Direct injection-carbon deposits

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Since many new car's are employing direct injection there seems to be a problem with carbon deposits.I've read that using a top tier fuel is a must and changing the oil at the right oil change interval will help.I also read that running the engine 'hard' will help too.What is meant by running the engine hard?High RPM?Thanks Joe
 
Wide open throttle (floored!) at the upper torque bump. you can do this at a lower gear on the highway without speeding. Roll on throttle to the floor, back off do it again a couple times. Wait a few mins and rinse and repeat. Usualy 3 times should do it. Some people beat their cars constantly so they don't have to do it
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Problem is with new emissions oil and higher power density you might break something, whereas you could run a car wide open for mins in the old days of 0.7HP/CU-IN and not kaboom anything
 
Premium fuel might keep the injectors in better health but will do nothing for carbon deposits on the intake valves.

Using a quality synthetic oil with a low NOACK Volatility less than 10% will cut down on the deposits. Most engines do fine on 5k-10k OCI's depending on driving. Short trips and extended idling is an "extreme" driving condition for GDI engines so error to the 5k interval if you find yourself doing this a lot.
 
The top tier fuel is mostly to benefit the fuel system, particularly the high pressure injectors. It doesn't make much of a difference to the valves.

At 90k miles my car still runs well with full power and fuel economy and it hasn't been taken apart for a valve cleaning. I subscribe to the "Italian tune-up" method, although I apply it more aggressively than most.
 
I have the new Fit. My concerns and questions would be similar as the OP.

I'll see how it goes but really, is there much you can really do?

I use Top Tier gas, synthetic oil (when first change is due), and plan on using Chevron Techron twice a year.

Also...I will try to limit excessive idling and stop and go traffic. Short trips as well.

As for the "Italian Tuneup" thing? Maybe once in a while.

Other than those plans...I won't let it concern me too much.
 
Originally Posted By: BikeWhisperer
Premium fuel might keep the injectors in better health but will do nothing for carbon deposits on the intake valves.

Using a quality synthetic oil with a low NOACK Volatility less than 10% will cut down on the deposits. Most engines do fine on 5k-10k OCI's depending on driving. Short trips and extended idling is an "extreme" driving condition for GDI engines so error to the 5k interval if you find yourself doing this a lot.



I agree totally. My DI engine only gets Top Tier gas which I consider more of a "marker" than "marketing" as some have said. There's a reason that automakers don't import their DI cars into certain countries based on the quality of the fuel. Having 10% or less ethanol and a low NOACK / TEOST oil will undoubtedly do more over time to keep valve deposits at bay than an "Italian tune up" which would have a greater effect on a MPFI engine than a direct injection one. Typically, I too don't go much over a 5K OCI to err on the safe side as it makes me feel warm and fuzzy that I might be doing preventative maintenance versus someone who thinks Top Tier gas is just "marketing" and that using a conventional oil with a NOACK of 16 in a DI engine will give the same results as actually caring.
 
Originally Posted By: BikeWhisperer
Premium fuel might keep the injectors in better health but will do nothing for carbon deposits on the intake valves.


Not true on two accounts:

1) Premium does nothing additional for keeping injectors clean. That role is filled by the fuel detergents which are the same in most grades for most gas providers. Some providers do have more detergents in their premium, but that is more the exception.

2) Running premium will help prevent/slow down deposit formation. DI engines will lean out the AF ratio on higher octanes in addition to advancing timing. This reduces fuel dilution in the oil. The reduction in fuel dilution helps reduce oil vapors coming back through the PCV which supposedly create the intake valve deposits.
 
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Originally Posted By: Vuflanovsky


... Having 10% or less ethanol and a low NOACK / TEOST oil will undoubtedly do more over time to keep valve deposits at bay than an "Italian tune up" which would have a greater effect on a MPFI engine than a direct injection one. ...


VW/Audi has stated before the benefits of the italian tune up, even in their engineering data. Here is a before and after picture of intake valves on a VW GTI with 60,000 km on it. The italian tuneup was 20min+ at 4,000+ RPMs (not full throttle, just light load high RPMs).

In_8.jpg


After

RB_2_15.jpg


Mazda engineers have also said getting intake valves hot is the key to intake valve reduction and prevention. They said getting the valves above 400F is critical.
 
If that's all it takes to get that kind of reduction in crud, my valves must be spotless.
 
