ACD Tuning Options - USDM CT9As, Read!
had another autocross today.. more of the same - power oversteer lol. still ran in snow (rain) mode though, autocross in my area tends to get pretty tight. I should just go and try it someday though, but i'm still on all season tires which is killing me
They will both help with promoting exit oversteer. I would honestly do the rear diff first, especially if you autox. The rear diff will have less negative side effects, like the binding issue with the race flash, and it will also give you a freshened up rear diff. With the flash your still working with a worn rear diff, that may or may not be working at its best depending on condition.
Binding issue?
I have the ACD reflash from Gruppe-S.
I run on 285/30/18 Hoosiers... the ACD sends the power to the back of the car as it says. However if you have a rear wheel in the air still...you're going to be laying down fatty tracks. The rear diff in my car has seen a lot of power (540whp) and a lot of abuse... its more or less an open differential now (most likely yours is too!)
The ACD splits the torque 50/50 when we would get on throttle coming up on corner exit. PRIOR to the flash we would do FWD burnouts until halfway down the straight and then the ACD would send the power to the rear and we would then accelerate.
My thought was...if we send the power to the rear sooner...we can push our way out of the corners and we'll rotate (oversteer)! wrong. We were faster overall, but worse off when it came time to put the power down. The torque is split front and rear (400wtrq) 200 up front and 200 to the rear. Since the inside rear is in the air and my Salisbury (clutch) type rear diff is wasted...acting like an OPEN diff. 0 torque x anything is still zero! So the rear end is putting down NO power. And we robbed 200 lb ft from the front tires to do so.
So instead of being a 400lb ft FWD car... we're now a 200 lb 3 wheel car doing INSIDE rear tire burnouts on corner exit leaving clouds of white smoke.
It didn't sound or feel good on the rear diff. I think Mitsu engineers definitely were on the right track with preserving the drivetrain with their OEM flash CONSIDERING the 3 wheel motion that we were doing.
NOW. That you have the impression that this is a bad mod and you're going to ish your drivetrain all over the track....
Coupled with the TRE diff or a fully functioning rebuilt rear diff.... THIS MOD WILL BE MAGIC. With pixie dust and all that jazz.
Cliff Notes.
ACD flash without rear diff = marginal benefit.
ACD flash WITH TRE rear diff = MAGIC.
I have the ACD reflash from Gruppe-S.
I run on 285/30/18 Hoosiers... the ACD sends the power to the back of the car as it says. However if you have a rear wheel in the air still...you're going to be laying down fatty tracks. The rear diff in my car has seen a lot of power (540whp) and a lot of abuse... its more or less an open differential now (most likely yours is too!)
The ACD splits the torque 50/50 when we would get on throttle coming up on corner exit. PRIOR to the flash we would do FWD burnouts until halfway down the straight and then the ACD would send the power to the rear and we would then accelerate.
My thought was...if we send the power to the rear sooner...we can push our way out of the corners and we'll rotate (oversteer)! wrong. We were faster overall, but worse off when it came time to put the power down. The torque is split front and rear (400wtrq) 200 up front and 200 to the rear. Since the inside rear is in the air and my Salisbury (clutch) type rear diff is wasted...acting like an OPEN diff. 0 torque x anything is still zero! So the rear end is putting down NO power. And we robbed 200 lb ft from the front tires to do so.
So instead of being a 400lb ft FWD car... we're now a 200 lb 3 wheel car doing INSIDE rear tire burnouts on corner exit leaving clouds of white smoke.
It didn't sound or feel good on the rear diff. I think Mitsu engineers definitely were on the right track with preserving the drivetrain with their OEM flash CONSIDERING the 3 wheel motion that we were doing.
NOW. That you have the impression that this is a bad mod and you're going to ish your drivetrain all over the track....
Coupled with the TRE diff or a fully functioning rebuilt rear diff.... THIS MOD WILL BE MAGIC. With pixie dust and all that jazz.
Cliff Notes.
ACD flash without rear diff = marginal benefit.
ACD flash WITH TRE rear diff = MAGIC.
Last edited by R/TErnie; Jul 20, 2010 at 09:49 PM.
Binding issue?
I have the ACD reflash from Gruppe-S.
I run on 285/30/18 Hoosiers... the ACD sends the power to the back of the car as it says. However if you have a rear wheel in the air still...you're going to be laying down fatty tracks. The rear diff in my car has seen a lot of power (540whp) and a lot of abuse... its more or less an open differential now (most likely yours is too!)
The ACD splits the torque 50/50 when we would get on throttle coming up on corner exit. PRIOR to the flash we would do FWD burnouts until halfway down the straight and then the ACD would send the power to the rear and we would then accelerate.
