legacycentral bbs

how would some one calculate the end horse power for a turbo'd car?

like say i gave my car 12 psi of boost. how more hp would that 12 psi give?

I believe I read some where (don't quote me one this) for every lb of boost is around 10hp. So 12 lbs would be around 120hp.

That's impossible to calculate. It is dependent on many many factors.

Pick a power goal, see what others have done to get there. There's no direct boost-power factor, but you can get an idea of what it takes to make 160whp or 200whp or 300whp and start from there.

You'd never be able to determine a hp/psi figure like that. Like alphius said, there's a ton of variables like what the ambient temp is, elevation, where the turbo is at in it's efficiency range, etc etc etc. If the turbo is not operating in the range that it's most efficient it will be producing more heat so the molecules will expand and 1 lb of pressure will contain a different number of molecules per square inch than at a different part of the compressor map. One turbo will make a certain power (given all other variables are the same for both turbos) than another turbo makes at the same PSI.

reason i asked me and a few guys in class were talking what my final hp will be. i have a 3" catless exhaust that claims 10 more hp and if i put my boost up to 11psi we were just wondering how much the final hp would roughly be

You could get a rough idea comparing to someone elses dyno numbers that has the same parts as you but even that would be ballpark. You'd need to dyno it to find out.

closest dyno for me it 4 to 6 hours away with out pulling the motor

kimokalihi wrote:One turbo will make a certain power (given all other variables are the same for both turbos) than another turbo makes at the same PSI.

Its not even that simple. A given turbo size will move a given volume of air at a given pressure. Change the turbo size and move more or less air at the same pressure. Then you have to account for how much heat each produces at the pressure.
Then all the engine mechanical parts need to be factored in...
However, you're on the right track with the given combo has produced X power and, therefor, a similar combo can be reasonably expected to give a similar output. But, as has been said, there are always variables.
Also, forced induction only increases the efficiency of the existing engine and its mechanical parts. Therefor, a good-flowing engine will produce more power from the same turbo as an inefficient one. Hence, the easier-attainable power from EJ25/20G/20K etc. heads than from (ported even) EJ22 heads.

so for s and g's would 175 to 180 be a good guess lol

Depends, if you only have 3-4 more psi and 3" exhaust, then i would estimate you to be about 200-210 CHP. Now that where the kicker is, CHP to WHP conversion. My WHP estimate on your car would probably be 130-145WHP

we were talking just engine hp

Yeah, probably close to 200 crank.

sweet thats more than my old 94 town car lol

Lol

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one day i'll upgrade the turbo injectors and fuel pump

Im still on stock pump. Might be time for an upgrade...

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i thought a bout e baying all my upgrades but i have to much into it to chance it

Dont ebay it unless youre looking for good deals on real parts.

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they are real parts just the prices seem to good

What kind of parts are you looking at? I like eBay for grabbing used OEM parts, not so much for new aftermarket parts.