Decarbonizing GDI Engines....

[3930dave]

1) How is your mileage and driveability affected (Year/Make/Model pls) ?

2) What are you using/doing to decarbonize the head ?

3) How often do you need to do it ?

4) If not DIY, what are you paying to get this done ?

Intake Valve Deposits in Gasoline Direct Injection Engines

Rgds, D.

 

[Snobdds]

Audi and BMW had really bad problems with this. However, most manufacturers have figured out how to prevent the slugging of the valves. Most use a process called reversion where the fuel injector fires off fuel on both the compression and exhaust stroke as the piston is coming up to put fuel on the valves as they open and close. Some call this pre-charging the cylinder, but it's the same thing, just semantics. They also use air scavenging, where the intake valve opens just a little to make the exhaust gas leave the cylinder head faster. It can only be done on double over head cam engines with intelligent valve timing.

 

[tcartwri]

Allot of people installing crankcase vapor separation cans. " Catch Cans "

They go inline with the PCV plumbing.

 

[buickanddeere]

Use the proper low ash engine oil instead of your favourite oil. Minimize putting around granny diving and minimize idling.
Drivers who use the remote start to warm the engine have more vehicle carbon problems vs those divers whose vehicles use the block heater.

 

[3930dave]

Allot of people installing crankcase vapor separation cans. " Catch Cans "

They go inline with the PCV plumbing.

I'd heard the term, but hadn't looked up where they were installed - makes sense, thnx.

Rgds, D.

 

[3930dave]

Audi and BMW had really bad problems with this. However, most manufacturers have figured out how to prevent the slugging of the valves. Most use a process called reversion where the fuel injector fires off fuel on both the compression and exhaust stroke as the piston is coming up to put fuel on the valves as they open and close. Some call this pre-charging the cylinder, but it's the same thing, just semantics. They also use air scavenging, where the intake valve opens just a little to make the exhaust gas leave the cylinder head faster. It can only be done on double over head cam engines with intelligent valve timing.

Interesting explanation...... I realize that you are probably describing only a small amount of fuel use during reversion, but that sounds like it would decrease fuel economy slightly.

Rgds, D.

 

[Snobdds]

Interesting explanation...... I realize that you are probably describing only a small amount of fuel use during reversion, but that sounds like it would decrease fuel economy slightly.

Rgds, D.

It doesn't really affect gas mileage, but it creates a lot of carbon because there is unburnt fuel going down the tail pipe. Look at the tail pipe of a GDI engine and it's all sooty. I've heard this might mean GDI engines will need a DPF if the EPA has their way. Hope not.

Would not recommend a catch can either, especially in cold climates where they can freeze up, not allowing your crankcase to breath at all. Plus, if the system is not set up correctly with the proper evacuation with check valves, you're doing more harm to the engine than good.

The only real fix is to use port and direct fuel injection together. Toyota and Ford are now using this to finally solve the issue. This means a V6 with 12 fuel injectors and a V8 with 16 fuel injectors. The new Tacoma has this technology and Fords Gen II 3.5 Ecoboost will have this in 2017. Need to wait and see how it goes...

Until then I just drive my truck hard, which is a TTGDI, and I don't really anticipate any problems.

 

[3930dave]

Use the proper low ash engine oil instead of your favourite oil. Minimize putting around granny diving and minimize idling.
Drivers who use the remote start to warm the engine have more vehicle carbon problems vs those divers whose vehicles use the block heater.

Points taken. Spec oil always matters, but I'd seen too many reports of problems for it to be solely neglected or improper oil.

Of those points, the toughest for many is slow-speed driving and idling.... in a lot of metro areas, you don't have much choice - assuming you want to keep your license .

Don't have a GDI yet, but was interested in these design weaknesses..... was talking with a guy recently who drives a 2013 Kia Rio with well over 100k km on it - got me thinking about this again, as he said he "had to do something with it, it sounds like a diesel !"

Rgds, D.

 

[3930dave]

It doesn't really affect gas mileage, but it creates a lot of carbon because there is unburnt fuel going down the tail pipe. Look at the tail pipe of a GDI engine and it's all sooty. I've heard this might mean GDI engines will need a DPF if the EPA has their way. Hope not.

Would not recommend a catch can either, especially in cold climates where they can freeze up, not allowing your crankcase to breath at all. Plus, if the system is not set up correctly with the proper evacuation with check valves, you're doing more harm to the engine than good.

The only real fix is to use port and direct fuel injection together. Toyota and Ford are now using this to finally solve the issue. This means a V6 with 12 fuel injectors and a V8 with 16 fuel injectors. The new Tacoma has this technology and Fords Gen II 3.5 Ecoboost will have this in 2017. Need to wait and see how it goes...

Until then I just drive my truck hard, which is a TTGDI, and I don't really anticipate any problems.

Innarresting..... as Neil Young would say ! :thumbsup:

I haven't been too impressed with fuel economy of recent engines, and had been wondering why..... unburnt fuel, DPF with gas engines....... there are many forms of tech I like, but this isn't a road I want to drive on.....

Edit - Not for the first time, what the EPA is propagating seems bass-ackwards to me...... oil also seems to be going down exhaust pipes in some modern designs (GM 5.3)...... instead of piling on more complex (read consumer expensive) tech to "solve" that problem, how about just not putting fuel and oil down there to start with ?

Your post reminds me of some reading I'd done a while back on the 3.5 EB from Ford..... some guys have taken the time to set up perhaps the sophisticated valving you refer to - I get your point - don't install a half-baked solution for a catch can.....

Being the closet luddite that I am , I'll be sticking with MPFI for a while.....

Rgds, D.

 

[MossRoad]

1) How is your mileage and driveability affected (Year/Make/Model pls) ?

2) What are you using/doing to decarbonize the head ?

3) How often do you need to do it ?

4) If not DIY, what are you paying to get this done ?

Intake Valve Deposits in Gasoline Direct Injection Engines

Rgds, D.

2013 Chevy Impala
58,000 miles (40,000 by us).
Still gets 31mpg on the highway just like the day we bought it.
Car still accelerates like a rocket and cruises very smooth.
Never looked into the potential problem, but may now that I'm aware of it.