My thought was...if we send the power to the rear sooner...we can push our way out of the corners and we'll rotate (oversteer)! wrong. We were faster overall, but worse off when it came time to put the power down. The torque is split front and rear (400wtrq) 200 up front and 200 to the rear. Since the inside rear is in the air and my Salisbury (clutch) type rear diff is wasted...acting like an OPEN diff. 0 torque x anything is still zero! So the rear end is putting down NO power. And we robbed 200 lb ft from the front tires to do so.
So instead of being a 400lb ft FWD car... we're now a 200 lb 3 wheel car doing INSIDE rear tire burnouts on corner exit leaving clouds of white smoke.
It didn't sound or feel good on the rear diff. I think Mitsu engineers definitely were on the right track with preserving the drivetrain with their OEM flash CONSIDERING the 3 wheel motion that we were doing.
NOW. That you have the impression that this is a bad mod and you're going to ish your drivetrain all over the track....
Coupled with the TRE diff or a fully functioning rebuilt rear diff.... THIS MOD WILL BE MAGIC. With pixie dust and all that jazz.
Cliff Notes.
ACD flash without rear diff = marginal benefit.
ACD flash WITH TRE rear diff = MAGIC.
I have the ACD reflash from Gruppe-S.
I run on 285/30/18 Hoosiers... the ACD sends the power to the back of the car as it says. However if you have a rear wheel in the air still...you're going to be laying down fatty tracks. The rear diff in my car has seen a lot of power (540whp) and a lot of abuse... its more or less an open differential now (most likely yours is too!)
The ACD splits the torque 50/50 when we would get on throttle coming up on corner exit. PRIOR to the flash we would do FWD burnouts until halfway down the straight and then the ACD would send the power to the rear and we would then accelerate.
My thought was...if we send the power to the rear sooner...we can push our way out of the corners and we'll rotate (oversteer)! wrong. We were faster overall, but worse off when it came time to put the power down. The torque is split front and rear (400wtrq) 200 up front and 200 to the rear. Since the inside rear is in the air and my Salisbury (clutch) type rear diff is wasted...acting like an OPEN diff. 0 torque x anything is still zero! So the rear end is putting down NO power. And we robbed 200 lb ft from the front tires to do so.
So instead of being a 400lb ft FWD car... we're now a 200 lb 3 wheel car doing INSIDE rear tire burnouts on corner exit leaving clouds of white smoke.
It didn't sound or feel good on the rear diff. I think Mitsu engineers definitely were on the right track with preserving the drivetrain with their OEM flash CONSIDERING the 3 wheel motion that we were doing.
NOW. That you have the impression that this is a bad mod and you're going to ish your drivetrain all over the track....
Coupled with the TRE diff or a fully functioning rebuilt rear diff.... THIS MOD WILL BE MAGIC. With pixie dust and all that jazz.
Cliff Notes.
ACD flash without rear diff = marginal benefit.
ACD flash WITH TRE rear diff = MAGIC.
also in that sense i guess while the tre diff would help it'd still be better to maybe switch back to stock sway bars, if this continues to be an issue.. thats why i returned my aftermarkets and decided to go with stock. a few other guys i heard of doing time attack did the same thing after upgrading to the tre (or cusco).
the binding issue comes from the front and rear wheels being locked together so aggressively that for tight turns the evo kind of resists turning in
but yea the drivetrain is always sending power, its just the acd determines the lock between the front and rear wheels
power should be going to all four wheels regardless of where the wheels are and what flash u have.. the flash just makes the locking between the front and rear wheels more aggressive and quicker.. if it's in the air and the rear diff is bad i guess you would just be losing the torque (not to mention other things) that goes to the lifted rear wheel.
also in that sense i guess while the tre diff would help it'd still be better to maybe switch back to stock sway bars, if this continues to be an issue.. thats why i returned my aftermarkets and decided to go with stock. a few other guys i heard of doing time attack did the same thing after upgrading to the tre (or cusco).
the binding issue comes from the front and rear wheels being locked together so aggressively that for tight turns the evo kind of resists turning in
but yea the drivetrain is always sending power, its just the acd determines the lock between the front and rear wheels
also in that sense i guess while the tre diff would help it'd still be better to maybe switch back to stock sway bars, if this continues to be an issue.. thats why i returned my aftermarkets and decided to go with stock. a few other guys i heard of doing time attack did the same thing after upgrading to the tre (or cusco).
the binding issue comes from the front and rear wheels being locked together so aggressively that for tight turns the evo kind of resists turning in
but yea the drivetrain is always sending power, its just the acd determines the lock between the front and rear wheels
Can someone tell me how you have the inside rear tire off the ground while accellerating?? Seems impossible. I would think the weight would shift to the rear and it would squat down. Also, if you are accellerating full throttle in a corner - your entry speed was probably too low??
