VERY disappointing Dyno Run

linda · February 7, 2006

I cant see how these numbers are correct. I would have thought this truck would do way better than this. This was a brand new dyno they had installed on Wednesday last week. Had a few other cars in there that seemed to have dyno'ed fine. Just wondering if they set my truck up wrong before the pull or something. Anyone with dyno experience, i would appreciate opinions here. He looked my truck up and found only one engine for the 2500HD on his list which showed him 50hp@21MPH or vise versa, i cant really remember now. Im just not on the up and up about how to setup for a dyno run, I was counting on them to have all the data correct. This truck just feels so much stronger than what this dyno portrays. Anyway here is the graph, take a look at why I am disapointed..........

linda · February 7, 2006

he did say that he saw quite a bit of torque management in there. I told him not to worry about it right now, that we could make all the changes once the blower goes on. That could account for the relatively low torque numbers i suppose.

Also, i did some more looking around and it does seem that the dyno i posted is on PAR for a stock 8.1L/Ally. Of course i dont know how well that speeks for the Var-a-ram and the 93 hot tune i have....

Haulin' 8.1 · February 7, 2006

What gear did he use for the tests?

Vernon

linda · February 7, 2006

He tried 3rd, then tried to upshift from 2nd to 3rd. Said something about having a hard time getting it to stay in gear when he was punching it. I guess it kept wanting to drop down.

linda · February 7, 2006

I dont think they can lock the converter either, because thats got to be done through the tuning software. I dont think anyone can program for these Ally's yet, unless it can be done through the engine PCM and not the Ally PCM.

Butch 02 Denali · February 7, 2006

Correct Linda, the Ally is controlled by it's own computer and has it's own torque management. The PCM has no control over this, but the tune does eliminate all the ABUSE management. Those numbers are about 50 hp/50 ft lbs down from other trucks setup like yours. I think it just comes down to a new dyno/new operator. If you need to see different numbers, try another dyno.

linda · February 7, 2006

Im wonderin the same thing Butch. Can you give me any insight as to what they could have done as far as setting up this dyno that would give me inaccurate numbers. I really liked these guys, they seemed very nice and wanted to work with me, im just worried they may not be as experienced as they need to be to get done what i want to get done. Not to mention they were giving me great deals on the dyno pulls and dyno tune when i need it.

Butch 02 Denali · February 7, 2006

There's probably some calibration for the Dyno that isn't quite right yet. It needs a comparison with another dyno to be sure. Trouble with dyno's is everyone puts out different numbers, big variation between dyno brands too.

linda · February 7, 2006

Well, we will see soon.... Got an appointment tomorrow with another guy a little farther away, but should produce a good comparison for sure. I will keep you posted.

Haulin' 8.1 · February 8, 2006

Keep the Allison in Tow/Haul and the convertor will stay locked in all gears after 1st. It also should make it a little easier to control the gear changes as it holds the gears longer so you can start lower in a gear without it shifting back down. Keep an eye on it because you'll have to reset it after every key off.

Vernon

linda · February 8, 2006

Thanks Vernon, will do.

linda · February 8, 2006

Okay, Semi- relieved. I went in for another run on a different Dyno and the numbers were considerably better.

261 RWHP +20hp over first run

346 RWT +42ft/lb's over first run

This was done with the trany in 3rd and T/H engaged. Still could not punch it without it dropping down a gear unless we were over 3000 RPM, and I know this truck has a bunch of power/torque at lower RPM that we cant measure. I will post the new Dyno sheet after work.