Di and valve crudding

[Devon K]

2 series forum member and prospective m235i buyer here, and I was wondering if the the N55 has major problems with valve crudding due to it not having a dual injection system. Do most 135 owners run into this problem? At how many miles, and what does it cost to fix?

TIA.

[135Pats]

Originally Posted by Devon K

2 series forum member and prospective m235i buyer here, and I was wondering if the the N55 has major problems with valve crudding due to it not having a dual injection system. Do most 135 owners run into this problem? At how many miles, and what does it cost to fix?

TIA.

Every DI motor will have this issue to varying degrees. Cost depends entirely on location and whether it's done through an indy. I've seen as low as $250, as high as $1000.

[johngrossi]

Valve cleaning should be routine maintenance on any DI car. Cost will depend on your location. Search around a bit and start to build a relationship with an Indy who works on these vehicles.

[mleskovar]

Originally Posted by johngrossi

Valve cleaning should be routine maintenance on any DI car......

Not so. Some strictly DI cars/motors don't have the problem. It's a balance of valve timing, piston crown shape, ignition timing, etc.............

[Iron Man]

Originally Posted by mleskovar

Not so. Some strictly DI cars/motors don't have the problem. It's a balance of valve timing, piston crown shape, ignition timing, etc.............

Interesting. What strictly DI motors do not suffer from carbon build-up? I know Toyota has used a combination of DI with port injection to prevent carbon build-up, but I have not heard of any DI only engine not having carbon issues.

[cheshirecat79]

Originally Posted by Iron Man

Interesting. What strictly DI motors do not suffer from carbon build-up? I know Toyota has used a combination of DI with port injection to prevent carbon build-up, but I have not heard of any DI only engine not having carbon issues.

The only ones I've seen that don't have DI issues are the ones that use port-injection like you mentioned. I've seen diesels (such as the Mercedes BlueTec) which uses EGR/Urea Injection and particulate filters to try to keep carbon down, and it supposedly works pretty well.

Supposedly Ford has "solved" the problem through different injection timing just like Mazda fixed it with temperature management on the intake valve. Both seem to still experience issues, albeit not to the point of the N54.

[Iron Man]

Originally Posted by cheshirecat79

The only ones I've seen that don't have DI issues are the ones that use port-injection like you mentioned. I've seen diesels (such as the Mercedes BlueTec) which uses EGR/Urea Injection and particulate filters to try to keep carbon down, and it supposedly works pretty well.

Supposedly Ford has "solved" the problem through different injection timing just like Mazda fixed it with temperature management on the intake valve. Both seem to still experience issues, albeit not to the point of the N54.

I see. I guess to me delaying the problem is not fixing a problem. If you still have to clean the valves at 100K, instead of 50K, while it may be better, it doesn't really eliminate the issue.

[mleskovar]

Originally Posted by Iron Man

Interesting. What strictly DI motors do not suffer from carbon build-up? I know Toyota has used a combination of DI with port injection to prevent carbon build-up, but I have not heard of any DI only engine not having carbon issues.

The Toyota port/di injection approach is for better gas mileage....reducing carbon buildup is a bonus. At higher rpms port injection is more efficient than di. There's been a lot of research done on carbon buildup with di motors and the results are interesting. The buildup has been analyzed and it turns out to be mostly coming from the gasoline being used in the US. "They" say the problem isn't noticed in Europe. It seems we/US have crap in our gas that they don't. But by playing with valve timing/overlap, piston crown shape, valve location etc. it can be minimized even with the crummy gas. It's the unburned gas that backs up into the intake track and gets cooked on hot valve and intake track that becomes the buildup. With no fresh charge to clean it off it grows. There's several cars that don't suffer the malady in the US and they don't use the port & di set up.

[Iron Man]

Originally Posted by mleskovar

The Toyota port/di injection approach is for better gas mileage....reducing carbon buildup is a bonus. At higher rpms port injection is more efficient than di. There's been a lot of research done on carbon buildup with di motors and the results are interesting. The buildup has been analyzed and it turns out to be mostly coming from the gasoline being used in the US. "They" say the problem isn't noticed in Europe. It seems we/US have crap in our gas that they don't. But by playing with valve timing/overlap, piston crown shape, valve location etc. it can be minimized even with the crummy gas. It's the unburned gas that backs up into the intake track and gets cooked on hot valve and intake track that becomes the buildup. With no fresh charge to clean it off it grows. There's several cars that don't suffer the malady in the US and they don't use the port & di set up.

Yes, I've also read about it not being an issue in Europe and related to US gas. I did not know there were any models in the US that were problem free (reading that both Ford and Hyundai owners are seeing the build up in their DI engines). I wonder though if some the design changes you mention to decrease the carbon problems also decrease the overall advantages of even using DI to begin with. Thanks for the info.

[rsjean]

Mines at the dealer right now getting a $700 cleaning. 2009 N54 with 50,000. Always run hot since I drive 25 miles each way to and from work at about 75 to 90 miles an hour in desert heat. Still crapped up.