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Discussion Starter #1
Intake valve coking from DI seems like it is becoming an issue with many of the newer DI motors. How bad does the LT4 suffer from this? With over 50K on the clock Im wondering how bad my valves look right now and how much performance is lost. Hopefully Ben and Co. can chime in and let us know what they have been seeing. Anyone else got any first hand knowledge?

 

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Wonder if methanol injection would keep that from happening.
 

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Wonder if methanol injection would keep that from happening.
From what Ive been reading meth isnt much help. Some guys with N54 motors did some testing and found it didnt help. Maybe if you start with freshly cleaned valves and ran meth full time it would mitigate the coking but once its on there the crystaline structure is hard to remove. normally requires media (walnut or dry ice) blasting to remove. Im just wondering how much buildup our motors are seeing because it defintely hinders flow.
 

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Makes sense. I had a Sky with the 2.0 DI engine and ran meth injection and the valves were clean when I decided to pull it apart to install forged pistons so it helped to keep them clean. As you mentioned, they would need to be clean to begin with to benefit from it.
 

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You can get a can of spray foam to squirt in the intake manifold of a running engine, that removes those coke deposits. Two person job because you need someone to keep on the gas or the engine will stall. And it makes a prodigious amount of smoke, like WWII Battleship Smokescreen levels of smoke. But it does work based on before/after borescope inspection. Not sure if you can put it through a supercharger though. I've only ever used it on a NA engine.

Also, detergent gasolines have additives to combat this. But it's usually only the highest grade of gas that has the detergents.
 

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Detergent gas won't help keep valves clean on a DI engine. DI has it's pro's and cons.
 

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Funny that the dealer offers a intake valve cleaning process now for all DI cars. Been a problem since the 3.6 v6 in the cts and camaros
 

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Ignorant input/question but it seems a catch can would help mitigate? I just put the MMS one on mine, at 8K miles, had quite a few small puddles of oil in the supercharger so it is obvious the current sealed system is just dumping that oil into the air.....
 

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You can get a can of spray foam to squirt in the intake manifold of a running engine, that removes those coke deposits. Two person job because you need someone to keep on the gas or the engine will stall. And it makes a prodigious amount of smoke, like WWII Battleship Smokescreen levels of smoke. But it does work based on before/after borescope inspection. Not sure if you can put it through a supercharger though. I've only ever used it on a NA engine.

Also, detergent gasolines have additives to combat this. But it's usually only the highest grade of gas that has the detergents.
That seafoam stuff doesn't do shit to the intake valve gunk buildup on DI motors.

AOS and catch cans will help prevent it but once you get buildup the only way to get rid of it is walnut blasting.

I have no idea how bad the LT4 is though, a lot of it depends on the PCV system
 

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add port injection :)
 

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Came here thinking this might be a drug thread...was mostly just curious about the title and whether or not it was some kinda weird typo!
 
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