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My experience with PI and carbon build up

anotero

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
Mosquito said:
My piston tops are super clean. As in new brake rotors clean.
Matter of fact. Until I took at look at them I had never seen a piston look that clean, ever.
52K miles myself. APR ST2 for 1K - 49K miles. Now on UM they look mostly the same.
Click to expand...

I wonder if mine are not sparkling clean because of CA gas.
 
M

Mosquito

Go Kart Champion
Location
FL
Mosquito said:
My piston tops are super clean. As in new brake rotors clean.
Matter of fact. Until I took at look at them I had never seen a piston look that clean, ever.
52K miles myself. APR ST2 for 1K - 49K miles. Now on UM they look mostly the same.
Click to expand...

I gotta take this last bit back. Did some small work on the car tonight and took a look at cylinders 2 & 3. Both are black and not how they've been the last 50k miles. I am chasing a few issues since changing tunes in November so it is either the new tune or those things.
 
jimlloyd40

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
anotero said:
Are yours nice and shiny?
Click to expand...

I don't know. I'll have to check next time I change the plugs. I imagine mine will look orange from the Torco octane booster. But I do run a fuel system cleaner regularly so it will be interesting to find out.
 
M

Mosquito

Go Kart Champion
Location
FL
Diggs24 said:
From what tune then to what tune now? I would guess it's the tune, especially if it's one where they manipulate valve timing more than typical. Probably creates more overlap.
Click to expand...

I went from APR ST2 to UM in November so I could eventually do MPI for the sake of cleaner intake valves, something that has become increasingly delayed due to a couple of issues.

Since then I went through a couple of OEM PCVs due to oil in cylinders and eventually landed on a Spulen V2 CC. UM said at the time that my problem is uncommon but has been seen before and the solution was. Either lower boost or change the PCV plate to something like VWR or Spulen. Their words, the OEM PCV does not vent boost right (I take it, high boost as in 29 PSI or more). I chose the latter, for now.

Have also developed an occasional EVAP purge flow error so I've been chasing charcoal canister, leak detection sensor issues since changing the N80 valve is not doing much. Then there was and still is slight oil in my exhaust manifold which meant I had to replace the pre-turbo gasket, that seems to be holding together for now but there still seems to be very little oil making it there, but no oil was/is making it to the turbo or DP though. Then there is the fact that MPG went to hell as soon as the OEM PCVs started to fail back in Nov., so I've been trying to get that under control. It's been an entertaining last couple of weeks and recently is making me remember why I got rid of my MK4 back in the day and skipped the MK5 altogether. Working on the car every weekend is starting to get old.

Going back to the piston tops. They were clean and shiny as far back as January, even early Feb. By then I had seen oil in cylinders more than once (OEM PCV), had changed to the Spulen CC and had solved that.
Had the blown gasket which I am confident did not have air going in since the leak was super small and oil filled. Had the occasional EVAP purge flow which recently seemed to be getting better. Really all I did in the last month for them to show black as they are now is switched plugs from IKH01-24 to stock OEM, gapped at 0.024 which I thought would burn more complete and I thought it did because it had a tendency to increase my positive LTFTs % from sub 10s prior to - to mid 10s afterwards regardless of the leaking exhaust gasket. Then, I changed the exhaust gasket too. I guess I'll have to go back to the racing plugs and see how that goes, but I doubt the problem is there.

Had I not seen the pistons clean, shiny and issue free for over 50K miles I would think the current look is more normal but I can't see it that way currently.
 
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V

vegatune

Passed Driver's Ed
Location
jax
Mpi definitely helps but I wonder if mpi is only running when it’s needed. If it’s set up like stage injection than it makes sense that it’s cleaning the valves less compared to running full time.
 
M

Mosquito

Go Kart Champion
Location
FL
Been going around alternating between 2 N80 valves recently. When one errors out, I clean the other one with electronics parts spray and install it. Usually goes on for a while without issue.
At first it took a while for the tank ventilation readiness to set and I had quite a bit of misfires after fuel fill up, but when it works mostly well, It sets readiness within a couple of hours, if not minutes and refueling misfires are near non existent. It doesn't seem to like fuel injector cleaners in the tank though as I went through 10 gas tanks without issue until I added it again last weekend. I've used fuel injector cleaner in the past quite often and perhaps too often?

In due time, I eventually I started looking at other things. A VW Tech told me not long ago that under normal conditions, the charcoal canister was supposed to weight 7 lbs or so. More would equate to fuel in it.
I used to top off to the neck, but no more. Mine came back at 5.5 lbs or so. Shook it a bit and it sounded like all dry charcoal, no fuel. The tech did suggest it is likely the LDS or something like (sensor on the tank) could be likely failing and throwing off the N80 valve in the first place. I heard it can affect AFR if it doesn't flow correctly too, hence drop in MPG. Lots of speculation really.
 
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