you really need to try a reflashed ACD ECU... it is really noticable..

As for driving without the pump... as it has been said, you can drive normaly, no problem, and nothing else will break. The diffs will not lock and you will notice more understeer at the limit + possible wheelspin if you overdo it..

 

Oh, I'm convinced of that. Once my pump is fixed, that's high on the list. The question is what to do in the rear. I'm going to be driving on pavement, too, so I'd like to keep the AYC, but there's not much that programming can do to make it work well on gravel (or so I've been told and it makes sense to me). The best option I see is to put a Cusco RS in the rear and disable the AYC on gravel. Or do you have a better idea?

edit: for those who don't know, Kiki (if he doesn't mind being called that) is THE expert on our pumps. If he and I ever disagree, ignore me and listen to him.

 

I'm interested to know more about this reprogramming of the ACD, what does it do, change how much lock happened?

 

There are lots of things that you can change: how soon it locks, how hard it locks, how quickly it opens when you lift or steer; whether it stays locked when you stay on the gas and steer at the same time.

The OE programs stink. It's often worse than nothing because it can really get in the way of rotating the car (at least, on gravel). It's Mitsu covering its own tush (as usual). They never allow the center to lock hard, for example; if it does, it throws a code.

People have been reprogramming the center for years and some good programs or entirely new controllers are available. The gap - from what I can tell - is in AYC programming. And there's a gaping hole in what's available when it comes to AYC programming for gravel, probably because most sanctioning bodies follow FIA rules and don't allow you to mess with more than one diff's program, so you either leave the AYC as is or (more often, it seems) dump the AYC entirely.

 

ahh,.. you make me blush..

ok, as for reprogramming..

the short answer is, yes it can help a lot especially on loose surfaces.

now for the long answer..

I have had the most enjoyable experience with it this winter... Recently I began using my E9 (EU model with full ACD AND AYC) mostly in winter to hoon around on snow covered back roads at night..

Anyway, the stock programming is quite conservative as it basically slows down the turn rate of the car in gravel and even more so in Snow setting. However, it must be said, that the car has unnatural amount of grip in front...it just doesn't like to oversteer much and is slow to turn from one side to the other..
It is even worse in Tarmac setting, when used on slippery surface, as it is really nervous and hard to control in slide.. at one point I just do not know what it will do..

This winter I went for a reprogrammed ACD&AYC controler from acd tuning, and I must say that the car is just perfect in the slippery stuff. In the end I went for a stock tarmac setting (I like how it works in the dry.. I know it is not the fastest, but it is fun for me as I can feel the AYC push the nose in the middle of the corner), one of the reprogrammed maps in Gravel and stock map in Snow, just to be able to compare... The result is a much much faster transition between side to side, when sliding the car around.. it is almost unbelivable.. Also, when in slide it is much more controllable and natural to drive..
I got hold of a couple of ACD controlers so that we can experiment with some more maps.. Also I understand that Matthew is working on a ACD tune with more maps and possibility of having several AYC maps (because the normal controller has 3 ACD maps but only one AYC map)... so this will be interesting..

 

Mitsubishi's active diffs are quite unique...

The ACD, the active central diff, has a open torque splitter in the gearbox, that splits torque 50/50 and the ACD can NOT change this ratio. However, the hydraulically operated clutch pack in the ACD can variably lock the front and rear axle togeather. Driving in a straight line locking the central diff will give you maximum traction, but if you do it in a corner (where you actually have different speeds of the front and rear axle) you can influence how the car turns... and this is why people have the feeling that the ACD changes the torque split.

Normally when you brake and want to turn into the corner the ACD will open and allow you to turn in better and then the ACD will lock on corner exit... With a ACD ECU reflash you can play with this... More ACD locking on braking.. for example.. for more stability and better braking.. earlier locking on corner exit.. etc..
For example, with the reflash, I noticed that the car is more stable and has more grip, but I have to commit better to the corner and position the car in a slight oversteer really early, for maximum effect... So, faster but you have to adapt a bit.

As for the AYC.. This diff is actually really trick.. Essentially it is a normal open diff. Then, you have a small gearbox, that increases the input shaft speed, and twin clutch packs that can transfer this "increased shaft speed" onto the left or right driveshaft. So, unlike the normal plate diff, that will just "lock" tje left or right driveshaft, this AYC can actually speed up left or right wheel.

The AYC map gives a relation of torque difference on L/R side of the diff, in relation to speed and steering wheel position. So by reprogramming that you can alter the way it works.. My guess is that on gravel you might like to try less torque split than on tarmac (as it is really agressive), but it would be fun to try different strategies... But, as I said, the ACD is the key.

 

the homologation for the car doesn't allow AYC.. so that is why rally cars have a normal plate diff in the back. But they all run reprogrammed ACD controllers..

 

Yep. In some classes, in North America, however, you can keep the rear AYC but can't change the programming. The FIA flat out doesn't allow two active diffs.

The thing that I don't quite follow is how fancy maps for gravel mode deal with the sawing of the steering wheel that might be needed in a turn on loose surfaces, switching from counter-steer to straight and back again, for example. When I've driven hard on gravel (before my pump died), I was getting crazy and unpredictable effects that I assume were coming from the AYC. A few times when I tried a flick (as in: turn out before turning in), I just about left the road. I suspect that gravel mode is a bit too much like tarmac: the AYC's program always assumes that, if I have the wheel turned right, I really want to go right, but that's often not true. I might be going around a left turn, but wanting to keep the radius large.

How dependent on the g-sensor is the AYC's program? Can it be set to rely more on this value than steering angle?

 

no, the ayc map is speed vs steering angle... but it doesn't matter, once you sort out the ACD maps, the car becomes more controllable.. At least that is what we got on snow.. which is a really low friction surface.. you can flick it anyway you want..

You can also lessen the torque difference in the rear diff, which might work better for gravel.

 

Do you still have the OE planetary in the rear or something else, such as a Cusco RS? I'd be very happy to hear that fixing the ACD's programming will be enough.

Also, do you have a steering quickener? That would reduce the steering angle input to the computer.

 

no, I have the stock diff...
You do not need the steering quickener, you can have the AYC map changed to have less torque transfer in the rear...

I think it is best to try just the remap first... it brings a very noticeable difference..
You can always switch to an RS rear diff later on, the ACD will still work normally...

 

I just got off the phone with PPDMotorsports and we had come to same conclusion. First try his tuner's gravel and snow maps with the OE diffs, then start thinking of spending money (that I don't really have).

edit: to the thread-starter ... I will try to use my ninja-mod skills and pull this discussion I'm having out of your thread as soon as I can

 

Haha, no problem, now that my pump is pretty much shot I want to learn all I can about the ACD to know my options! Doesn't reprogramming it cause a lot of stress for the LSD?

 

Yes, allowing it to lock harder put a bit more stress on the pump and a lot more stress on the clutch, itself. How quickly ACDs wear out when you allow it to lock hard is something that you'd have to investigate.

 

This discussion started as an OT in a thread concerning a dead ACD/AYC pump. Rather than continue to ruin that thread, I've moved it here.

What started it all was this comment I made: "On gravel, at least, the car is much better without the AYC."