Heat soak might not be the correct word to describe it. To me it's the normal affects on a turbocharged engine in high ambient temperatures.

Hot air is less dense, meaning there aren't as many oxygen molecules per unit volume entering/exiting the turbo. The turbo then must run harder to keep up with the desired power output; it can't keep up, so ECU alters timing to prevent engine knock.

End results is the engine is down on power full throttle, high-end power.

 

20 min track session.... you are ON boost and OFF boost so the i/c system has time to recover.

1/4 mile Wide Open Throttle for 12 seconds you are WIDE OPEN THROTTLE FULL BOOST for the entire run.

A difference.

 

Awesome JP

 

I haven't heard of anyone testing these cars talking about power loss yet (like they did on the new Vette Zo6) and quite a few magazines have tested them and with pros driving both straight line and track.
I would be very disappointed if MB could not engineer a 12 sec run and on most road courses the straights are longer than 12 sec runs.

 

It's not so much a factor in the specific design of the engine but just the reality of a turbocharged engine.

 

Just speculation. We'll see when we get some data-logging on some runs.... and after we run these cars in 40 deg weather...... good DA...... if MPH picks up DRAMATICALLY.... I suspect this is the issue.

 

But it definitely does depend on the design and quality of the charge cooling hardware. That is why we see so many aftermarket big intercoolers for boosted cars from a few years back.

I really hope AMG designed the charge cooler to be sufficient for a full 1/4 mile run.

As others have said, we shall see when the when fall and winter come.

 

I believe the C63S stock boost is 16 or 17psi....... which is a pretty healthy boost level..... and would require considerable water cooling system.

The E55 guys required i/c system upgrades when upgrading to less boost than this......

Not totally apples to apples.... but from a cyl pressure side this is important.

 

Drag strips are quite different than the track. In high summer temps, the staging lanes get super hot, so your intake air temperature is climbing before the run even starts. Then you blast down the 1/4 mile for 12 seconds, go back to the pit, shut down and continue to heatsoak the engine because the turbochargers are red hot. It's very hard to cool off turbocharged cars before/after runs unless you have bags of ice or something like that -- ideally, jumping on the highway and cruising for a few minutes, but that isn't possible at a drag strip.

On the track, you're constantly getting cooler, fresher air because you're traveling at speed. The W204 definitely had cooling issues at the track that caused limp mode, but the W205 has a twin liquid-air intercooler which in theory should perform very well on a road course.

Of course, none of this is an issue when temps are 75F and below. I've been racing turbocharged cars for over a decade and heatsoak at the track during summer months is always a battle - even with modern turbocharged engines.

 

Thanks for the info Alex
I have never run a FI car and it will be very interesting to see results from data logging when it is cooler. And of course see what trap times do.

 

Hey guys, i'm doing my 1st ever roll race tomorrow "1/4 mile" c63s on Dunlop 265/35zr19. Any advice on when to drop the hammer. Rules are I can't go past 30mph before the Christmas tree, but I want to know if I step on it will I get enough for the 30 mph limit or should I wait. No practice run here.

 

Still been done sorry say.