Power calculation

[jpajkos]

I dynoed at the wheels 281 so your telling me if i was to slap a charger on my car with 10psi of boost i will be capable of making over 400? Geez I can't wait till i have a blower!!!

 

[96SVTCobra]

9psi+current set up = 467rwhp... must...get...forced....induction....

 

[Dalamar]

lol you guys...

OK, there's no cut/dry formula for exact power gains.
this will give you a close number if you know what your power is before.
(Rear wheel's better so you don't have to account for drivetrain loss)

Take into account that you'll need good flowing parts, like heads, exhaust ect, or they will become restrictive under boost.
Like a blower on NPI heads for example.
cam specs will effect it too.

I think that turbo's give you a little higher numbers for 2 reasons:
1- there's no crank drag
2- the exhuast system is upgreaded with your turbo kit, and flows better.

So this forumla is a CLOSE.

You agree with that Spyder?? :hammer:

 

[Spyder]

i have no argument at this time :ass3:


Just playin, yeah thats about the best way to explain it without going into too much detail.

If you adding a turbo to a stock car, you actual numbers will be higher than the formula.
If you adding a turbo to a modded car, the numbers will be closer to the formula.

 

[AaRoN]

POST #600.
oh yeah. Good info.

 

[98vortech]

i did the little equation thingy and came out wit 530 hp..waaaahoooooo :behind: :behind: :bunny3:

 

[SonicStang]

409 at the crank... woo!

 

[Teal_Beast]

i know i make 170whp all motor, because i acidently had a fubared dyno run when tuning my turbo. 0psi

so ([15.2-14.7]+1) * 170 = 345whp. . . but at 15psi i make 388 ;(

i guess v6's suck lol


edit: although its prolly just because that formula is for a supercharger and im running a turbocharger

 

[Spyder]

was your baseline on 170 done bone stock?

Did you have any mods done to it?

 

[Teal_Beast]

was your baseline on 170 done bone stock?

Did you have any mods done to it?

the 170whp run was done on the same day as my 388whp run, my longblock is totally stock down to the throttle body, all i have is a twin turbo kit (so that means exhaust, duh)

Basically same car 170whp @ ambient and 388whp @ 15.2psi

 

[Dalamar]

You have turbo's on there?

If so, that shows how turbo's are more efficient, as discussed above

 

[Teal_Beast]

You have turbo's on there?

If so, that shows how turbo's are more efficient, as discussed above

Yes and yes. ;D

 

[quickstang_1994]

Nice my before and after dyno are almost perfect.

 

[tooslow]

another thing just to add, that will give you a really close answer, but if you can figure out your exact atmospheric pressure at the time of the dyno you will get much closer resualts.

14.5 or 14.7 is thought of as the average, but it can vary from that depending on altitude and weather conditions. in a science lab we've calculated the atmospheric pressure to be as high as 16psi with little humidity at near sea level. higher up, it can be as low or lower than 13.

engine design also makes a difference, so far i'm talking N/A. actual atmospheric pressure on the back of the intake valve will be closer to 11psi than 14psi N/A because of heat, and various other things dealing with the engines design.

an example, i'll use boost vs displacement. boost can be thought of as a multiplication of displacement almost. a boosted 3.0l engine should have similar output as a N/A 6.0l if the 3.0 is on 14psi. most times the boosted engine will out power the larger N/A engine because 14psi is higher than the actual in cylinder pressure of the N/A engine. in this case it would be 3.0l with about 26 true psi and 6.0l with around 11-12 true psi

let me know if that doesn't make any sense at all.

 

[Dalamar]

Yes that makes sense Tooslow, I think they figure that in, and if you dyno it in the same area I'd think the difference wouldn't be that much.
I guess it depends on how accurate you want it to be.

Nice my before and after dyno are almost perfect.

Sweet!

 

[Thomas_W]

according to that.. i should make 636rwhp @ 22psi of boost... i dont think thats going to be anywhere close, but we'll see soon enough.

 

[Brian95SVT]

was your baseline on 170 done bone stock?

Did you have any mods done to it?

the 170whp run was done on the same day as my 388whp run, my longblock is totally stock down to the throttle body, all i have is a twin turbo kit (so that means exhaust, duh)

so your v6 stock makes 170rwhp and a 96 GT makes 183rwhp? 13 more hp?
Basically same car 170whp @ ambient and 388whp @ 15.2psi

 

[Dalamar]

so your v6 stock makes 170rwhp and a 96 GT makes 183rwhp? 13 more hp?

Sad truth.
the GT does have a better torque curve down low.


Thomas- the formula is close suited for superchargers.
Turbo's use a different forumla. It's also based on true rear wheel HP as a base.

 

[mitch22]

Edit - I removed your comment from the quote - Dal.

Do you ever find yourself saying:

"how much power will this add?"
"how much boost should I run?"

I find this equation handy:
[(boost / 14.7) +1] x base HP

best to add rear wheel HP because it accounts for your drive train loss.
plug in base HP and boost - this is very close to what your power will be.

Other factors to keep in mind:
posative displacement or roots type blower will give you a longer torque curve.
Centifical gains are more on the top (obviously)
Turbo's are a little different because they don't take power off the crank to operate.


Hope you guys find this info helpfull. ;D

thats what i expected (96 cobra) to put down to the tires with 14#s of boost. I actually made 490RWHP on 91. Built motor low compression 8.5:1 custom fuel system with 2 190 lbh flow, 2.96 pully (SQ2-vortec) 6 rib belt (I think the problem lies here). Stock throttle bodie (57mm, may need to change to accufab) with 60lb injectors. Oh also have SCT tune with SCT 2400 MAF. I think slight slip is occuring. Looking for T-Trim to up RWHP to 600. This was tuned in PHX in 102 degree weather, thats prolly a big factor as well. so my guess is that you calulator is right on. Fluid dynamics is a pretty well understood science thanks to Bornoulli and his famous equations.

 

[ripper]

Hmmm 557hp woohoo Im gonna jack the boost up to 20=lbs soon as i get my ds1 converter. Im at 18psi now so am i correct with that number? Im maxed on my little ps1. Taking into consideration i have an 01+ pi motor?