My experience with PI and carbon build up

[805mk7gti]

So my car may be a one off, but figured I'd share none the less. I installed PI at around 79k miles I believe. Since I removed the intake manifold for PI, I opted to walnut blast my intake valves. You can see what they looked like here: https://www.golfmk7.com/forums/index.php?threads/mk7-walnut-shell-blasting-adapter-review.355553/

I recently had a built motor and built cylinder head installed. I kept my original motor so I decided to tear it down to see why I kept destroying spark plugs on cylinders number 2. That could be another thread all on its own, crazy detonation on all four pistons but no cracked ringlands or skirts I could see.

What surprised me was the amount of carbon build up on the intake valves. Head had maybe 10k miles on it since walnut blasting, and car was run on full e85 for majority of those 10k miles. And yes I ran a Spulen catch can. Added pics of old pistons just for kicks.

 

[Diggs24]

Looks like you had a shitton of blowby. My pistons on e30 looked much cleaner albeit not at your mileage.

 

[Gvazquez]

So my car may be a one off, but figured I'd share none the less. I installed PI at around 79k miles I believe. Since I removed the intake manifold for PI, I opted to walnut blast my intake valves. You can see what they looked like here: https://www.golfmk7.com/forums/index.php?threads/mk7-walnut-shell-blasting-adapter-review.355553/

I recently had a built motor and built cylinder head installed. I kept my original motor so I decided to tear it down to see why I kept destroying spark plugs on cylinders number 2. That could be another thread all on its own, crazy detonation on all four pistons but no cracked ringlands or skirts I could see.

What surprised me was the amount of carbon build up on the intake valves. Head had maybe 10k miles on it since walnut blasting, and car was run on full e85 for majority of those 10k miles. And yes I ran a Spulen catch can. Added pics of old pistons just for kicks.

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I actually noticed the same thing on mine. Installed PI and rebuilt engine a few thousand miles later and I had minor carbon buildup as well. I wonder how bad itll be 40k miles from now..

 

[2slowvw]

That's a pretty good amount for 10k

 

[jimlloyd40]

That's a pretty good amount for 10k

That's a hell of a lot for 10K miles. Mine didn't look that bad at 50,000 miles and I also have the Spulen OCC system.

 

[CHHA]

That poor piston was running much too hot.

Here is a pic of a Octavia RS (same engine as MK7 GTI but with ROW engine spec -> DI + PI ) valve after almost 60k miles. 40k miles with APR stage 1. Fuel was Aral Ultimate 102 - which is approx 97 in US.

I think especially the shaft of the valve looks much cleaner.

 

[JerseyDrew77]

Damn OP! At 71k miles, I had mine looked at when I had MPI installed with a Euro intake manifold and barely had any carbon build-up.

 

[The Dude]

so MPI doesn't make a substantial difference then, what about WMI?

 

[Hoon]

Blowby will do that.

My hurt cylinder had oil and carbon on the intake side. Like all VVT engines, we have EGR done via valve overlap. If a cylinder isn't sealing well, the oil will end up in the intake tract.

 

[The Dude]

so is it safe to say that if you have substantial buildup, perhaps an overall health and wellness check would be a good idea?

 

[hans611]

so MPI doesn't make a substantial difference then, what about WMI?

Basically what i figured would happen, the injector sprays the dirty valve and it just cleans the top of it...

With the fuel and gunk then kinda run down the valve a bit but still pool up on the base of the valve....

So without MPI, the entire valve is dirty... WIth MPI, the gunk accumulates lower in the valve... Maybe less gunk accumulates, but not a worthwhile mount....

It makes sense as the fuel basically atomizes to vapor when its sprayed into the intake valve... its not going to clean much....

 

[The Dude]

well that saves me some cash I suppose. I wonder if WMI has shown any tendency to prevent that same buildup.

 

[Hoon]

well that saves me some cash I suppose. I wonder if WMI has shown any tendency to prevent that same buildup.

Nope it's less useful than MPI

 

[GroceryGTIer]

I guess that kills the catch can helping theory ??

 

[The Dude]

so is there anything that has been proven to reduce/reverse carbon buildup on the valves?