What exactly does the Spiffy ADC AYC whatever do?
Sep 27, 2003, 04:44 PM
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Not to be rude, but there is a SEARCH function. Here is some info about ACD and AYC, quoted from Claudius:
"AYC Evos have always been measured as being less performant than non AYC versions. This is due to a certain weight difference between the AYC and the non AYC models (non AYC weighing less) and to the fact that non AYC gives natural handling ad the limit of rear wheel adhesion, when AYC is unnatural.
Without AYC, on corner exit, you can get the car to drift nicely just like you can with RWD cars, only faster.
With AYC, when applying throttle at the rear grip limit on corner exit, you get a loud rattling sound, sometimes hear a tyre squeal, but the back end of the car wont step out. However, the front will now lose traction and you understeer out of the corner (I have yet to meet someone who likes that type of behavior).
You CAN get an AYC equipped car to break traction at the rear, by forcing it (scandinavian flick as if you wanted to spin it) but it feels very strange and insecure; you cannot tell how much the rear will break away beforehand and may get surprised: I once spun my AYC equipped Evo 6 TME on a small track here when I flicked it, it slid ok like 20 - 30° angle, then one rear wheel touched the curb and the car spun immediately and very violently. I took the AYC out after that and now the car is almost perfect, very neutral, high grip, oversteer on demand, etc. "
and
"A lot of people on here started complaining when they heard that the US Evo will not have AYC and ACD, when in fact they have never tried the systems and dont know exactly what they do when actually driving the damn thing.
In fact, telling from the specifications, the US Evo will be the best Evo made, except for the engine, but you can upgrade that to 350 bhp with an exhaust and boost controller, so no worries there. The US Evo is only marginally heavier than the previous Evolution 7 due to even stiffer body and increased fuel tank and a few bits and pieces. It only appears heavier on paper because the weight given in Japan and Europe is without fluids and the US demand the weight to be quoted "ready to go".
The ACD (active center differential) is another thing that sounds good on paper but isnt that great in reality: it allows to vary the speed at which the center differential locks up and thus hw fast the 50/50 front-rear traction is distributed through the transmission. Which could lead you to believe you can set it to handle more aggressively (with an increased oversteer bias) when in fact that isnt possible. On tarmac, you get 50/50 all the time, on the gravel and snow settings, this is slowed down and you have more of a FWD car.
Another point to keep in mind is that "the more electronic BS you have on the car, the more electronic BS can break" (I know someone who replaced the ACD in the UK and paid $1500 - $2000 for that) so the US Evo sounds like it will be as reliable as a 6, with a stiffer body. I couldnt think of a better car than that (stock). "
"AYC Evos have always been measured as being less performant than non AYC versions. This is due to a certain weight difference between the AYC and the non AYC models (non AYC weighing less) and to the fact that non AYC gives natural handling ad the limit of rear wheel adhesion, when AYC is unnatural.
Without AYC, on corner exit, you can get the car to drift nicely just like you can with RWD cars, only faster.
With AYC, when applying throttle at the rear grip limit on corner exit, you get a loud rattling sound, sometimes hear a tyre squeal, but the back end of the car wont step out. However, the front will now lose traction and you understeer out of the corner (I have yet to meet someone who likes that type of behavior).
You CAN get an AYC equipped car to break traction at the rear, by forcing it (scandinavian flick as if you wanted to spin it) but it feels very strange and insecure; you cannot tell how much the rear will break away beforehand and may get surprised: I once spun my AYC equipped Evo 6 TME on a small track here when I flicked it, it slid ok like 20 - 30° angle, then one rear wheel touched the curb and the car spun immediately and very violently. I took the AYC out after that and now the car is almost perfect, very neutral, high grip, oversteer on demand, etc. "
and
"A lot of people on here started complaining when they heard that the US Evo will not have AYC and ACD, when in fact they have never tried the systems and dont know exactly what they do when actually driving the damn thing.
In fact, telling from the specifications, the US Evo will be the best Evo made, except for the engine, but you can upgrade that to 350 bhp with an exhaust and boost controller, so no worries there. The US Evo is only marginally heavier than the previous Evolution 7 due to even stiffer body and increased fuel tank and a few bits and pieces. It only appears heavier on paper because the weight given in Japan and Europe is without fluids and the US demand the weight to be quoted "ready to go".
