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Discussion Starter #1 (Edited)
Hey everyone this afternoon I felt like checking out my intake valves for carbon and soot buildup as I hand scrubbed them 10,000 miles ago at 50k (you can find these images on page 2). I was pretty surprised to see a moderate amount of carbon build up on the right most valves and quite a bit of oil residue on the intake gasket mating surface itself. The other valves showed minimal to moderate carbon spotting but nothing too extreme.

Mazda does actually have a baffling system (oil separator) to reduce the total amount of oil entering the intake manifold (found behind the intake) but it simply is not enough to mitigate the effects of oil/contaminate blow by.

Here is a link if you would like to know what and where this baffling system/oil separator is.

https://imgur.com/Nh0y6DV
https://imgur.com/cWvmLo2

Anyways, I am going to clean my valves once again install an oil catch can and record results to:
1.)See how much blow by the oil catch can system collects
2.)See if carbon build up is reduced or even stopped due to inclusion of the catch can

If it is something that is worthwhile and effective I will provide an install post at a later date if you guys would like one.

Thanks.
 

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Glad you are doing this! Since you cleaned your valves 10k miles ago and now have seen the direct results from 10k miles driven, it will be interesting to see how much of a difference a catch can will make. I hope you took pictures of your post 10k mile buildup so we can see the difference for ourselves. If not, hopefully you can take pictures after another 10k miles with a catch can to see how well it protects the motor. Good work. Keep us updated!
 

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Pictures of the buildup at 50k miles would be great as well as at 10k later.

How did you 'hand scrub' them? Could you please describe the process.

What measurable and demonstrable benefits have you achieved since this 'hand scrubbing' ?
 

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If your intake valves were that dirty, what did your MAF look like?

The MAF isn't the issue since it is upstream from any recycled air flow. The PCV recirculation goes directly from the crank case to the intake manifold right next to the intake valves. No MAF involvement.
 

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Ok first off, pics or it didn’t happen. Lol.

And second...

I’ve stressed over an oil catch can for years now, ever since JBR posted pics of a new engine with 5k miles on it and carbon build up on the valves.

I thought that with that much build up in only 5k on a new engine that this problem will surely plague all Skyactiv engines soon... but it hasn’t.

I wanted to pull my intake manifold since like 15k miles to examine what my valves look like but decided not too, since there is absolutely zero performance effects that I can tell, even if there is some build up on the valves.

I now have 80k miles on the engine and still, absolutely zero issues that I can feel thru the ol’ butt dyno.

At this point I’ll probdbly pull the intake manifold at 100k when I do the spark plugs, etc, just to clean it and finally see what 100k miles of carbon looks like. Lol. I’m dying with anticipation.

I plan to dyno the car prior to cleaning the valves and the redyno afterward to see exactly how many ponies are lost due to what I feel is probably very small amounts of carbon actually effecting air flow. If it’s 5hp over 100k miles, then... we ain’t got nothing to stress about here. Mazda did their homework and it’s “good enough” for your average Joe.
 

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Discussion Starter #7
Glad you are doing this! Since you cleaned your valves 10k miles ago and now have seen the direct results from 10k miles driven, it will be interesting to see how much of a difference a catch can will make. I hope you took pictures of your post 10k mile buildup so we can see the difference for ourselves. If not, hopefully you can take pictures after another 10k miles with a catch can to see how well it protects the motor. Good work. Keep us updated!

Correct that is exactly what I plan to do, sorry for the late reply just logged back on. My photos are saved on my computer at home and I am currently out I will upload them later this evening!
 

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Discussion Starter #9 (Edited)
Pictures of the buildup at 50k miles would be great as well as at 10k later.

How did you 'hand scrub' them? Could you please describe the process.

What measurable and demonstrable benefits have you achieved since this 'hand scrubbing' ?
Of course I can explain the process:

1.) I Removed the intake manifold

2.) The cleaner I used was actually actually a bit unconventional, it was "Techron concentrate" I will link it below.

** I chose to use this as my cleaner for 2 main reasons. The first being that this is considered a fuel and engine detergent meaning it is a great carbon buildup cleaner (made primarily of polyether amines). The second reason is that I feel confident it will not damage any components in the long run as it is designed to run through the engine/fuel system as is basically the best clean you could achieve with the least amount of associated risk.

