Steering Feel & Pull Drift Compensation (PDC)

[Hinch42]

Looking to hopefully start a discussion in the Mustang community regarding PDC. Pull drift compensation has been a heavy topic in the Focus RS and F-150 worlds for a while but I found little info on it for mustangs.
This past weekend I finally got ahold of Forscan and all of its features. Digging through the interwebs in the F150 forscan spreadsheets I dug into the Power Steering Control Module PSCM and found pull drift compensation. Curious, I went out to my car, disabled it, and went for a drive. This car drives totally different! After building out the suspension on my S550 I always found myself dissatisfied with the car- particularly the steering. Anytime I would come to a stop the steering would basically become loose and aggressively follow any rut in the road. Also, while passing at HWY speeds, the car felt darty and erratic with generally poor steering compared to other sports cars. I’ve ventured down the rabbit hole of wheel bearings, bent wheels, and much else. Id like to hear others opinions on this and see, by chance, if anyone wants to confirm my findings with their car. I found a few other settings like “soft end stops” and “active return” but did not bother- although I now seem to wonder what would happen if they too were switched off.

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[Buldawg76]

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[lugbolt]

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[KingKona]

You're not actually explaining what difference in steering was created/achieved by shutting off the PDC.

Just that it "...drives totally different!" and "....I was absolutely blown away..."

Also, it would be very helpful if you put in your sig line what mods you've done, and the basics of your car as-built. I'd like to know what "......completely building out the suspension...." means.

 

[Hinch42]

You're not actually explaining what difference in steering was created.

My bad. It totally eliminated the inconsistencies in feel and steering weight I would get in a number of situations. Like I described, the car would follow ruts and as coming to a stop the steering would become loose? Also when hitting bumps/imperfections at speed 50-60+ the steering would become instantly loose at the point when the front wheels impacted the road imperfection. It’s a hard feeling to describe besides saying it did not inspire confidence. Now, after turning PDC off, the steering remains CONSISTENT in all conditions relating to effort input and communication. No more tiny minute adjustments mid-corner when running canyons and also no more dartiness/erratic behavior when changing lanes. One thing I always found after increasing front tire width, decreasing wheel weight (rotating mass) and modding the front suspension was that the steering almost felt like it was fighting itself- correcting for the wider tire but then overcorrecting leading me(the driver) to intervene. This meant that on mostly any road surface (especially rough roads) I found myself having to constantly make minute adjustments to correct for what I think was the pull drift. Take a look at the Focus RS forums. I had a couple family members who also have seat time in ///M and RS cars take it for a drive and they agree with me that steering feel has improved. I would like to note that with PDC off you will find yourself having to correct for more road imperfections but it’s in a predictable manner. I’d prefer more communication/feedback/control of the wheel than to let the system “think” what’s necessary. This never really became an issue until suspension mods making me think it’s somewhat related to the cars PSCM not agreeing with my mods so much.

Also, tried to list my mods in sig line. That’s mostly all of them- I’m sure I’m blanking on a few things. This car has been pieced together in a few stages like most here.

 

[Mike Pfeifer]

Interesting. Will be watching this for sure.

 

[Hinch42]

For everyone wanting some more info, I did some digging today. In my '18 non PP car I had PDC, soft end stops, and active return enabled in my asbuilt from the factory. I did try to enable active nibble control (ANC) but I could not get the car to retain the changes after a key cycle. I'm unaware if this is affected by me having PDC off. Some other guys in the F150 forums tried to enable ANC as well but experienced the same thing as me. I also feel like, in our application, ANC would not be beneficial as, in concept, it seems to reduce feedback to the wheel.

I also did some more driving today and noticed another area of improvement. When exiting the road onto something like a driveway, where there can be a dip/transition, the front wheels no longer seem to "fall" into the dip. The wheel stays firm in my hand pointing where I told it to point- no negative feedback. Also still noticing the improvement when changing lanes on a crowned road at high speed.

