Changing rear gears and my tune.
11-09-2017, 07:55 AM
#1
On The Tree
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Changing rear gears and my tune. I was wondering if changing out my rear gears from 4.10 to 3.55 would affect the tune very much? I know it will change the speedo. Wanting to go to a more turbo friendly ratio. It is a 6spd car. Thanks.
11-10-2017, 08:48 PM
#4
It actually depends on how close to "correct" your tune is. There are tables that affect transitional fueling that may be affected, as well as additional heat load considerations. The difference can be readily apparent when logging dyno runs loaded vs unloaded, such as with a Mustang vs Dynojet comparison. If ALL aspects of the tune are right, there will be no difference. In reality, this is one of the reasons some old-school racers tune at the track and scoff at dyno tuning, because so many "great" dyno tunes aren't really good enough for the street or track. The simple answer to your question, however, is one post above mine. You are not likely to have any issues other than speedo.
11-11-2017, 09:15 AM
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In a detailed explanation that is correct. It could load the motor slightly differently and hit cells of fueling that didn't get hit before. Most tuners will blend info in areas around good data to make sure if it goes off course it's still pretty correct. But, the reality is, stock tunes can be way off, and the car still runs well. The reason is on an NA application the tuning window is big, meaning the average person wouldn't notice if the motor was running 13.5 afr or 15.5 afr driving down the road. It will simply run decent with anything in between as an example.