I keep reading where the new engine design should reduce carbon buildup. I have 6000 miles, the engine started stumbling and got the engine warning symbol. Dealer said carbon buildup, the carbon cleaning procedure was performed and the mini is running adequately with some idling issues. I only use 93 octane gas.

It is a six speed and I drive the **** out of it.

Just wanted to put the "lets wait and see if the new design helps" discussion to rest. I evidently doesn't.

 

I think the carbon build-up diagnosis you received is a stinkin' load of BS. I don't recall seeing any of the former N14 engines showing symptoms of carbon build-up as early as 6K miles. Something else is the root cause. Mark my words. Maybe the HPFP.

I don't think anything will be "put to rest" on the design changes until there are some N18s with 30K+ miles on them.

 

Sounds like your dealer has no idea whats wrong with the car

 

Carbon buildup @ 6000 miles. That's hard to believe. No, that's impossible to believe. I hope you didn't pay for the service. I have to raise the flag on this.

 

HPFP? Or a bad sensor, but carbon in 6k miles is nearly impossible unless you idle the engine all night like a trucker.

 

Took 35K miles for mine to need carbon cleaning

 

Does driving over 80 for an extended period still clean out all the carbon?

 

minimix: I drove my '07 MCS like I stole it from day 1....don't believe in the "baby the new engine" theory of break in. I also give it an "Italian tune up" every chance I get which I believe keeps things clean. Perhaps I am fortunate living in the Nevada desert as we've got lots of wide open spaces where you can run flat out for good stretches.... I have never experienced any of the carbon build up problems mentioned here on the forums. Maybe you should find a deserted long stretch of road and have some fun!

 

The only way to prevent carbon build up is to delete the rear PCV pipe. This pipe connects the top oil gallery to the inlet manifold and subsequently the inlet valves. It is possible after such a low mileage that excessive oil has carbonized around the valve.

What is your oil consumption like?

 

The oil consumption is surprising low, if I am reading the dip stick correctly. The oil has been changed at 1K and 4K, the oil I collected was as expected. The dealer changed the oil after the carbon cleaning.

After getting the car back I have driven snot out of it, hopefully mechanically keeping the valves clean.

 

Because of the arrangement of the rear PCV, driving it hard will only carbonize the inlet valves more than driving gently. The THP engine is direct injection, so means the injector injects gas straight into the combustion chamber after the inlet valve, therefore leaving the inlet valve to collect oil deposits from the badly designed PCV system

Like I said above, The ONLY way to prevent carbon build up on the inlet valve is to delete the rear PCV.

 

The PCV's on the camshaft cover are not of a bad design, they do exactly what they have been designed to do, and that is to separate the oil particles from the crankcase gasses, and they do this quite effectively, and before anyone comes back and says "they don't" just have a little think about how little carbon you actually find on the backs of the inlet valves, when you think of the real time, miles covered and the engines piston speed all the time you are driving!

That's a whole lot of crankcase gas produced per mile per engine piston speed/crankshaft revolutions, just so you can get some sort of idea, your factory stock 175hp N14 turbo engine, produces 4.37 CFM of crankcase gas at idle, and decreases with RPM, yes I hear you all saying "surely the more RPM the more compressional blow by (crankcase gas) is produced"

The faster the piston speed (engine RPM) the greater the cylinder pressures and that in turn generates heat, and the extra heat helps the piston rings seal more effectively, thus less blow by (crankcase gasses) are produced, that's why we see more carbon deposit build up on engines that are driven nice and gently in comparison to engines which are driven hard using the entire RPM range, your given a set RPM range with a RPM soft holding limiter at red line, so why don't you use it ? that's what it's there for!

There is a whole lot more I can explain on PCV's, oil catch cans and carbon deposit, but for now I hope this helps you all understand things a little clearer.

 

Explain then why the engine designers have deleted this rear PCV using these from their latest THP engined vehicles then?

 

Quite simply the N18 engine cylinder head is a re-design and in order to deal with progress, the engineers deemed it suitable to remove the necessity for a rear PCV reliant on inlet vacuum draw to help with crankcase evacuation of the gasses, the variable valve lift reduces combustion filling volume pressure and this in turn reduces crankcase gas from compressional blow by.

 

I confess to difficulty in understanding the specifics of the discussion. Could you please let me (and other technically challenged members) know if this
means that the 2011 MCS with the new valve train is or is not susceptible to
carbon build-up ?

Thanks,
Mark

 

As long as the N18 or N14 engines vent their crankcase gasses (blow by) into the air intake stream, whether this be direct into the inlet manifold as seen on the N14 engine or indirectly via the turbo as seen on the newer N18 engine, they are still going to eventually suffer from the effects of carbon deposit on the backs of the inlet valves.

 

Are oil catch cans, then, the only prevention method with regard to both the N14 and N18 engines?