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Old 06-13-2011, 05:34 PM   #1
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Default Rear End Gears and their effect on Dyno Numbers

There seems to be a lot of skepticism on a lot of forums about how it will effect dyno results. The general consensus I've seen is that the smaller the ratio (2.73) more power to be made vs. a larger ratio (4.10) which will lower the results by a certain percentage.

What is your take on this Joe? Is there a conversion factor that can be computed into the dynojet so there isn't a variance between gear ratios?
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Old 06-14-2011, 12:25 AM   #2
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It does make a slight difference, but not substantial. I did the tests on my jeep, but they are stuck on my old dyno computer that is broken. I did 2nd, 3rd, 4th, and 5th gear pulls, but 5th was cut short because of the speed limiter. I'll do it again when I have some time.
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Old 06-14-2011, 12:32 AM   #3
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Quote:
Originally Posted by Joe@Trick Tuners View Post
It does make a slight difference, but not substantial. I did the tests on my jeep, but they are stuck on my old dyno computer that is broken. I did 2nd, 3rd, 4th, and 5th gear pulls, but 5th was cut short because of the speed limiter. I'll do it again when I have some time.
Oh I know there's a slight variance between transmission gears, but what about the rear end? Found a discussion on LS1 Tech about it: http://www.ls1tech.com/forums/dynamo...ct-dyno-s.html
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Old 06-14-2011, 02:30 AM   #4
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Its all the same thing. If you use a lower gear on the tranny, its like having more gear on the axle. The thing that matters is the engine rpm to tire rotation ratio.
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Old 06-14-2011, 05:07 AM   #5
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Quote:
Originally Posted by Joe@Trick Tuners View Post
Its all the same thing. If you use a lower gear on the tranny, its like having more gear on the axle. The thing that matters is the engine rpm to tire rotation ratio.
Is the engine rpm to ties rotation ratio adjustable on a dynojet to adjust for different gearing? Because 5th gear w/ 3.73's is way off the correct revolution from 4th gear with 3.27's. And 4th gear between 3.27's and 3.73's is pretty far off as well.
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Old 06-14-2011, 02:58 PM   #6
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Not really. It doesn't really matter much. I use 4 gear for any size gears in the rear end.
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Old 06-14-2011, 03:19 PM   #7
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Not really. It doesn't really matter much. I use 4 gear for any size gears in the rear end.
Gotcha I'm just worried I'm going to see a decrease in power from previously due to using a steel flywheel again as well as the gear ratios. I'm not sure how much of a difference on a dyno a JLT, t/b and plenum make, I'm just scared I'll be disappointed lol.
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