I had my car dyno tuned a while back and we did my pulls in 2nd gear (th350) since my car still has stock 2.73's and would take FOREVER to pull through 3rd.

When I change the rear end gears to 3.73 and do the pull in 3rd should I expect to see any gains from the gear change and pulling in 3rd? I've heard people tell me that the numbers I have now are inflated since the pull was done in 2nd. I have also heard that I will pick up power from pulling in 3rd.

What do you think?

 

It will pick up power in third. I tried this before on a few cars, if your not in the 1:1 gear it loses power. Thats my observations. We tried every dyno trick in the world a few years ago.

 

Thank you, I was being told too many things.

Now just to see how much I pick up and not to do dyno pulls on 99 degree days with a ton of humidity

 

Any time you dyno try to use 1-1 ratio aka 3rd for our A4 trannies, Also post your before and after dyno sheets i'd be interested in seeing them, i think there could be 5% hp and more than that in TQ
Also its Much better to tune the engine in 3rd because thats where the engine see its highest load over a much longer period, In fact it would be better to just dial in the tune separate for all gears, probably take too much time though

 

I know the 1:1 ratio gets you the most accurate reading. I would've done the dyno pull in 3rd but with 2.73 gears, 1:1 ratio, a 27 inch tall tire, spinning to 6500 rpm is something around 190 mph. lol, we would be there all day waiting to get to peak rpm. I will post the difference when I get the differential built but that might not be for a while. Life is claiming my time and money every where else except my car

 

Interesting point on the 1:1 ratio. Now, with the new 6L80E transmission there is no 1:1 ratio so it probably should be done in 4th gear with the 1.15:1 ratio. I assume there would be a very slight horsepower loss compared to a true 1:1 ratio?

 

^you are correct. Most dynos are calibrated to 1:1, supposedly. There isnt much diff on a 6l80, but its something. could make the diff between say, 395 and 400hp

 

Unless you have a load dyno like myself. A low powered car with 2.73's will overheat the motor trying to do 1-1 dyno pulls. 2nd gear is safer on a setup like that and they have plenty of load. The numbers will be lower in 2nd, but they are only the dyno numbers, not the engine.

 

^ agreed. if you have 150 hp and a 2.73, you are lucky to make a full pull. I wonder if anyone has tried dynoing a malibu wagon or old trans am that had 2.41? gear in them

 

We dyno'd a honda once. Started the pull, went out and got coffee, came back and it was 1/2 way done..LOL

 

Now that's some sig worthy **** right there!

 

^

 

The car made 368rwhp and 342rwtq on a mustang dyno.

I'll let everyone know what it does when the rear end is done and can do a 1:1 pull