Anyone else notice that when the acd is changed from Tarmac mode to either snow or gravel that timing gets pulled? It was raining here a little today so I thought I would try to see how the car responded in a different acd mode and I was also logging with EvoScan. When I looked at a third gear pull I was surprised to discover that my timing was like 4-5 pretty much accross the rpm range. After a few minutes (and a few WTF's) it dawned on me that maybe the ACD mode in Gravel was telling the ECU to pull timing for lower likelihood of losing traction or some other unknown reason. I put the ACD selector back in tarmac mode and logged steady state throttle and changed ACD modes and the next log proved my thoughts correct. Although I have not spent a lot of time on this it looks like both gravel and snow pull the same amount of timing and the change happens "on the fly" because I started in tarmac then went to gravel and snow and back to tarmac and could clearly see my timing correspond to the correct cells after switching back to Tarmac. Maybe someone else could verify to make sure I am not crazy in what I experienced.

Anyway someone who is into it or one of the developers might be able to look into this further I could see where it might be beneficial to push a button and alter timing without having to reflash but I also realize the ACD parameters change.

PS Maybe this is old news I didn't bother searching or anything

 

nice find

 

Thanks,

this could be used If not for anything like excessive knocking from bad gas then changing acd mode would lower timing until bad fuel drained or burned up.

wow does this make sense hope so kinda tired

 

wow that would be pretty amazing.

I wonder what the advantage to ACD of the car making less power... interesting

might be worthwhile as a map selector - but as you say the ACD characteristics would change as well which isn't ideal...

 

My thoughts are that by making less power you are less prone to wheelspin which increase likelihood of losing control etc. etc..

Here is the link to the Sticky on the ACD system it explains it well..

https://www.evolutionm.net/forums/sh...d.php?t=175195

a quote from the ACD sticky..

D. How the Tarmac/Gravel/Snow switch influences the ACD

Despite popular belief, this switch DOES NOT change the torque split. The differential is geared at 50:50 and cannot be changed by the push of a button. What this switch actually does is quite simple. Each setting determines how long the ACD will delay in freeing the center differential after a steering input is made. In addition, it will determine how much locking force the ACD will exhibit on the clutch pack and center differential. (10) (11)

Tarmac is the setting to be used in dry, paved conditions. In this setting, the ACD will almost immediately allow the center differential to go into a free state upon detecting a steering input. Additionally, this mode provides the strongest limited-slip clamping force of the three modes. (7) (12)

Gravel is the setting designed for wet or loose roads. In this setting, the ACD will delay in freeing the center differential for a moment (possibly 2-3 seconds). Of the three modes, this one has the second strongest clamping force. (7) (12)

Snow is the setting designed for, you guessed it, snow. In this setting, the ACD will delay in freeing the center differential for much longer than the other two settings (possibly 4-5 seconds). Of the three modes, this one also provides the least amount of clamping power. (7) (12)

 

interesting...Do you have an 8 or a 9??? I have an VIII but never logged in a different mode...i have noticed at the drag strip though that when i try to shift over 6500 i get completely locked out of gear until the revs come down....

Could this be why the IX's have three timing maps??? Three different modes??? If you have a IX then this could get us one step closer to the three different timing maps....

 

nah the timing maps are todo with Mivec advance or retard...

 

Gotcha! Thanks!

 

Shizzle....

I wonder if while my ACD is messed up, if my car is running timing in the "reduced" mode or not... I don't believe it is, but I haven't logged it since it's been messed up yet..

 

Can you get better gas mileage in snow mode? lol

 

My gas mileage seems to decrease in gravel or snow as opposed to tarmac.

SQ

 

Alan I do have a 9 and on a side note I live nearby you in SoCal N. San Diego county But anyway I thik because so much timing is pulled that would contribute to poor mileage. although you are making less power the engine is not running anywhere near max. efficiency. Those that know "cam speak" and ignition timing could explain it better. the timing is pretty flat across the board and does not seem load dependent like being able to match up to anything on the existing timing maps.

I believe when the ACD button is pushed it activates a section of the ECU to tell it to use X-X degrees of timing and x seems to equal 4-5 degrees based on my limited testing and logging.
All I do know for now is that power runs with ACD in anything other than Tarmac mode for me will not make as much power due to less timing. If anyone likes I can try to post logs but my laptop is in the car as the car owns the laptop

 

I guess dyno sheets with the only change being ACD would be good... Still an interesting concept thou

 

good info

 

well i'll be damned. very interesting find.