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Discussion Starter #21
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.
That actually makes complete sense, since your engine is new the blow by is likely minimal, this blow by will increase as the engine ages. Also a very helpful tip, try and keep your catch can in the coolest section of the engine bay as cooled oil vapor will fall out of suspension and collect more readily. The hotter your catch can and its external surface the less likely vapor is to condense within.
 

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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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My 2014 cx5 began to loss its edge around 55k. Maintenance schedule was followed. I had averaged around 30 mpg in mixed driving for the 55k. When I got it, I timed 0-60, 8.5 with 2 aboard.
mileage began to drop little by little at that 55k point and when I traded it off at 68k it was more like 27.5 and rarely exceeded the 30 which had been normal. 0-60 stretched to 9 secs.

I just always assumed this was due to intake carbon buildup. Left it for the dealer or next guy to deal with. Granted these were not earth shattering differences, and might have gone unnoticed by some.

Ironically the new 2017 CX5 I traded for got about 27.5 mpg and 9 seconds 0-60 from the get go. I still buy mazda's without fear of this because I usually trade early. I held on to the 14 longer than usual.

As far as I know ever DI engine out there has this problem regardless of who makes it, except those like Toyota who use a second upstream injector.
 

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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.
Thanks for the pics. I wouldn’t say it looks bad. Sucks they aren’t clean but that’s freakin Di for ya.
 

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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.
I'm getting similar results and my 3 is just over 125k kms now. Guess what? Not much difference from when it was new. I'd say slight drop but not enough to really nail down as a problem.

But just for fun, as I've mentioned elsewhere on these forums, I'll be pulling the intake to check the valves this spring.

By then let's say 130k on it, lots of highway but enough city too, no cleaners or additives,just oil changes on time with synthetic. Should be enough use to see something but the least amount of variables possible. I also have a scope and a DSLR with a 90mm macro lens. Should be fun.

Looking at the pics here, yes there's some buildup but I would hardly call it significant. Any effect should be minimal if noticeable at all. What I'm interested in is will it get worse with time or has it settled out?

With how Mazda has increased valve temperature to reduce carbon buildup, its entirely possible that a thin layer of carbon is both expected and normal. It may never go beyond that. This is what I'm hoping I can show with my 3. If its about the same, or better with high highway time, that really does tell us something.
 

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Discussion Starter #25
I'm getting similar results and my 3 is just over 125k kms now. Guess what? Not much difference from when it was new. I'd say slight drop but not enough to really nail down as a problem.

But just for fun, as I've mentioned elsewhere on these forums, I'll be pulling the intake to check the valves this spring.

By then let's say 130k on it, lots of highway but enough city too, no cleaners or additives,just oil changes on time with synthetic. Should be enough use to see something but the least amount of variables possible. I also have a scope and a DSLR with a 90mm macro lens. Should be fun.

Looking at the pics here, yes there's some buildup but I would hardly call it significant. Any effect should be minimal if noticeable at all. What I'm interested in is will it get worse with time or has it settled out?

With how Mazda has increased valve temperature to reduce carbon buildup, its entirely possible that a thin layer of carbon is both expected and normal. It may never go beyond that. This is what I'm hoping I can show with my 3. If its about the same, or better with high highway time, that really does tell us something.
Please note my photos were taken only at 10,000 miles after my initial cleaning. The first time I cleaned the valves it was around 50,000 and the valves appeared to look like "lumps of coal." I have provided a reference image below (not my vehicle) essentially displaying what I had observed the day iI cleaned. If you are 125 kms (roughly 77,000 miles) I'm sure you'll be shocked at the amount accumulated, please keep me posted hopefully you take photos.
 

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Please note my photos were taken only at 10,000 miles after my initial cleaning. The first time I cleaned the valves it was around 50,000 and the valves appeared to look like "lumps of coal." I have provided a reference image below (not my vehicle) essentially displaying what I had observed the day iI cleaned. If you are 125 kms (roughly 77,000 miles) I'm sure you'll be shocked at the amount accumulated, please keep me posted hopefully you take photos.
I plan to. I want to make a good comparison. One bad apple doesn't mean the whole bushel is bad.
 

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I'm getting similar results and my 3 is just over 125k kms now. Guess what? Not much difference from when it was new. I'd say slight drop but not enough to really nail down as a problem.

But just for fun, as I've mentioned elsewhere on these forums, I'll be pulling the intake to check the valves this spring.

By then let's say 130k on it, lots of highway but enough city too, no cleaners or additives,just oil changes on time with synthetic. Should be enough use to see something but the least amount of variables possible. I also have a scope and a DSLR with a 90mm macro lens. Should be fun.

