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Discussion Starter · #1 ·
seeing mention in another thread of the possibility of a sports ecu for the ayc got me thinking...

firstly the ayc system appears to be getting a bad rap so first a few opionions (note this is not a defence but simply trying to sort out the facts)

1 its a traction control device
-no its not because typical 'traction control' devices reduce engine power and it doesn't

2 its not an lsd
-yes it is because when accelerating in a straight line, if excessive slip is detected on one wheel it transfers torque to the other non spining wheel thus limiting slip

3 its makes the car slower
-not necessarily because it is (up to a point which i will come to) better able to transfer power into forward motion rather than sideways motion. depending on the surface, this will generally make the car faster if goes where it is pointed rather than assing out all over the place

4 it's for less skilled drivers
-firstly it's still entirely possible to go sideways given enough power and lacking enough grip. remember it does NOT reduce engine power so by transfering torque it may be able to delay this but it can't overide the laws of physics which brings me to the most serious issue i have with it but which is not often mentioned,when it does go sideways the break away can be quite sudden and it is less 'progressive' than the mechanical arrangement. you may actually need to be a 'more skilled driver' to take an ayc car to the absolute limit and avoid spinning it

so as a compromise why not 'alter its map' so that the straight line lsd function is retained but the cornering characteristics are altered? given it's an electronic system the characteristics should be infinately variable compared to the fixed settings of the old fashioned mechanical lsd and if done correctly it should be far superior. after all you can't say that electronic engine management is bad compared to a carburator and points just because it's been mapped for economy and not power...

i soon see another debate: should i get a 'ralliart sports ecu' or 'fully mappable one'.....for the ayc


Discussion Starter · #2 ·
I'm not sure if anybody can change the AYC characteristics, but it would certainly be better to get a less intrusive AYC.

The AYC function will not make the car faster in corners, it will just keep you from telling it where to go. As it avoids the back from sliding, it will not allow you to position the car right to accelerate out of the corner faster, therefore you lose time. In fact, it is faster while it is not sliding, but less fast since you cannot accelerate early enough (understeer).

I would be interested to know if there are people able to remap the AYC. Maybe Ralliart or PE?

Discussion Starter · #3 ·
I quite agree with you on all your points above and as you say the problem lies with the AYC breaking away suddenly on the limit unlike the more progressive and predictable nature of a standard LSD. I think this is why people don't like it (then again if you want arse out oversteer all the time then buy a RWD car!). As you say AYC will be faster and more composed around a corner 98% of the time than a standard LSD car.
I thought I would reply as I started looking into converting the AYC to LSD electronically a while back but didn't take it too far as I was going to sell my car. I posted my thoughts on here hoping someone would take it up but I don't think anyone did? Why pay out mega bucks to whip out a perfectly good plated rear diff only to replace it with a standard LSD? (e.g. Cusco conversion)
Anyway my thinking is the following:
The AYC acts as a normal LSD in a straight line with it just sensing the wheel slip and transfering torque accordingly so why not make the AYC ECU think its going in a straight line all the time and hence normal LSD operation all the time? If you replace the lateral G sensor (also longitudinal G and Steering wheel sensors but not sure) with the equivalent feedback as if was going in a straight line (i.e. zero G) then it will fool the AYC ECU into normal straight line LSD operation. I think it is just a case of replacing the sensor outputs with the appropriate steady voltage which I think is 1.5 volts for zero G (I forget but its in the WSM), you could make it switchable between AYC and LSD operation as well all for probably less than £60.
I am suprised someone hasn't looked into this yet, it would make an interesting project. The only thing that needs clearing up is if the Steering wheel position sensor and logitudinal G sensor play signifigant roles in activating the AYC in a corner as you wouldn't want that, just normal LSD mode. I think the Steering wheel sensor may need masking but I am not too sure on the logitudinal G sensor. The Evo 4 doesn't have a lateral G sensor so the logitudinal G sensor may have a more important role than I think, hence I am unsure on this. It needs some testing with a meter while cornering to find out. I haven't bothered taking this further because I'm selling my Evo but I am sure it could be done quite successfully.
Check out 21st Century Performance for a similar thing done to a Skyline to vary the front/rear torque split via a home made box with a dash mounted dial.

Discussion Starter · #4 ·
What happens when you just switch it off (fuse out)? Does it behave as an LSD then? I know Simon Evo has disconnected his.....

Discussion Starter · #5 ·
If you pull the fuselink on the AYC it will just act like an open type diff, i.e. no torque transfer will occur as the hydraulics won't be working to activate the clutch plates at any time.
I would rather have AYC than an open diff.

Discussion Starter · #6 ·
The WRC has an electronic rear diff, rather than a mechanical LSD.
How is the electronic rear diff different from the AYC then ?


