ACD Tuning Options - USDM CT9As, Read!
English's tune has three settings, rotate (snow), more rotate (gravel), and "look at the steering wheel and the car rotates" (tarmac). All of which are more aggressive than any of the stock maps. It makes a night/day difference in the attitude of the car.
Okay... now that sounds really fun LOL. As soon as I can do without my ACD ECU for a few weeks, I'll send it to Tom. Or I'll get a Tactrix 2.0 cable...
whichever comes first.
Mine does this:
Tarmac_Gravel: Tarmac settings with good grip, lock is reduced with lateral G-force (=hard turn). A lot of people run this on the road course.
Tarmac_Snow: Less lock, can be tail happy (at wet especially) but should understeer less at track. Might need good tires to get all out. This can be drifted on in wet surface.
Gravel_Snow: This is for snow surface. Gives more lock pressure with lower TPS input so I would not run this daily as pump can run more often, so in theory it can wear more quickly. In practice, not a big difference but I'm letting you know. In snow and gravel surfaces more lock is needed to get more grip and a good driver can be faster.
Few random things wrote in the past:
1) Yes it will help. Understeer is one of biggest issues with AWD car but active center differential (ACD) can make it better by reducing lock-up in situations where it typically under steers due to too high of lockage and where lock is not needed to keep car stable. Remember, too low of lock can make the car unstable in some situations like hard braking on slippery/loose surface so its always a bit of compromise to find values which give best overall performance. Also important point is, ACD alone does not solve basic problems, it is important to work cars suspension first (aligning, suspension itself, front/rear differential lock setups etc) and give it the best possible tuning and after that make it better with ACD tuning if some problem is still unsolved.
2)Tarmac_Gravel: Lock pressure is not minimized when you accelerate/decelerate so it gives pretty good grip and stability (remember, too low of pressure can lead to instability in certain conditions) But we reduce this pressure when there's lateral G-force, IE; when you turn the car into a tight turn. So, it under-steers less but should still have good stability. When tuning, We always lose some stability if we try to reduce under-steer, that's just how it is and the trick is to find values which are compromise for both worlds stability and good turn in abilities.
3) Stock settings are created with stability in mind and for stock power level, And these settings work pretty well on stock cars. On loose surfaces like snow/gravel, The benefits are there even with a stock car but these surfaces are more demanding for the driver to max it all out. On tarmac, If the driver feels it understeers too much, it might help to reduce pressure a bit, But this happens on the cost of stability (tail happiness, oversteer, drifting feeling). So simply, Yes you can gain something but I do not recommend starting car modifications of your car with ACD tuning.
4) With tuned settings its possible in theory that pump operates more often due to more dynamic operation of hydraulic pressure control. In practice pumps do not wear out mechanically but they break due to corrosion, pump is poorly protected for water and when water gets in, It corrodes the pump. Our tunes are not aggressive unless somebody demands, I'm not worried about wearing out anything.
5) Everything has effect to everything in suspension/chassis side. It depends what is wanted and if driver wants to get every single tenth of second from his lap time, then individual tuning is always needed after changes. But generic programs work pretty good so its not absolutely needed.
6) We can achieve less understeer AWD cars suffer as nature of them, more grip with higher power cars (=more lock so it adds grip), more grip on low friction surface like snow and its like part of finishing touches for otherwise tuned vehicles. Stock settings are great for stock cars. Tune it for more power and you might want to tune ACD too, to match it with your new power level.
We can also make all 6 maps custom as well, So in theory, You could have your ER maps implemented into our maps having both together. I'm Sure the ER is similar to ours though. You can only do so much improvement.
Tarmac_Gravel: Tarmac settings with good grip, lock is reduced with lateral G-force (=hard turn). A lot of people run this on the road course.
Tarmac_Snow: Less lock, can be tail happy (at wet especially) but should understeer less at track. Might need good tires to get all out. This can be drifted on in wet surface.
Gravel_Snow: This is for snow surface. Gives more lock pressure with lower TPS input so I would not run this daily as pump can run more often, so in theory it can wear more quickly. In practice, not a big difference but I'm letting you know. In snow and gravel surfaces more lock is needed to get more grip and a good driver can be faster.
Few random things wrote in the past:
1) Yes it will help. Understeer is one of biggest issues with AWD car but active center differential (ACD) can make it better by reducing lock-up in situations where it typically under steers due to too high of lockage and where lock is not needed to keep car stable. Remember, too low of lock can make the car unstable in some situations like hard braking on slippery/loose surface so its always a bit of compromise to find values which give best overall performance. Also important point is, ACD alone does not solve basic problems, it is important to work cars suspension first (aligning, suspension itself, front/rear differential lock setups etc) and give it the best possible tuning and after that make it better with ACD tuning if some problem is still unsolved.
