nevermind

 

It does not look like EVO is your problem here...

 

posted this in the ACD thread, but just to wrap up this discussion:

http://www.motec.com/filedownload.ph...pdf?docid=4399

 

Well, considering I'm pretty good with trail braking, it would make sense that my car seemed to push all the time without the ACD functioning.

 

This bolded part doesn't make much sense at all to me! With ACD not working all of the diffs are pretty much running in an open mode, so any power application that would make car to push would most likely send power to the inside wheels that have lower amount of grip (compared to the outside ones). Limited power on those wheels (due to wheel spin) will not create much of tendency to push (especially in the front, a bit more so in the rear, which stops the car from rotating a bit).

What is more likely is push will be driver induced by getting into the corner too fast/braking too late and asking too much of the outside front tire.

So, all of this AWD system control stuff has to work with the driver for it to do the right thing. If driver is making mistakes, system can compensate it only so much. I do believe that it is much more important to drive the given car the right way and than see what else control system can help with it. I don't believe that going to other way will reach as far as people would like it to go!

 

I'm not doubting your experience, just noting the oddity as that is the exact opposite of what is supposed to happen, according to logic & motec's testing per that article. bizarre

 

Yeah totally a driver issue.
If the ACD fails, you have to driver the car differently. You go into a corner at 130mph, and that system isn't functioning when you're expecting it to, it's a significant surprise. The attitude of the car on the breaks is different, turn in is different, and when you get on the throttle on exit, power doesn't go to the rear tires as expected. You can't call it a "driver issue" when the car goes from having an active center diff, to an open center diff and major handling deficiencies arise. The chassis is tuned around that center diff working. All of a sudden it's an open diff (not even a VCU, just straight open), and everything changes.


I have an 8, with mechanical front and rear diffs. A wavetrac front diff, and TRE maxlok rear diff. There was no unloading power to the inside tires. So only the ACD stops working when the ACD fails, I don't have AYC.

 

Well, that is completely different scenario when something brakes at the wrong time and has nothing to do with above discussion about ACD gadgetry!

This also changes how car will behave with an open center diff only. Your example seem to have two pretty good diffs that have no clue what the center is doing. Since, rear end is lighter than the front, chances are that rear will be the first to loose the traction. Sine your rear diff will make sure all of that extra will go to the wheel with most traction, it will be the outside one. That will create crazy oversteer issue, but not push. One more thing to point out here is there will be difference in behavior regarding to how fast the power was applied. Faster power raise would snap particular car quicker as well!

Either way, this is pretty complicated subject and without knowing all particular details about the given car, all of it is just guestimate at best. I though we were talking about the stock diffs (and in particular, stock EVO X, because article Sam brought was pointing to it).

 

So, my ACD pump noise issues are finally over! Mitsu gave me another pump and ever since it was installed, the noise is gone! Lets hope that this one will last a bit longer, since this is the pump v4.0 on this car.
Racing this sunday, but I am going to slow things down a bit and race in HS instead! Kind of more appropriate with my age! Car is FiST and owner is a fast guy, so it will be nice to see how I am going to fair with FWD that I have never raced at autoX before!! Either way, I am pretty excited about this! More on it after event! Happy 4th guys!

 

just to be clear - if the ACD fails, only the center diff doesn't work. the front and rear diffs will still work.

congrats - always a relief to get an issue on the car totally resolved, I feel you

 

True for 8/9 EVOs. X has AYC and the same pump is used for both.

Thanks! It was a relief for sure!

 

good clarification, thanks for that.

 

Last Sunday was my second event with the new shocks and alignment, and I'm really beginning to like the new setup now. I placed 2nd in my class narrowly losing to a S2K by 0.024 sec . Pax was 8/87. My other runs indicate that my 'perfect' run would have been at least half a second quicker, which would have placed me third in pax.

Revalved Bilsteins and rear toe-in definitely made the car much easier to drive, especially in slaloms. Now I can really throw it around without fearing about it spinning out of control. Corner exit doesn't seem affected. Maybe the AYC just works harder and compensates for it? In any case, it's a win-win .

Results here.

 

that's actually my theory. it measures yaw, if it's more or less, will compensate by doing more.

 

So, the main question here is are be better off with tight alignment so AYC works more aggressively, or looser one to make AYC act less?