Hi all,
I had a thought about the known issue of carbon build up in our engines and was wondering if any of you more mechanical types might be able to support of correct my idea.
The carbon build up is caused by oil cooking onto valves and seats etc and this happens because these parts get really hot and the oil sits there not being cooled or rinsed by fuel ( correct so far i assume ). This is where my thought comes in, back in the day we all used to install turbo timers on our cars to allow the internal parts of the turbo to cool before stopping the flow of oil and having it cook into coke ( carbon crust ).
Is there any value in letting the engine cool for a few minutes before turning it off thus letting the engine components cool to a point that they wont cook the oil?
Or does the carbon build up while actually driving?

I'm going to tear apart the engine and clean it out and was wondering if this might keep the carbon from coming back, or at least slow its build up.

 

I'm thinking even if you idle down your engine you're still getting a lot of heat on the valves,(due to the internal conbustion taking place in the cylinder)I don't think it would make a difference.

 

For what its worth, a Mini tech suggested a few years ago that I let my MCS (09) idle for a few minutes before turning it off to help prevent carbon buildup. I don't do this as it didn't make sense to me but I'm no mechanic.

 

Well I was thinking that a running engine does generate heat, yes, but a driven engine generates a lot more. The question is do our engines at idle cool enough to reduce or eliminate the carbon build up. This will help the turbo itself live longer if nothing else.

 

Letting the engine idle a minute before shutting it off is suppose to help cool down the turbo. I don't believe it's going to do anything for the carbon buildup.
I was under the impression that the carbon buildup is generated more by people using their cars for short runs and not allowing the engine to get up to operating temps.
That's what was explained to me by my SA and MA.

 

I guess the big question is does the oil vapor coke more during running operation or during idling.

 

Carbon build-up or coking occurs when intake air speeds are SLOWER; that's when more collection occurs.
Higher engine revolutions, when air intake speeds are greater, reduce the amount of collection.

A mechanical way to reduce build-up would be to install a low-pressure fuel nozzle before the intake manifold, which would was the backside of the valves.
The new VW / Audi 1.8L EA888 engine has a dual-injector system for reducing / removing carbon deposits:



Since that's not on the Prince 1.6L N14's / N18's, look into getting a catch can, blocking off the PCV system, and using a heavy dose of water / methanol.

- Erik

 

Synthetic oil typically doesn't coke and the auxiliary water pump will run after the car is shut off to keep cooling the turbo. I think all newer turbocharged cars have this, which is why you don't hear about turbo timers so much anymore. In any event oil temperature won't affect carbon buildup on the tops of the valves.

If I'm running the car hard, I'll drive it gently for a couple minutes or so before shut off. Another thing you could do to prevent the buildup is to install a catch can as bluefox280 said. Also, I've noticed that dealers tend to overfill the oil when they change it; this is probably also part of the problem.

 

I agree with you. I still let mine cool off a minute but I think my OCC really helps alot as well. Time will time.
I also throw in a bottle of Chevron techron every 3K miles.
I don't know what else to do to ease the issue except not drive it - that's not gonna happen.

 

Thanks for the input, and the diagram! (where do you find stuff like that?). I guess its an OCC going on the to do list. For what its worth, I work in the petro chemical extraction and refining field and the synthetic oils do coke on hot surfaces if there is a low flow situation. The biggest difference between the conventional and syn. is that conventional oils coke in a thick crust and syn. is more of a powder. Not sure if they behave the same way in an engine though.

 

BSH puts out an excellent OCC. Remember also, you'll need the boost tap as well for the intake side (passenger side).