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[Webby the Bear]

Carbon build up on valves can cause power loss due to it acting as a restriction to flow (and presumably volume if air). valve ''jobs'' are done to ''de-coke'' valves. that I get.

I remember I posted a thread ages ago about some crazy dude who thought pouring water in to the inlet would de-coke his engine and in that same thread we deduced that the omega engine wouldn't have built up carbon. that's fine.

when I stripped the top end down on my car I found the valves to have some black stuff on but it was more like a ''thin layer'' of what was hard burned stuff as opposed to the hideous photos you can find online of what look like valves dipped in a pot of caviar!!! lol

so anyway my question....

will this ''thin layer'' affect performance? if not why not?

and finally, the last time I had myinlet plenum of it looked liked it was all burned inside (black crap build up)...will this affect performance by reducing the amount of air we can cram in?

[Nick W]

Even on older engines, full engine management systems have eliminated the need for de-cokes. Although a well set-up and maintained healthy engine didn't suffer much anyway.


The simple answer to your questions is: No, don't worry about it.

[Webby the Bear]

Not concerned about it at all mate. just throwing out some thoughts 

Was going to get my spare plenum and soak it in diesel to get the crud out. worth it? I take it not.

[Kevin Wood]

A modern engine will build up a small layer of carbon the first time you start it up. Due to the accurate fuelling control on modern engines, as said, they will never allow a troublesome amount to build up.

A thin layer is actually good for the engine. It insulates the components, meaning they run cooler, and less heat loss from the combustion chamber makes the engine more efficient.

[X30XE]

A modern engine will build up a small layer of carbon the first time you start it up. Due to the accurate fuelling control on modern engines, as said, they will never allow a troublesome amount to build up.

A thin layer is actually good for the engine. It insulates the components, meaning they run cooler, and less heat loss from the combustion chamber makes the engine more efficient.

Unless it's a modern BMW diesel... and then it will coke itself up a treat... big time. 

[Nick W]

Not concerned about it at all mate. just throwing out some thoughts 

Was going to get my spare plenum and soak it in diesel to get the crud out. worth it? I take it not.

You've nothing to lose, although I suspect you will need a more aggressive solvent than diesel.
Standard cellulose thinners is my favourite, as it's effective and cheap.

[Crazycarzowner]

Unless it's a modern BMW diesel... and then it will coke itself up a treat... big time.

Yup you're right there!!! Our '12 plate X5 is at BMW at the moment being treated to a 'De-coke'   

[Kevin Wood]

Unless it's a modern BMW diesel... and then it will coke itself up a treat... big time.

Yup you're right there!!! Our '12 plate X5 is at BMW at the moment being treated to a 'De-coke'   

You're clearly driving it far too sedately.

But yes, with tractors, all bets are off.

[Webby the Bear]

Unless it's a modern BMW diesel... and then it will coke itself up a treat... big time.

Yup you're right there!!! Our '12 plate X5 is at BMW at the moment being treated to a 'De-coke'   

whats theirt procedure for this Jason? out of interest

have they had one of those bore cameras in and seen its all clogged?

[X30XE]

Unless it's a modern BMW diesel... and then it will coke itself up a treat... big time.

Yup you're right there!!! Our '12 plate X5 is at BMW at the moment being treated to a 'De-coke'   

whats theirt procedure for this Jason? out of interest

have they had one of those bore cameras in and seen its all clogged?

Have a look on youtube Webby. Media blaster and a vacuum cleaner (with a special adapter for intake port).  Modern BMW = dog turd.

[Webby the Bear]

Thanks x30' will do