Walnut blasting 335i

[xxChrisxx]

aeropilot said:

Has to be other engine design factors in conjunction with DI, rather than just DI on it's own, as this is a specific N54 issue.
The N55 is DI, but also with Valvetronic and doesn't suffer from the same coking up problem.

Happens on R56 Cooper S. VAG tfsi engines also suffer.

no idea why some are better than others though.

[anonymous-user]

xxChrisxx said:

aeropilot said:

Has to be other engine design factors in conjunction with DI, rather than just DI on it's own, as this is a specific N54 issue.
The N55 is DI, but also with Valvetronic and doesn't suffer from the same coking up problem.

Happens on R56 Cooper S. VAG tfsi engines also suffer.

no idea why some are better than others though.

Most brands have engines that are affected, though later ones supposedly have better oil separation in the breather systems so shouldn't be so bad. Time will tell.

[trashbat]

They all do that, sir. This is from my Alfa JTS:





fk you, direct injection. VW Group TFSI engines suffer badly from it too.

I had the head rebuilt. There is no cure short of engine re-design such as introduction of another injector to provide washing. An oil catch can may reduce it a little, as would different timing.

Anyway, out of interest, how much for walnut treatment?

[E30M3SE]

^^ How many miles on the motor and what sort of driving?

[trashbat]

Not sure how many miles. The above was done at 108k. However, before I owned it, the cambelt snapped at 54k and so the engine was rebuilt. I don't know what they did but it had new valves so you'd assume it was OKish at that point.

It's driven reasonably hard throughout the rev range so if you're hinting at whether it can be burnt off by an Italian tuneup, it can't.

[trashbat]

I should add that it wasn't rebuilt explicitly because of the buildup, i.e. it ran reasonably well, if probably down on power. It was cambelt time and it seemed like a reasonable time to refurbish the head.

Also it was run on decent fuel, had very regular oil changes, occasionally got BG44K or similar and is generally looked after.

Finally, early versions of this engine were even worse. Alfa changed the inlet cam to reduce the overlap. My Alfa thread on it's here: http://www.alfaowner.com/Forum/alfa-147-156-and-gt...

[E30M3SE]

Aware carbon build up can't be burnt off with italian tune up just wanted to know if it had done lots of stop/start short journeys.

[trashbat]

My commute used to be 10-20 miles, and otherwise only used for long trips, so not really

Edit: it does burn a fair bit of oil, up to 1l/1000km specced as acceptable and not much less in practice, and that can't help.

Edited by trashbat on Friday 17th October 19:09

[theador]

I'm pretty sure BMW recommend the process on 335is