3.) When cleaning please make sure the valve is seated against the engine case, if it is open and you begin cleaning you run the risk of dropping carbon pieces in the engine. Upon startup they may scratch the cylinder walls or even clog the catalytic converter downstream. In order to seat the valve set you are working on you simply need to rotate the crankshaft pulley until the desired valve is seated.

4.) I used a soft copper/brass pipe cleaner to just work away at the carbon deposits after letting them sit in the Techron concetrate for a few minutes. Anything that was too hard to scrub off I chipped away at with a small metal pick being very delicate and cautious. I am investing in a hex shank attachable copper/brass pipe cleaner set as this will most likely be much more effective next time around and save a hell of a lot of time if you use a drill (I will also provide a link for that set down below).

**PLEASE NOTE you MUST use a soft metal or nylon material when cleaned valves. DO NOT use steel/iron or any other highly tensile metal as it can scratch and valves causes surface abrasion and in extreme cases hair line cracks when reaching operating temps. This is the same reason walnut media is used for blasting as walnuts are soft.

5.) Lastly I used an air compressor to blow out each valve set (when they are closed and seated against the engine case) This is to ensure any remaining bits of carbon particles fly out.


Cleaning Solution
[ame]https://www.amazon.com/Chevron-Techron-Concentrate-System-Cleaner/dp/B00092893E[/ame]

**I think autozone does a buy one get one free for this items as well, you may save some money and you'll get a bottle for next time!

Scrubbing Set
[ame]https://www.amazon.com/TEMO-Plastic-Bristle-Dremel-Compatible/dp/B00C050WD8/ref=sr_1_5?crid=2NVXBSJNH9GXO&keywords=nylon+brush+for+dremel&qid=1553906803&s=gateway&sprefix=nylon+brush+for+drill%2Caps%2C336&sr=8-5[/ame]

[ame]https://www.amazon.com/Innovative-Products-America-8081-Piece/dp/B009TC6B08/ref=sr_1_10?crid=26109HYA96HH7&keywords=wire+brush+hex+shank&qid=1553457059&s=hi&sprefix=wire+brush+hex+%2Ctools%2C225&sr=1-10[/ame]

As far as benefits go let me explain the importance of clean intake valves. Valves are made with a machined surface to create a very precise seal with the engine block. When this precise seal is impeded by carbon buildup you get a loss of compression in the cylinder as air is "seeping back" through the intake valve space created by the carbon blockage leading to reduced power and performance in all aspects. This carbon also creates a turbulent flow of air entering the cylinder as you no longer have a smooth contoured valves surface but a lumpy dis-formed one (air attachment is disrupted. Dirty valves can affect fuel economy, acceleration, throttle response, air fuel ratios, etc.

Hope I helped, sorry for the long read haha.
 

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Honestly, has anybody ever seen a documented case where a SkyActive engine actually experienced problems due to carbon build up? I don't mean somebody showing pictures on youtube, I mean an actual car that had actual issues. There are a pretty fair number of cars out there now with 100k or more, how many have had a failure or required some sort of repairs that can be traced directly to carbon build up?
I've seen the pictures, read the fear mongering by vendors eager to sell you a catch can, but in all reality for the small amounts that the can does catch is it really worth it? The SA motor is designed to mitigate deposits to a significant extent and if driven properly it does a pretty good job of preventing carbon issues.
 

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Honestly, has anybody ever seen a documented case where a SkyActive engine actually experienced problems due to carbon build up? I don't mean somebody showing pictures on youtube, I mean an actual car that had actual issues. There are a pretty fair number of cars out there now with 100k or more, how many have had a failure or required some sort of repairs that can be traced directly to carbon build up?
I've seen the pictures, read the fear mongering by vendors eager to sell you a catch can, but in all reality for the small amounts that the can does catch is it really worth it? The SA motor is designed to mitigate deposits to a significant extent and if driven properly it does a pretty good job of preventing carbon issues.
I would say the $40 I spent on my catch can is worth it. Ebay special, then slightly modified to be more effective. Whether or not the fear mongering is true, I like to know that I am doing a little bit more to help my engine stay healthy, longer. They're not selling snake oil, they're just pushing for sales. Yes there are a bunch of Mazda 3s out there, but how many of those owners are on mazda forums reporting issues? How many of those owners know enough about cars to notice if the car is running / sounding a bit different if/when something is damaged? How many of those owners will simply drop the car off at the dealer when the check engine light goes on, take the techs word for what the problem is, and just pay the bill? I'm willing to bet most consumers will see 75k on the clock and just attribute any performance issues to old age.

