I did a dyno test yesterday, and the results were 175.44 whp and 129.94 torque. I am using off size tires 205/50-16 instead of 195/55-15. There is a 2.7% tire difference so if I change back to use the 195/55-15, will my whp & torque increase by 2.7% as well?

 

What kind of dyno was it? Dynapack? Dynojet?

 

yes is dynojet

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by QQ &raquo;</TD></TR><TR><TD CLASS="quote">I did a dyno test yesterday, and the results were 175.44 whp and 129.94 torque. I am using off size tires 205/50-16 instead of 195/55-15. There is a 2.7% tire difference so if I change back to use the 195/55-15, will my whp & torque increase by 2.7% as well? </TD></TR></TABLE>

No!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by QQ &raquo;</TD></TR><TR><TD CLASS="quote">I did a dyno test yesterday, and the results were 175.44 whp and 129.94 torque. I am using off size tires 205/50-16 instead of 195/55-15. There is a 2.7% tire difference so if I change back to use the 195/55-15, will my whp & torque increase by 2.7% as well? </TD></TR></TABLE>

a 2.7 difference in what? different tire size changes your gear ratio a tiny bit, but should affect hp... a difference in tire/wheel weight can make a difference in how fast your car is, can't be a great of difference if from one light wheel to another.

 

the 205/50-16 tire diameter is 611.4 mm and 195/55-15 is 595.5 mm so my pick up will be decrease and top speed faster is it? that why i thinking is the tires size affect the dyno test.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by QQ &raquo;</TD></TR><TR><TD CLASS="quote">the 205/50-16 tire diameter is 611.4 mm and 195/55-15 is 595.5 mm so my pick up will be decrease and top speed faster is it? that why i thinking is the tires size affect the dyno test.</TD></TR></TABLE>

english please

 

A smaller tire will be less rotating mass closer to the center of rotation

I figure this is a negligible impact upon the WHP measure...but you may gain a little (not 2.7%)

 

Yes tire size does effect power. Both the weight and the diameter.

The general calculation for rotational mass is its equal to around 7x dry weight, and dry weight is equal to around 1/10hp per lb.

Thus 1lb of rotational mass should be equal to around .7hp.

 

He's not asking about rotational mass. He's asking whether the torque and horsepower readings are affected by the fact that the outer diameter of his tires is 2.7 percent larger than stock.

I'm not sure I agree with those who are quick to say no. Torque at the wheels is equal to engine torque, minus drivetrain losses, times gearing. If you change the gear ratio by 2.7 percent - which is effectively what you're doing by using these oversized tires - doesn't that change the torque at the wheels by the same percentage?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">
He's not asking about rotational mass. He's asking whether the torque and horsepower readings are affected by the fact that the outer diameter of his tires is 2.7 percent larger than stock.</TD></TR></TABLE>
Oh okay, I couldnt decifer that. Regardless there will be a hp loss in 205 tires vs 195 tires due to weight.
Also if they're 2.7% bigger in diameter, that means the weight is further away from the center, thus more hp loss.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">
If you change the gear ratio by 2.7 percent - which is effectively what you're doing by using these oversized tires - doesn't that change the torque at the wheels by the same percentage?</TD></TR></TABLE>
I would think it would change it. What percentage I dont know. Theres probably an equation for it. A drastic example would be doing a dyno pull in 5th gear instead of 4th. Its not going to read the same number.

 

Thank You all for your opinions. I will try to put back the stock size tires and retry the dyno.

 

That seems like a really bulky tire for an Integra, I would go back to stock size, or 205/50/15 max.