Modding chassis to CS-spec

Racer20 · 09-25-2018, 01:51 PM

Quote:

Originally Posted by melvyn

Quote:

Originally Posted by Racer20

Picked the car up today with the correct CS rear bar and fresh alignment. The bar fixed the roll balance. The suspension balance of the car is quite good now. The steering . . . I'm not so sure about.

For most of the summer, I had the GTS EPS coded in along with my stock suspension. The GTS EPS has a pronounced U-shape to the effort curve . . . it's pretty light on center and builds up quickly off center as the tires load up and lat-g increases. The effort build matched the response of the tires and the rate of load transfer pretty good with this setup. I had no complaints about the steering feel or response.

The CS setup loads the tires and gets to a steady state attitude more quickly, and seems to change direction more quickly as well. The steering effort then needs to build quicker to match this behavior, but so far it doesn't seem to.

When the transient of corner entry is over and the car is leaning on its springs and bars, I want the steering to have the same feeling of taking a set, like I can "lean" against the torque on the wheel and it'll push back firmly and maintain the line. A stable equilibrium between my input torque and the wheel torque imparted by the tires and steering gear if you will. This gives the car a "crisp" response and a sense of solidity and confidence in a corner. I'm not sure this setup is 100% there yet.

I'm going to check the coding again and play with tire pressures a bit, I'll report back if I find anything interesting.

Are you running 19s on front and 20s on rear

No, 19's. Looking at my alignment sheet, it looks like the shop took it upon themselves to set my alignment to non-stock settings since I told them I use the car on the track. So the response of the rear isn't exactly what a CS should be at the moment.

That said, I do this stuff for a living, and while rear toe and 20" wheels will surely affect steering feel and response, I'm not sure either of those changes will improve this particular issue. The F82GTS EPS cal just doesn't seem right for this car.

The last thing I can think of is that we know there's more separation between the M3 and M4 CS than there has been in any other version of the F8X. Maybe the F80CS uses a different EPS cal than the F82CS. Once it stops raining, I'll try VO coding again and see what the vehicle type gets set to.

Racer20 · 09-26-2018, 08:07 PM

Played around with EPS coding today. I don't seem to have F85Comp or F86Comp options to FDL code. I have F82GTS and "veh6", "veh7" and so on to "veh10". I tried setting it back to the F80 standard setting, and so far I like it better. I might try VO Coding the EPS module using the comp or CS typecodes again this weekend to see if I can feel any difference. But for now, the base EPS cal seems to work best with my suspension.

CanAutM3 · 09-26-2018, 09:24 PM

Quote:

Originally Posted by Racer20

Played around with EPS coding today. I don't seem to have F85Comp or F86Comp options to FDL code. I have F82GTS and "veh6", "veh7" and so on to "veh10". I tried setting it back to the F80 standard setting, and so far I like it better. I might try VO Coding the EPS module using the comp or CS typecodes again this weekend to see if I can feel any difference. But for now, the base EPS cal seems to work best with my suspension.

...and tires.

I assume you are running PSS. From what I understand, the CS was optimised around the PSC2, so I believe this must have an effect on how the EPS was calibrated. When I switched from the PSS to the PSC2 on my M4cs, it made a noticeable difference on the steering.

CanAutM3 · 11-06-2018, 11:41 PM

Racer20

With the equipment available to you, did you get a chance to verify the spring rates of the MP-HAS kit?

Remonster · 11-07-2018, 04:06 PM

Quote:

Originally Posted by EricSMG

Good stuff. I'm mostly interested in the top end - the ZCP car has the perfect midrange ramp up... it's just at the upper edge of what's controllable = perfect. But I would like a little more rip above 6.5k, more similar to the S65/S54 engines that I come from.

I'm also interested in more consistent WOT performance - less surge and lag.

Curious on your input here.

The PTF guys who make Bootmod3 must have read your mind, there is a CS+ map which is what I currently run daily in my car. It's virtually identical to the M3 CS factory tune but with a bit more boost from about 5k to redline giving a little stronger top end. I absolutely adore this tune file.

