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Discussion and questions related to the course EFI Tuning Fundamentals
I have been watching the modules and notice that Andre always do a pull in 4th gear on the dyno. I am wondering why 4th gear is chosen instead of 3rd gear. I have had my car tuned and every time it was with 3rd gear. I just want to understand what is the difference between the two and why Andre prefers 4th gear.
Hello, using a 4th gear on the dyno the engine increase rpm more slowly, with this you can see what is happening in the engine and correct some parameters with more time.
As Rodrigo has said, using 4th gear allows more control, it also usually gives a 1:1 gear ratio so dyno figures are more accurate.
There's also traction issues that can come from using lower gears, the lower the gear the more torque is generated at the wheels giving dynos a harder time trying to control the rate of acceleration
It's worth mentioning that it can sometimes be advantageous to use a lower gear for parts of the steady state tuning, the extra torque applied to the dyno can allow you to hit load cells that are impossible to get to in the higher gears.
Thanks guys! What everyone said make total sense. I wonder what the dyno graphs look like when comparing the two; one 3rd gear pull and the other a 4th gear pull.
If traction levels remain the same they should over lap, reality is though it's likely differ a few lbft/bhp here and there