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It's an interference engine yes? Then it will get to them. Won't happen instantly, but it will get to them.
Being an interference engine means nothing in this instance. The intake valves are not being sprayed by the gas, and thus cannot be washed off by the additives in the gas.

You can run snake oil in your gas all day long with no deleterious effects, but you're not gonna convince me that it will magically clean your intake valves.
 

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It's an interference engine yes? Then it will get to them. Won't happen instantly, but it will get to them.
Don't understand how being an interference engine matters, here. The Skyactiv-G engines have considerable scope to control the timing of both camshafts... and particularly the intake camshaft. This means that on the compression stroke, some of the time more than other-times, the intake valves will remain open for an extended duration. Some of the effective compression will leak out the valves... (and so despite being nominally 13:1 CR - it effectively will be considerably less than that when the SkyActiv PCM wants it to be less). In any case, as a direct-injected engine the timing and even the number of injection events... can be and is closely controlled. I personally do not know if a partial injection event occurs in and around Bottom Dead Centre... whereby Mazda engineers can cause a small bit of air/gasoline mixture to leak outwards... onto the valves, as the piston starts its way up (on the compression stroke). This MAY be occurring. I don't know. This would not waste fuel, as that air/gasoline mixture would then subsequently make its way into the compression stroke 720 degrees of crankshaft rotation later.

Delayed intake valve closure may provide some beneficial effect on solvency on carbon, etc... on the backsides of the intake valves... but whether the engine is interference or not - seems to me is not germane to the discussion.
 

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It's an interference engine yes? Then it will get to them. Won't happen instantly, but it will get to them.
Uhh, what does being an interference design have to do with fuel delivery? Do you know what that means? An interference design is one where the valves and the pistons will occupy the same space at different points in the rotational cycle of the engine, so if the timing chain brakes the pistons will hit the valves. Nothing to do with fuel delivery at all....
Fuel is injected directly into the cylinder, bypassing the valves completely. Additives don't get anywhere near the valves.
 

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Typically with interference motors and especially With the higher compression, you typically have more overlap to create more power as you go through higher rpms. That valve overlap is part of what causes the carbon buildup on the valves themselves. This simply helps with that.
 

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You are saying that with overlap, potentially, hot exhaust gasses make their way in to the intake manifold where they will bake-on pcv flow related oil mist. I suppose. However being an interference design only maybe loosely correlates with overlap...
 

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Discussion Starter #28
Threads like this are pointless without pics. Excuse or not, you have a cell phone im sure. And scopes are effing cheap for phones these days.
Yeah, I hear reading is difficult these days...not enough attention span in our culture. Truth is, I went almost 3 years without any online access...and NOW I remember why. It's hilarious though...seeing such a weak human hide behind a keyboard and not contribute to the discussion. No pictures and you took the time to complain? What, are you 5?

Look, I came on this forum to share my experience with this vehicle. In the past I was on Honda, Nissan, etc. forums because I am very experienced in this world, and an engineer to boot. I won't go into my 5 years of racing, building engines, designing engines, etc. or all my friends that do it professionally. Nor will I go into depth on how I've had to fix a lot of government vehicles on the fly in combat zones because of poor engineering, mostly because I know you won't read it.

Cheap...LMAO. Cheap is relative...I'm chasing my dream--a borescope is on the WANT list. Not NEED...but hey, I'm sure you would have just thrown it on a credit card and slaved away at work to pay it off. Well, I'm free of that burden and wise enough to know how to spend my money--so go suck on you ba-ba, and leave the adults to their "READING".
 

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Yeah, I hear reading is difficult these days...not enough attention span in our culture. Truth is, I went almost 3 years without any online access...and NOW I remember why. It's hilarious though...seeing such a weak human hide behind a keyboard and not contribute to the discussion. No pictures and you took the time to complain? What, are you 5?

Look, I came on this forum to share my experience with this vehicle. In the past I was on Honda, Nissan, etc. forums because I am very experienced in this world, and an engineer to boot. I won't go into my 5 years of racing, building engines, designing engines, etc. or all my friends that do it professionally. Nor will I go into depth on how I've had to fix a lot of government vehicles on the fly in combat zones because of poor engineering, mostly because I know you won't read it.

Cheap...LMAO. Cheap is relative...I'm chasing my dream--a borescope is on the WANT list. Not NEED...but hey, I'm sure you would have just thrown it on a credit card and slaved away at work to pay it off. Well, I'm free of that burden and wise enough to know how to spend my money--so go suck on you ba-ba, and leave the adults to their "READING".
And here I was thinking I was being a little rough. Good job.
 

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Discussion Starter #30
Not a fan of trolls...but I am interested in whether or not we can theorize the usefulness of fuel additives in our vehicles. I tend to agree that there would have to be some blow by into the intake manifold that would essentially coat the valves in P.E.A., even if only marginally--it should keep the carbon from "baking" on. Assuming you're driving it between 3-5K RPMs as much as possible (a hypothesized guess of the necessary vacuum pressure/and blow by in those ranges). If you drive the car as daily as possible, get regular oil changes, change the fluids every 50K, warm it up for at least 30 sec., buy quality fuel, and add fuel additives every few tanks...I would think that you could avoid this entirely. This is my plan at least.

