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Discussion Starter · #1 ·
As my QV just passed 5k it makes me wonder if there is anything proactive that should be done with AR’s direct injected engines before carbon deposits become a bigger issue? It makes sense the QV needs its spark plugs to be changed out relatively early before they start adding to carbon deposits. Does the QV have a oil catch can or should one be added? Just wondering if anyone else has given any thought to this. Is the good ole’ Italian tuneup the best solution?:wink2:
 

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As my QV just passed 5k it makes me wonder if there is anything proactive that should be done with AR’s direct injected engines before carbon deposits become a bigger issue? It makes sense the QV needs its spark plugs to be changed out relatively early before they start adding to carbon deposits. Does the QV have a oil catch can or should one be added? Just wondering if anyone else has given any thought to this. Is the good ole’ Italian tuneup the best solution?:wink2:
We have 15,000 mile on our Ti (2.0) with no noticeable signs of carbon build up. I also have 30,000 miles on my 4C (1.75) with no noticeable carbon issues.

Including the QV (2.9), all three engines are AR, direct injection, variable valve timing and turbo charged. Also computer controlled.

Modern fuel (gasoline) has tons of additives in it to help prevent carbon build-up. I'm inclined to think carbon won't be a problem. But what do I know?
 

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Discussion Starter · #3 ·
Including the QV (2.9), all three engines are AR, direct injection, variable valve timing and turbo charged. Also computer controlled.

Modern fuel (gasoline) has tons of additives in it to help prevent carbon build-up. I'm inclined to think carbon won't be a problem. But what do I know?
Well that’s the problem. Normal port injection washes the back of the intake valves down with gasoline, with the additives you mentioned, so with each squirt the valves are getting a nice cleaning. DGI has no such washing of the valves. Add to that a turbo which might leak a little oil and any recirculated exhaust gasses being dumped into the intake ports without the benefit of the valves being washed with the gasoline it can be a problem on many GDI engines...
 

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Years ago we used what was called "top engine cleaner", a GM product, to clean the deposits off of the tops of the pistons and the intake valves. With the engine running at a high idle, one slowly poured it into the carburetor and then, nearing the end of the 12-16(?) oz. bottle, pour the remainder in to stall the engine. Allow to soak for an hour or two and then restart the engine. HUGE clouds of exhaust smoke! But, it worked really well. Then, when fuel injection was introduced, we found small and large vacuum hoses to use to SUCK in the fluid. The small to slowly suck in, then use the large to stall the engine. Same positive results. I believe the same and-or similar products (Sea Foam, for example) are still available. I see no reason that similar efforts couldn't be used on our newer DI engines.
 

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As a side note, the new Euro6D version of the 2.9L V6 has a second set of port injectors (added for emissions reasons), so it won't be susceptible to those issues in the first place.
 

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2017 Alfa Romeo Giulia Quadrifoglio
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Several Manufacturers are now adding port injection to their DI engines to prevent carbon build up on top of the valves. I am glad Alfa is doing that now. Carbon build up is a real problem with DI engines and it will rob HP sooner or later. Some engines start seeing noticeable performance drop and carbon build up as early as 30k miles.
 

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The reason why Alfa did it on the Euro6D V6 is emissions compliance. By adding the second set of injectors, they were able to avoid having to adopt particulate filters.
 

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Carbon build up is mostly an issue on DI cars that are:
1) not driven hard
2) often driven without getting up to operating temp

I had a Mark 6 GTI which were highly prone to carbon build up. Mine made it about 80k before needing to be cleaned because I drove it hard all the time. It is good for it.

I would anticipated we will need to clean the QV in the future but probably not till 60-70k miles.
 

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Carbon build up is mostly an issue on DI cars that are:
1) not driven hard
2) often driven without getting up to operating temp

I had a Mark 6 GTI which were highly prone to carbon build up. Mine made it about 80k before needing to be cleaned because I drove it hard all the time. It is good for it.

I would anticipated we will need to clean the QV in the future but probably not till 60-70k miles.
Yes, driving the engine to high rpms does help. Not necessarily with load but just high rpms. The mechanical vibrations and movements of the valves at high RPM can loosen carbon buildup deposits. But it also stresses the components. Double edge sword.
 

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Discussion Starter · #12 ·
Carbon build up is mostly an issue on DI cars that are:
1) not driven hard
2) often driven without getting up to operating temp

I had a Mark 6 GTI which were highly prone to carbon build up. Mine made it about 80k before needing to be cleaned because I drove it hard all the time. It is good for it.

I would anticipated we will need to clean the QV in the future but probably not till 60-70k miles.

Yeah DI carbon build up seems to affect certain cars more than others. I was looking into it and there is stuff from CRC made specifically to clean this which amounts to opening up the intake system and spraying it into a running engine.

CRC 05319 Intake Valve Cleaner 11 Oz

With all the sensors and other things I’d wonder about fouling something. Long gone are the days of dumping stuff down the carburetor with reckless abandonment lol. Also with the cylinder deactivation on the QV I do wonder about carbon build up differences from side to side.
I’m also wondering
 

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Correct Jerry. Cylinder deactivation is another whole topic. One bank will have x amount of more combustion cycles than the other and definitely more wear and tear including unwanted carbon build up. The QV's engine is like 2, 3 cylinder engines matted to each other.
 

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Correct Jerry. Cylinder deactivation is another whole topic. One bank will have x amount of more combustion cycles than the other and definitely more wear and tear including unwanted carbon build up. The QV's engine is like 2, 3 cylinder engines matted to each other.
Your carbon build up will likely be WORSE on the deactivated side as those cylinders will be theoretically cooler.

That said, I think any harm of cylinder deactivation is greatly over blown (to the point of it being a non-issue), but that's for a different thread.
 

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I'm confused now. Carbon build up in the combustion chamber is reduced by running the engine hard because it is possible to get the combustion chamber temperature high enough to burn the carbon. However, it appears to me that carbon buildup in the intake manifold is a result of high intake manifold temperatures and is likely aggravated by shutting the engine down too quickly after running it hard and unlikely to be improved by any kind of "Italian tune up".

Is this flawed reasoning?
 

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Discussion Starter · #18 · (Edited)
For carbon to build up on the intake valves you have to have carbon actually present to build up. The main reasons it happens is exhaust recirculation due to gases blowing by the piston rings in the cylinder into the crank case and being captured and resent to the intakes due to emissions regulations to be burned up and ultimately catalyzed like your fuel. Another common way is the seals on your turbo is leaking oil into the intake so you get the oil burning on the back of the valves. Normally with a good gasoline with additives washing the valves this never becomes a problem. What some manufactures donis actually affix an oil catch-can so the recirculated crankcase emmisions get cleaned of most of the oil before getting dumped back in the intake. The intake valves run cooler than the exhaust because they always have a charge or fresh relatively cold air coming in as compared to the exhaust valves. Anything that causes incomplete ignition and unburned fuel can also contribute to the problem. I do wonder if DI is one reason the QV has a very short spark plug change interval...
 

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To my knowledge there is no preventive measures. As fuel in direct injected there is no cooling so gas hits hot valves. On my 335xi after 80000 miles throttle response was still good. My friend had an Audi RS4 and he had to have the valves cleaned every 10k miles. Do our 2.9 engines for 18 have the port injection?
 

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Discussion Starter · #20 ·
As a side note, the new Euro6D version of the 2.9L V6 has a second set of port injectors (added for emissions reasons), so it won't be susceptible to those issues in the first place.
What’s the Euro6D version?
 
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