[sleeknsilver]

i'm posting about gear ratios everywhere.. lol but i wanted to ask the dyno section a specific related question.

how much would changing the gear ratio effect dyno #'s?

i have/had a 6spd 3.13 gear and made around 650whp at 19-20psi.

i was really interested in going with an auto 3.77 gear. would it be similar to the 3.13 dyno #'s or be significanlty lower?

i ask because i know auto's dyno lower but that is mainly due to the torque converter and stall? just curious how much gearing affects dyno #'s

thanks

 

[AlexH]

You should always dyno in the gear that is 1:1 or closest to it...that's 5th on the manual and 3rd on the Auto (i think)

 

[Ubermensch]

But can you explain why?

 

[AlexH]

Yep sure can, cause 1:1 means the drive line is revolving at the same speed as the crank....therefore it's not suffering any "spoofing" from gearing. Effectively they become 1 in the 1:1 gear.

 

[Steve Theodore]

So, in a nutshell, you're going to have to figure out what gear is closest to your 1:1 after doing the swap. If domestics can serve as any lesson, C5 guys tend to dyno lower when they do more aggressive rear end gearing (ie: 3.42 -> 3.90).

Steve T.

 

[sleeknsilver]

So, in a nutshell, you're going to have to figure out what gear is closest to your 1:1 after doing the swap. If domestics can serve as any lesson, C5 guys tend to dyno lower when they do more aggressive rear end gearing (ie: 3.42 -> 3.90).

Steve T.

3.9 gearing huh..

that's weird i'd think you would dyno it at the same gear or higher if the gears are lowered.

i think the problem people don't dyno supras in 5th gear 1:1 gear is because the speeds get way too high?

 

[supradupaflyguy]

1:1 in almost ALL manual trannies is 4th gear, including the supra, BUT 1:1 is NOT including the final drive ratio so in all reality the engine is spinning 3.13 times as fast as the wheels. you will see a little variation in dyno numbers because of the gears but in a perfect universe the numbers would be EXACTLLY the same, gearing has NOTHING to do with hosepower, only how you put it to the ground.

 

[Lagtime]

1:1 in almost ALL manual trannies is 4th gear, including the supra.

5th gear is 1:1 for a V160, you know, the 6 speed in a MKIV Supra.

 

[figgie]

hmm

even if you are down in the lower gears, wouldn't multiplying by the ratio give you the numbers you seek?