I've been reading on my350z.com that a lot of people do their dyno pulls in 5th gear. I did mine in 4th. Its something about a 1:1 ratio. any one know of a difference?

Andrew

 

On the Dynapack, you have to set the Gear Ratio for whatever gear you are pulling in & that ends up being the adjustment for the 1:1 so that the RPM reads correct. On the Dynojet, they use a RPM Pickup for that but, recommend to pull in a 1:1 ratio for the readings... 4th gear on the 5AT is the 1:1 though, so you are fine.

Mark

 

We have a whole new support team here now & January will hold some suprises to advance everyone.... Thank You for the support!!

Mark@SGPRacing

 

Yes, what he said

 

I know you can select 4 so it won't go into 5th. But how do you go WOT and prevent it from downshifting into 3rd?

 

Question. How do you get a 1:1 gear ratio (crankshaft torque plate to A/T output shaft) with a TC (torque converter) in the middle?

As many have proven to ourselves on mutiple A/T G35s and 350Zs, dynoing them in third "gear" gets the most consistent results.

We've found that early cars won't hold in 3rd "gear" unless the RPMs are above 3600-3800 and if it downshifts on the dyno's rollers you're basically done for the day, or at least for a while due to high A/T fluid temperature. Less A/T fluid viscosity - less TC energy transfer. (That's why your shifts are "stronger" on cold days.)

Why not forth "gear"? Read your factory service manual. Hint: Pay attention to the the 4th "gear" partial TC lock-up info. There is one exception to 3rd "gear". If you elect to find the wires that lock up the torque converter in forth and provide them with a proper signal then you'll have the forth gear 1:1 gear ratio you seek. We haven't aren't inclinded to do so.

 

I dyno on a Mustang dyno . And we always use 3rd with my AT5 . We have tried 4th and the results never very more than 2 whp either way .

 

was 3rd the higher hp?

 

2 to 7 peak HP advantage to 3rd "gear" is what we've seen. Our charts show it's over the whole range.

 

Mechanical engineering tells you that for every gear mesh or/and gear direction change the frictional losses increase by 1%.
Usually 2% differences in any non direct gear even 5th/6th.

Don't confuse the tire frictional changes with speed of interface [tire to roller] or the tire diameter gain which changes under higher speed [greater than 100 mph].