor and intercooler? If it's between the two, expect some PSI loss there, so you can't calculate the hp gain with a value of 2 bar.

Incidentally, what kind of losses are you guys seeing with the ICs? 10-15%?

ChrisD

[QUOTE]Originally posted by MacGyver
[B]


You got the 720 crank hp part right, but not the resulting (if perfect) wheel hp...for a 17% tranny loss, that equates to 598 wheel hp, not 650 hp.

terry@spool

Its all about volumetric efficiency. How the turbo system was designed, manifold flow, I/C efficiency and pressure drop and the size of the turbine, turbine housing, compressor and compressor housing. The more cfm a turbo can flow at a given (constant) psi the more power.....like I stated before not how much boost you are eunning but the efficiency of the system In regards to cooler air being more efficient....I am unsure of this. Like you stated the air is denser thus needing more fuel and creating more power. But from an engineers point of view or explanation, I cannot help you there.......anyone care to chime in

MacGyver

20 psi is 1.36 bar, not 2.0 if that's what you were referring to. At 20 psi, that's the equivalent of 566 crank hp. Roll that through 17% tranny losses and you're at 470 wheel hp, pretty darn close to that 450 wheel hp you quoted. I'm willing to let a few hp go here and there due to tuning and additional losses at greater torque (increased friction as spinning components are twisted closer to their oiled sidewalls, etc.). From that standpoint, I'd say the numbers you're seeing match up pretty well.

In a nutshell, per psi, one should expect roughly 16 crank hp and 13-14 wheel hp.

Losses certainly aren't restricted to the IC when going FI, but you can expect the majority of your pressure loss through it. At a 10-15% loss, that equates to 2-3 psi when running the compressor at 20 psi. If you're assuming the compressor is at 20 psi and expect to get the 477 whp figure mentioned above, you'll fall short a good 30-40 whp due to IC losses.

MacGyver

Terry, I would probably say the reverse of your statement is the correct way to say it...the more psi a compressor can push at a particular flow rate (cfm) the more power that's available. For a particular rpm, the engine will need a set amount of air (cfm)...the trick to more power is making that volume of air more dense by raising the psi.

chris, It's difficult to answer your question about efficiency without understanding your definition of efficiency in this context. As you stated, a cooler air charge (i.e., more dense) will obviously hold more power potential. One could argue that the hotter charge would affect the bearings and make them slower due to increased friction, one could argue it heats up the engine with the same effect, one could argue all kinds of things, but I'm not so sure it would be useful here. Cool the charge as much as humanly possible before it hits the cylinders and you'll have done the best you can do.

mr3

You guys are calculating your losses due to the drivetrain incorrectly. Tranny losses do not depend on the amount of horsepower your engine developes. It requires a certain amount of power to drive your transmission, which is about 40 horse power for the s2000. So, if you make 300 or 400 horse power it will still take the same amount of power to drive your drivetrain. With that said you will need about 320 hp at the crank for your 280whp.

derryck

Holy cow that's weak... I'm only running 15 psi and I'm right at 500 RWHP. Just kidding (about the weak part)... 450, that's pretty good. When are you going to 2 bar?

ChrisD

As soon as my wastegate spring arrives.

VTECS2000

I think that it all would depend on what kind of supercharger or turbo charger you have on the car. Some are bigger and they can put up with more boost than others.