When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If you have the Tactrix OP 2.0 and ECUFlash all you need is a wire to one of the pins on the ACD ECU. You plug the other end into the flash port on the OP 2.0 and then you can read the ACD, change the tables, and flash it back in the car. It takes 10 minutes to set up. Everyone should be doing it it's so easy.
Imagine you are braking hard for an auto-x turn. As you begin your turn in, the ACD opens fully, and at maximum lateral acceleration, you lift the rear inside wheel. Before the apex, you still are turning hard, waggling that rear inside wheel, and yet you need to get on the gas, to finish the corner off and, to get maximum speed down the next short straight.
As you mash the gas pedal, the ACD stays open, sending 50% of available torque to the front wheels, which try to pull you out of the corner, contributing to understeer. Most of the other 50% of available torque is used to accelerate that inner rear wheel waggling in the air. The outer rear wheel only gets whatever torque was required to overcome the friction of the rear LSD clutches.
The waggling, spinning wheel doesn't lock up your rear LSD, or finish off the corner, or push you out onto the straight. Almost all 50% or the torque supplied by the ACD to the rear axle is wasted spinning the inner rear wheel. Its speed quickly exceeds that of the fronts and the outer rear.
The part of the ACD supplying torque to accelerate your waggling wheel is now spinning much faster than the part supplying torque to the front. At this point as you unwind the steering, the ACD starts to lock up. The front and rear halves of the ACD are forced to rotate at the same speed and the torque lost to the waggling wheel is returned to the drive drain. Deceleration of the inner rear wheel forces the spider gear pins up the ramp in the rear diff, compressing the clutch plates and locking up the rear LSD, Most of the wasted torque is redirected to the outside rear wheel, you finish the corner faster, get maximum acceleration out of it, and maximum speed on the next straight.
Tuning the A maps to lock up sooner when throttle is applied can increase your speed out of the corners.
Look at the two A maps attached below. The top one is stock and the bottom one is the Ralliart K2 tarmac rally map. Look how much sooner and harder the K2 locks the ACD.
Hey raptord - can you post your ACD maps so we can learn from your own experience?
Don't have anything worth posting right now. If I remember correctly the map I have on the car right now is the one Merlin posted a while back, which was moderately tuned. Hopefully this spring/summer I'll get around to make a better harness for reflashing and do some tuning of my own.
If you have the Tactrix OP 2.0 and ECUFlash all you need is a wire to one of the pins on the ACD ECU. You plug the other end into the flash port on the OP 2.0 and then you can read the ACD, change the tables, and flash it back in the car. It takes 10 minutes to set up. Everyone should be doing it it's so easy.
anyone have the link to the how-to? i've been searching for two days LOL. thanks in advance and sorry if i'm sidebusting
Here are my latest tarmac A/B/C maps. I increased the throttle lockup adder some more and I'm now very happy with the drive out of corners in the wet and dry . (NB: I have the TRE Maxlock rear diff).
1. Year: 2005
2. Market: USDM
3. Model: Evo 8 GSR
4. ACD only
5. Increased lockup on acceleration out of the corners speeds rotation through over steer which finishes the corner off well.
Last edited by CDrinkH2O; Jan 23, 2016 at 11:15 AM.
Reason: Added Year/Market/Model/etc.
Bringing this thread back to life since I decided to start playing with the ACD myself. I want to get a better feel for what changes effect the cars behavior and will try to get the pump pressure logged with RaceCapature/Solostorm to see what the pressure is vs car dynamic. I have my own assumptions of what the ACD SHOULD probably do and what it specifically SHOULDNT but need to try and induce those scenarios.
First test, and I hope this is something the ECU is cool with, is to make all 3 maps the same and vary just one of the tables for the 3 settings with getting increasingly more aggressive in some way. So I can run all 3 and get a feel on course + data in what feels best.