- ronnie

Discussion Starter · #7 ·
Lots of food for thought and here is some more. Ralliart actually have the sports ECU for the AYC. However, they admit they don't have the spec of waht it does so are going to test it before selling any ( bit sensible really!). I have been doing some reading and I notice that the ACD and AYC have a joint ECU. So, the question is what do we think that the sports ECU will do.

Problems in modifying the car seem to be many. If, as I suspect, the ECU is a joint one, then anything done to fool the AYC could effect the ACD. I am fairly certain that to get the type of behavior that HH6 is after you would need to do something about steering angle, longitudinal G and Lateral G sensors. I don't think that you would have to do anything about the individual wheel speed sensor but am uncertain about the throttle opening sensor.

I am beginning to believe that the AYC is, in principal, good. The issue is whether the programming is ideal. Like anything that effects the handling, the set up is personal choice. To date, I haven't found the AYC intrusive but I do sense that on the edge it might not be as progresive as a car without it. Therefore, what is really needed is a way of re-programming.

Discussion Starter · #8 ·
Original Post:I am beginning to believe that the AYC is, in principal, good.
Don't let Claudius hear you say that! ;)

Interesting discussion, the Skyline tha HH6 mentions was vastly improved by the addition of the tweak box. Maybe the cure for those who don't like the 'feel' of the AYC as it could be dialled in or out as mood and the conditions dictate. Now all it needs is some brave soul to try it out! Must be someone in Japan that has already tried this, no?

Discussion Starter · #9 ·
ok so there is nothing wrong with the AYC other than the settings are fixed and not optimal for the 'enthusiast driver' (apart from weight, cost and fragile anyway!) but given its computer controled the characteristics can (in theory) be changed on the fly and fine tuned so the potential is there

sports ecu (if/when available) is one option but you are just changing one non optimal fixed map for another of course, and the advent of acd is certainly another complication...

obviously a mappable ecu would be the ideal but none appears to exist so interfering with the sensor signals as suggested seems to be the way to go

probably the easiest thing todo is to log the various inputs and outputs of the the ecu using some data aquisition software and hardware with the laptop and drive around for a while, this should make it possible to figure out what effects what

once this is done then hopefully the cost of building an intercept box would be cheap and if (for instance) it was just a case of interfering with the g sensors (a la skyline controller) then you could also make it adjustable with a pot

with the right settings the mechanical diff is going to look like a musem piece


Discussion Starter · #10 ·
I was purely thinking of switching between AYC and LSD operation and not varying the map which I feel could possibly damage the diff if you are not careful (just look at the AYC recall which was allegedly due to an incorrect map activating the hydraulics at the wrong time causing premature wear). Just switching between the two would be far easier and safer to set up than varying the G sensor outputs via a pot. You could rig up the switching and false sensor outputs very cheaply whereas changing the map would be more costly and complex. I was also only just considering the AYC on the Evo 4-6 and not the combined ACD/AYC on the 7 which could be even more complex to set up.

Discussion Starter · #12 ·

yeah it seems like prematurely engaging the clutch could be the cause of the excessive wear but i am probably more thinking along the lines of delaying the engagement so hopefully shouldn't be a problem

i think i have figured out how it operates but once i have logged it i'll know for sure

agreed making it adjustable is more complex but i like the idea of being able to fine tune it

obviously 7 is another step up but the same rules apply


Discussion Starter · #13 ·
I asked for an AYC controller when I was in Japan again, and there still isn't anyone that makes one... There must be a reason for this as you can get similar stuff for the Skyline. Either the market isn't big enough, or it's easy to damage it. Can it not be possible to wear out the diff if you set it at a constant voltage? AFAIK it'll be designed for relatively short corrections, i.e. short times that the clutch plates will be engaged. Will a continuous setting not just damage the diff??

Discussion Starter · #14 ·
Hi Simon
I was under the impression the SPORTS ACD for the Evo 7 altered the ACD characteristics ONLY and not the AYC??
Have you heard something else?? There are 2 versions of ACD ECU upgrade available - Fast Road and Rally and I suspect they both increase the hydraulic pressure in the centre diff (the rally one being more extreme) thus allowing for tighter control and a faster response of the unit.
This is a superb thread and if a solution could be found for the premature intervention of the AYC unit (or a system which allowed the AYC to feel more like an LSD and allow you to progressively drive the car on the throttle), I am sure this would be valuable to 6 and 7 owners alike.
It would actually give you the best of both worlds - half chips and half rice !!
First I guess we need to find out how the thing works and what signals come to and from the unit - Anyone got a manual / buddy in Mitsu/Ralliart that would give us this info?

Discussion Starter · #15 ·

There is a lot of confusion over what this sports ECU does! As I am sure you know, the ECU on the 7 controls both AYC and ACD. I am waiting for Toney to test it and do some more digging.