2)Tarmac_Gravel: Lock pressure is not minimized when you accelerate/decelerate so it gives pretty good grip and stability (remember, too low of pressure can lead to instability in certain conditions) But we reduce this pressure when there's lateral G-force, IE; when you turn the car into a tight turn. So, it under-steers less but should still have good stability. When tuning, We always lose some stability if we try to reduce under-steer, that's just how it is and the trick is to find values which are compromise for both worlds stability and good turn in abilities.
3) Stock settings are created with stability in mind and for stock power level, And these settings work pretty well on stock cars. On loose surfaces like snow/gravel, The benefits are there even with a stock car but these surfaces are more demanding for the driver to max it all out. On tarmac, If the driver feels it understeers too much, it might help to reduce pressure a bit, But this happens on the cost of stability (tail happiness, oversteer, drifting feeling). So simply, Yes you can gain something but I do not recommend starting car modifications of your car with ACD tuning.
4) With tuned settings its possible in theory that pump operates more often due to more dynamic operation of hydraulic pressure control. In practice pumps do not wear out mechanically but they break due to corrosion, pump is poorly protected for water and when water gets in, It corrodes the pump. Our tunes are not aggressive unless somebody demands, I'm not worried about wearing out anything.
5) Everything has effect to everything in suspension/chassis side. It depends what is wanted and if driver wants to get every single tenth of second from his lap time, then individual tuning is always needed after changes. But generic programs work pretty good so its not absolutely needed.
6) We can achieve less understeer AWD cars suffer as nature of them, more grip with higher power cars (=more lock so it adds grip), more grip on low friction surface like snow and its like part of finishing touches for otherwise tuned vehicles. Stock settings are great for stock cars. Tune it for more power and you might want to tune ACD too, to match it with your new power level.
We can also make all 6 maps custom as well, So in theory, You could have your ER maps implemented into our maps having both together. I'm Sure the ER is similar to ours though. You can only do so much improvement.
Evolved Member
Joined: Jul 2003
Posts: 638
Likes: 7
Disagree strongly with you on those two points.
I think the stock maps are atrocious and make the car an understeering pig under light throttle in high speed sweepers.
If I could only modify one thing on a stock USDM Evo IX it would be the ACD mapping.
YMMV
I think the stock maps are atrocious and make the car an understeering pig under light throttle in high speed sweepers.
If I could only modify one thing on a stock USDM Evo IX it would be the ACD mapping.
YMMV
Evolved Member
Joined: Mar 2002
Posts: 1,760
Likes: 22
From: Reading, MA
If you are using light throttle you are telling car not to be that aggressive with amount of yaw it creates...if you want more, perhaps you should create more, instead of taking it easy...
Perhaps whether undesteering pig under light throttle is caused by you using light throttle or ACD settings is something that should be figured out here first.
If you are using light throttle you are telling car not to be that aggressive with amount of yaw it creates...if you want more, perhaps you should create more, instead of taking it easy...
If you are using light throttle you are telling car not to be that aggressive with amount of yaw it creates...if you want more, perhaps you should create more, instead of taking it easy...
With my car, there seems to be a fine line between understeer and powering into over steer.I have to be gentle or romp. No in between LOL
Last edited by kaj; Sep 4, 2016 at 12:21 PM.
Evolved Member
Joined: Jul 2003
Posts: 638
Likes: 7
That's woken up a few people!!!Note that I wrote on a stock USDM Evo ...
Understeer is an issue on a stock USDM no matter how you skin the cat. Yes if you can drive flat out, it's not so bad. If you gotta lift as is common in road use it's not great for fluid fat road use. A JDM, AUS or EDM car has AYC and behaves differently. We got shafted to a point in that the whole package stock is inferior dynamically, even though the driveline is stronger.
A simple software change makes the car close to perfect dynamically, at least for road use and IMO not really worse than a AYC car and in some ways I even prefer it.
This is the only modification where after 5 minutes in the car on a slightly spirited drive on a windy road my wife commented that the car drives different and way better - this was unsolicited and she didn't know that anything had been changed ...
