Carbon Build up with Direct injection Engine in the CX5

my point is there is the most people who would not have issues and some small % who may have due to their driving conditions. But its nowhere that bad as you dont see many people complain on the 2.5na skyactiv.

I am also a strong supporter of driving on highest grade fuel possible and changing synt oil regularly for optimal benefits.
 
That cylinder deactivation video is interesting, or 2018 GT has it, but if it shuts the intake AND exhaust valves, isn*t there a compression issue?
Cylinder deactivation has been done this way since 1980's when GM implemented it on its V6 and V8's. Of course it failed miserably due to the reason you just said and imbalance of thermal effects between active and inactive cylinders which leads to many other issues such as oil consumption*fouling spark plugs*and even pre-mature cylinder wear. This also makes the cylinder deactivation being not as efficient as most people believe as the energy is wasted to compress the air in inactive cylinders. The saving of fuel with cylinder deactivation is very minimum, but it adds more complicate components and weight, with questionable reliability issue. That's why Mazda is the only one to offer CD to a 4-cylinder in the US. Many owners are anxious to disable the CD if their engine has such feature based on past experience.
 
Not to stray even further off topic, but I agree with yrwei. I disabled CD on my 17 Honda Odyssey and the gas mileage drop is minimal. Id rather pay slightly more for gas over a decade than risk failed active motor mounts, oil bypass/fouled spark plugs, etc.
 
Cylinder deactivation has been done this way since 1980's when GM implemented it on its V6 and V8's. Of course it failed miserably due to the reason you just said and imbalance of thermal effects between active and inactive cylinders which leads to many other issues such as oil consumption*fouling spark plugs*and even pre-mature cylinder wear. This also makes the cylinder deactivation being not as efficient as most people believe as the energy is wasted to compress the air in inactive cylinders. The saving of fuel with cylinder deactivation is very minimum, but it adds more complicate components and weight, with questionable reliability issue. That's why Mazda is the only one to offer CD to a 4-cylinder in the US. Many owners are anxious to disable the CD if their engine has such feature based on past experience.


I think the new 2020 GMC Acadia is going to have a 2.0L turbo with CD.
 
Based on reading the internet, the driver will experience loss of power and a reduction in mpg once the carbon builds up, with some cars as little as 30K miles. But there are people here driving with a skyactiv with over 100K miles and they get the same mpg that they did when they had 2K miles. This makes me think that intake valve carbon is not an issue on the skyactiv. As for cylinder deactivation, we are the test cases. I never notice when or if it happens.
 
...Also I read somewhere its kept open more to help with the knocking and high compression.
If all that is true, I dont see major issues with carbon on valve. Of course except if you drive your car,for 2 miles only and it never reaches normal operating conditions.

Interesting comment. I've read this motor is a pseudo Atkinson cycle engine. If this is true a portion of the intake charge will be pumped into the intake manifold maybe allowing for some cleaning of intake valves in the process. I have not seen the valve timing for a CX-5 to determine what is what.

In any case a city life for the car is hard on it.
 
Yep. As far as I remember the inlet valves timing is electronically controlled on the skyavtiv g which gives more 'freedom' and probably more efficient and fast response....
vs exhaust valves timing which is pure oil hydraulics with a mechanical valve and phaser which relies heavily on good oil/pressure and unobstructed oil paths.
 
Hope you can find time to do at least one of your SA-G engines, especially the higher-mileage one. Chris_Top_Her once removed his intake and found pretty bad carbon build-up on his CX-5 if I remember it correctly. Hence he put a catch can after that. He's an airplane pilot and we all know he's a spirited driver.


It seems whoever took the intake out by need or curiosity all found pretty bad carbon build-up on their CX-5 even with low miles.

Next project is most likely going to be stainless steel brake lines. Power and MPGs are consistent between the two engines. Then again we drive 40 through 55 miles per day for each vehicle so engine is always hot not to mention we live in a hot environment.
 
I have had my 2010 Speed3 intake ports and valve tops blasted with crushed walnut shells and carburetor cleaner, and had moderate buildup only in the central 2 cylinders and not much in the 2 outboard ones. I see no change in performance after the blasting. More peace of mind was found with having rebuilt injectors and new CorkSport injector seals.

I have an oil catch can as well, but only collect moisture in it, as checked at each oil change. Mine is turbocharged.

All of this said, we also own a 2016 CX-5 GT and I wasnt aware that it was also a gasoline direct inject (GDI). I see no exhaust soot buildup in the tail pipe of the CX-5, as I do in my Speed3.

Like many of you, I use only Top Tier fuel, but if the CX-5 Skyactive is a GDI, then the detergents dont do a lot of good in cleaning the intake valves. That said, I still use Top Tier gas in both cars.

So, this is interesting to me.....
 
My can captures oil based products as well as water. I've left it in a container before to separate out. It's definitely worth it when you consider the amount of gas that comes out of an injector.. any contaminants are a potential loss of power and or fouling of your components.


I found this new video about OCC's

 
If you use top tier or a gas with detergent, which is pretty much all gas stations and use synthetic oil and change it regularly the motor will stay like new clean. Mazda's injector pattern cleans as well as cools the combustion chamber with jets of fuel instead of a mist, as you can see in this video:

https://www.youtube.com/watch?v=fDFgiLrEX1o

Also it is important to get the engine to normal operating temperature.

Thanks for that.

Very interesting, I've never seen injectors demonstrated like that.

Also makes me feel better about only putting Top Tier gas in my CX-5 (my 2005 truck gets Sheetz). I thought I was possibly wasting my money, since I assumed the gasoline and the intake valves never touched each other.
 
Well that demonstrates how gas can pass the rings into the oil. Direct injection into the cylinder. Unless the injection stream hits the intake valve, I don't see how it would prevent carbon buildup. I think Mazda runs the intake valve at a high enough temperature to burn off deposits. Anyway, it doen't seem to be a reported problem.
 
https://www.savagegeese.com/reviews/mazda-cx-9

SAVAGEGEESE:
How is carbon build up managed and additional blow created from turbo associated with DI?

DAVE COLEMAN:
Carbon buildup on DI intake valves has two contributors. The oil itself getting on the valves, and the valves being at a temperature that promotes the formation of hard deposits.

We've dramatically reduced the oil in the intake stream compared to our last DI Turbo through several measures. First, oil blowing past turbo seals directly into the intake stream has been reduced with better turbo oil seals and lower oil pressure in the turbo itself. Actual blow-by has been reduced across the board with SKYACTIV engines by improving the roundness of the cylinder bores through improved analysis of casting, machining and assembly stresses that can slightly warp the bores. Taking this into account in the design process has given us much better blow-by performance.

Finally, the realization of the sensitivity to intake valve temperature has allowed us to design the cylinder head structure, cooling system and calibration to manage intake valve temperatures to prevent carbon buildup.
 
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