[GerardzM]

Is it really 'normal' to have oil on the turbo like that?

I would think that would be cause for concern, especially when driving hard!

[Proctor750]

Originally Posted by GerardzM

Is it really 'normal' to have oil on the turbo like that?

I would think that would be cause for concern, especially when driving hard!

Merc CDI (inline 6 turbo diesel) were notorious for this due to their pcv system and oil gets all over the insides of the charge piping and intercooler. The only real solution is an external catch can. I have a really nice Mahle one with replaceable filter. If put inline it should resolve it.
This is assuming it's the pcv and not another seal further up which failed causing the same symptoms.
I'm not S55 expert but maybe it's worse after break in and not quite as bad later (I'll find out).

Also - the valvetronic V3 is crazy compact! My buddy and I (not S55 familiar) weren't even sure it had it at first.

We also stared at the boomerang carbon fiber "strut brace" and just can't seem to figure out how it does anything. Can someone explain the physics? There is an aluminum piece under the shrouding that does connect and actually even connects up at the firewall as well (weak?). But not sure how the carbon piece is really adding rigidity the way it's mounted/shaped etc.



Some other observations;

The extra triangulated gusseting supports are pretty neat.

The bane of my existence electric power steering (manual rack swap would be great)

Looks like the gap in bodywork and headlight feed to intakes?

I had to adjust the felt on a power junction to keep it from chaffing. One of the larger gauged wires does chaff (sp?) but luckily bmw put a plastic guard there do you don't burn your car down..
Nice electrical tape..

The almond paste looking corrosion coating is sweet. There is also a lack of sound deadening in many places BMW formerly installed which is interesting considering how quiet the car is with windows up in comfort and ASD disabled.

[M2guru]

Originally Posted by 3tekcorps

Mine still does it with DTC off. Or at least what I'd consider wheel hop in 1st when launching on wet pavement. Instead of just spinning the back end you feel this horrible shuddering through the chassis.

Ditto. This has only been a problem for me in a straight line. I have yet to have hop when making donuts or U-turns.

[Poochie]

Originally Posted by Proctor750

We also stared at the boomerang carbon fiber "strut brace" and just can't seem to figure out how it does anything

I sincerely believe that the carbon fiber section of strut brace is nothing more than eye candy. The concealed aluminum section that actually attaches both strut towers, I can see that having some meaningful impact on rigidity.

Of course, saying anything that might be remotely interpreted as negative about the sanctimonious M2C here is considered blasphemy and will be followed by subliminal verbal attacks and being labeled as a "troll" so I kept it to myself, even if it's blatantly obvious..

[3tekcorps]

Originally Posted by M2guru

Ditto. This has only been a problem for me in a straight line. I have yet to have hop when making donuts or U-turns.

After the first couple times I decided not to try again until tires are almost gone.

I recall the same thing on my 2016 M2.

[Poochie]

WoW, the S55 turbos are smaller than I expected but it's ok; a beautiful woman once told me that size doesn't matter, while crossing her fingers...

I'm pretty sure she was telling the truth..

[Robin_NL]

About wheelhop. I got that sometimes with my ex 1M and Michelin PS2. Annoying I remember.
Some say it's because of that type of tyre.

Grippy summertyres on dry surface because in the wet no problem off course, wheelspin galore.
But half wet wheelhop occurred also.

Why should it be an LSD thing in the first place and not the PSS
(In my case)

Just asking.

Cheers
Robin

[M-Pilot]

Found a solid explanation by CanAutM3 (as always ) that is inline with what I used to experience in my M4:

Originally Posted by CanAutM3

To answer this question, I'll simply quote what I have posted in another thread:

[M Fifty]

Originally Posted by Proctor750

I don't think it's that simple.

EDIT: disregard - I just saw doughboy's post and wasn't aware that the majority of the load is managed by the front 4 bushings and the rear is simply a dampener. If this is the case then adding a second ear would probably not fix the issue. I knew the end piece was for dampening but assumed that it doubled as a mount since it connects through the subframe itself.

EDIT 2: Looking at Real OEM paints a different picture. It appears the vibration damper is attached to the rear of the actual rear diff MOUNT which there is only 1. Since it indeed has a normal rubber mounting, and only one at that - having a second one would certainly help. Sorry for the poor photoshop my red line goes to the wrong bush in the pic

Interestingly, BMW use exactly the same part on the M3 and M4, including the M4 GT4. The latter example suggests it's not a major issue in racing conditions. The GT4 does use different suspension components though.

[M Fifty]

Originally Posted by Poochie

I sincerely believe that the carbon fiber section of strut brace is nothing more than eye candy. The concealed aluminum section that actually attaches both strut towers, I can see that having some meaningful impact on rigidity.

Of course, saying anything that might be remotely interpreted as negative about the sanctimonious M2C here is considered blasphemy and will be followed by subliminal verbal attacks and being labeled as a "troll" so I kept it to myself, even if it's blatantly obvious..

The points that the front mounts bolt to do look a little flimsy, but the part itself appears to be remarkably strong. Pictures of used items on eBay show bits of the front mounts ripped off an apparently undamaged carbon structure.

[Poochie]

Originally Posted by M Fifty

The points that the front mounts bolt to do look a little flimsy, but the part itself appears to be remarkably strong. Pictures of used items on eBay show bits of the front mounts ripped off an apparently undamaged carbon structure.

I don't have any raw data to back it up but if you look at how it attaches to the alloyed frame, common sense will tell you that it's just there for ornamental purposes..

