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Discussion Starter · #1 ·
Well guys i am going to the Dyno on Saturdayand i have a question. I have recently installed 4.10 gears in my car and i was wondering if this is going to hurt me on the dyno? Will i see lower numbers because of this?
 

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Discussion Starter · #3 ·
So if i put on my 28 inch slicks i will get the right read out?
 

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if you keep the same tire diameter.. yes.

Part of why dyno numberd don't matter as much as the track.

mk
Why would changing his gear ratio change his dyno numbers?

The dyno references engine RPM to drum speed and calculates the driveline ratio which takes into account trans ratio, rear end ratio as well as tire diameter.

HP numbers do not change. Dynojets don't even have an option for tire size or gear ratio.
 

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if you keep the same tire diameter.. yes.

Part of why dyno numberd don't matter as much as the track.

mk
Yes but changing gears and tires will change your track times but not change power made hence the reason track numbers are overrated. Its not showing only power but also showing suspension setup, tires, track condition, and weather.

Why would changing his gear ratio change his dyno numbers?

The dyno references engine RPM to drum speed and calculates the driveline ratio which takes into account trans ratio, rear end ratio as well as tire diameter.

HP numbers do not change. Dynojets don't even have an option for tire size or gear ratio.
In theory you are right but many times I have seen 3.08s to 3.73 or 4.10s people lose as much as 25rwhp on the same dyno.
 

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So torque multiplication with gears changes nothing?
Nope. No matter what the torque output it, horsepower is the ability of an engine to rev up through the torque.

Since Power is Work/Time, gear ratios will change one aspect in a direct relationship to the other. So while the car might have to do twice the work with a lower gear ratio, it'll also take twice as much time outputting the same power. Or with higher gears, it might take 10% less work to get the drum up to 6500 RPM, but it'll also take 10% less time.

http://en.wikipedia.org/wiki/Horsepower

We've covered the topic previously in depth.
 

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In theory you are right but many times I have seen 3.08s to 3.73 or 4.10s people lose as much as 25rwhp on the same dyno.
The only reason gear changes would change HP numbers if one gear set is more or less efficient than the other.

I've had my car lose 10-15 HP on the same dyno in the past, changing nothing.

Dynos are also not a perfect method of calculating power.
 

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The only reason gear changes would change HP numbers if one gear set is more or less efficient than the other.

I've had my car lose 10-15 HP on the same dyno in the past, changing nothing.

Dynos are also not a perfect method of calculating power.
Correct but the questions was " Will 4.10's Hurt My Dyno #'S????" and the answer is yes it can. Not guaranteeing it, but it can.
 

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It can and probably will. I have seen it with my own four eyes.
 

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One thing is for certain is that inertial losses will go up with a higher numerical gear. This drops meas'd power. Increased gear friction and/or tire slip can also affect the numbers. Typically, power will go down a tad. Yes, it has been discussed before. See thread below:
Link => Effects of gearing on power
 
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