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With the shutdowns and empty roads I'm getting 20mpg with the 2.5

Do i have carbon build up? Or maybe it's my right foot is the problem...
In all likelihood it's your foot. Lower fuel economy on its own is not an indication of a carbon problem. That coupled with reduced power might be.

We tend to jump to the conclusion that valve carbon is the problem when there may very well not even be a problem. Never make assumptions. Assume is spelled ASS U ME
 

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To those with catch cans, what is the inner diameter of the hose between PCV and intake manifold. Don't want to pull the intake manifold to find out...
 

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In all likelihood it's your foot. Lower fuel economy on its own is not an indication of a carbon problem. That coupled with reduced power might be.

We tend to jump to the conclusion that valve carbon is the problem when there may very well not even be a problem. Never make assumptions. Assume is spelled ASS U ME
Very true, I am not claiming the increase in fuel economy is directly related to the can just an observation. I suppose this whole system is more focused on engine longevity and performance in the long run. I suppose time will ultimately tell if the can is doing anything at all or if valve deposits will need intervention in the future for now we wait!
 

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Hello again everyone IM BACK FINALLY with some results. Since the last valve check I racked up 10,000 miles and dissembled the intake once again to see how the catch can has been performing.
Once again the valves are in order started with 1A being the left most and 4B being the right most valve, exactly as it was in the other photo. After performing this experiment I have emptied the catch can roughly 4 times to ensure it never accidentally overfilled and have the intake suck in excess oil. Just from what I have seen there is almost no build up of carbon since I began, with the exception of valve 4B which looks slightly more soot covered. This occurrence actually makes sense this the PVC intake line is connected to the right lower portion of the intake manifold meaning that valves 4A and 4B will see the most oil blow-by. I collected roughly 2.5 ml every time I emptied the can for a total of ~10 ml. This mixture smelled of burnt oil and fuel.

Conclusion, this does in fact collect crankcase blow by, although it may not be gallons or pure oil it is still collecting something. Whether or not this will ultimately affects engine longevity will become more clear as time goes on. For now, and this is mostly my opinion, this is slowing (if not mitigating) oil splashing on the intake valves of my vehicle. After installing the can the vehicle has has absolutely no issues, no check engine light, a slight increase in my typical fuel economy (.7-1 mpg increase), and no sputtering, jolting, or odd engine behavior.

Please ask any questions I will do my best to answer.

**Also for some reason my old account was disabled and I needed to remake the account I can assure this is the OP Lemurmarco.
Is the oil in the coke bottle the total collected over the 10k?

I much appreciate the update. I’ve been thinking about an oil catch can for a while now but since my Lil 2.0L is running so good after 90k miles (only oil changes thus far) I’m hesitant to touch anything since it’s obviously working and isn’t causing harm. Lol.

I plan to crack her open soon though to finally replace the spark plugs, coolant, and check out / clean the valves. Based on what I’ll find, that will be the deciding factor if I will install a catch can for the next 100k or not.
 

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Here....


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Unfortunately the hose diameters from the picture are not correct...
Today tried to install the catch can and when removed the hose was surprised that inner diameters are bigger.
12.2 mm intake manifold side and 15.7 mm pcv side. That's very close to AN8 and AN10 hose diameter. I was prepared to install AN6 hose and fittings... now have to start over..
 

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As many of you know, I did my own little investigation last year. Cleaned out the valves manually with picks and then walnut blast. I did see some carbon buildup for sure, but it wasn't horrible. Result was about what I expected. No real world change in power or fuel economy. Nothing that I could measure without a Dyno anyway.

After seeing this and the fact that there are precious few reports of carbon buildup actually doing anything, it's safe to conclude that there is no problem with our engines and carbon. Just because there's a bit of carbon on the valves doesn't mean it's doing anything as was my case.

Yes there will be the odd one or two that have a problem. This is likely due to some other defect causing excessive buildup. It's the same with any car out there, no matter how good it is there will always be a couple of defects.

I do suspect that those of us who drive mostly in the city and those who make short runs are going to be more prone to carbon issues. Less time for the valves to be hot which was the whole idea when Mazda designed this engine.

So with all this junk in mind, do we NEED a catch can? The short answer is no, absolutely not. There is no evidence that it is going to help you out in any way.

That being said if it makes you feel better having one, who am I to tell you how to spend your money? There's no downside to installing a catch can. Sure removing that oil can be seen as a good thing. We just don't have anything to show us it matters and I doubt we ever will at this point.

Forgot these forums for a minute. This engine cam out in what, 2013? Might be off on the year. Regardless, that's 7 years or more of this engine being produced and it has found it's way into multiple models. In all those vehicles after all this time, has there been any reports of widespread carbon issues? Nope. In comparison if you drive a Hyundai with the gamma engine you bet there is.

People reporting issues on these forums or not reporting them is meaningless. Major issues with cars doesn't go unnoticed these days partly thanks to the internet. If there was a big problem we'd know by now.
 