It's probably light as styrofoam and it can't and doesn't take any brunt of the twisting forces. The alloy brace would have to bend first before the carbon fiber piece kicks in as 'reinforcement.' And that's never going to happen unless the vehicle is in a major side-impact collision, which moots any supposed purpose..

I know you guys just love it to death and is going to defend its purpose to the bitter end but it's pretty obvious that the alloy brace is doing all the work but the carbon fiber piece is there to take all the credit..
Reminds me of my manager...

[Poochie]

Skimming through the old Bimmerpost archives, it appears the pre-LCI F82 M4 was tuned, stock, to be tail-happy and suffered from many cases of wheel hop.

On later iterations of the M4, BMW turned down the spiky front-heavy tune, making it more progressive throughout the RPM band to help with this and to make the power more manageable i.e. less 'low end torque'

Keeping with this trend, it explains why in the newer BMW M2C they "weight optimized" the the boost to help alleviate this and similar launching issues..

It seems that it's a known problem but proper right foot pedal modulation and proper season-appropriate tires will help to minimize it.

[CSBM5]

Wheel hop is a massively complicated non-linear vibrations problem in a car with IRS. *ALL* IRS cars are susceptible to wheel hop vibration, and since tires are a significant portion of the equation, varying them along with tread depth, rubber thermo-oxidative aging (heat cycles), along with the road surface, etc,etc all will change the dynamic response of the chassis (like how on a certain dry road you might be able to lay down 50' of rubber cleanly but come back when the road is wet and get wheel hop like crazy).

If you go about changing bushing stiffness, you'll simply change the frequency where the oscillation occurs.

It's actually a really cool vibrations problem to analyze since so many aspects of car's suspension and the chassis (body-in-white) and subframe properties are all part of it. That wind-up/release forcing function CanAutM3 refers to is one of amazing parts of the equation, and is very difficult to model.

The best solution so far was found by Cadillac during the 2nd gen CTSV development a number of years ago and involves having halfshafts of different torsional rigidity. When you properly size the differing polar moments of inertia of the two halfshafts, it allows different levels of dynamic torsional deflection...which nicely eliminates (or greatly reduces) the wheel hop wind-up condition in the system.

[Poochie]

Originally Posted by CSBM5

The best solution so far was found by Cadillac during the 2nd gen CTSV development a number of years ago and involves having halfshafts of different torsional rigidity. When you properly size the differing polar moments of inertia of the two halfshafts, it allows different levels of dynamic torsional deflection...which nicely eliminates (or greatly reduces) the wheel hop wind-up condition in the system.

Isn't this what the M torque-vectoring LSD is suppose to mimic, with a varying degrees of torque to each wheel? Or does it go beyond wheel power distribution?

[CSBM5]

Originally Posted by Poochie

Isn't this is what the M torque-vectoring LSD is suppose to mimic, with a varying degrees of torque to each wheel? Or does it go beyond wheel power distribution?

No, the LSD has nothing to do with varying levels of torsional deflection on each side. Power distribution is unchanged in the Cadillac solution. It allows a transient variation in in rotational stiffness on each side of the IRS. There is now way to simulate such with any design of the differential/LSD. Completely different animals.

[M Fifty]

"*ALL* IRS cars are susceptible to wheel hop vibration". Not just IRS...

[M Fifty]

Originally Posted by Poochie

I don't have any raw data to back it up but if you look at how it attaches to the alloyed frame, common sense will tell you that it's just there for ornamental purposes..:

Looks good for tension - and some compression - though. The bits that bolt on the back of the alloy brace linking the strut towers to the a-pillar appears to back this up.

The original item in the M235i Racing must have been there for a reason - whether that applies in the M3/4 and M2C is up for grabs.

[Proctor750]

having halfshafts of different torsional rigidity.

I knew the loosing traction and regaining (oscillations) was the cause but that is an interesting idea as solution. So the "give" in each shaft is different so that it disrupts the oscillations "wavelength" so to speak? (can't think of the correct term)

The original item in the M235i Racing must have been there for a reason - whether that applies in the M3/4 and M2C is up for grabs.

Are you saying the M235i (R) has the carbon strut brace? I don't remember seeing that when I last saw one and isn't it specific for S55?

[M Fifty]

Originally Posted by Proctor750

I

Are you saying the M235i (R) has the carbon strut brace? I don't remember seeing that when I last saw one and isn't it specific for S55?

RealOEM shows a part the same shape as the CFRP brace, and also indicates that it was superseded by the CFRP item.

https://www.realoem.com/bmw/enUS/sho...diagId=51_9764

[Proctor750]

Originally Posted by M Fifty

RealOEM shows a part the same shape as the CFRP brace, and also indicates that it was superseded by the CFRP item.

https://www.realoem.com/bmw/enUS/sho...diagId=51_9764

Very interesting. I do know they also use AP racing or PFC calipers - I am curious the build difference between those and whoever made (brembo?) the 2NH brakes.

The last thing I want is piston boots like this guy (cts V) after only 2 months needing a rebuild (thanks to the bus stop and turn 1 at wg):

[CSBM5]

Originally Posted by Proctor750

The last thing I want is piston boots like this guy (cts V) after only 2 months needing a rebuild (thanks to the bus stop and turn 1 at wg):

Use Ti shims between the piston and backing plate and also don't run race pad thickness below about 1/3 of new...

[3tekcorps]

Feels like there's a lot of flex in the drivetrain to me. My 1st -> 2nd shifts are not very smooth when getting back into power like there's some excessive flex somewhere.

Anyone else have slopping 1st/2nd shifts? I've rowed a lot of gears in my life and don't recall this before.