How about dummy dyno rollers for AWD dyno'ing?

[jesepes]

What is everyone's take on making a set of portable dummy dyno rollers for the front wheels of AWD's to roll on? I know this won't work well for those with VC's in the center diff, but for spool/welded center it should be quick and easy to dyno.
-Jesse

 

[Lof8]

you'd be getting a dyno reading that is only about 1/2 the power you're really making. The different load on the front and rear wheels would cause problems too. Doesn't seem like a good idea.

 

[Cirus_93TSI]

rollers would be a quick and easy if you need to tune your awd on a 2wd dyno, but you wolnt get any accurate horsepower or torque numbers like that. but even in that case, having all the load on 2 of the wheels cant be good for your drivetrain, you would be better off tuning on the street.

 

[jesepes]

lof8: Why only half the power? The dyno is the only resistance/power absorber that the engine will see. (The power it takes to turn a set of dummy rollers is negligible.) Why would a difference in power between front/rear axles cause problems? What do you think happens on the drag track when front tires slip, doesn't ALL power go the rears for just a second until car catches up with the front wheels? Remember that there is a stipulation of having a spool in the center diff.

cirus: Yes, I am aware of the dyno readout discrepancy. People dyno their AWD's on 2wd dynos often by removing either front halfshafts or Tcase/driveshaft. I have not heard of any serious detriment resulting from operation the car that way.

On an interesting side note, dynoing this way will at least keep accurate the force it takes to turn the front axles and tires and brake disks, unlike disconnecting the front halfshafts. I know, and is obvious to me that the AWD dyno is the best route. Some people simply don't have one closer than hundreds of miles away. For them I think the second best option is using dummy rollers.

 

[Defiant]

lof8: Why only half the power? The dyno is the only resistance/power absorber that the engine will see.

That's the trouble. When the viscous coupler feels the rear tires slipping -no load on them- it'll seize up and try to put it all through the fronts. And, it'll 'splode. Bad. There's a reason that in the 15+ years of the DSM drivetrain layout that no one's caught on to using this. An expensive reason.

 

[Jehu]

And that's the same reason why you can't just disconnect the driveshaft from the Tcase to dyno...

 

[jesepes]

Defiant and Jehu:

I understand that guys with a center VC wouldn't work as I posted originally, and reiterated in my next post. This I idea is put forth for those with spools/welded center diffs. When I re-read my original post, it seems clear enough to me that is what I meant. What broke the link in effective communication, I wonder?

Anyhow, if you guys have a take on the question in full context, that would be great.

Thanks,
-Jesse

 

[MNGSX]

I got the drift..

However, spooled/welded VC's and disconnecing the driveshaft or a dummy t-case seems more common...

 

[Syndicate13]

Defiant and Jehu:

I understand that guys with a center VC wouldn't work as I posted originally, and reiterated in my next post. This I idea is put forth for those with spools/welded center diffs. When I re-read my original post, it seems clear enough to me that is what I meant. What broke the link in effective communication, I wonder?

Anyhow, if you guys have a take on the question in full context, that would be great.

Thanks,
-Jesse

But if you had already went through the trouble of installing a welded diff or spool why not just drop the xfer case and driveshaft?

 

[GVR4592]

Do you have a welded center diff or vce?

 

[PRESSURIZED]

I just dyno'd my car like this 2 days ago, wish I would have read this thread first. Makes sense now as I tried to dyno in 3rd gear and I got what sounded like my clutch slipping at around peak hp area......it was the VC slipping actually.

I did get a 'decent' pull in fourth but my numbers could have higher if I was able to put all the power to the rollers.

I reconnected the driveshaft and the car is fine otherwise.

 

[GVR4592]

You deleted your other post or am I going crazy?