dynos - educate me

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Mar 8, 2005 | 01:50 PM

7Deuce

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Racer

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From: Hartland WI

dynos - educate me

I've never run a car on a dyno before. A friend and I want to take our Vettes and do some runs this spring to see what numbers our cars are producing. Some of my questions...

One shop I called said I could operate the car on the dyno. What's the proper procedure for this? I have a MN6 tranny...any particular gear/rpm range to get the best #'s?

This shop had a dynojet. Should I assume that they will give me my numbers adjusted for humidity/temp/etc or do I have to specify?

If I'm not changing anything (tuning) does it really matter if I do one pull vs multiple pulls?

Price.. the shop nearby wants $95 for 2 pulls or $75/hour. Does this seem reasonable?

I guess I'm basically wondering what I should expect or things I should know about ahead of time.
Thanks for any info

Mar 8, 2005 | 02:21 PM

Dan_the_C5_Man

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From: Atlanta metro Ga.

Dyno operators will walk you through what you need to do..

You want to use 4th gear..

*Make sure you have the traction control turned off.*

Basically, after they strap the car down, you go through 1 - 3 gears, get into 4th at about 1.5 -2k RMS..

Dyno operator will tell you to "hit it". You can floor it, or for slightly better results, "roll on" the throttle, keeping it just ahead of the motor..

I usually let it rev to the limiter..

Then push in the clutch.. Let the dyno operator stop the rear wheels.. Or he may ask you to hit the brakes slightly..

Multiple runs will usually result in one or two HP increases on each run.. 2 is usually sufficient for me.. No need to pound on the car.

Let us know how it works out.

Last edited by Dan_the_C5_Man; Mar 8, 2005 at 04:19 PM.

Mar 8, 2005 | 03:29 PM

Mark VerMurlen

Drifting

Joined: Sep 2000

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From: Bothell WA

Quote:

Originally Posted by Vette Rx

This shop had a dynojet. Should I assume that they will give me my numbers adjusted for humidity/temp/etc or do I have to specify?

If I'm not changing anything (tuning) does it really matter if I do one pull vs multiple pulls?

Price.. the shop nearby wants $95 for 2 pulls or $75/hour. Does this seem reasonable?

I guess I'm basically wondering what I should expect or things I should know about ahead of time.
Thanks for any info

I think its a good assumption that they'll give you numbers that are SAE corrected. It should say on the chart. If it doesn't, ask them.

1 or 2 pulls should be adequate. The only time I've seen more pulls made on a car is when its being tuned. They'll change the tune and run a pull to see the effects of the change and repeat until satisfied.

The cost of $95 for 2 pulls sounds a little high compared to the charge of $75/hour, unless they require that you rent multiple hours. I've seen shops that can run 2 or 3 cars through the dyno per hour with 2 pulls on each car. The most significant amount of time is putting the car on the dyno and taking it off. Each run only takes a couple of minutes.

- Mark

Mar 8, 2005 | 03:58 PM

JoshVette

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From: Dallas/Grand Prairie Texas

But do at least 2 pulls to get a better reading, I just did mine last week, the techs did it all for me though. I have a A4 too. Only costs like $65-75$ for a couple pulls, I wouldn't pay more then that.

But the first pull came out 296.7RWHP and 315.7RWT, and the second pull was 308.6RWHP and 321.1RWT. 12HP difference (no tuning), I asked why, he said because the drivetrain and all was heated up more on the second one and runs better that way. Mines bone stock 02 A4.

It shouldn't take you more then an hour to do both cars. They're loud too, I was surprised when I had to plug my ears.

Mar 8, 2005 | 04:42 PM

VetteDrmr

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From: Hot Springs AR

Also the first pull typically has some spark retard due to preignition caused by carbon buildup. Some of that buildup gets cleaned up during that run, so the second run doesn't have near as much spark retard (or none at all).

That price seems steep; check around for a group doing dyno pulls at a local shop. Around here you'll spend about $40 for 2 pulls during a dyno day.

Have a good one,
Mike

Mar 8, 2005 | 04:53 PM

JoshVette

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From: Dallas/Grand Prairie Texas

I actually got my 2 pulls for $45, but I believe they charge $65 normally.
Good deal and I got some good #'s in return, I'm happy.

Mar 8, 2005 | 05:17 PM

7Deuce

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From: Hartland WI

Seems like the $95 may be a little steep based on what others have paid. This is the only dyno that I know of in the Milwaukee area. Maybe that's why they charge a higher rate. I did find one in Madison that charges $75 for 3 pulls. Maybe we should just go there instead.