I can assure you...as well as many other people watching...as evident by the smoke and black lines that I was burning the inside rear tire on corner exit. (285/30/18 R6's BILLOWING WHITE SMOKE) and no we're not rubbing.
If you get on throttle before the corner is finished...our tire is in the air. I watched it happen myself.
http://www.vimeo.com/13417056
turn the volume WAY up and listen to the car do a burnout. You can audibly hear it upon corner exit. The corners about 5-6 from the finish line are where its the worst... not to mention turn 1, 2, and 3.
@ time 1:27 its pretty bad 2:11, 2:38, 3:16, 3:22 etc.
To fix it...
Front springs 10k to 12k
rear springs from 12k to 16k
25mm rear bar to stock ARB
Entry speed is definitely not low.
Evolutionary...what size front bar do you have?
If you get on throttle before the corner is finished...our tire is in the air. I watched it happen myself.
http://www.vimeo.com/13417056
turn the volume WAY up and listen to the car do a burnout. You can audibly hear it upon corner exit. The corners about 5-6 from the finish line are where its the worst... not to mention turn 1, 2, and 3.
@ time 1:27 its pretty bad 2:11, 2:38, 3:16, 3:22 etc.
To fix it...
Front springs 10k to 12k
rear springs from 12k to 16k
25mm rear bar to stock ARB
Entry speed is definitely not low.
Evolutionary...what size front bar do you have?
Last edited by R/TErnie; Jul 21, 2010 at 08:47 PM.
Wow, that looks more like an autocross than a road course! 
Cart track?
My rear rates are close to yours and I have a rear bar set full stiff. My front rates are much higher than yours and I also have the Tanabe front bar which is stiffer than stock. If you stiffen up the front it will put your rear tire down. My car now only lifts the rear tire maybe an inch, but that's only on decel into a corner (trail braking). Steady state hard cornering both front and rear are barely touching the ground, and as soon as I get on the gas the rear is planted. . .
Sounds to me like the main problem you are having is a result of a weak rear diff. . . if it were not slipping it would put power to the outside rear, thus giving more rearward weight transfer and more overall rear grip. . .
Cart track? My rear rates are close to yours and I have a rear bar set full stiff. My front rates are much higher than yours and I also have the Tanabe front bar which is stiffer than stock. If you stiffen up the front it will put your rear tire down. My car now only lifts the rear tire maybe an inch, but that's only on decel into a corner (trail braking). Steady state hard cornering both front and rear are barely touching the ground, and as soon as I get on the gas the rear is planted. . .
Sounds to me like the main problem you are having is a result of a weak rear diff. . . if it were not slipping it would put power to the outside rear, thus giving more rearward weight transfer and more overall rear grip. . .
I can assure you...as well as many other people watching...as evident by the smoke and black lines that I was burning the inside rear tire on corner exit. (285/30/18 R6's BILLOWING WHITE SMOKE) and no we're not rubbing.
If you get on throttle before the corner is finished...our tire is in the air. I watched it happen myself.
http://www.vimeo.com/13417056
turn the volume WAY up and listen to the car do a burnout. You can audibly hear it upon corner exit. The corners about 5-6 from the finish line are where its the worst... not to mention turn 1, 2, and 3.
@ time 1:27 its pretty bad 2:11, 2:38, 3:16, 3:22 etc.
To fix it...
Front springs 10k to 12k
rear springs from 12k to 16k
25mm rear bar to stock ARB
Entry speed is definitely not low.
Evolutionary...what size front bar do you have?
If you get on throttle before the corner is finished...our tire is in the air. I watched it happen myself.
http://www.vimeo.com/13417056
turn the volume WAY up and listen to the car do a burnout. You can audibly hear it upon corner exit. The corners about 5-6 from the finish line are where its the worst... not to mention turn 1, 2, and 3.
@ time 1:27 its pretty bad 2:11, 2:38, 3:16, 3:22 etc.
To fix it...
Front springs 10k to 12k
rear springs from 12k to 16k
25mm rear bar to stock ARB
Entry speed is definitely not low.
Evolutionary...what size front bar do you have?
A Quaife would be better IMO, but for the money... I'd rather make more power. 
Evolutionary... would you recommend running a stiffer front bar for that track?
12kF
16kR
stock rear bar with extra holes drilled in it for adjustment.
Should I add a front ARB in your opinion?
The car is on jackstands right now....and both ends are apart lol. Diff is out. It's ready for a remodel!