Smog guy ran my evo on 2wd dyno. Any damage?
Normally most vehicles which have an active center diff will open the clutches when the parking brake is applied to prevent damaged... it has nothing to do with being a rally car, I find it humorous sometimes how many ppl pull the rally card out about these vehicles when in reality the differences between your OEM vehicle and a $300k evo rally car are very different.
The reason why you can't 2wd dyno a evo is because it would have to continuously hold the clutches open the entire time, something that the durability of the pump would not be able to do, in addition the vehicle was never made to do something like this so the heat would be pretty intense.... This system is much different than say a Haldex VW R32 system which you can dyno in 2wd as its an electronic controller closing the clutches to transmit power, these systems are normally 2wd until FR wheel slip is indicated to activate the RR diff.... This is the difference between all time AWD and AWD.... there are other systems as well but that is the general scope.
The reason why you can't 2wd dyno a evo is because it would have to continuously hold the clutches open the entire time, something that the durability of the pump would not be able to do, in addition the vehicle was never made to do something like this so the heat would be pretty intense.... This system is much different than say a Haldex VW R32 system which you can dyno in 2wd as its an electronic controller closing the clutches to transmit power, these systems are normally 2wd until FR wheel slip is indicated to activate the RR diff.... This is the difference between all time AWD and AWD.... there are other systems as well but that is the general scope.
To the OP.
I just got through having a conversation with Jack (www.jackstransmissions.com).
He said most likely there was no damage done, although it is not an ideal condition for the ACD.
Jack said to tell you to launch the car, ( I think a gravel road will give the best result and be easier on the driveline) if only the front wheels break traction then the ACD is toast.
This thread is turning into nonsense, please post up your result as I am curious.
Jack just took myself and everyone else in the shop at that time to school. I never imagined the complexity of the ACD system.
I just got through having a conversation with Jack (www.jackstransmissions.com).
He said most likely there was no damage done, although it is not an ideal condition for the ACD.
Jack said to tell you to launch the car, ( I think a gravel road will give the best result and be easier on the driveline) if only the front wheels break traction then the ACD is toast.
This thread is turning into nonsense, please post up your result as I am curious.
Jack just took myself and everyone else in the shop at that time to school. I never imagined the complexity of the ACD system.
Despite the stated good amount of incorrect logic in this thread...
It states in the owners manual specifically that the parking brake being engaged will deactivate the center diff.
I would never just "rely" on that happening, and in no way should anyone be doing 2WD dynoing, or burnouts in their car without expecting serious (and extremely expensive) consequences.
It states in the owners manual specifically that the parking brake being engaged will deactivate the center diff.
I would never just "rely" on that happening, and in no way should anyone be doing 2WD dynoing, or burnouts in their car without expecting serious (and extremely expensive) consequences.
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To the OP.
I just got through having a conversation with Jack (www.jackstransmissions.com).
He said most likely there was no damage done, although it is not an ideal condition for the ACD.
Jack said to tell you to launch the car, ( I think a gravel road will give the best result and be easier on the driveline) if only the front wheels break traction then the ACD is toast.
This thread is turning into nonsense, please post up your result as I am curious.
Jack just took myself and everyone else in the shop at that time to school. I never imagined the complexity of the ACD system.
I just got through having a conversation with Jack (www.jackstransmissions.com).
He said most likely there was no damage done, although it is not an ideal condition for the ACD.
Jack said to tell you to launch the car, ( I think a gravel road will give the best result and be easier on the driveline) if only the front wheels break traction then the ACD is toast.
This thread is turning into nonsense, please post up your result as I am curious.
Jack just took myself and everyone else in the shop at that time to school. I never imagined the complexity of the ACD system.
I'm not disagreeing with to not dyno on 2wd. I am disagreeing on how the ACD pump and clutch plate system works. If I'm not mistaken, the ACD pump pressure is to lock the ACD clutch plates and not for unlocking. The ACD plates unlock when the fluid pressure is released from the clutch plates.
From an engineering stand point, the pump would constantly have to provide pressure even with the accumulator to constantly give AWD.... there is just no pump that could ever with stand that type of durability. Even thought the VW system is backwards to our system, it only engages when it sees FR wheel slip, which isn't constant, so it deactivates rather quickly under normal driving.
The Evo system is extremely similar to the Acura SH-awd RR diff. When the power is being transferred from side to side, its actually opening up the clutch pack on one side which transmits the power to the other side... its basically opposite to what you actually think.. and the same concept of the clutch on your transmission, its always engaged and you manually disengage it with the clutch pedal.... in this case the ACD pump is the clutch pedal.
EvoJoe I hope that raised your IQ back... I don't claim to be an expert on the evo drivetrain or drivetrains in general, and there's a chance I'm still wrong... but I do design car chassis for a living (not drivetrains) and that's my educated understanding.
Last edited by GTijoejoe; Mar 22, 2012 at 06:45 PM.
Not sure this would work on jack stands. The hydraulic fluid would build enough pressure to turn the wheels without any of the clutch packs engaged. There is a scientific term for this hyd-fluid property but is absent from my thoughts right now.
If I were in this circumstance, I would do exactly what Jack said to do. He lives and breathes this stuff. I am still interested in the final outcome. Keep me posted.
If I were in this circumstance, I would do exactly what Jack said to do. He lives and breathes this stuff. I am still interested in the final outcome. Keep me posted.
Thanks a lot for the info. I will try to launch my car on gravel or grass maybe to make it simpler within next few days. Car is on jack stands right now- swapping my exhaust back from stock (smog). Or maybe I can just start it up on jack stands and see if front and back wheels are spinning- would that work?
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im waiting for this guy. 
be serious about what? apparently A LOT of the community did not know about the ebrake disengaging the acd. i am one of them, its very informative to know, aside from some of the other nonsense.
be serious about what? apparently A LOT of the community did not know about the ebrake disengaging the acd. i am one of them, its very informative to know, aside from some of the other nonsense.
Yes it does.. there is a thread roaming the interwebs on STI burnouts 
meaning... put the ebrake up and you can do 2wd burnouts, some guys are pretty smart over on those forums
You have to think about it from an OEM standpoint, they also design cars for stupid people not to destroy them and have them replaced under warranty...
A drum parking brake can hold a ton of torque, they are highly effective, especially while the wheels are moving will create a self-servo effect, the faster the wheels are spinning the more it will grab the brake shoes.... potentially this will damage your drivetrain, or at the very least make your parking brake explode or crack your drum in the your rear disk....
...so they try to protect for stupid ppl... secondly there is a government regulation that the parking brake has to give ~1.43m/s of decel in the case all hydro braking fails....This maybe an ECE-13 regulation not FMVSS135 (can't remember), but either way OEM's protect for multiple regulations as the same vehicles go to different markets.
meaning... put the ebrake up and you can do 2wd burnouts, some guys are pretty smart over on those forums
You have to think about it from an OEM standpoint, they also design cars for stupid people not to destroy them and have them replaced under warranty...
A drum parking brake can hold a ton of torque, they are highly effective, especially while the wheels are moving will create a self-servo effect, the faster the wheels are spinning the more it will grab the brake shoes.... potentially this will damage your drivetrain, or at the very least make your parking brake explode or crack your drum in the your rear disk....
...so they try to protect for stupid ppl... secondly there is a government regulation that the parking brake has to give ~1.43m/s of decel in the case all hydro braking fails....This maybe an ECE-13 regulation not FMVSS135 (can't remember), but either way OEM's protect for multiple regulations as the same vehicles go to different markets.
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