What I am most interested in is the comments about premature intervension of the AYC. What does it feel like. I don't believe that I have felt anything in particular and I believe that I have had the car close to the limit and in the wet I have had the car moving around a reasonable amount. Maybe I have no feel, couldn't spot it even if it hit me in the face :D

My feeling is that whilst you cannot feel the AYC working, it does mask the limit and that, compared with the non AYC cars, the breakaway is more sudden and more difficult to control. Thought please. Where are you Claudius!

Discussion Starter · #16 ·
today i have driven an evo 7 with ayc it is less intrusive on an evo 7 than on a 5 or 6 that s for sure

this is my opinion

but i love to hear other opinions



Discussion Starter · #17 ·
I have been studying the AYC system in the technical manuals and I have also been looking at the wiring diagrams and I have hit a slight snag (this is for the LSD conversion and not the map tweak).
The sensor outputs that need masking are the Lateral G and the Steering Wheel Position sensors.
The Longitudinal G is jointly shared between the AYC and the ABS so I don't suggest that is touched (however I don't know why the ABS needs it, I thought ABS purely relied on the wheel speed sensors?).
At a standstill the Lateral G sensor ouputs between 2.4V-2.6V but on the move it varies between 0.5V to 4.5V. I have worked out a circuit to provide a constant 2.5V output to swap over with the normal G sensor output to make the AYC ECU think it is not cornering by the G sensor. The G sensor part is not a problem. The problem comes with the Steering wheel position sensors, yes sensorS, there are 3 sensors in total! One sensor just detects whether the steering wheel is in the neutral (or straight ahead) position (called sensor ST-N). The other two sensors work out the rate or speed at which the steering wheel is being turned and they constantly 'flash' an output voltage between 0.5V and 3V (sensor ST-1 counterclockwise and sensor ST-2 clockwise). The rate at which they 'flash' is directly proportional to the rate at which the steering wheel is turned (probably a Hall effect device for you techies out there ;) ). 'This is not a problem' you might think, 'just replace the sensor outputs with a constant 0.5V and hey presto the AYC ECU will think the steering wheel isn't being turned'. Well actually that is quite correct except that it is possible the AYC ECU may produce an error code.
I thought I had this sorted in my head when starting to write this but going back over the 'Japlish' in the WSM it is confusing to say the least. I think the error codes they refer to are when the two sets of steering sensors (rate and neutral) don't tally up i.e. the neutral sensor says the steering wheel is in the neutral position but the steering rate sensors say the steering wheel is moving therefore one of the sensors is telling porkies so it must be faulty and the ECU outputs an error code. I think if all 3 sensors are 'switched' into 'straight ahead mode' at the same time by the black box then it shouldn't be a problem.
I have just thought of another potential problem though! If you switch off the 'straight ahead mode' black box while in the middle of a corner it may cause a serious conflict in the AYC ECU! It all depends on how the sensors work.
Blimey this gets more complicated by the minute now I know why I gave up on it ;)
I will have to rest the old grey matter for a bit, still its a lot more interesting mod to work out than an induction kit ;)

Discussion Starter · #19 ·

good to see you are not an ayc victim anymore (well you still are at the moment but the problem is being worked on)
btw i can solve your slow problem as i am making good headway on mapping my ecu (which at ony 500 pounds is cheap) i'm up to 1.5 bar plus (held ) and the car is a rocket ship |PLS| on the 'summit road' i am a gear higher now... still i do have a lean problem (still got the std pump) i have the lambda map on my site now and u can see it go lean at high boost/revs, have the bits to rewire fuel pump which i am going to try first as volts at pump only 11.8 vs 13.5 at battery and power is proportional to volts squared so should be able to get about 30% better with rewire

also claudis i can get rid of your understeer u can fix this with the right wheel car does not understeer in fact its quite 'taily' mind you i had about 6 wheel; alignments (to my specs not the operators) before i got it right

anyway back to the ayc


thanks for your analysis and this has caused a problem!! for what i was thinking as i didn't realise there were three steering wheel sensors so i am going to have to think about that some more i was thinking the sensor just said whether the wheel was turned or not

i wonder whether clutch action is on/off or proportional? what are you able to deduce?

as i say i need to data log it which basically means recording all the inputs and outputs this way i should be able to figure out what it is doing

finally on the abs as i drive on gravel a bit the abs will allow some lockup which doesn't normally happen as it is trying to optimise for maximum g deacceleration and not just stop wheel lockup via wheel speed sensors and again an abs system that does this properly could be very good indeed

on the subject of gravel provided you are brave and keep the boot into it the ayc car actually works surprisingly well allowing you to control sideways motion on the throttle (will snap back straight and possibly fishtail if you back off)

enough rambling and will sleep on it (night here in nz)

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