Quote:

Originally Posted by Racer20

Looking at my alignment sheet, it looks like the shop took it upon themselves to set my alignment to non-stock settings since I told them I use the car on the track.

I'm curious, what specs did the shop set your alignment to? If you have the alignment changed, let us know how it affects your feeling of the car.

Racer20 · 11-07-2018, 10:12 PM

Quote:

Originally Posted by CanAutM3

Racer20

With the equipment available to you, did you get a chance to verify the spring rates of the MP-HAS kit?

Unfortunately no. I can measure spring rates, but I don't have a dedicated spring tester. To do it on my equipment would require some fixture design and fabrication that's beyond what I could justify using my work resources for in the time I had. I just wanted to get them on the car.

Racer20 · 11-07-2018, 10:14 PM

Quote:

Originally Posted by Remonster

Quote:

Originally Posted by EricSMG

Good stuff. I'm mostly interested in the top end - the ZCP car has the perfect midrange ramp up... it's just at the upper edge of what's controllable = perfect. But I would like a little more rip above 6.5k, more similar to the S65/S54 engines that I come from.

I'm also interested in more consistent WOT performance - less surge and lag.

Curious on your input here.

The PTF guys who make Bootmod3 must have read your mind, there is a CS+ map which is what I currently run daily in my car. It's virtually identical to the M3 CS factory tune but with a bit more boost from about 5k to redline giving a little stronger top end. I absolutely adore this tune file.

Quote:

Originally Posted by Racer20

Looking at my alignment sheet, it looks like the shop took it upon themselves to set my alignment to non-stock settings since I told them I use the car on the track.

I'm curious, what specs did the shop set your alignment to? If you have the alignment changed, let us know how it affects your feeling of the car.

I never bothered to change the alignment. Once the car settled a day or so later, the steering calmed down a bit. I'm quite happy with the car as it sits now.

EricSMG · 11-08-2018, 07:05 AM

Quote:

Originally Posted by Remonster

The PTF guys who make Bootmod3 must have read your mind, there is a CS+ map which is what I currently run daily in my car. It's virtually identical to the M3 CS factory tune but with a bit more boost from about 5k to redline giving a little stronger top end. I absolutely adore this tune file.

Yep, I've noticed that tune and it's exactly what I'm looking for.

Just to big of a wuss to tune my new car

jim1013yyf · 12-01-2018, 03:14 PM

Hey looks like I just a found another Ann arbor ///M.

09-26-2018, 08:07 PM	#24
Racer20 Major 1030 Rep 1,190 Posts Drives: F80 M3, 228i THP, E46 ZHP Join Date: May 2009 Location: Ann Arbor, MI iTrader: (0)	Played around with EPS coding today. I don't seem to have F85Comp or F86Comp options to FDL code. I have F82GTS and "veh6", "veh7" and so on to "veh10". I tried setting it back to the F80 standard setting, and so far I like it better. I might try VO Coding the EPS module using the comp or CS typecodes again this weekend to see if I can feel any difference. But for now, the base EPS cal seems to work best with my suspension. __________________ 2015 M3, 2005 330i ZHP, 2015 228i 6MT Track Handling Pack, 2007 M Coupe (Sold)
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11-06-2018, 11:41 PM	#26
CanAutM3 General 21115 Rep 20,741 Posts Drives: 2021 911 turbo Join Date: Jan 2012 Location: Montreal iTrader: (1) Garage List 2022 Audi RS6 [10.00] 2021 Porsche 911 turbo [10.00]	Racer20 With the equipment available to you, did you get a chance to verify the spring rates of the MP-HAS kit? __________________ Porsche 911 turbo 2021 992 GT Silver Previous cars: M4cs 2019 F82 Limerock Grey / M4 2015 F82 Silverstone / M3 2008 E92 Silverstone / M3 2002 E46 Carbon Black
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12-01-2018, 03:14 PM	#31
jim1013yyf Lieutenant 306 Rep 419 Posts Drives: YMB M4 Join Date: Jan 2014 Location: Bay Area iTrader: (1)	Hey looks like I just a found another Ann arbor ///M.
	Appreciate 1 Racer201029.50 Quote