[rrrocketman]

I have a 2011 impala with the 3.9 and the 4t65e trans in it. I tried to get it dynoed and 2 different guys said it wouldn't work because the auto trans would downshift. That said, I had a grand am a while back with 3.4 4t45e combo and that dyno'd fine but I don't know what the trick was then.

What is the correct procedure for dyno'ing an automatic and specifically with the 4t65e (since transmissions may differ) ?

Thanks!

[ChibiBlackSheep]

I don't see why they are having issues with an automatic. You don't do it in drive, you do it in 3 on the 4t65e. You turn off the fuel cut off and go.

In 3rd gear the car might try to still activate the converter, so you just need to wait until the car does that before you punch it. Then when the run is done, take your foot off the throttle and throw it in D so the car can naturally grab 4th without being under power and come to a slow

[rrrocketman]

Intuitively that sounds 100% like what happened with the grand am but just so I'm sure I understand you...

1) You put the console shifter in 3
What fuel cut-off are you referring to? High RPM limiter?
2) You let the car upshift 1-2 and 2-3
3) When you go WOT at any RPM thereafter it is impossible for it to downshift?

In my GAGT, it had a tune on it but nothing specifically for dyno day. The shift table was essentially normal and the shift table for 3 would have been untouched. In this impala, I'm sure that table is stock.

[ChibiBlackSheep]

I haven't tuned a 3900, but you would turn off a part of the tune that allows the car to limit the speed/rpm cutoff by cutting the fueling to the car. Either the RPM limiter or the speed limiter.

And yeah, you let it upshift, wait for it to hit the converter and blip a little throttle to get it out of that and when you are at like 3k past the converter hit you should be fine to hit it on the dyno.

You could also be super safe and adjust the tune just for the dyno, make the downshift speeds something low, like 25, so it won't downshift

[rrrocketman]

Originally Posted by ChibiBlackSheep

wait for it to hit the converter and blip a little throttle to get it out of that

By this do you mean wait for the torque converter clutch to engage and the blip the throttle so that it disengages (fluid coupling only instead of mechanical for the dyno pull) ?

[ChibiBlackSheep]

You got it. Shouldn't be too much of an issue.