I have not played around with the soft end returns or active return settings. I do not have a lot of info on these features although I do have an interesting point. In the F150 forums, some owners of newer, higher trim (lariat/platinum) trucks say that they have soft end returns and active return enabled. Some owners of older trucks or lower trim trucks seem to have these features disabled. I would be interested in experimenting with these features if anyone has some more info on them.

I also had the idea to look into the PSCM as built for PP2 and GT350 cars to see what their settings are. I will report back when I do.

Some people in the F150 forums noticed a significant improvement by disabling PDC and re-enabling after a week or so. I do plan to re-enable mine to see if it improves although at this point I have no reservations keeping it off.

Does anyone with forscan and an altered suspension geometry want to try disabling PDC and reporting back? The code line changes in my first post worked on my '18 car so it should work for '15-'18 cars. I'm unaware for '19/'20/'21 cars as I know as built data revisions occurred for some of those years.

Also here are some links to F150 and Focus RS forums about PDC:
https://www.f150forum.com/f118/pull-drift-compensation-elimination-443737/

https://www.f150forum.com/f118/forscan-pscm-epas-changes-434605/

https://www.focusrsoc.com/threads/pull-drift-compensation-turned-off.323298/

https://www.focusrs.org/threads/disabling-annoying-stuff-pdc-feng-with-daftracing-vm.122387/

 

[K4fxd]

OK I tried this today. I disabled the soft stops (active return) and the PDC. I don't know what ANC is or what parameter it is. I'd like to see if my car takes the setting.

I was able to push the car on an on ramp that I thought caused bad bump steer, well my bump steer was the rack setting. It didn't totally go away but it is more normal feeling to me. Just slight movement in the steering wheel vs large movements. It has better road feel a lot closer to the C6 vette feel.

The bad;

When the rear steps out due to throttle or whatever, it was easy to catch by just letting go of the wheel, so PDC or Active return does do something for driver aid. It still works just slower. I suppose I will want to add some more caster to get some of this back.

I think I will reactivate "active return" and see what this does. I may not need caster adjusters.

I will update if I find other things good or bad.

Thanks for starting this thread.

 

[K4fxd]

Looking to hopefully start a discussion in the Mustang community regarding PDC. Pull drift compensation has been a heavy topic in the Focus RS and F-150 worlds for a while but I found little info on it for mustangs.
This past weekend I finally got ahold of Forscan and all of its features. Digging through the interwebs in the F150 forscan spreadsheets I dug into the Power Steering Control Module PSCM and found pull drift compensation. Curious, I went out to my car, disabled it, and went for a drive. This car drives totally different! I was absolutely blown away. After (EDIT- not trying to get into a discussion of what constitutes a built suspension) building out the suspension on my S550 in the pursuit of creating something inspired by the likes of ///M, RS, and AMG I always found myself dissatisfied with the car- particularly the steering. Anytime I would come to a stop the steering would basically become loose and aggressively follow any rut in the road. Also, while passing at HWY speeds, the car felt darty and erratic with generally poor steering compared to other sports cars. I’ve ventured down the rabbit hole of wheel bearings, bent wheels, and much else. I’ve owned ///M examples in the past and have plenty of seat time in both them and Audi’s RS variants and this car could never compete in terms of steering feedback and confidence. After turning PDC off through Forscan, I can confidently say this car handles AND feels like a true competitor for the aforementioned cars. Id like to hear others opinions on this and see, by chance, if anyone wants to confirm my findings with their car. I found a few other settings like “soft end stops” and “active return” but did not bother- although I now seem to wonder what would happen if they too were switched off.

What software is that screenshot from?

