The beef with GDI and valve coking


Pewter-Camaro

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Yeah, LSPI gets blown out of proportion. Its a real thing, but the way they talk about it you should never, EVER get into boost under 3000rpm because you'll detonation and blow all the rivets of your floorboard out.

But I never had a lick of issues with any of my turbo cars.
At least on The Fords stock tune has Several tables Dedicated to LSPI protection. With the tiny super fast spoiling turbos on them it really is required. I know early on there were some tuners removing that which really was scary to see in a tune.
 

Kaeghl

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My jag has a 5.0 with gdi and a blower. We had a bulletin from jag corporate that a lot of the issue could be mitigated by using higher end gas, Bp, Shell, Mobil (I stick to shell or BP) they guys that use the cheaper gas get a lot of build up, at 120k my car has almost none.
 

Thirdgen89GTA

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At least on The Fords stock tune has Several tables Dedicated to LSPI protection. With the tiny super fast spoiling turbos on them it really is required. I know early on there were some tuners removing that which really was scary to see in a tune.
Yeah, the Focus ST turbo turns on like a light switch at 1700rpm. I remember many times leaving from a stop and wanting more power only to get a Thanos snap and instantly turn the front wheels into smoke.

The RS turbo is bigger, and even with the increased displacement still has a higher threshold. Maybe about 300rpm or so.
 

Kensington

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My jag has a 5.0 with gdi and a blower. We had a bulletin from jag corporate that a lot of the issue could be mitigated by using higher end gas, Bp, Shell, Mobil (I stick to shell or BP) they guys that use the cheaper gas get a lot of build up, at 120k my car has almost none.
When I bought my Flex, I dropped a boroscope down and the valves looked pretty awful. Tried to find a place to do the media blasting, but no one would touch it. Performance hadn't degraded yet, and Ford wouldn't do anything until the car was missing or surging, and then their "fix" was to just replace the heads. Ran "good" gas and "good" oil at normal intervals for a year, dropped the boroscope down again, and it had almost all disappeared. Maybe I was just lucky :dunno:
 

Kaeghl

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When I bought my Flex, I dropped a boroscope down and the valves looked pretty awful. Tried to find a place to do the media blasting, but no one would touch it. Performance hadn't degraded yet, and Ford wouldn't do anything until the car was missing or surging, and then their "fix" was to just replace the heads. Ran "good" gas and "good" oil at normal intervals for a year, dropped the boroscope down again, and it had almost all disappeared. Maybe I was just lucky :dunno:
there was a lot of talk of how top tier gasolines all have detergents and that they help keep the vales clean with a bit of blow back during combustion (the same way the coking gets there).
there is media blasting available like walnuts, or you can try to find a dry ice media blasting place, the media just evaporates.
 

Mr_Roboto

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I recall toyota adding a an extra injector to the intake just to wash the valves with fuel during operation.
the audi's v8 and v10 have huge issues with coking. There was a guy in the r8 forums that lost about 30% of power (on dyno) due to how thick the valves were coated.
I was going to say if it's direct injection turbo it seems like a good excuse to get methanol injection to me.

I also wonder if driving cycles have something to do with it too. e.g. you have people that either beat the piss out of it or don't beat the piss out of it.
 

b4black

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Toyota and Ford have both moved to combination (dual) PFI and DI systems. Lots of benefits, including being able to clean the valves with the PFI injectors.
 

torquelover

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On my Ecoboost 2.0 it seems to be missing a bit on cold start (37k on it).

I'll take a look this spring.

The Mazda with 55k no issues what so ever.
 

b4black

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Cold start miss is a common problem for DI. Nothing to do with valve deposits. It's one of the problems improved by going to a dual PFI/DI system
 
OP
DEEZUZ

DEEZUZ

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Cold start miss is a common problem for DI. Nothing to do with valve despots. It's one of the problems improved by going to a dual PFI/DI system
I do very rarely have a cold start stumble. Hoping when I do plugs it fixes it. I still don't know much about GDI.
 

smug

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Guy at work has a cold start issue and he cleaned all the sensors on the air tract including the intake manifold
 

Kaeghl

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weird, the jag never has a cold start issue but it does the hot start thing to get the cats warmed up faster. When you start the engine it holds a higher rev than normal as it dumps some gas to get everything hot.
 

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