Maybe I'll buy a borescope before I rip the car apart next time...or maybe I'll NOT be lazy, and actually enjoy the process of getting to know my vehicle.
 

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With fuel additives, anything that gets on the intake valves will be extremely tiny. Not even worth mentioning. Saying that the fuel is going to get onto the backside of the intake valves is a little like saying your fart will make a noticeable breeze. The concentration would be so low that it wouldn't do a thing. If it did, you'd probably have to be running pure cleaner chemical.

In conclusion, the fuel does not contact the intake valves in any significant or meaningful way.

The strategy Mazda took to reduce the carbon buildup was to heat the valves up more. Carbon has trouble sticking to hot valves. I mostly drive highway and have no problems. Cleaning the valves resulted in no noticeable benefit. I can see this being a different story if you're driving more city or if your engine tends to use a little oil.

Without taking things apart, best way to clean things up is to generate more heat. Italian tune up. Rev it hard and get the valves as hot as you can.
 

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LOL...Italian Rev up ..Never heard that one before. Must be in my italianGenes ... i do that every day ,,, take her to the Red line after she has been warmed up nicely.
 

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Discussion Starter #33
With fuel additives, anything that gets on the intake valves will be extremely tiny. Not even worth mentioning. Saying that the fuel is going to get onto the backside of the intake valves is a little like saying your fart will make a noticeable breeze. The concentration would be so low that it wouldn't do a thing. If it did, you'd probably have to be running pure cleaner chemical.

In conclusion, the fuel does not contact the intake valves in any significant or meaningful way.

The strategy Mazda took to reduce the carbon buildup was to heat the valves up more. Carbon has trouble sticking to hot valves. I mostly drive highway and have no problems. Cleaning the valves resulted in no noticeable benefit. I can see this being a different story if you're driving more city or if your engine tends to use a little oil.

Without taking things apart, best way to clean things up is to generate more heat. Italian tune up. Rev it hard and get the valves as hot as you can.
First off, my farts can move windmills...

I agree that the concentration would be low...but it takes a whole hell of a lot of heat to melt that carbon too. So, we'll assume this argument is still null and void...but we tried. After some thought, I believe my mission was accomplished.

1. I saw the level of carbon build up at 90K with no prior cleaning...1-2 cm of build up in the runners and on the tops of the valves. 2 of the valves had pearl sized bits floating on the stems...possibly being pushed upward by the design of the intake runners (very steep).

2. Intake valve cleaning would not be necessary with regular hard driving, oil changes, etc.. I could easily see where a few areas had been cleaned of carbon by the heat generated...all the hard deposits looked as though they had melted and re-hardened many times over.


Unfortunately, halfway through another tank of gas...and I'm seeing a +1mpg gain...which could easily be attributed to new plugs over the cleaning. So #2...lol. But hey, now there is even more information saying the same stuff. Isn't the internet great!
 

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2. Intake valve cleaning would not be necessary with regular hard driving, oil changes, etc..
I think this sums up the entire thread and lines up with my past findings. I likely have not been having problems because my commute is an hour each way on the highway.

I had the little pearl sized balls of carbon too. Removing them didn't help any. The rest of the buildup was nowhere near as bad as you describe.
 

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I am awaiting final diagnosis of this issue on the 2018 Signature Mazda 6 (2.5 turbo engine). Car is shooting an error code for misfire in Cylinder #2, is running rough and idling extreme low and they seem to think it's a carbon build up issue (they scoped the car during my last visit). My 6 has about 106,000 kms on it now, and it's primarily highway driven. I occasionally drive it aggressively, but most of the time I am trying to keep things as fuel efficient as possible.
 

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Discussion Starter #37
I think this sums up the entire thread and lines up with my past findings. I likely have not been having problems because my commute is an hour each way on the highway.

I had the little pearl sized balls of carbon too. Removing them didn't help any. The rest of the buildup was nowhere near as bad as you describe.
Yeah...it seems these cars need to be driven. Maybe I'll do some homeade port injection, just need a pump (check), a fuel injector (to do) and a reservoir full of PEA...AHAHAHAHAHAHHAHA. Wonder if it would work like NOS??? :p
 

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Discussion Starter #38
I am awaiting final diagnosis of this issue on the 2018 Signature Mazda 6 (2.5 turbo engine). Car is shooting an error code for misfire in Cylinder #2, is running rough and idling extreme low and they seem to think it's a carbon build up issue (they scoped the car during my last visit). My 6 has about 106,000 kms on it now, and it's primarily highway driven. I occasionally drive it aggressively, but most of the time I am trying to keep things as fuel efficient as possible.
I'll keep a look out for the thread...THX
 

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Carbon buildup in the valves/intake isn't something that would be found in UOA right?

With the few fellas surpassing the 300k mile mark, for the majority of us with the 2.0/2.5L motors, I presume we are fine without ever never "needing" walnut cleanings.

After 90K miles and some pretty hard driving over the last 30K since I bought the car..
It is a bit unfortunate that we don't really have a record of how the OP's vehicle was utilized in the first 60k miles of it's life, so is it safe to guess that it was mostly city driven? Probably right?
 
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