 

[Cobra Jet]

Looking to hopefully start a discussion in the Mustang community regarding PDC. Pull drift compensation has been a heavy topic in the Focus RS and F-150 worlds for a while but I found little info on it for mustangs.
This past weekend I finally got ahold of Forscan and all of its features. Digging through the interwebs in the F150 forscan spreadsheets I dug into the Power Steering Control Module PSCM and found pull drift compensation. Curious, I went out to my car, disabled it, and went for a drive. This car drives totally different! I was absolutely blown away. After (EDIT- not trying to get into a discussion of what constitutes a built suspension) building out the suspension on my S550 in the pursuit of creating something inspired by the likes of ///M, RS, and AMG I always found myself dissatisfied with the car- particularly the steering. Anytime I would come to a stop the steering would basically become loose and aggressively follow any rut in the road. Also, while passing at HWY speeds, the car felt darty and erratic with generally poor steering compared to other sports cars. I’ve ventured down the rabbit hole of wheel bearings, bent wheels, and much else. I’ve owned ///M examples in the past and have plenty of seat time in both them and Audi’s RS variants and this car could never compete in terms of steering feedback and confidence. After turning PDC off through Forscan, I can confidently say this car handles AND feels like a true competitor for the aforementioned cars. Id like to hear others opinions on this and see, by chance, if anyone wants to confirm my findings with their car. I found a few other settings like “soft end stops” and “active return” but did not bother- although I now seem to wonder what would happen if they too were switched off.

Interesting.

I had compiled this thread a bit ago for EPAS/PSCM info since not many folks really know anything about the S550's "modem steering tech".
https://www.mustang6g.com/forums/threads/s550-epas-pscm-tech-accumulation.160616/

There may be something of interest In it for you and your research.

I had also questioned very early on if anyone knew how to reprogram an existing EPAS unit using Forscan to match that of a PP2, GT350, GT500, Mach 1, Etc - because the EPAS/PSCM calibrations are different between the S550 platforms. You may be hitting on or getting close to the answer to my questions...

Do you see anything in Forscan that is identifying the calibration such as for a GT, PP1, PP2, etc?

 

[K4fxd]

Do you see anything in Forscan that is identifying the calibration such as for a GT, PP1, PP2, etc?

I've compared a few VIn's and only found differences due to model year. 15 to 17 are all the same and 18 up so far have been the same. Gt350, mach bullit , pp1 pp2. All the same

I haven't looked further than the PSCM and there might be other modules controlling the modes.

Any ideas where to look? SCCM?

Whatever software he took a screen shot of I'd like to have as it puts a description of every line.

 

[Mike Pfeifer]

That looks like it’s just a spreadsheet maybe?

 

[K4fxd]

That looks like it’s just a spreadsheet maybe?

I think you are right.

 

[Hinch42]

Sorry for the late reply. Its exciting to see some people in the Mustang world talking about this! That screen shot is from the huge F150 spreadsheet. I will link below.

Also, @K4fxd thanks for trying the line codes out. Happy to hear I'm not the only one that noticed a difference. If you don't mind, is your suspension modded? I'm thinking theres a correlation between altered suspension geometry and the PDC software not working correctly. Also, when you changed the soft end stops did you also change the active return line? As I'm understanding these settings work in conjunction with one another. If one is enabled the other needs to be enabled. If one is disabled the other needs to be disabled. Since you tried this and your steering did not seem to implode I think I'm going to give this a shot as well. So far I have only disabled PDC.

I have NOT re-enabled my PDC so far. I've been messing with suspension tuning for the past week. I am interested in re-enabling soon to see if it makes it better as some reported in the F150 forums.

As for the GT350/PP2 calibrations. I have not had the chance to track down their asbulit yet. I see someone did and it appears there is no differences in the PSCM module. I have a feeling we're missing something in relation to these calibrations. Forscan appears to be showing us the entire modules code makeup so I'm not sure if these calibrations are in a different module or not. Very interested in this though. @Cobra Jet your thread is what convinced me to dig further into this! I think we're on the right track.

 

[Hinch42]

Also, am I missing something or do some of you NOT have access to the PSCM in your Forscan asbuilt?

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