A couple of weeks ago I dynoed my car. I got 172 HP to the wheels and 184 lb-ft of TQ. Now my question is this:

Shouldn't my crank hp be 207 HP or 200 HP??

The guy calculated my crank hp by multiplying 172 x 1.17=201. The assumption was a 17% loss thru the 5 speed tranny. I thought that calculation was wrong because he really increasing the 172 by 17%

I calculated this way: there's the same 17% loss,

So 100%-17%=83%

Therefore 172 is 83% of my crank hp, or

(crank hp) X 0.83 = 172

So, moving the above formula around,

(crank hp) = 172/0.83 = 207 HP

Wishfull thinking, or correct?

DW

 

Yes, you are correct. If the drivetrain loss is 17%, then the wheel HP will be

WheelHP = CrankHP*0.87

If wheel HP is known, then
CrankHP = WheelHP/0.87

In your case,
CrankHP = 172/0.87 = 207 HP

Dem dyno operators sumtahms have trouble wit dem dang ol' math thangs.

 

Thx. Glad to see my mods are doing something I wasn't happy with that 201 at all.

DW

 

I thought it was more like a 15% drivetrain loss on the 5spd's? 17 HP from a intake and RT is way to much

 

Haven't updated my sig. Also have a Y

DW

 

You were saying?

172/0.87 = 197.7, but that would be a 13% drivetrain loss. I'm sure it was a type-o, but it was funny none the less.

 

I forgot to mention...I am a dyno operator.

(Sigh)

 

What dyno shop Kev. Do we get dyno deal in Austin

 

Now, that makes sense!