Im starting with the old merlin tune and just changing the lockup vs tps. I think from my reading this one is actually 0 = open, 30 = full pressure? One bit Im thinking of doing is actually lowering the lockup on launch for the first few feet to give one end the ability to spin and then adding in pressure as speed picks up but relatively quickly. My thinking is if the front spins a little it may lead to less chance of bog or broken parts and then the ACD can ramp in to get more and more to the rear. I'll think about this one a bit more, but for now I havent added it in.
Heres the first bit of change Im trying. Only change Speed vs TPS, with 0 below 50% throttle and 50-90% ramping from 0 to 10, 15, and 20. 100% just holding 90% since there may be some error in the TPS or my foot actually hitting 100% but at 90% you might as well be asking for 100%.
I have no care about gravel and snow specifically, so I hope this pans out so I can work on 3 incremental steps when I change things.
Thinking about it a bit, I was wondering what else could be going on in the background of the code that would make the 3 settings different. All I can see is whats available in the XML.
Just looking through things, it seems Table E1.1 and E2.1 are different than E1.2, E1.3, E2.2, and E2.3. Any clue what the E tables are for?
.
EDIT: Ok, looks like this is part of the lock scaling factors. Makes sense gravel/snow would try and lock up more at lower speed than tarmac. Will try shifting them all the the .1 values.
Yes mate, if you're wanting to make and feel for specific differences across the modes when you tune them, then yes, you have to "baseline" all three modes (T, G, S) to all the same settings. The ECU is fine with you doing this, you just need to find all tables and addresses that relate to the specific modes. Depending on your XML, there may be some hidden changes (unknown defined tables) that you will have to make to ensure that there's nothing else playing a role to the change that you are feeling when you change modes. But what you're doing is exactly what I do. I baseline my modes so they are all the same, and then make table specific changes and see what one feels/works best.
To answer your question above, the E tables are a coefficient to the D tables. ie, D result x E result = output.
With your throttle maps, you can push the values of lock all the way to 100%, but I've found anything over about 35% has negative effects.
I'm currently working my way through the ROM, but I'm starting to get out of my depth with following the code and need help. What I can tell you though is the P map, the big 9x36 table plays a massive role to the handling of the car and is not an AYC map. Accel and Decel tables are not that either. They are a config 1 or config 2 table set by whether pin 50 is grounded or not. What I've found is *1.* tables = w/AYC (pin 50 n/c), and *2.* tables = ACD only/no ABS (pin 50 grounded).
Yes mate, if you're wanting to make and feel for specific differences across the modes when you tune them, then yes, you have to "baseline" all three modes (T, G, S) to all the same settings. The ECU is fine with you doing this, you just need to find all tables and addresses that relate to the specific modes. Depending on your XML, there may be some hidden changes (unknown defined tables) that you will have to make to ensure that there's nothing else playing a role to the change that you are feeling when you change modes. But what you're doing is exactly what I do. I baseline my modes so they are all the same, and then make table specific changes and see what one feels/works best.
To answer your question above, the E tables are a coefficient to the D tables. ie, D result x E result = output.
With your throttle maps, you can push the values of lock all the way to 100%, but I've found anything over about 35% has negative effects.
I'm currently working my way through the ROM, but I'm starting to get out of my depth with following the code and need help. What I can tell you though is the P map, the big 9x36 table plays a massive role to the handling of the car and is not an AYC map. Accel and Decel tables are not that either. They are a config 1 or config 2 table set by whether pin 50 is grounded or not. What I've found is *1.* tables = w/AYC (pin 50 n/c), and *2.* tables = ACD only/no ABS (pin 50 grounded).
Interesting stuff on the "accel" and "decel" maps. So sounds like one is basically not used but we make them the same just incase maybe.. Would really be nice to know what the Pmap really does. Seems that one is pretty unknown. Wonder if I try and change it dramatically if I'll see a can log a difference in pressure. Its unfortunate to not have a proper definition though because at this point its just guessing.
I would also like to know if we're missing tables in the XML when trying to make all the maps the same to know if there are some missing to effect the results in me trying to change one at a time.
Jan 6, 2016, 09:14 PM
