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Re: Calculation for "CRANK" HP when you already know WHP (1fastmk3)

WHP / .85 = CHP <--- using the accepted 15% loss
Example:
121 whp / .85 = CHP
142.35 = CHP
To go the other way.......
CHP * .85 = WHP
115 * .85 = WHP
97.75 = WHP ( I had 96 whp when my car was stock)
 

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Re: Calculation for "CRANK" HP when you already know WHP (AllMotor8v)

Thanks J
I figured you'de be my first responder..LOL
 

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Re: Calculation for "CRANK" HP when you already know WHP (1fastmk3)

Quote, originally posted by 1fastmk3 »
Mathmeticians?
I know roughly around 14/15% loss, but what is the exact equation ?

There is no way to accurately get crank numbers unless you take the motor out and dyno it on a engine dyno.
 

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Re: Calculation for "CRANK" HP when you already know WHP (1fastmk3)

Well, maybe if I get this job I am going to talk to a recruiter about today I won't be able to respond so fast.
 

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Re: Calculation for "CRANK" HP when you already know WHP (AllMotor8v)

Quote, originally posted by AllMotor8v »
WHP / .85 = CHP <--- using the accepted 15% loss

That's only asuming 15% is accepted. I've heard 12% thrown around alot but we'll never know unless someone dynos their car on a chasis dyno then takes out the motor and dynos that on an engine dyno, then we can find the true driveline loss %.
 

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Re: Calculation for "CRANK" HP when you already know WHP (MikeBlaze)

my thoughts:
if you had a baseline, good tune and no mods dyno. then you could calculate the loss from the WHP to CHP.
if you dont have one then its a guess mostlty. i have heard anything from 12% on really efficient 5speeds. to near 25% for crappy autos.
15% is a good thought. but it could be +/- a few percent.
 

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Re: Calculation for "CRANK" HP when you already know WHP (dunhamjr)

Quote, originally posted by dunhamjr »

if you had a baseline, good tune and no mods dyno. then you could calculate the loss from the WHP to CHP.

How, you still need to know driveline loss? Stock or not wouldn't really matter, still guesses...
 

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Re: Calculation for "CRANK" HP when you already know WHP (MikeBlaze)

you can get better guesses by using the stock rated output...

but yes they are still guesses http://****************.com/smile/emthup.gif
 

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Re: Calculation for "CRANK" HP when you already know WHP (dunhamjr)

Quote, originally posted by dunhamjr »
you can get better guesses by using the stock rated output...

but yes they are still guesses http://****************.com/smile/emthup.gif

Oh, now I see what you and Jeff are talking about with the stock manufacturers figure. Didn't pick that up before. One of these days I'll dyno a motor and drop it in a car and dyno it again, see what the deal is. I know of at least one shop with an engine dyno in PA.
 

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Re: Calculation for "CRANK" HP when you already know WHP (MikeBlaze)

That is why I used the stock rated hp using 15% loss to show whp, compared to what I dynoed stock.
 

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Re: Calculation for "CRANK" HP when you already know WHP (AllMotor8v)

Quote, originally posted by AllMotor8v »
That is why I used the stock rated hp using 15% loss to show whp, compared to what I dynoed stock.

Giotcha, I didn't notice that at first. I wonder how accurate the stock rating is? Ah...F'it.
 

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Re: Calculation for "CRANK" HP when you already know WHP (MikeBlaze)

Quote, originally posted by MikeBlaze »

One of these days I'll dyno a motor and drop it in a car and dyno it again, see what the deal is. I know of at least one shop with an engine dyno in PA.

I think alot of us on here would be interested in seeing what you find out. http://****************.com/smile/emthup.gif
However, make sure you don't take any shortcuts and use like just the exhaust mani w/ dp, no airbox..etc etc etc. If possible, try to replicate the under-the-hood situation...but I'm sure I'm just ramblin' about stuff you already thought of. Still though, I'd be interested in seeing what happened...
 

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Re: Calculation for "CRANK" HP when you already know WHP (mk3dub)

Quote, originally posted by mk3dub »

I think alot of us on here would be interested in seeing what you find out. http://****************.com/smile/emthup.gif

I would too for sure. Half the reason I bought the Rabbit was to be able to test stuff out like this and learn from it. As far as test conditions are concerned I don't see a problem nearly duplicating the parts that are used. The intake would remain the same, exhaust isn't a big deal either even if the engine is dynoed with just a header (my rabbit has one), I can always disconnect the rest of the exhaust for the chassis dyno.
 

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Re: Calculation for "CRANK" HP when you already know WHP (MikeBlaze)

http://****************.com/smile/emthup.gif
 

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Re: Calculation for "CRANK" HP when you already know WHP (mk3dub)

my 1 cent- Drivetrain loss also depends on what oil is in the gearbox, size of wheels, and god knows what...so u r basically gonna be wrong no matter what u do. Also, I have heard from numerous sources that VWs crank "estimates" are not very accurate at all. They say that they are higher tha reality.
 

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Re: Calculation for "CRANK" HP when you already know WHP (deathperformance)

Quote, originally posted by deathperformance »
Also, I have heard from numerous sources that VWs crank "estimates" are not very accurate at all. They say that they are higher tha reality.

Funny, everyone knows the 150hp 1.8t was really more like 160hp
 

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Re: Calculation for "CRANK" HP when you already know WHP (AllMotor8v)

Does anyone wonder why we just accept 15% as law? For example..Lets say you have 100 hp. 15% give you 85 hp. So your drivetrain is taking 15hp. So now you get a turbo and make 200 hp. Your drive train still only takes 15hp but under the 15% rule it would say your drive train now need 30 hp to do the same work as before. Now what kind of sense is that?
 

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Re: Calculation for "CRANK" HP when you already know WHP (GTIRACER2.0t)

In my Watercooled Performance book it lists a different formula to calculate crank hp.
crank = (whp / 0.8) + 8
But my problem with that is my stock engine would've had an indicated 128 hp.
 
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