ACD may help on dirt or gravel but I'm not about to f-up my paint trying to find out LOL. On dry pavement whether in a straight line or in a zig zag it doesn't "feel right" to me.

I still don't regret going from the 03 to the 06 but if ACD were an option I would have avoided it. The two things I dislike about my 9 is the lower 3rd and 4th gears and the ACD.

.... and yes our cars are very heavy. I have an SE and it tips the scales at 3200lbs.

 

As a driving instructor I have been in the car with alot of "amatuers" that think AWD will save them without fail. I have seen ACD do some huge things to stop a car from spinning on a big tank slapper. Some instances where you know the car is going to spin but then all of a sudden holds on amazes me.

Personally, my opinion is much of the same as Toovira. Tarmac has the most oversteer feel. Gravel goes more neutral and tends to understeer when pushed. Snow has major understeer.

Interesting to note that alot of guys that race their Evo's (tarmac rally, auto-x, sprints, hillclimbs etc) in Australia tend to use the Gravel setting when they don't run an aftermarket ACD controller (e.g Ralliart programmable). Those that come from more of a go-kart background tend to use Tarmac.

 

haha tank slapper
sport bike rider much?
i have to agree though having owned non acd equipped awd cars
i find the acd sorts things out better than the mechanical version
when things get crazy i feel the acd gets things settled way faster
in high hp awd cars its even more noticable on corner exit

 

The question you should ask yourself is which ACD mode is more like an entirely mechanical mechanical LSD like the 04 RS. I see people saying ACD makes noticable improvments on a loose surface. Everything I've read claims that tramac mode is the most "open" of the three. So gravel/snow is attempting to make the car behave more like the pre-ACD lsd diffs.

I haven't found anyone that prefers ACD over non-acd w/front lsd.

 

Remind me again why are we comparing front diff with center diff???? Any physics/explanation behind the theory of Helical front is better than ACD?

To me, front diff has one purpose....to prevent the front wheels from slipping.

Try entering the corner by full steam ahead, threshold brake, turn in, apex, accelerate and track out. Now to remind you, if you drive it like a race car, you'll feel the difference.....and if you turn correctly, your rear end of the car should swing.....and no, I don't mean losing control. And yes, your tires should be squealing, but not because of out of control.

If non ACD splits about 50/50 at the center diff, I'll take ACD car on Tarmac any given day. I'll take neutral/overstter over understeer any given day in other words.

 

Both cars ACD and non-ACD need the front LSD to perform at their best. Most everyone that has driven a non-ACD car with front LSD say they like the non-ACD platform better especially on tarmac.

If you haven't drive both then this topic is not for you. Most people coming from on 03-04 claim the ACD is much better but the reality of that is the front LSD improved things. If they had installed a front LSD in the 03-04 most would probably find the ACD useless.

 

Nope, perhaps not.....just seems to me something fundamentally wrong about comparing front LSD mod VS center diff.

 

We aren't doing that. We are comparing the standard 03-04 center diff to the ACD diff in the 05-06.

The point being made is this.....the ACD cars feel better on that track because all 05 and 06 cars got the front LSD and most 03-04 cars didn't. But when you compare and 03 with front LSD to an 05 with ACD and LSD that prefered platform is the 03.

 

I still think this is a biased answer. Has anyone attempted to modify the ACD mapping for use on tarmac? If not, all you can say is that people feel the non-ACD equipped cars are better...but I fully beleive that the ACD equipped cars are superior...if you change the mapping. Like any other part of the car, the ACD can be modified to suit your tastes and make the car faster.

Dave

 

That was my weight on the first day of SCCA solo nationals in topeka. I would think their scales are pretty accurate and it has been verified by a couple of sets of intercomp racing scales. I believe it was the lightest AWD STU car and I haven't even began to take weight out.

d

 

The only thing you can change with mapping is how much or how little lock the clutches provide. You can mechanically change the split but that is a big money job and the same thing could be done to a non-acd xfer case.

 

That's exactly correct...but that gives you so many more 'lockup' options than a viscous center. You can change all the parameters of when this lockup or unlockup occurs based on wheel speeds, steering angle, brake, and e-brake inputs going into the ACD ECU.

That's a whole other discussion, I was under the impression we were just discussing the impact that the OP wanted to know if ACD was better than non-ACD for track use (assuming both cars have front LSDs).

Dave

 

Honestly, I've been giving this a TON of thought over the past week and for virtually every application I can ponder (save one), the ACD makes sense.

The ONE exception... as odd as it sounds, I'm thinking that RALLY Racing may not be the best place for the factory Mitsubishi ACD. Don't flame me, here's why:

From what I can see, the ACD uses an array of sensor inputs. Many of which are in systems that we disable on a Rally Car. Antilock brakes, for instance. They gotta go... but what does this do to the ACD ECU and its needed information and control?

Secondly, I have heard from several reliable sources (but have not experienced it myself) that the ACD is susceptible to complete drive failure in the event that the car looses an axle, CV or in many cases in Rally, an ENTIRE WHEEL. This failure results in the system sending all available power to the missing drive component thus rendering the car completely immovable.

For example, if you were to pull the ebrake on an ACD car, dump the clutch, you could do FWD burnouts all day long. Well... if your front end is in the air, you're bound up, or say that one of these wheels are missing... I would very much rather SOME of that power be driving the wheels that are still connected to the motor.

I could be completely WRONG on this, as again... I've not had an ACD car until now and I have yet to experience this for myself.

But... the added level of complexity plus the additional parts plus the issues in getting the systems to work around certain disconnects plus the unknown issues I will be facing on a Rally Course...

I'm thinking the ACD is off my list for Rally Wants.

Your thoughts?

RallyDSM

 

Remember, ACD can only lock the front & rear wheels to force the front & rears to spin at the same speed, or it can leave the center diff open. If you're front is in the air and spinning, ACD will lock the system down (50/50) due to the difference in wheel speeds, which will give the rears some power. I'm not sure how it would deal with no sensor input from a corner though, but if that's your problem, there's some other issues that are more pressing. I'm sure that sensors for that get knocked off the cars all the time, or just fail, and I haven't heard of anyones car refusing to move b/c the ACD system is confused.

IIRC, the RS models have ACD and no ABS. I *think* the wheel speed monitors that the ABS uses connect into the ACD ECU...so, if you don't have ABS, the same wheel speed pulses will still go into the ACD ECU. I've yet to work out the wiring issues thought...

Honestly though...all the top rally teams in PWRC use active diffs, presumably because they just plain work. One of the only requirements I had when shopping for a new rally car was that the car had to have active diffs. Sure you can race without it, but if you're starting from scratch, might as well give yourself the best shot as winning as you can, and starting out by handicapping your vehicle isn't a smart move. If you're starting with a car that doens't have the ACD that's fine, but I certainly wouldn't remove it from a car that came equipped with it.

Dave

 

I still find it intrusive and upsetting on most medium speed tight radius tracks.

There are situations where the car is not in a skid but you can feel the ACD lock up a diff. It makes the car feel like its gonna jump. I'm not the only one that has noticed this. All of my long term track **** buddies say the same thing.

It might be a beautiful thing with AYC but ACD isn't going to save you from a spin. That stuff you saw on top gear was a full on AYC/ACD evo and not the US edition.