Does tranny gearing or tire size affect your numbers on the dyno?

 

Not on a Dynapack
It can have a measurable effect on a roller dyno though.

 

I dyno'd on a roller dyno, 182 whp, with a 195/50/15. Would I need to go to a bigger or smaller tire to pick up a few hp?

 

I recently dynoed my car with 195/50/15 and my HP was 170. I recently dynoed it with new tires 205/55/15 and it was lower. That and the tempature was different outside to.

 

which affects the numbers more ( on a roller dyno), tire size or tranny gearing?

 

I am no roller dyno expert, by any means, but here is a graph of my old 2 liter motor.
Red=3rd gear.
Black=4th gear.

Back to back, no changes.

 

Shorter gearing will read higher on a roller. Going to a bigger tire is an effective change of the final drive. Weight also plays into it similar to a flywheel adding power on some dynos.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">I am no roller dyno expert, by any means, but here is a graph of my old 2 liter motor.
Red=3rd gear.
Black=4th gear.

Back to back, no changes.</TD></TR></TABLE>

are you sure its not the other way around... in 4th gear its usually a bit higher than in 3rd.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by codyellis &raquo;</TD></TR><TR><TD CLASS="quote">I dyno'd on a roller dyno, 182 whp, with a 195/50/15. Would I need to go to a bigger or smaller tire to pick up a few hp? </TD></TR></TABLE>

Your engine won't actually have any more horsepower by changing tire size. So why do you want the highest dyno numbers?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris Tune &raquo;</TD></TR><TR><TD CLASS="quote">

are you sure its not the other way around... in 4th gear its usually a bit higher than in 3rd. </TD></TR></TABLE>

I think you are mistaken. 4th is closer to 1:1 which is why most people make a pull in 4th to get more accurate (not inflated) numbers. Then again I have been wrong before......once.

 

because its JDM

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gibsanez &raquo;</TD></TR><TR><TD CLASS="quote">

Your engine won't actually have any more horsepower by changing tire size. So why do you want the highest dyno numbers?</TD></TR></TABLE>



bigger brakes will also show a decrease in power, wouldnt be able to say how much.

 

Wheel weight also affects roller dyno readings even when the wheels have the same overall diameter. I have seen this numerous times whith guys running 17's vs 15's on the same car.