Forged engine carbon build up on pistons?

dac69er

dac69er

Super Moderator
Noticed I have a lot of carbon build up on the tops of my pistons. A worrying amount based on the mileage! It wasn't even that bad on my stock pistons when I took the engine apart!!!!

It's a forged build that has only done about 1000km.

Engine doesn't seem to use any oil. I've done a compression test and got 170,170,165,165

Any ideas?
 
dac69er

dac69er

Super Moderator
Jay said:
Can't keep them gleaming forever :D

Does it look equal across all four?
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I'm not expecting shiny, but they are worse than 80k mile pistons and they have done less than a thousand miles!!!

Build up is Pretty equal from what I can see. Number 2 plug is a bit darker than the rest, so I suspect the injector is leaking a bit or something. I did have them cleaned and tested so should be fine.
 
G

gorganl2000

Lifer
just dropping some thoughts/questions as i'm not too clued on this situation
but is it possible it could be due to the bore/ring tolerances and the engine still being quite young---still bedding/running in?
how about the type of gas being used--any ethanol content?

as jay mentioned,, the type of driving being done---since its a new engine, that could be a lot of slow/calm driving in that 1000km

the relatively similar compression and carbon across the cylinders does seem like everything is good with the engine though

i've seen clean intake and engine cylinders/pistons only when water injection is used---acts like a steam clean when driving
 
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dac69er

dac69er

Super Moderator
gorganl2000 said:
as jay mentioned,, the type of driving being done---since its a new engine, that could be a lot of slow/calm driving in that 1000km
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I've been beating on it pretty hard considering it's low mileage tbh. Definitely haven't been driving it slowly apart from when I get stuck behind old dears

I've noticed the exhaust seems to spit more black carbon spots out all over the back of the car compared to my reasonably stock GT. I assume it's just running on the rich side. I probably need to tweak the map a bit tbh, but I was just concerned with the amount of carbon build up after such a short period of time!?
 
Jay

Jay

Admin
Worth a quick chat with the tuner I'd say.

The compressions sound within tolerance so you might just being seeing the results of a rich mixture.

Could run a bit of injector cleaner through it as well in case it helps too. Obviously stick to the super unleaded best you can.
 
dac69er

dac69er

Super Moderator
Jay said:
Worth a quick chat with the tuner I'd say.

The compressions sound within tolerance so you might just being seeing the results of a rich mixture.

Could run a bit of injector cleaner through it as well in case it helps too. Obviously stick to the super unleaded best you can.
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I have stuck some injector cleaner in it just incase.

I could give the tuner a call, but tbh, I don't think I will get much from them tbh. They were ok, but aren't that clued up on starlets or power FC.

I will see what they say though
 
dac69er

dac69er

Super Moderator
I checked my daily GT and that does actually have black specs over the back, so scrap what I said about that. I guess I just don't notice it as much on the daily as it is either a bit dirty anyway or gets washed off with all the rain we have!

It is overfuelling, but isn't by loads.

I have bought a little cleaner thing and will try and get some of the bigger bits off. It may have got some build up from before when I was only running it for short periods after the rebuild. I would have thought it would have blown out by now though!!!
 
dac69er

dac69er

Super Moderator
Picking this one back up again as it is still an issue :(

I'm still getting build up on top of the pistons that is oily. Number 2 piston is the worst.
It cleans off quite easily with a rotary plastic brush.

Done compression test on a few more occasions under different conditions and am in the ballpark of 160-165 across all 4.

Have done about 1300 miles on the new engine in total.

I get intermittent smoking that is greyish. It tends to puff some out when I am driving really slow and then accelerate lightly. Coming to a junction and then turning into it and it would puff a bit of smoke.

Any ideas?
 
G

gorganl2000

Lifer
off the top of my head, my initial thoughts are piston ring clearances may be a bit on the wide side to accommodate higher boost levels, and a distant second are valve stem seals.
the fact your compression is consistent and within reason across the board is a good thing
are you noticing any excessive drop in your oil level?
 
Jay

Jay

Admin
What sort of use is the car seeing Duncan?

Any build ups I've seen on mine have been due to me not driving them, or not giving them a 'proper' run up to temp and enough time to burn the stuff out.

Your smoke description kind of suggests valve stems though. If you spend a lot of time on over-run then put it in neutral and rev it, can you see any puffs of smoke? Would still recommend a dose of fuel additive to see if it helps, octane booster has its benefits.

Just on that - have you looked inside the tank recently? I've had two now where the fuel has been contaminated from rotted pump filters! One had got to the stage where it was barely starting but the other had no real symptoms at all.
 
dac69er

dac69er

Super Moderator
No noticeable drop in oil level, I do have a leak from the cam cover somewhere that I need to attempt to repair again.

I have tried all the normal things for valve stem oil seals like excessive amounts of overrun and then flooring the throttle and nothing.

Usage wise, it is generally fairly short outings tbh, but took it for a good run the other day and it still had smoking issues.

I replaced the pump when I did the rebuild. It was clean as a whistle and the pump filter should be fine.
 
dac69er

dac69er

Super Moderator
Just done a leak down test and all good.
I got some redex as was on offer in the supermarket, so will chuck that In just to tick that box.

Nothing is pointing to an issue, it's a hard one to work out!!!!
 
dac69er

dac69er

Super Moderator
SKINY said:
Redex
You may as well just piss into the tank
Complete snake oil that stuff lol
Dipatane is Thee 1 you want to get Bud :)
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Tbh I don't think any of them are really worth bothering with as the concentration and contact time is so short.

I have used redex in my ultrasonic cleaner to clean Injectors myself and it seems to do something and costs peanuts.
 
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