as the title reads i'm wondering how in the hell you would manage to dyno an auto cobalt.
i'm getting trifecta tuned and i want to see the difference of before tune and after tune. but i can't figure out how i would manage to dyno it without having the trans kick the gear back when you step on it in 3rd.

noobish questions, yes, but i need to know!!

hopefully maven can answer this one!

 

I did a search and it seems there are several methods. I don't know which one applies to the Cobalt, but its a shot. In some cars, I guess you can lock the trans via the computer. Some testers will run the car up to a certain speed before punching the gas... the runup speed is usually done to where it is too high for the car to downshift. I've also heard of some people disabling what is known as a Kickdown switch.

 

swap it out for a 5 spd

 

oh man that's a good one.

now either try to answer my question or GTFO my thread.

kthx

 

Lock the shift lever in I. At partial throttle 45 mph is the shift point for 3rd. Once you're there it's your problem. Have you ever tried forcing the gear shifts with your trans. I downshift quite a lot and @ 71k, trans fluid changed @ 56k and I've had no problems with her yet. Original owner.

 

what i would say is the operator would have to run the car around 40mph on the dyno and roll into the gas so it can downshift

 

There's alot of auto cars out there.. I'm sure any respectable dyno operator could tell you how to do it.. lol. Never really thought about it myself, but if the place can't tell you - find a new place.. lol

 

um the car is strapped down.. to the dyno or bolted to the hub.. there called load strap's and you car will move alittle but wont go off it if secured properly. ive dynoed auto tbucket's and LS1's NO PROBLEM.. even with the kick down.

 

the OP isnt concerned with his car flying off the rollers, I think he's wondering how you would get a dyno to show the powerband below 4krpms, since the car will downshift to keep the RPMs high as sson as he goes WOT, unless you do a first gear dyno pull

im a little confused... the shift point for 2nd to 1st is at ~30mph, and the shift point for 3rd to 2nd is at almost 70mph, unless youre at partial throttle like you said...so are you suggesting he dyno while only going partial throttle?

 

Yeah, the concern is primarily the downshift causing the reading to be inaccurate. You always want the gear that is closes to being 1:1 ratio for dyno pulls.

 

not exactly what i meant. with the lever in I the car wont upshift as long as the pedal pressure keeps consistent on the way down, no hesitations. give it a try. i've become quite famailar with the behavior of this transmission.

 

okay so you're trying to say keep it in I, which is primarily second. then let it upshift to 3rd at 45 and then give it the gas? and that should give me an accurate reading?

i didn't mean kicking the car off the dyno man, i was talking about the auto trans kicking it from 3rd to second. not throwing it off the rollers.

 

well it's been a few year's for me i forget excatly how i did it.. IIRc throttle manipulation and having the shifter in the right designation. aslong as the dyno is calibrated properly you should be fine..

 

i wont go as far as to say accurate however you will have more control over how quickly the car will upshift or downshift. I is more like 2-3, where as L is 1-2 and fourth don't matter much. I top out 3rd at 135mph. If you leave the lever in L at a light the engine will redline 1st, shift to 2nd and proceed to bounce off the limiter. That is unless you shift the lever up to I at with point it will shift into 3rd and ride out whatever power band you got left.

 

HPT or a Tech-2 will do it, my local dynometer place uses their Tech-2 and locks it into gear.

 

well hopefully they have tech2 or hp tuners. lol

thanks for your help guys

 

I dint know hp tuners had anything for our cars yet? I thought all we had was trifecta???

 

You can unclip the harness from the transmission and it will keep it in third.

 

so why are people still talking about hpt when they don't tune our cars?

 

pwned

 

My thought exactly...

 

when i dyno'd mine we did a second gear pull from ~20-71mph

 

I always just thought you just left it in 1st gear

 

1st gear has too much torque. That and it would be a quick dyno pull

 

First gear only goes to 35 mph, would take about 3 seconds to get there from a stop.