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07-18-2000, 05:54 PM | #1 | |
Scooby Newbie
Member#: 27
Join Date: Jun 1999
Location: Montreal, Quebec, Canada
Vehicle:9805 STi V3 -LegGT05 Rally Blue - Satin White |
Dyno Runs.. AWD car on a 2WD dyno... WTF
Hi guys, here is a message that I have receive from a friend.. Her story seen to be really good, but like her, I never heard of anyone doing it..
Can someone help us on that ? Here is the message : Quote:
Let me know what you think.. thanks Mike M
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07-18-2000, 06:07 PM | #2 |
Scooby Guru
Member#: 67
Join Date: Jul 1999
Chapter/Region:
SCIC
Location: San Diego, CA
Vehicle:1999 Outlasting the competition. |
it will make the center diff go BOOM!!!
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07-18-2000, 06:18 PM | #3 |
Scooby Newbie
Member#: 27
Join Date: Jun 1999
Location: Montreal, Quebec, Canada
Vehicle:9805 STi V3 -LegGT05 Rally Blue - Satin White |
kartboy, thanks for the reply, but why it will make it go boom ? Is it because the rear will be too much free ? In comparaison to the front that will have some tension on them and not the rear ??
Thanks Mike M |
07-18-2000, 06:23 PM | #4 |
Scooby Newbie
Member#: 46
Join Date: Jun 1999
Location: Saratoga Springs, NY
Vehicle:2001 Jetta 1.8T White |
Mike,
There is a way on DSM's to disconnect the center diff and you can dyno a awd DSM. (Rallispec dos this) But on the subie i don't know. I wouldn't do it, just wait and find a 4-wheel dyno.. It is safer and more reliable/accurate. |
07-18-2000, 06:56 PM | #5 |
Scooby Guru
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Join Date: Sep 1999
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MWSOC
Location: Carol Stream, IL USA
Vehicle:MY05 PSM GGA !STOCK MY99 RS-RIP / MY95 MX-5 |
Spinning it like that will cause the center diff to start overheating, because it will go nuts trying to compensate for the zero resistance in the rear tires.
Overheat it long enough and then your warrenty won't cover damages (because it says not to do that in the manual). So before trying that procedure, make sure that the guy doing the dyno will guarentee you a new diff when he blows it. |
07-18-2000, 08:02 PM | #6 |
Scooby Specialist
Member#: 32
Join Date: Jun 1999
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Hello,
Well, the other problem is that dyno'ing that way is pretty silly. You have absolutely no way of knowing what percent of power is being transfered to the rear wheels due to driveline losses, VLSD efficiency, etc. And like others have said, the VSLD will heat up and make a mess. Now, one good thing could come out of that sort of dyno'ing. I suppose if you did it like that and then with a locked center diff, you could map out the efficiency of the center diff over it's rotation rate... That could be interesting Joel Oh yeah, mah fran-says ess tre mal may ton copeen esse peer que mu-ah hee hee hee Translate the following: Pas de liex Rhone que nous. . . . . . give up? Paddle your own canoe... |
07-18-2000, 08:27 PM | #7 |
Scooby Newbie
Member#: 1284
Join Date: Apr 2000
Vehicle:2005 Legacy GT Royal Blue Pearl |
I was thinking (oh no ...). Why doesn't the dyno manufacture the front and rear rollers w/ a pulley? That way, if someone wanted to dyno a AWD car, just attach a belt between the front and rear rollers. Now, all the wheels would be connected to the dyno, and if both the pulleys are the same size, then the resistance would be the same for the front and the rear.
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07-18-2000, 08:31 PM | #8 |
Scooby Guru
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Join Date: Jul 1999
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AKIC
Location: Where the Navy sends me...
Vehicle:1997 Legacy 2.5GT 1996 Impreza coupe |
I've thought of doing that kind of thing myself, but I figured the center diff wouldn't like it. As the guys above pointed out, you'd smoke the diff due to the (most likely) huge speed difference between the front and rear ends.
Of course, a WOT dyno run only takes a matter of a few seconds, so maybe it wouldn't be too bad. So the other concern would be what Joel pointed out - how much power is going to spinning those free-wheeling wheels? Pat Olsen '99 Legacy 2.5GT 5speed sedan |
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