The ACD (active center differential) is another thing that sounds good on paper but isnt that great in reality: it allows to vary the speed at which the center differential locks up and thus hw fast the 50/50 front-rear traction is distributed through the transmission. Which could lead you to believe you can set it to handle more aggressively (with an increased oversteer bias) when in fact that isnt possible. On tarmac, you get 50/50 all the time, on the gravel and snow settings, this is slowed down and you have more of a FWD car.
Another point to keep in mind is that "the more electronic BS you have on the car, the more electronic BS can break" (I know someone who replaced the ACD in the UK and paid $1500 - $2000 for that) so the US Evo sounds like it will be as reliable as a 6, with a stiffer body. I couldnt think of a better car than that (stock). "
Sep 27, 2003, 04:55 PM
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The Active Center Differential
What it is not :
1. A driver aid.
2. Traction control.
3. Crap.
The Active Center Differential replaces the viscous unit (vcu) in post Evo 6 models. The US evo as you know still has the VCU. As you know, the role of the 'center' diff is to distribute driving force to the front and rear wheels depending on cornering/traction conditions. The torque is fixed mechanically to 50:50 by the gearing, what the ACD does is to regulate the clamping force @ superman speeds!
It consists of a set of hydraulically moved plated clutches that are under the control of the acd/ayc ecu. The goal is to better regulate slippage of the center diff throughout the corner:
1. Entry.... the diff clams up to aid in deceleration/engine braking force to all wheels.
2. Corner ... diff opens to allow for better steering input
3. Exit .... diff locks up to aid in out of corner acceleration.
The ecu is under a 3 preset software strategy, selected by a little button where your foglight button is on the US evo:
Tarmac : highest ultimate locking value, but the diff realeases instantly on turning into a corner
Gravel : medium ultimate locking value, the diff takes longer to release (2-3sec) ... putting more traction to the road.
Snow : lowest ultimate locking value, diff takes 4-5 secs to release.
A UK groupN team tested the pressures/response of this ACD diff and found out that the diff was so fast that normal guages were unable to show the rapid changes in pressure. They came to the conclusion that the ACD reacts as fast as some of the WRC electronic diffs!! It is said that ACD is 3x better in the locking force it can apply than the VCU.
The goal of the ACD is to improve driving response and traction in and out of corners, over the ordinary viscous diff
What it is not :
1. A driver aid.
2. Traction control.
3. Crap.
The Active Center Differential replaces the viscous unit (vcu) in post Evo 6 models. The US evo as you know still has the VCU. As you know, the role of the 'center' diff is to distribute driving force to the front and rear wheels depending on cornering/traction conditions. The torque is fixed mechanically to 50:50 by the gearing, what the ACD does is to regulate the clamping force @ superman speeds!
It consists of a set of hydraulically moved plated clutches that are under the control of the acd/ayc ecu. The goal is to better regulate slippage of the center diff throughout the corner:
1. Entry.... the diff clams up to aid in deceleration/engine braking force to all wheels.
2. Corner ... diff opens to allow for better steering input
3. Exit .... diff locks up to aid in out of corner acceleration.
The ecu is under a 3 preset software strategy, selected by a little button where your foglight button is on the US evo:
Tarmac : highest ultimate locking value, but the diff realeases instantly on turning into a corner
Gravel : medium ultimate locking value, the diff takes longer to release (2-3sec) ... putting more traction to the road.
Snow : lowest ultimate locking value, diff takes 4-5 secs to release.
A UK groupN team tested the pressures/response of this ACD diff and found out that the diff was so fast that normal guages were unable to show the rapid changes in pressure. They came to the conclusion that the ACD reacts as fast as some of the WRC electronic diffs!! It is said that ACD is 3x better in the locking force it can apply than the VCU.
The goal of the ACD is to improve driving response and traction in and out of corners, over the ordinary viscous diff
Last edited by jemm; Sep 27, 2003 at 05:02 PM.
Sep 27, 2003, 05:14 PM
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Active Yaw Control
This has been around since the Evo 4 and has been a somewhat controversial item!
Some folk view it as a driver aid, some view AYC as an overly heavy diff that does nothing but cut short the fun of oversteer!