Looking at the pics here, yes there's some buildup but I would hardly call it significant. Any effect should be minimal if noticeable at all. What I'm interested in is will it get worse with time or has it settled out?

With how Mazda has increased valve temperature to reduce carbon buildup, its entirely possible that a thin layer of carbon is both expected and normal. It may never go beyond that. This is what I'm hoping I can show with my 3. If its about the same, or better with high highway time, that really does tell us something.
Please note my photos were taken only at 10,000 miles after my initial cleaning. The first time I cleaned the valves it was around 50,000 and the valves appeared to look like "lumps of coal." I have provided a reference image below (not my vehicle) essentially displaying what I had observed the day iI cleaned. If you are 125 kms (roughly 77,000 miles) I'm sure you'll be shocked at the amount accumulated, please keep me posted hopefully you take photos.
Is that even a skyactiv engine?
 

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Debbie Downer here... but in the US, be prepared to remove the oil catch can prior to an emissions test. The car will not fail OBD emissions testing but "Would, Could & Should" fail visual inspection 100% of the time. As you know it is entirely illegal to alter the PVC system in a car and if the smog tech does what they are suppose to, they will find the OCC, and fail you. Again, it's a hit and miss, so don't think every smog tech sniffing gas all day long is there just to get the inspection done.
 

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Debbie Downer here... but in the US, be prepared to remove the oil catch can prior to an emissions test. The car will not fail OBD emissions testing but "Would, Could & Should" fail visual inspection 100% of the time. As you know it is entirely illegal to alter the PVC system in a car and if the smog tech does what they are suppose to, they will find the OCC, and fail you. Again, it's a hit and miss, so don't think every smog tech sniffing gas all day long is there just to get the inspection done.
So you don't cut into the original hose. Get new tubing and drop in.
 

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Depends on the inspecting authority. Check you local listings.

Sent from my SM-G960U using Tapatalk
 

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Discussion Starter #32
So you don't cut into the original hose. Get new tubing and drop in.
This is exactly what I have done with my new catch can set up. I actually used the original PCV tubing added an adapter to the end then dropped in an additional line and when I am ready for smog I will simply bypass the catch can and connect the tubing directly to each other making it seem making it seem like OEM tubing.
 

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Since a build-up of carbon on the valves is generally not a threat to the longevity of an engine because carbon can be cleaned off very effectively if the engine operation is affected enough to notice, I'll wait to see if a problem develops before taking action.

I know that direct-injection engines are known to have more carbon build-up on the back of exhaust valves than other designs; I just don't know how it specifically affects the modern Mazda designs since the factory specifically says they have addressed the issue with additional heat during engine operation.

As far as mine, I see no performance problems at 36,000 miles, so I'm waiting for something to show up, at which time I'll do something to correct and prevent it.

In the meanwhile, thanks to the folks who are proactively addressing the issue and posting pictures and discussing what they are doing. It's all very interesting and potentially very helpful!
 

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Hi guys, long time lurker but first time poster. Thank you all for the great threads!

I understand the ongoing debate about using an oil catch can on a Skyactive engine. From what I can tell, the stock system works pretty well at limiting detrimental amounts of carbon buildup when the engine temperature is high enough.

My issue is that my daily commute is only about 8 miles, medium/fast city traffic, and ~10 stoplights. I’m not sure if everything is working so efficiently under those conditions. Would an oil catch can be more relevant to these specific types of driving conditions? Appreciate any thoughts or opinions.

FWIW, I live in Hawaii so I’m not worried about freezing issues.

2016 Jet Black Mazda 3 sGT ~28K miles
Eibach ProKit and Progress RSB being installed in a week or two.
 

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After cleaning out the intake valves of a good friend's Hyundai accent couple weeks ago, I'm going to take a look at my 3 very soon. Expect a post with pics (if I can get them) in a week or two.

I'd think my 3 would be a good candidate for this statistically. Its 4 years old, 130k km, mostly highway, and well maintained. Oil changes are always synthetic. I don't drive insane, but I do like to accelerate a little hard. As much as the 2.0L can anyways....

I also don't have anything that would affect buildup good or bad. No mods, tunes, catch can, etc. So I figure if I'm seeing significant buildup, its a problem.

We'll see. My scope doesn't have good resolution so not sure if that will work but I might be able to look in with my camera and macro lens. We shall see.
 

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Interested in pics of what you find.

I’m at over 80k miles on my 2014 with 2.0L and still haven’t touched a thing but oil changes. Still runs like new with no issues.
 
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