M vs Non-M subframe reinforcement

JohnDaviz

Sergeant
Jan 6, 2019
362
213
0
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335i E92 DCT
Leaving the undertray away is an aerodynamic catastrophe. Lift on the front at high speeds will increase significantly.
 
  • Agree
Reactions: Torgus

Torgus

Major
Nov 6, 2016
1,899
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Boston
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ACF 6466 E92 + METH
fwiw, recently i have tested a m3 and my 335 back to back at the same corner a few times

both cars have the same tires (bridgestone re71rs, 18 inch wheels, 255/265 on 335, 245/275 on m3)
similar mods
(m3 has stock front control arms, full set hardrace rear control arms, nitron r3 suspension)
(335 has turner monoball m3 front control arms, full set hardrace rear control arms, turner solid alu rear subframe bushings, mfactory lsd, stock sways, ast 5200 suspension, rear poly top mounts, solid bottom mount)

difference... alignment and spring rates, the m3 is a 8/10k spring setup, running stock front camber/toe, i think -2 or 2.ish camber in the rear, i am running 9k/14k spring setup, -3 front camber and -2.6 rear camber

with dsc off
m3 will understeer at the limit (as expected), front and rear feels planted and communicative the whole time, however, i could not put the power and have the rear step out and have to lift until the car stops understeering
my 335 is setup to oversteer at the limit, front feels pretty similar but the rear..theres room to improve on compared to a m3

with that being said, i have the rear m3 braces sitting at home, i am just waiting for the ultraracing center brace to come so i can get it installed
i also got the hardware sitting at home to make and install the the front subframe braces like the one in the first post

dont hold your breath for an update though, i will eventually get around installing it... but ive been lazy and playing with other stuff

Any news on the ultraracing brace?
 

AzNdevil

Sergeant
Nov 4, 2016
426
181
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Hong Kong
Any news on the ultraracing brace?

not yet...my friend picked it up for me... but i still havent picked it up yet though
i bought this because i cant find the stock m3 plate for sale... and i dont want to cut up my stock e92 V brace just for the center plate

a pic of the brace i bought
1621958149464.png
 

RTA

Lurker
Jun 17, 2020
18
5
0
direct fit on e92 n54?

Was considering stuff from UR to beef up my chassis as it used on track days.
 

Asbjorn

Lieutenant
Mar 10, 2018
826
557
0
European, based in China
Ride
Z4 N54 DCT
Did it impact like you hoped?
God no. Not in any way. But man was it alot of fun.

Doing stuff like stiffening up the suspension arm bushings, anti-roll bars, suspension and tires offers a much larger difference to the driving experience. Not to forget engine mounts.

Check out the golf ball design of the undertray of the new cayman gt4 for some professional sillyness instead. I believe engineering explained has a YouTube video about it.
 

RTA

Lurker
Jun 17, 2020
18
5
0
Will have a look at that Porsche engineering art ;-)

I have done most like you mentioned front rate: 350, rear 750, JRZ suspension, Drexler, Camber plates, M3 bits, m3 bars, all mounts. (will change the bars for a slightly stiffer and more neutral set.

I do sense some potential for extra stiffness mid car, on the other hand, I plan to install a cage next year, that also might take care of extra stiffness and the bars will also impact the overall dynamics.

Best track improvement is my brake config (together with the suspension), ebc pads, zimmerman disks, copper end pieces where the brakeline enter the calipers, proper brake fluid, and decent brakelines topped with some custom front feed brakeducts. The ducts gave me 20 minutes extra laptime before cooldown,in the past it was one big melting party at the front brakes.
Any how, a bit off topic ;-)

So will take UR chassis bits of the list... will spend that money on a dry-sump like solution...
 

Asbjorn

Lieutenant
Mar 10, 2018
826
557
0
European, based in China
Ride
Z4 N54 DCT
Will have a look at that Porsche engineering art ;-)

I have done most like you mentioned front rate: 350, rear 750, JRZ suspension, Drexler, Camber plates, M3 bits, m3 bars, all mounts. (will change the bars for a slightly stiffer and more neutral set.

I do sense some potential for extra stiffness mid car, on the other hand, I plan to install a cage next year, that also might take care of extra stiffness and the bars will also impact the overall dynamics.

Best track improvement is my brake config (together with the suspension), ebc pads, zimmerman disks, copper end pieces where the brakeline enter the calipers, proper brake fluid, and decent brakelines topped with some custom front feed brakeducts. The ducts gave me 20 minutes extra laptime before cooldown,in the past it was one big melting party at the front brakes.
Any how, a bit off topic ;-)

So will take UR chassis bits of the list... will spend that money on a dry-sump like solution...

When you say EBC pads I assume you mean the orange stuff? I used them for some time. Went through three sets front. Then I tried Hawk DTC pads. This made me realize that the orange stuff pads wear quite fast. They are very gentle on the rotors for a track pad. I got longer life and more confidence out of the hawk pads, but they also grip quite a bit harder and are not as easy to modulate during trail braking. (At least not the DTC70, maybe 50 or 60s are better, but they arent sold in China)

Anyhow, the flex mid-car is most likely going to be very insignificant compared to the flex you have in the M3 bits. On the other and the M3 bits are such a nice compromise between stiffness and NVH. I street a full bearing setup now and while the steering is super telepathic, its also quite an NVH party. Fortunately the roof goes down and then everything is ok.