The fact that somebody can pick up more than 3 seconds on a 50 second slalom course speaks volumes by itself https://englishracing.net/collection...8-9-acd-tuning
$300 and a few minutes with a screw driver, it is one of the least intrusive mods and totally reversible ... turns in better, steers better, brakes better and most of all it doesn't plow anymore
... don't know what gives guys ... don't need the personal attacks 
And now given Jon's (TRE) info we know why
didn't program it that way from the factory - not desirable for new gears during break-in ... warranty claims ...
sounds similar to my "theory" of generally how you want the evo to behave - you want the center diff to be locked minimally in corners - which the ACD can read via steering angle, g force, whatever else it measures. if it's locked too much, just like any other LSD, it's going to cause understeer. then, on power out, you want to it to lock to some degree for max grip/torque distribution.
There's timing at play too, but it always felt like the stock ACD tune, as well as a few I've tried here - re: Gruppe S, had too much lock all the time, when in reality, you don't want it locked so much on turn in. That's one of the first things I noticed with ER's tune, and I'm sure it's the same on Tom's - improvement in turn in more than anything else. in my situation, i notice less on power out, as i have an extremely aggressive rear differential, and not enough power to break traction
There's timing at play too, but it always felt like the stock ACD tune, as well as a few I've tried here - re: Gruppe S, had too much lock all the time, when in reality, you don't want it locked so much on turn in. That's one of the first things I noticed with ER's tune, and I'm sure it's the same on Tom's - improvement in turn in more than anything else. in my situation, i notice less on power out, as i have an extremely aggressive rear differential, and not enough power to break traction
Mine does this:
Tarmac_Gravel: Tarmac settings with good grip, lock is reduced with lateral G-force (=hard turn). A lot of people run this on the road course.
Tarmac_Snow: Less lock, can be tail happy (at wet especially) but should understeer less at track. Might need good tires to get all out. This can be drifted on in wet surface.
Gravel_Snow: This is for snow surface. Gives more lock pressure with lower TPS input so I would not run this daily as pump can run more often, so in theory it can wear more quickly. In practice, not a big difference but I'm letting you know. In snow and gravel surfaces more lock is needed to get more grip and a good driver can be faster.
Few random things wrote in the past:
1) Yes it will help. Understeer is one of biggest issues with AWD car but active center differential (ACD) can make it better by reducing lock-up in situations where it typically under steers due to too high of lockage and where lock is not needed to keep car stable. Remember, too low of lock can make the car unstable in some situations like hard braking on slippery/loose surface so its always a bit of compromise to find values which give best overall performance. Also important point is, ACD alone does not solve basic problems, it is important to work cars suspension first (aligning, suspension itself, front/rear differential lock setups etc) and give it the best possible tuning and after that make it better with ACD tuning if some problem is still unsolved.
2)Tarmac_Gravel: Lock pressure is not minimized when you accelerate/decelerate so it gives pretty good grip and stability (remember, too low of pressure can lead to instability in certain conditions) But we reduce this pressure when there's lateral G-force, IE; when you turn the car into a tight turn. So, it under-steers less but should still have good stability. When tuning, We always lose some stability if we try to reduce under-steer, that's just how it is and the trick is to find values which are compromise for both worlds stability and good turn in abilities.
3) Stock settings are created with stability in mind and for stock power level, And these settings work pretty well on stock cars. On loose surfaces like snow/gravel, The benefits are there even with a stock car but these surfaces are more demanding for the driver to max it all out. On tarmac, If the driver feels it understeers too much, it might help to reduce pressure a bit, But this happens on the cost of stability (tail happiness, oversteer, drifting feeling). So simply, Yes you can gain something but I do not recommend starting car modifications of your car with ACD tuning.
4) With tuned settings its possible in theory that pump operates more often due to more dynamic operation of hydraulic pressure control. In practice pumps do not wear out mechanically but they break due to corrosion, pump is poorly protected for water and when water gets in, It corrodes the pump. Our tunes are not aggressive unless somebody demands, I'm not worried about wearing out anything.
5) Everything has effect to everything in suspension/chassis side. It depends what is wanted and if driver wants to get every single tenth of second from his lap time, then individual tuning is always needed after changes. But generic programs work pretty good so its not absolutely needed.
6) We can achieve less understeer AWD cars suffer as nature of them, more grip with higher power cars (=more lock so it adds grip), more grip on low friction surface like snow and its like part of finishing touches for otherwise tuned vehicles. Stock settings are great for stock cars. Tune it for more power and you might want to tune ACD too, to match it with your new power level.
We can also make all 6 maps custom as well, So in theory, You could have your ER maps implemented into our maps having both together. I'm Sure the ER is similar to ours though. You can only do so much improvement.
Tarmac_Gravel: Tarmac settings with good grip, lock is reduced with lateral G-force (=hard turn). A lot of people run this on the road course.
Tarmac_Snow: Less lock, can be tail happy (at wet especially) but should understeer less at track. Might need good tires to get all out. This can be drifted on in wet surface.
