betrezra

My wife is taking a half day session tomorrow @ MSR in angel ton (road racing class)..... in her 2014 C63 Sedan. And we need a few pointers on setup:

Stock tires - tire pressure.
Run in S or S+
I presume since this will be only her 2nd track event... 1st being AMG driving academy @ COTA.... she should leave TC on.

She will be running 4-6 20 min sessions with 30 min cool down each session.
Can we expect to go into limp mode in 100deg F houston heat with this type of activity?

Thanks All.

Jeff

zcct04

Jeff,
It does look like we'll be pretty close to triple-digit temps tomorrow. If she is pushing the car hard, she's quite likely to run into limp mode. Oil temp hitting 278F will trigger it. It will happen a lot faster in S or S+. Running in C seems counterintuitive on a race track, but it avoids the extended high rpm sessions that raise oil temps quickly. If she hits 278 and it goes into limp, she doesn't have to quit. She can slow the pace a bit until temps come back down and then pick it back up.

It appears that a separate limp mode can kick in if the tranny temp gets too high. I've not experienced that, can't describe symptoms or solutions.

There's been good discussion the last couple days on tire pressure for the track. Do a search and you'll find some good guidance from some pros.
Hope yall have fun tomorrow - I'm envious! Let us know what you think of the track - I'm driving it in a couple weeks with friends in the Cobra club.

betrezra

Zcct - I've driven the track last year in my old C5 Z05... it is a great place to learn, and the instructors are super knowledgeable and super friendly. They let me run solo on my first day because I'm old and cautious

I'll get some good pics of her day in the morning.

I'll prob go with stock tire pressure, and keep it in sport for tomorrow...... and start from there....

Thanks for the guidance on s and s+. We'll see how hard she pushes it......... part of me says she'll take it easy.... and the other part see's her pushing it HARD>

Jeff

Once my c63s is fully broken in, i'll hit MSR, and then cota for some fun.

D3-AMG

One tip for tire pressures, start out higher than the stock pressures, 5-10psi. After a run, look on the sidewall right where it meets the tread for a little ^ shape pointed at the tread. If the tip is worn down you are spot on. If it isn't worn, pressure is too high. If it is worn past the ^ and onto the sidewalls, pressure is too low.

betrezra

Thx d3. We used to do that at autocross. Thx

odonnks

Any pictures of what your are describing ? I think I understand but am not certain.
Thanks !

zcct04

I've been asking the same question, and the answers I'm getting suggest that pressure for track events is quite the opposite from what we do at an autocross. Here's an example from forum member Diabolis. Discussion is at https://mbworld.org/forums/c63-amg-w...d-courses.html


Originally Posted by zcct04: For those of us not yet equipped with spare wheels and R-comps, what would y'all suggest doing with pressures when running a street tire like the MPSS? Does going down below MBZ street pressures make sense?

Originally Posted by Diabolis:zcct - at the track, yes. Your tire pressures will likely go up about 6-8 psi instead of 3-4 on the street. On a dry track you'll get the most grip when your contact patch is the largest, which is at lower pressures - so the "chalk mark wear indicator" is your best friend. At the AMG DA events I seem to recall that we were running the OEM 19" 235 & 255 Continentals on the 507s around 40 psi F and 38 psi R hot. That probably means that you want to let them out to about 33-34 psi cold F & R and start from there (I assume you've got the TPMS sensors so you can see what the tire pressures are in real time). Don't push while they're cold, give them a full 4 or 5 laps to properly warm up instead of just 2 or 3 as otherwise the thread portion of the tire gets up to temperature and start to stick but the tire carcass rubber is still cold and hard, and you end up chunking the tires.

The recommended cold pressures on the fuel door take into account the fact that you may be driving the car with four passengers in it at ~40 km/h in December at near freezing temperatures when the tires will never warm up and the ambient temperature at the shop or in your garage where they were checked may have been 24 C so you will actually lose 4 psi from what they were set at. As a general rule of thumb, slightly over-inflated tires are safer than under-inflated tires as they are less likely to blow out, so if you are going to err, err on the high side. Maybe only let them out to 36 psi cold to begin with (in which case they likely won't go over 44 hot), drive your session and on your cool-down lap check the readings. On the heavier cars like the C63 you don't want your hot pressures to dip much below 40 psi, but running them at, say, 38F and 36R even if that means starting with cold pressures of 30 psi is OK for as long as you don't do 280 km/h on your first three laps. I suspect that at anythign below 38 psi or so you'll be rolling over the sidewalls on the fronts a fair bit, so I think you'll find the sweet spot on the PSS somewhere around 40 psi.

604 C63

Pop your grill out. Makes a massive difference in cooling. Takes 2 mins.

Re limp mode for the transmission - it cuts power and will not shift when you want it to. In sport you do not see what gear its in (you just see the S) and it will not let you put it into Manual. Then when you stop for even two minutes everything is back to normal, but unfortunately if you roll on it will go right back to limp almost immediately.

betrezra

Thx guys for all the input. She had a good day @ MSR today, and the W204 performed great no overheat issues, no brake fade, no limp mode.

She ran in S mode, and got a few sessions in.
We ran the stock tire-pressure.
Also ran with TC on, since we're newbs.

We'll have some rear brake pads to service @ next svc intvl.

betrezra

Thx guys for all the input. She had a good day @ MSR today, and the W204 performed great no overheat issues, no brake fade, no limp mode.

She ran in S mode, and got a few sessions in.
We ran the stock tire-pressure.
Also ran with TC on, since we're newbs.

We'll have some rear brake pads to service @ next svc intvl.

betrezra

dchl21

tc on eats rear brakes. turn tc off and take it easy next time

Merc63

The car isn't going to fly off the road with TC off, just take it easy on the throttle coming out of the corners.

betrezra

Yeah our instructor advised the same.... but....

I'm not putting my wife on a track (her 2nd time) without TC LOL.

Rear brakes look good after...... I"m sure she was learning quite a bit @ 5/10's