And again - tires - its amazing how big a difference they make on how the car feels to drive. If you are on michelins or other performance street tires there will be quite alot of flex going on just in the tires.
 

RTA

Lurker
Jun 17, 2020
18
5
0
Indeed the Orange ones, as I kind of understand those I sticked with them, will order some hawk pads to test, if you have choice, 50,60 or 70?
Most of the bearings have been done, not solid but it was a lot of extra feedback, I did all mounts and bearings at once, which did take out the option to see each individual effect.

My first step to manage the "flex" i think I notice is to get some H&R bars (F/R), this to fix my corner exit as the M3 bars still feels a bit to soft, this has increased post the installation of my current spring rates (Which was a very good thing as I was driving for years with soft M-Suspension springs who do not match the extra torque the car has. Stability went up a lot, however a little increase on F&R sways would probably give a more balanced neutral touch.

Tyre wise i'm on Michelin Cup 2's who are kind of good at the track, (They have 4-6 heat cycles) and ok on street, but at the street they never get real warmed up so PS4's are better for that purpose, probably will switch to a pure track tyre when the Cup's are done.

Overall the Cup2's are quite a big step on the track when at the right pressure and temp compared to the PS4's. they gave me around 2sec win on a 1:48 race lap compared to the PS4's and I think even more when I trust myself and the car a bit more. Cup2 are also still useable at a wet highway, a thing I would not recommend for the former Cup1.

I see that you run progressive springs, you prefers this above linear springs?
 

Asbjorn

Lieutenant
Mar 10, 2018
826
557
0
European, based in China
Ride
Z4 N54 DCT
Well, if you are ok with the life/wear and bite of the orange stuff then there is no reason to change. My problem with them was that they wore out very quickly and took forever to bed in as the rotors got worn. This affected the fronts more than the rears, so I would end up having a brake bias that was a bit too much towards the rear over the majority of the pad/rotors life span.

I would probably start with the DTC60 front and rear if I had the choice. Preferably on new or good condition rotors. Then I would do some sessions, or at least two with plenty of cool down between them (ie 2 hours or so). Look at the brake data from each session (I use DME connected AiM data logger). Does ABS activate both front and rear during heavy braking? If you dont have datalogging, you can use a custom configuration of MHD to log the wheel speeds. Problem is the frequency probably wont be high enough to see whats going on. In the end you can also just try to feel what the car does under braking using the butt dyno or by looking at video recordings. You also need to evaluate how the car behaves under trail braking. Does it tend to push or slide? Is it easy to modulate trail braking with the brake pedal or is the bite very sensitive? If it pushes, or if the front abs activates much more than the rear, I would swap to DTC70 rear. If the rear ABS is working much harder than the front ABS, and the car wants to slide when trail braking, and the brake pedal isnt too sensitive, then I would swap to DTC70 front. If the brake pedal feels too sensitive and hard to modulate, then go DTC50 rear instead of DTC70 front.

I have been running H&R bars myself, but ended up modifying the front bar to make it adjustable, and had the rear bar custom made to be a bit stiffer. I like the stiffest setting front and had to stiffen the rear to kill some of the under-steer on my car. This in turn has made corner exits more of a handful, but overall the car is faster when balanced towards over-steer.
As for springs I just run oem front and H&R rear with a "spring spacer" to bring the rear back up to the stock ride height. I dont think this is ideal for track use (hello bump stops), but it makes the car somewhat acceptable for use on the street and further helps to kill under-steer. I have never tried linear springs, but I am sure they are wonderful on track.

As for the original topic - flex - I would look into other tires first. I cannot think of a softer track tire than the cup2s. The grip is amazing in the beginning, but I am pretty sure that any other track tire you might select will cause less flex in comparison... be it trofeo r, ventus td, or pretty much any semi or full slick tire. The ps4 tires are even softer, and of course overheat after one lap on the track as they are meant to work well on the street, in the rain etc. Personally I swap wheels and brake pads at the track and use semi-slicks or full slicks in the right sizes. The tires transform how connected the car feels, and it amazes me every time. Depending on the compound, semi slicks (like Hankook TDs or Z214s) might only make you a second or two faster compared to a brand new set of cup2s, but they will feel so so much better to drive on track. Unfortunately you cant use them on the street as they would wear out in no time

As long as you are using rubber in your suspension arm bushings, dont worry too much about chassis or subframe flex. Do the easy stuff (like the bolt on bars) if you are bored, but know that these are heavy street cars and most or the flex will be happening in the suspension and tires anyway. Just look at the rear tires in this random picture.

flex.jpg
 

JohnDaviz

Sergeant
Jan 6, 2019
362
213
0
Ride
335i E92 DCT
God no. Not in any way. But man was it alot of fun.

Doing stuff like stiffening up the suspension arm bushings, anti-roll bars, suspension and tires offers a much larger difference to the driving experience. Not to forget engine mounts.

Check out the golf ball design of the undertray of the new cayman gt4 for some professional sillyness instead. I believe engineering explained has a YouTube video about it.

An undertray only in the front area of the car wonĀ“t lead to any noticable effect. You can create areas that will pull air out of the undertray when the incoming air from the front of the car can be routed to those exits. Like the cooler from the M3 which is pointing downwards.

But to get some real downforce effect and the main reason for closing the undercar areas you have to close the whole bottom side of the car and create a diffusor in the rear. Look at the new porsche GT4 on engineering explained. what a beatuy and best practice example.