Hellbert

well...ive seen these post all over every forum. "how much horsepower can i make with this amount of boost on this car with this done to the motor." sometimes people get the "search mother ******!" response and sometimes people are actually given fairly legit responses. i was thinking earlier, how do people get this "estimate"? is it from people that have built their cars with a similar setup or is there something else to it that im missing? ive got a stock LS in my crx and im shooting for 250-275. i know this can be done because i saw 301 hp out of a stock LS sometime ago and hear about 300 hp LS motors all the time and that is the only reason i know. the reason i ask is because i had a rich kid buddy that had a built *** b16 sleeves crank rods pistons tons of head work full race kit it was easily a $10k honda motor. after all that he only made like 360-390 i cant remembe exactly but it wasnt nothing extravigant. from looking at other setups this car should have made 600+ hp. how did tuner dude know to stop there or why did tuner dude stop there? why didnt he bust out over 500 hp? what else is there to it, if anything, other than "this guy i know had that same set up and made this HP befor it went all to hell"

Braineack

there's a few math formulas.....

the easiest is simple.

you make 120rwhp now, and want 300rwhp.

300/120 = 2.5 or 2.5PR over atmospheric, or 22psi

very rough estimate if you will....


or start by find a turbo that's a good match, 300rwhp is about 36-37 lb/min. (HP x AFR x BSFC/60)


with that you can estimate how much boost is need to achieve said lb/min:

[lb/min x constant (639.6) x (460 + intake temp) / VE x RPM/2 x Cubic Inches] - 14.7


36 x 639.6 x 560° (12894336) / 100% x 3500 x 97.7 (341950) = 37.7 - 14.7 = 23psi


again, its just math, lots of factors change these numbers. I think they always end up high, but it gets you in the ballpark.

Hellbert

im not sure what boost ol dude was running if im not mistaken it was some where around 20 psi. ive ran through compressor maps after maps just trying to understand them. there is a thread somewhere on here that tells how to read them and how to figure out where your car should land in them. for some reason i just cant understand it. if i wrote the formulas out myself i think i would probably have a little better understanding of them i just havent taken the time to do it.


yea 22 psi sounds aweful high. the guy i was talking about i think was running 14 psi making the 301. the way i got it figured i should be able to get around 250 at about 12 pounds based off of other peoples set ups. idk well see im just trying to figure out how people base their numbers

Braineack

i gave you awfullyrandom numbers based on a 1.6L and 7000RPM. technically, the higher the RPMs the less boost is needed. I just took my latest dyno numbers and logs and the formula was within .5psi, whihc is kinda interesting.

I believe the LS is a 1.8L? what do you rev to 8K? if so then:

36 x 639.6 x 550° (12660480) / 100% x 4000 x 109.8 (439200) = 28..8 - 14.7 = 14psi



compressor maps are kinda easy. read the lb/min or CFM on the bottom (correct CFM to lb/min by dividing by 14.47).

the max the compressor outputs is the amount of horsepower is can support.

example, my T3 Super 60 wheel outputs 35 lb/min.

use the formula I gave you HP * AFR * BSFC/60

so 35 / 12 / .00916 = 318HP.

so you know that, my turbo can support about 280-300rwhp or so.

take that same airflow volume, and do the long formula for the boost level.....now you can plot the lb/min and PSI (PR * 14.7 - 14.7 = PSI).



you'd end up with something like this:



which, for what I ploted, looks like it would be a good turbo if you were only looking for 200rwhp (25lb/min).

Slo_crx1

^^^This man knows his ---- here, and may I say one of the few new guys I've seen on here lately that has a good background on turbochargers.

Basically to expound upon what Braineack just said (and a little more in layman's terms), when looking at the flow charts you want to find a compressor map that places you in the center island (in his example the 74% efficiency range) with the cfm/lb per hour flow that you want to reach your hp goal. This way it keeps compressor efficiency high, and keeps heat low. Of course too large a compressor running at too low of a pressure can land you outside that center island (sometimes by quite a bit) and can have the same effect as having too small of a turbo efficiency wise.

Braineack

I tried simplifing as much as I could. However, this tool is easier. I still prefer the math.

http://www.---------------/turbocalc/index.php

TorganFM

Awesome, I'll need like 20psi out of a 16g 428cfm which puts me right at the top of the center island and a cool 350hp.

Dive_Miguel

Maybee the guy's tuner is not much of a tuner or he though pumping all that money in it and running a lower boost with a good tune would make it last longer. It is hard to say without knowing more info.

Hellbert

you my friend are the man, i believe i understand the maps now. maybe still not 100 % but im sure if i try to work out a few more ill start to really get it. i appriciate it and im sure that helped some other people as well.

im still not sure how people get hp numbers though. i know when you buy rods mainly but other engine parts too they always have rated for X hp. im sure those numbers have a lot to do with it right? ive been reading a lot of magazines and looking at different peoples setups trying to figure out some sort of method behind all the madness. i found an old DSport mag and it has stephanie eggums 1100 hp civic. shes running what looks to be a honda gsr block, not a dart block or something like that but that doesnt mean anything cant really tell from the pics. reading through her spec list it doesnt seem to be anything really nutty that has been done. no custom one off anything other than manifolds and head work. why arent their more 1100 hp hondas running around or atleast 500hp? seems like any jack leg half of a mechanic oughta be able to put together a bunch of off the shelf parts and have someone tune in big numbers, right?