Originally Posted By: badtlc
Originally Posted By: BikeWhisperer
Premium fuel might keep the injectors in better health but will do nothing for carbon deposits on the intake valves.


Not true on two accounts:

1) Premium does nothing additional for keeping injectors clean. That role is filled by the fuel detergents which are the same in most grades for most gas providers. Some providers do have more detergents in their premium, but that is more the exception.

2) Running premium will help prevent/slow down deposit formation. DI engines will lean out the AF ratio on higher octanes in addition to advancing timing. This reduces fuel dilution in the oil. The reduction in fuel dilution helps reduce oil vapors coming back through the PCV which supposedly create the intake valve deposits.


Would you be so kind as to provide some documentation to support this?

And BTW...notice I said premium MIGHT keep the injectors clean. Because as you mention some premium fuels have more detergents but not all premium fuels have more detergents.
 
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I wonder how often one must do an italian tune up? Every 1k miles? More often? Less often?
 
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I try to get one in every 10k miles.

Assuming it is true that 4000+ RPMs at cruising throttle for 20-30 minutes gets enough heat in the valves to do the trick, then it's hardly an inconvenience.
 
Originally Posted By: VR6OOM
I wonder how often one must do an italian tune up? Every 1k miles? More often? Less often?


No good studies done on this. My personal practice is about once every 6,000 miles. LIke the previous post said, it isn't that inconvenient. I go on a trip to my parents house where I drive about 25min at 79 MPH (75 speed limit) in 4th gear which puts me around 4,600 RPMs.
 
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badtlc, where did you get the pictures and info on that method?

In the past I've been skeptical of that because I wasn't convinced that running at high RPMs at cruising throttle would get enough heat into the valves. I'd like to read more about that particular experiment if there's more to read.
 
Originally Posted By: Mykl
badtlc, where did you get the pictures and info on that method?

In the past I've been skeptical of that because I wasn't convinced that running at high RPMs at cruising throttle would get enough heat into the valves. I'd like to read more about that particular experiment if there's more to read.


Start here:

http://www.google.com/patents/US6866031

The last 1/3rd is the most interesting.

here is the critical part:

"An additional approach for reducing the formation of carbon deposits on the intake valves 20 is to increase the intake valve temperature, at least temporarily, since, surprisingly, it was found that any carbon deposits possibly present are removed at temperatures above 380° C. To this end, the intake valve unit, which comprises, among other components, the intake valves 20 and the valve stem guide 28, is designed with means that hinder heat dissipation in such a way that increased surface temperatures of more than 380° C. develop at least in the area of the neck 68 of the intake valves 20 in at least one predetermined region of the load characteristic diagram 74 of the internal combustion engine. This is illustrated in FIG. 4. The intake valve temperature is above 380° C. in the shaded region 112 b of the characteristic diagram. At these temperatures, carbon deposits on the intake valves 20 are removed. This region 112 b of the characteristic diagram occurs, for example, at speeds over 3,000 rpm, and in that speed range. extends essentially to full load. Even if the internal combustion engine is not operated most of the time in the region 112 b during normal driving operation of a motor vehicle, nevertheless, carbon deposits that could adversely affect the operation of the internal combustion engine cannot build up, since their removal in the shaded region 112 b of the characteristic diagram occurs very quickly. For example, operation of the internal combustion engine in this region 112 b of the characteristic diagram for a period of, for example, 20 min., is sufficient to remove even a thick layer of carbon deposits. In other words, a routine expressway trip cleans the intake valves 20 sufficiently. In addition, this region of the characteristic diagram can be entered in the course of maintenance or repair work on the internal combustion engine in an automotive workshop."
 
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^ I actually came back to the thread to post exactly that, but I see you edited your post to include the relevant portion.

This is the second document I've seen that says that, although the first one I read didn't spell it out as clearly as this one does. The first one I read said, and I'm paraphrasing, get the valve temps above XXX° C, this one actually provides a technique for doing so.

Good to know, and it's advice I can pass along to family members who get DI equipped cars.
 
Originally Posted By: Stewie
I seem to be doing italian tune ups everytime a stupid beige corolla
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gets in front of me on the highway, so no build up

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Be patient with the poor fool; he's trying to save money so that one day he can be one of those rugged individualists who drive a Bold New Camry...
 
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