#78916, "alright god damnit!! whats the significance of doing a 3rd vs. 4th gear dyno pull?"
i hear things but, now i wanna know. can ya show more HP in 4th or something, whats the gig, man?
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#78917, "RE: alright god damnit!! whats the significance of doing a 3rd vs. 4th gear dyno pull?" In response to Reply # 0
When cars are tested at DynoLab, tests are always done in 4th gear (usually the gear closest to 1:1 ratio). This emanates any variations in drivetrain loss and should provide the most "true" reading.
#78961, "RE: alright god damnit!! whats the significance of doing a 3rd vs. 4th gear dyno pull?" In response to Reply # 1
Originally posted by siueclipse When cars are tested at DynoLab, tests are always done in 4th gear (usually the gear closest to 1:1 ratio). This emanates any variations in drivetrain loss and should provide the most "true" reading.
Think about what you just said once... Now think about the final drive.
The main reason for the 1:1 gearing when on the dyno goes back to the days of automatic muslce cars... in an automatic the toraue converter has a tendency to multiply torque at certain times... so you want an automatic to stay in 1:1 and not change gear to try and keep the torque multiplying to a minimum.
As far as a manual transmission, one reason you may want to do it is because some trannys have a direct drive when in 4th/1:1 and so this cuts down on drivetrain loses. But also, when you place the car in a higher gear on the dyno, you increase load on the car, and show a better example of the cars true output under load. Don't forget that on a turbo car boost buildup is related to load
In the end though Siu's car would make almost exactly the same power on the dyno if he was in 3rd gear or 4th gear. Sorry siu, that's hoow it works. 3rd on our cars is more than enough to put load on the motor. And our tranny design does not have a direct output when in 4th gear
Another hting to bear in mind is safety, how fast are you going on the dyno when your in 4th at 7000 rpm?
#78962, "RE: alright god damnit!! whats the significance of doing a 3rd vs. 4th gear dyno pull?" In response to Reply # 4
Originally posted by MrSlick And our tranny design does not have a direct output when in 4th gear
4th is still closest to 1:1 out of the rest of the gears. It's like 1.03:1.
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#78972, "RE: alright god damnit!! whats the significance of doing a 3rd vs. 4th gear dyno pull?" In response to Reply # 7
that and the bell housing.
USED TO HAVE...Everything you wish you had, and then some...
You are somebody special Tim, you matter! - from the admins (but nobody likes you, because your username is just like that other guy's, and you whine a lot)
#78982, "RE: alright god damnit!! whats the significance of doing a 3rd vs. 4th gear dyno pull?" In response to Reply # 5 Nov-05-04 02:20 PM by MrSlick
Originally posted by DarkOne
Originally posted by MrSlick And our tranny design does not have a direct output when in 4th gear
4th is still closest to 1:1 out of the rest of the gears. It's like 1.03:1.
When I say direct output I mean on some manual rear wheel drive trannys, the input shaft is coupled directly to the output shaft, without any idler shaft in between when in 4th. Hence a direct drive 1:1...
Even in 4th, our tranny is still using the input/output shaft combo... so no matter what gear your in, the drivetrain loss will be about the same.
As far as ATX dyno runs, there are ways to force the tranny into certain gears.
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