The AYC consists of a hydraulically controlled multiplate wet clutch (like a motor cycle) that shifts torque between the Left and Right REAR wheels depending on cornering. Its MAIN goal is to reduce Understeer and extend the cornering limits.
In the Evo VII and Evo VIII the system is controlled by the same computer as the ACD, so one should speak about them together. (see pic).
Having owned a evo without AYC for 4 yrs... and now I have it on this car, i can say that i miss the ability to get the back out easily and in a controlled manner ... for example when you want to provoke some oversteer to negotiate a hairpin..... but properly driven, this ayc/acd system makes this car that i have now corner like a mother@#!$er!!!!!! The difference can be seen objectively on the track in Japan where the ayc Evo 8 consistently beats the non ayc RS car in lap times...
p.s. you can change the ACD/AYC ecu to facillitate more spirited (read oversteer) driving!!
This has been around since the Evo 4 and has been a somewhat controversial item!
Some folk view it as a driver aid, some view AYC as an overly heavy diff that does nothing but cut short the fun of oversteer!The AYC consists of a hydraulically controlled multiplate wet clutch (like a motor cycle) that shifts torque between the Left and Right REAR wheels depending on cornering. Its MAIN goal is to reduce Understeer and extend the cornering limits.
In the Evo VII and Evo VIII the system is controlled by the same computer as the ACD, so one should speak about them together. (see pic).
Having owned a evo without AYC for 4 yrs... and now I have it on this car, i can say that i miss the ability to get the back out easily and in a controlled manner ... for example when you want to provoke some oversteer to negotiate a hairpin..... but properly driven, this ayc/acd system makes this car that i have now corner like a mother@#!$er!!!!!! The difference can be seen objectively on the track in Japan where the ayc Evo 8 consistently beats the non ayc RS car in lap times...
p.s. you can change the ACD/AYC ecu to facillitate more spirited (read oversteer) driving!!
Last edited by jemm; Sep 27, 2003 at 05:33 PM.
Sep 27, 2003, 05:23 PM
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With all good and due respect to our buddy Claudius, most of his experience with AYC is in the pre Evo 7 iteration.... the combination of the AYC and ACD is much more seamless, less intrusive and progressive system to drive hard than what was on the Evos 4-6.
Do I think its something that the US market should insist on? NO
its more expensive item and adds weight. I got along fine for 4 yrs without active diffs. And I had a ****load of fun!
US folk : Learn to drive your rear limited slip diff Evo... you will be a better 4wd driver in the long term!
Do I think its something that the US market should insist on? NO
its more expensive item and adds weight. I got along fine for 4 yrs without active diffs. And I had a ****load of fun!
US folk : Learn to drive your rear limited slip diff Evo... you will be a better 4wd driver in the long term!
Last edited by jemm; Sep 27, 2003 at 05:30 PM.
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Sep 27, 2003, 06:36 PM
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Nice to see someone who feels the same way about AYC as me.
I agree with all of jemm points and like to add another about reliablity.
If you're gonna do a lot of racing (track/drag) and have a high powered evo then the AYC is gonna **** itself, it doesn't like big power and i'm guessing it doesn't like repeated standing starts.
I have an evo4 RS and I chose this car with that factor as a main point, aswell as low weight etc.
Theres nothing wrong with the US evo setup, it's probably one of the strongest setup's there is, i'm pretty much using the same setup (kinda) and i've got no complaints.
I agree with all of jemm points and like to add another about reliablity.
If you're gonna do a lot of racing (track/drag) and have a high powered evo then the AYC is gonna **** itself, it doesn't like big power and i'm guessing it doesn't like repeated standing starts.
I have an evo4 RS and I chose this car with that factor as a main point, aswell as low weight etc.
Theres nothing wrong with the US evo setup, it's probably one of the strongest setup's there is, i'm pretty much using the same setup (kinda) and i've got no complaints.
Sep 27, 2003, 06:46 PM
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if Alfred had ACD/AYC, his diffs would have shat themselves a long time ago! Case in point :
http://www.wheelsjamaica.com/wheels_...;threadid=5106
Sep 27, 2003, 06:54 PM
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In one of the Best Motoring videos, I think "The EVO Strikes Back", they show a couple of EVO's equipped with ayc+acd, and a advan rally evo without ayc. You can somewhat see a difference the AYC makes
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