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There was an equation I used a couple years back to approximate what your HP would be after boost. Does anyone know/remember this. I'd like to know how many ponies my boost will add so as not to go past 400hp.
Thanks
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"Funny thing about weekends when your unemployed...they don't mean quite so much" Primus
It probably involves manifold absolute pressure and standard atmospheric pressure, and there may be an temperature correction as well. Ideal gas law stuff, and a direction to get started in, anyway.
That's probably close enough, though I think if you're being picky that you'd use something a bit lower than 14.7.
WOT in a NA engine does not result in 14.7 psia manifold due to flow restrictions through everything ahead of it (airbox, filter, inlet tube, throttle body, MAF, etc.).
Just to try to put some numbers on this, 4-barrel carb flow ratings were made at 1.5" Hg, or about 0.7 psi. In this case, substitute 14 everywhere you see 14.7.
EFI throttle bodies likely permit somewhat smaller losses than all but the larger carbs, so maybe deduct 0.3 psi and use 14.4 instead.
It looks like their intercooler/aftercooler entry addresses the temperature effect (that you get from the heat of compression).
Yes, that tells you what you really do have after you've built it.
But I think the OP wants to have some idea what he's going to end up with before he buys anything, let alone turns any wrenches. At that stage of the game, knowing that you're going to be closer to (say) 500 than 450 or even 500 vs 400 may be good enough. "Calculating" 481 vs 472 and then using those specific numbers for anything is a waste of time.
Yes, that tells you what you really do have after you've built it.
But I think the OP wants to have some idea what he's going to end up with before he buys anything, let alone turns any wrenches. At that stage of the game, knowing that you're going to be closer to (say) 500 than 450 or even 500 vs 400 may be good enough. "Calculating" 481 vs 472 and then using those specific numbers for anything is a waste of time.
Norm
ah i see. i used to have a program called pc dyno. you enter in your motor size, head style, valve size, runner size, compression ratio, boost level, efficiency of your intercool (if you have one), etc, etc. it asked for everything. we used it when building my last motor and when all was said and done, the pc dyno over estimated hp by only 50fwhp. not too bad for something i downloaded for free.
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7.25 @ 95.17MPH with a 1.70 60' on street tires and low boost-untuned and never been on the dyno
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Hp calculation
