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      09-13-2009, 09:32 PM   #1
AMPowerJ
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3rd or 4th Gear for Dyno

Hi Guys -

Going to be getting a baseline dyno done soon ... based on my search it looks like some have used 3rd gear and other 4th gear. Does it matter and if so can anyone tell me why? I would assume you enter the gear ratio so any gear would work but I might be wrong.

Thanks!
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      09-13-2009, 10:05 PM   #2
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It DOES matter. It's actually most efficient in fifth, but if the speed governor is still on your ECU you can't use that. I got my next-best results with 4th. We're only talkiing a hp or two, so it's not a really big deal, just use the same gear for all subsequent runs.

Dave
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      09-13-2009, 10:38 PM   #3
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I have asked the same question and PG has told me the most productive gear is the 3rd. but I know GIAC always dynos on the 4th. I don't know why. But I was using a Dyno pack maybe it has something to do with it.
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      09-13-2009, 10:50 PM   #4
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Yeah, I remember that discussion PG, BUT my car gives the highest reading for hp and torque in 5th on a Dynojet.

Some think that the higher speed of the drum might have some impact on inertia's interaction with the reading mechanism of the drum. The Dynojet operator reports that hp and torque decreases on every car he's tested where the final drive is raised numerically. To me it says that there's likely some error in Dynojet's conversion calculations.

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      09-14-2009, 08:04 AM   #5
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Thanks guys looks like I will be using 4th gear since I will probably be dynoing on a Dynojet but it is the model that has load cell capability. Not sure if that matters to this discussion but my understanding is it can be toggle between load cell and inertia modes. Should I ask for one in particular? Also does the operator have to enter the gear ratios?
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      09-14-2009, 10:00 AM   #6
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The dyno calculates the gear ratio by comparing engine speed to drum speed, so no worries there. I don't know the answer to the other part of your question. I didn't realize that Dynojets had some optional measuring methods.

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      09-14-2009, 08:06 PM   #7
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I have another question please if the OP does not mind...

Is there anything else we need to do other than disabling traction control when we dyno the car??

Where I want to go with this question is that I went to a shop which has a Mustang dyno. He always starts the run of the car he's dynoing from an rpm of 4000. When I asked him why, he said that when he has the car at a lower rpm and then goes WOT the gear automatically shifts one or two gears lower. Of course the cars on test I watched were automatics. However I noticed that almost all the runs I see in this forum starts from around 2500 rpm. Does this have to do with the setup of the car before dynoing?
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      09-14-2009, 08:18 PM   #8
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Good Lord, starting at 4000 rpm leaves off tons of data that is helpful at understanding how the car will perform.

You need to insist that he start between 1000 and 2000. Of course a 6MT will stay in whatever gear you chose. For the DCT set it in manual mode.

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      09-15-2009, 07:50 PM   #9
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Quote:
Originally Posted by dcstep View Post
Good Lord, starting at 4000 rpm leaves off tons of data that is helpful at understanding how the car will perform.

I know, the problem is there is not many dyno shops where I live and the one I go to is almost 100 miles away.


Quote:
Originally Posted by dcstep View Post
You need to insist that he start between 1000 and 2000. Of course a 6MT will stay in whatever gear you chose. For the DCT set it in manual mode.
Even when in manual mode, the gear shifts down when activating WOT.
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