Hello,

I recently had a chance to examine the top of no.4 piston (after it was replaced for piston slap).

I hoped to see a nice even brown varnish over the top of the piston with no signs of det damage, but found that there was quite a bit of carbon deposited around the outer lip of the piston.

Given that the car spends most of it's time in London traffic is this normal? Would an 'italian tune-up' (fast blast) burn this off?.

Comments please...

Cheers,

Alex


[This message has been edited by AlexM (edited 08 May 2001).]

 

Alex
If you do a lot of idling in trafic i would sugest you use a product called Nitrous Formula Street or Super Street octane boost.
I use the Street one every 5000ks or so.
Its great stuff
It has cleaners to fix your problem.

 

Alex,

1st&2nd green led on LambdaLink is indeed rich on zero throttle. That's one thing i hate about the Link ECU being notoriously difficult to lean out for idle (though not impossible) without compromising idle stability. Ideally as per JECS ecu, A/F ratios "rock" back and forth to avoid "bore washing" the cylinders and pistons.

Your observation of the excess carbon deposited around the outer lip of the piston is symptomatic of bore washing.

Nitro, what made you say a dose of NF octane booster can effectively remove [hardened]carbon deposits? This is only something the manufacturers like to claim but whether it actually does so is something else altogether.

 

Hi AlexM, since you sit in traffic alot, get out on the motorway and do a good 80 mph for at least 15minutes on weekends. This should burnoff the excess carbon build up. A higher speed would be ideal but then you could get nabbed for speeding. I dont know what the speed limits are in the UK.

 

Jan

The Nitrous Formula I suggested contains a combustion chamber cleaner.
In a brocher that i was reading it said it passed the D5500 BMW test what ever that is.
You can read about it on their site

 

Hi there,

Depending on the ammount of carbon, a high speed/temp run wont shift it.

Carbon deposits can be "stronger" than the piston itself... and wont simply burn off.

J.

 

Ooops.