What gear do they run Dyno's in?
 

Hi Guys,

I spent a couple hours putting together an acceleration spreadsheet for our cars. So far my acceleration times are off when compared to stock specs. My input data was a run with a max hp of 280 and a max tq of 225. What gear would this have been in on a automatic on the dyno? Gear 7? or do they have a way to lockout gears when on the dyno.

I know generally you want to use a 1:1. Also if a gear other than 5th was used do they scale the graph accordingly?

The reason I ask is with the data I currently have and my calculations it is taking way to long to wined out 1st gear (5.47 seconds) and I am just trying to figure out where I went wrong.


Thanks

Mitch:tiphat:

if its an 7AT it would be in 6th. :tiphat:

Excuse my ignorance, but why 6th? Wouldn't 5th (1:1) be better? If 6th is better than 5th, why not 7th?
[assumes lotus position and awaits enlightenment]

I think it would depend on the dyno, as long as you take into account torque advantages (or disadvantages) you would get the same numbers.

Which is why I am wondering if they do scale it to a 1:1.

it's 5th.

7th is considered an overdrive, at 0.77 something from my knowledge, 6th would be closer to 1:1 (around0.8) 5th might be a straight 1.00 either 5th or 6th would be an ideal gear. But I think 5th is the right one not 6th :tiphat:

5th Gear 1:1

7AT gear ratios:

1 - 4.924
2 - 3.194
3 - 2.043
4 - 1.412
5 - 1.000
6 - .862
7 - .771

I got it figured out. I mathematically calculated the acceleration for every gear with a 3.357 FD in a AT. On paper I have a 0-60 time of 4.1s not including shift time (so right around what you would expect). I also have a top speed of right around 162 mph which where the wind resistance overcomes the power.

This was all done with a 280 hp rear wheel dyno chart, so your typical stock car. I started making it yesterday to show the differences a change in the final drive will cause you both in acceleration and top speeds. I am going to tidy it up and then post it up.

I also charted out all the FD's with respect to gearing.

sounds like too much math. just get in it drop the hammer and see what happens.

I've had 1 dyno in 3rd gear, 2 dynos in 4th gear, and 1 attempted dyno in 5th gear. So my baseline/modded numbers don't match up at all. :mad:

That's why I wanna get a tune so they can take off the 155mph limit and I can actually do a full 5th gear run for accurate numbers.



Also, don't they when they tune do the pulls in 4th gear?

typically the 6MT is 4th and 7AT is 5th due to gearing. 5th in the 7AT is exactly 1.00

Of course, but once you're pretty well modded, you'll top out at 155 before you top out at 7500 rpms. Thats why they had to do mine in 4th.

well arent you special :bowrofl: