Intake valve cleaning
- Thread starter erhayes
- Start date
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- Canada
I'm at the equivalent of 45000 miles on my 2018 CX-9. I see no reason to consider a valve cleaning/inspection at this time.
A valve cleaning would be recommended if you're experiencing poor fuel economy or reduced engine performance. When it comes to carbon buildup, my understanding is that with direct-injection vehicles, driving habits can be a major determining factor, in that the issue is more likely to occur if your usage consists of a lot of short trips that don't allow the engine to get up to operating temperature. I assume that this is the main reason Mazda did whatever they did to get the engine to run hotter. In my particular case, the engine almost always gets up to operating temperatures, and it sees 4k RPM+ at least once a day (in the summer). Fuel economy has been the same (more or less, it fluctuates very slightly depending on what tires I have on, whether I have my throttle controller engaged, or whether I have the CS intake or OEM intake installed).
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- Mazda
A simple inspection would be to run a scope by pulling a sparkplug have peek. My guess is you are not going to like what you see. The carbon build will be there. To what degree that is the question.
Operating the engine at any RPM has little carbon preventive effect on a DI engine. Its air that travels into the intake manifold and by the intake valve on its way to the combustion chamber no fluid runs over the back of the intake vale or stem to prevent carbon build up and heat is a very small facture to reduce carbon from forming in that area.
We have been testing water injection at low engine speeds with good results. But and I do say BUT the issue is that in order for water injection to be safe at reducing or stopping the carbon build up the ECU "must" be calibrated for the extra amount of fluid and less air at the different throttle % used.
Operating the engine at any RPM has little carbon preventive effect on a DI engine. Its air that travels into the intake manifold and by the intake valve on its way to the combustion chamber no fluid runs over the back of the intake vale or stem to prevent carbon build up and heat is a very small facture to reduce carbon from forming in that area.
We have been testing water injection at low engine speeds with good results. But and I do say BUT the issue is that in order for water injection to be safe at reducing or stopping the carbon build up the ECU "must" be calibrated for the extra amount of fluid and less air at the different throttle % used.
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- Canada
Absolutely there will be some amount of carbon buildup. All I was saying is that for my vehicle, I don't think that valve cleaning is necessary at this time because there is no discernible loss in fuel economy or engine performance.
It's like taking the shoes I wear everyday and scrubbing them clean, then going right back to using them normally. They provide the same function before and after the cleaning. Now, if I had just walked through a muddy field, it would make sense to clean them because the caked on mud would make the shoe heavier, and affect the tread of the shoe.
Maybe I'm wrong and periodical intake valve cleaning is better than waiting until the symptoms arise and cleaning at that point. Is it that much harder to clean carbon deposits after a certain period of time? Does the carbon weaken or corrode the intake valve?
It's like taking the shoes I wear everyday and scrubbing them clean, then going right back to using them normally. They provide the same function before and after the cleaning. Now, if I had just walked through a muddy field, it would make sense to clean them because the caked on mud would make the shoe heavier, and affect the tread of the shoe.
Maybe I'm wrong and periodical intake valve cleaning is better than waiting until the symptoms arise and cleaning at that point. Is it that much harder to clean carbon deposits after a certain period of time? Does the carbon weaken or corrode the intake valve?
The carbon comes from oil vapor from the positive crankcase ventilation (PCV) system venting crankcase vapors into the intake manifold. The oil vapor hits the backside of hot intake valves which are not washed by gasoline vapors (due to the direct injection of gas into the cylinders) and the oil vapor bakes to carbon.
Several on this forum have installed oil catch cans to collect the PVC oil before it gets to the intake manifold. All the reports I've seen show that there is no oil for the catch cans to collect. The catch system built into the engine must be doing a very good job. Also, I haven't seen any reports of carbon build up causing engine problems as sm1ke writes.
Part of the benefit of the current oil category, ILSAC GF-6A, is, "Introduced in May 2020, designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, improved high temperature deposit protection for pistons and turbochargers, more stringent sludge and varnish control, improved fuel economy, enhanced emission control system protection and protection of engines operating on ethanol-containing fuels up to E85." (Emphasis mine)
https://www.api.org/products-and-se...categories-and-classifications/oil-categories
In case the symptoms sm1ke describes do occur there are ways to clean the intake valves, either chemical cleaning (here is one example: https://www.bgprod.com/services/gasoline-fuel-services/gdi-fuelair-induction/ ) or kinetic cleaning where the head is removed and disassembled and the valves blasted with walnut shell abrasive.
Several on this forum have installed oil catch cans to collect the PVC oil before it gets to the intake manifold. All the reports I've seen show that there is no oil for the catch cans to collect. The catch system built into the engine must be doing a very good job. Also, I haven't seen any reports of carbon build up causing engine problems as sm1ke writes.
Part of the benefit of the current oil category, ILSAC GF-6A, is, "Introduced in May 2020, designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, improved high temperature deposit protection for pistons and turbochargers, more stringent sludge and varnish control, improved fuel economy, enhanced emission control system protection and protection of engines operating on ethanol-containing fuels up to E85." (Emphasis mine)
https://www.api.org/products-and-se...categories-and-classifications/oil-categories
In case the symptoms sm1ke describes do occur there are ways to clean the intake valves, either chemical cleaning (here is one example: https://www.bgprod.com/services/gasoline-fuel-services/gdi-fuelair-induction/ ) or kinetic cleaning where the head is removed and disassembled and the valves blasted with walnut shell abrasive.
Given the posts on this forum, it appears that you are more likely to suffer a cracked cylinder head than carbon deposits on the intake valves.
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- Mazda
This is not really accurate. While some better-quality catch cans may slow down and capture some of the oil vapor there is still oil vapor that goes into the intake and will cause carbon to form on the intake valves and piston tops and cylinder head chambers. I am sure if you check with independent service shops, they can inform you how many DI engines each month they recommend a carbon cleaning. Mazda has no special means as of date to prevent that carbon from forming.
I would say for the more DIY you can pull your Throttle body and shine a flash light in the intake runners and I am sure you will sill a slight oil film on the intake walls.
Now I am not suggesting that you all be worried only don't think it does not happen. As for not feeling or seeing a drop off of power or MPG, it so gradual that the time the carbon is bad that's when most will start thread asking why both have increased. For some that claim no difference after 40k miles if you are really curious have your engine analyzed on an oscilloscopes and have the Technician look closely at the ignition data.
Or just have the intake manifold and combustion chambered scoped!I did notice that, on the Skyact engine diagram that the oil/air separator is uniquely different from the simple poppet valve PCV. Possibly this unit and running the intake valve at 400C+ will be effective enough to limit too much buildup over say 125,000 miles. I would hope so. Ed
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- Canada
This is not really accurate. While some better-quality catch cans may slow down and capture some of the oil vapor there is still oil vapor that goes into the intake and will cause carbon to form on the intake valves and piston tops and cylinder head chambers. I am sure if you check with independent service shops, they can inform you how many DI engines each month they recommend a carbon cleaning. Mazda has no special means as of date to prevent that carbon from forming.
I would say for the more DIY you can pull your Throttle body and shine a flash light in the intake runners and I am sure you will sill a slight oil film on the intake walls.
Now I am not suggesting that you all be worried only don't think it does not happen. As for not feeling or seeing a drop off of power or MPG, it so gradual that the time the carbon is bad that's when most will start thread asking why both have increased. For some that claim no difference after 40k miles if you are really curious have your engine analyzed on an oscilloscopes and have the Technician look closely at the ignition data.
I think you may have quoted the wrong post. This sounds like it was in response to @PTguy's post.
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- Mazda
Yes good eye.
I was reading the resent responses and simply responded not paying attention to the quote captured. It can still hold value even without the quote from any member, I should think?
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- Canada
Yes good eye.
Absolutely, if I caught it I'm sure everyone else knew too. I'll edit the post for you, just in case
TSB for the early SkyActiv on Mazda3... not sure if this standard procedure at a dealer if you request DI valve cleaning.