Gravel_Snow: This is for snow surface. Gives more lock pressure with lower TPS input so I would not run this daily as pump can run more often, so in theory it can wear more quickly. In practice, not a big difference but I'm letting you know. In snow and gravel surfaces more lock is needed to get more grip and a good driver can be faster.
Few random things wrote in the past:
1) Yes it will help. Understeer is one of biggest issues with AWD car but active center differential (ACD) can make it better by reducing lock-up in situations where it typically under steers due to too high of lockage and where lock is not needed to keep car stable. Remember, too low of lock can make the car unstable in some situations like hard braking on slippery/loose surface so its always a bit of compromise to find values which give best overall performance. Also important point is, ACD alone does not solve basic problems, it is important to work cars suspension first (aligning, suspension itself, front/rear differential lock setups etc) and give it the best possible tuning and after that make it better with ACD tuning if some problem is still unsolved.
2)Tarmac_Gravel: Lock pressure is not minimized when you accelerate/decelerate so it gives pretty good grip and stability (remember, too low of pressure can lead to instability in certain conditions) But we reduce this pressure when there's lateral G-force, IE; when you turn the car into a tight turn. So, it under-steers less but should still have good stability. When tuning, We always lose some stability if we try to reduce under-steer, that's just how it is and the trick is to find values which are compromise for both worlds stability and good turn in abilities.
3) Stock settings are created with stability in mind and for stock power level, And these settings work pretty well on stock cars. On loose surfaces like snow/gravel, The benefits are there even with a stock car but these surfaces are more demanding for the driver to max it all out. On tarmac, If the driver feels it understeers too much, it might help to reduce pressure a bit, But this happens on the cost of stability (tail happiness, oversteer, drifting feeling). So simply, Yes you can gain something but I do not recommend starting car modifications of your car with ACD tuning.
4) With tuned settings its possible in theory that pump operates more often due to more dynamic operation of hydraulic pressure control. In practice pumps do not wear out mechanically but they break due to corrosion, pump is poorly protected for water and when water gets in, It corrodes the pump. Our tunes are not aggressive unless somebody demands, I'm not worried about wearing out anything.
5) Everything has effect to everything in suspension/chassis side. It depends what is wanted and if driver wants to get every single tenth of second from his lap time, then individual tuning is always needed after changes. But generic programs work pretty good so its not absolutely needed.
6) We can achieve less understeer AWD cars suffer as nature of them, more grip with higher power cars (=more lock so it adds grip), more grip on low friction surface like snow and its like part of finishing touches for otherwise tuned vehicles. Stock settings are great for stock cars. Tune it for more power and you might want to tune ACD too, to match it with your new power level.
We can also make all 6 maps custom as well, So in theory, You could have your ER maps implemented into our maps having both together. I'm Sure the ER is similar to ours though. You can only do so much improvement.
Has anyone here done any of the plate upgrades to the rear diff and the ACD tune? Would you suggest doing one over the other, or just doing both, and why? I just finally got my EVO running great again after a 2.5 year nightmare, and I'm getting it track worthy again.
I had no idea you guys did ACD tuning as well. I definitely want to look into that too.
Has anyone here done any of the plate upgrades to the rear diff and the ACD tune? Would you suggest doing one over the other, or just doing both, and why? I just finally got my EVO running great again after a 2.5 year nightmare, and I'm getting it track worthy again.
Has anyone here done any of the plate upgrades to the rear diff and the ACD tune? Would you suggest doing one over the other, or just doing both, and why? I just finally got my EVO running great again after a 2.5 year nightmare, and I'm getting it track worthy again.
As far as which first, hard to say. I think they are complements to each other. Ultimately I think I would choose the rear diff first, as that is the most crucial piece that we did not get on our USDM cars. On the other hand, never driven a car with just the ACD tune and no rear diff, so hard to say.
I had no idea you guys did ACD tuning as well. I definitely want to look into that too.
Has anyone here done any of the plate upgrades to the rear diff and the ACD tune? Would you suggest doing one over the other, or just doing both, and why? I just finally got my EVO running great again after a 2.5 year nightmare, and I'm getting it track worthy again.
Has anyone here done any of the plate upgrades to the rear diff and the ACD tune? Would you suggest doing one over the other, or just doing both, and why? I just finally got my EVO running great again after a 2.5 year nightmare, and I'm getting it track worthy again.
I'm trying...LOL
just to add to this - I've never driven a car with just the stock diff restacked, but I'm almost certain it's not enough. I think my cusco is about right for how aggressive a mechanical rear diff should be on these cars and it's got as many plates in it as an os giken