When properly installed and maintained, what harm does a catch can cause? Other than a dent in your wallet based on how much you spend, nothing. What good does it do? Collects a little bit of icky dirty air before it goes back into your motor. Clean(er) valves are never a bad thing. I wouldn't pay $250 for a catch can that claims to create a superior internal flow to maximize condensation, but I would pay $40 on ebay, make a couple tweaks to maximize the basic function and enjoy emptying the collected contents every so often knowing that much less is passing by the valves. And it made for a fun DIY project as well!

I'm not saying it is necessary. Do it or don't. I did it for piece of mind.
 

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but in all reality for the small amounts that the can does catch is it really worth it? The SA motor is designed to mitigate deposits to a significant extent and if driven properly it does a pretty good job of preventing carbon issues.
My catch can catches about 100ml per 1k miles just off the PCV, I haven't put in a catch for the valve cover vent. I do drive my car pretty hard(Lots of living around 3-4k rpm, redlining, and highway travel) and I am on a 93 tune with a 7k redline. From everything I have seen, the design and operation of the motor is such that detrimental accumulation on the valves is quite well minimized but the PCV system is not ideal and a catch can helps to further reduce the formation of deposits that can lead to problems.
 

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Discussion Starter #15
Hey everyone sorry for the delay I have been extremely busy at work and promised you guys some valve photos! I took some high resolution photos of my valves which you can view down below. The valve images are labeled based on their location with 1A being the valves most left and 1B being the next port over (2A, 2B, 3A etc...). Please note there were cleaned thoroughly 10,000 miles ago and this is the current build up. Also note the oil residue on the mating surface of the intake and the block.

I have also included an image of the PCV system and oil separator labeled in a red circle with PCV outlet in the yellow circle in case anyone needed a better understanding of the system flows.

Please let me know if you have any questions.
 

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Discussion Starter #16
Honestly, has anybody ever seen a documented case where a SkyActive engine actually experienced problems due to carbon build up? I don't mean somebody showing pictures on youtube, I mean an actual car that had actual issues. There are a pretty fair number of cars out there now with 100k or more, how many have had a failure or required some sort of repairs that can be traced directly to carbon build up?
I've seen the pictures, read the fear mongering by vendors eager to sell you a catch can, but in all reality for the small amounts that the can does catch is it really worth it? The SA motor is designed to mitigate deposits to a significant extent and if driven properly it does a pretty good job of preventing carbon issues.
Yes I can attest to the issues caused by carbon buildup at only 50k. Before I cleaned my valves my fuel economy was horrendous like 23 city even when I babied the throttle, that's now 33 consistently with no change in oil type, distance traveled, or routes taken. All around the cars responsiveness has increased, if you have doubts about the performance benefits of clean valves clean them yourself and see the difference.
 

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Yes I can attest to the issues caused by carbon buildup at only 50k. Before I cleaned my valves my fuel economy was horrendous like 23 city even when I babied the throttle, that's now 33 consistently with no change in oil type, distance traveled, or routes taken. All around the cars responsiveness has increased, if you have doubts about the performance benefits of clean valves clean them yourself and see the difference.
Sorry, still don't buy it. My car got ~25 mpg around town with 9 miles on the odometer, at 15k its still getting 25 or better and high 30s on the highway with no discernible loss of power. And yes, I have been monitoring the engines performance across the full range of available sensors and nothing is different. Perhaps there is some placebo effect going on here?
 

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Discussion Starter #18 (Edited)
If you are barely getting high 30s even with the 2.5 on the freeway I'd rethink that position. I get 42mpg going 78mph every time I hit the freeway, again you don't need to "buy" anything but you can't refute an argument without performing and testing it yourself first as I have, with positive changes observed.
 

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I can get 40+ if I try but I'm talking about overall long term numbers. The computer registers 25-26 most times but on the few long highway runs it quickly goes up through the 30s. I don't do a lot of highway driving so I don't really know how high that long term figure will go.
 

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I've had a JBR catch can on my 2016 2.0 since about 5,000 miles. I can't tell if it *actually* did anything in the long run (now sitting at 32xxxk miles.) But regardless, I still drain the can monthly, and I get a couple of mL's each time I do so; I guess it works. The stuff drained is milky yellow, and is likely condensed water, a little bit of oil, and gas all mixed together. Sorry, I don't have a picture or anything.
 
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