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As many of you know, I did my own little investigation last year. Cleaned out the valves manually with picks and then walnut blast. I did see some carbon buildup for sure, but it wasn't horrible. Result was about what I expected. No real world change in power or fuel economy. Nothing that I could measure without a Dyno anyway.

After seeing this and the fact that there are precious few reports of carbon buildup actually doing anything, it's safe to conclude that there is no problem with our engines and carbon. Just because there's a bit of carbon on the valves doesn't mean it's doing anything as was my case.

Yes there will be the odd one or two that have a problem. This is likely due to some other defect causing excessive buildup. It's the same with any car out there, no matter how good it is there will always be a couple of defects.

I do suspect that those of us who drive mostly in the city and those who make short runs are going to be more prone to carbon issues. Less time for the valves to be hot which was the whole idea when Mazda designed this engine.

So with all this junk in mind, do we NEED a catch can? The short answer is no, absolutely not. There is no evidence that it is going to help you out in any way.

That being said if it makes you feel better having one, who am I to tell you how to spend your money? There's no downside to installing a catch can. Sure removing that oil can be seen as a good thing. We just don't have anything to show us it matters and I doubt we ever will at this point.

Forgot these forums for a minute. This engine cam out in what, 2013? Might be off on the year. Regardless, that's 7 years or more of this engine being produced and it has found it's way into multiple models. In all those vehicles after all this time, has there been any reports of widespread carbon issues? Nope. In comparison if you drive a Hyundai with the gamma engine you bet there is.

People reporting issues on these forums or not reporting them is meaningless. Major issues with cars doesn't go unnoticed these days partly thanks to the internet. If there was a big problem we'd know by now.
Have thought about catch cans early on knowing DI engines(think Bimmers) require blasting as periodic maintenance to keep performance. Like @zero_gravity, I've checked on Sky carbon buildup 1st hand, even did some demo blasting w/ the local dealership...it's nothing near seen on other makes. I can say Mazda really did dig into stretching the build up period.
Having owned the BM3 6years, the can remains a thought. Though I've a few kits in the parts bin, it's a good project I'll reserve for boredom therapy. Blasting probably much much later when a drop in performance is felt.
For now, I'll just keep driving. Still feels like day 1.

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Have thought about catch cans early on knowing DI engines(think Bimmers) require blasting as periodic maintenance to keep performance. Like @zero_gravity, I've checked on Sky carbon buildup 1st hand, even did some demo blasting w/ the local dealership...it's nothing near seen on other makes. I can say Mazda really did dig into stretching the build up period.
Having owned the BM3 6years, the can remains a thought. Though I've a few kits in the parts bin, it's a good project I'll reserve for boredom therapy. Blasting probably much much later when a drop in performance is felt.
For now, I'll just keep driving. Still feels like day 1.

Sent from my SM-G970F using Tapatalk
Mazda did pretty good with this one. Last summer I helped a friend pull the intake off his Hyundai accent. That thing was a mess of oil and carbon sludge. It was unreal how bad it was. I pulled my intake shortly after that and was expecting to see a similar show. Have to say I was pleasantly surprised.
 

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I agree with Zero Gravity and Minsanity. Adding a catch-can generally won't hurt but be aware that in cold ambient locations PCV flow CAN freeze. The rerouting / lengthening of the PCV flow piping results in more of a chance for this, even if creating low-spots is judiciously avoided with your design. In these cases heat-tracing and insulating the lines at least (using a minor slip-stream of engine coolant, say, along with a needle valve to regulate same... from a minor flow-to-fully shut off when it gets warmer outside) would generally adress this. Too hot though and it lessens the coalescing of aerosols (which is what you want).

Complications. Simple, stupid is often best (i.e. factory-stock). Also, it's easy for a "wanna-be" automotive engineer to screw-up 😐.

If you REALLY want a catch can the one I think is good is a Mann-Hummel Provent 200. Very well designed; removable aerosols filter, centrifugal-flow droplets coalescence, etc. Not 'real cheap to buy. If you want weird hose size adapters there's an outfit in Australia that has those (could look it up). I'm sure Others have 'em too.
 

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I agree with Zero Gravity and Minsanity. Adding a catch-can generally won't hurt but be aware that in cold ambient locations PCV flow CAN freeze. The rerouting / lengthening of the PCV flow piping results in more of a chance for this, even if creating low-spots is judiciously avoided with your design. In these cases heat-tracing and insulating the lines at least (using a minor slip-stream of engine coolant, say, along with a needle valve to regulate same... from a minor flow-to-fully shut off when it gets warmer outside) would generally adress this. Too hot though and it lessens the coalescing of aerosols (which is what you want).

Complications. Simple, stupid is often best (i.e. factory-stock). Also, it's easy for a "wanna-be" automotive engineer to screw-up .

If you REALLY want a catch can the one I think is good is a Mann-Hummel Provent 200. Very well designed; removable aerosols filter, centrifugal-flow droplets coalescence, etc. Not 'real cheap to buy. If you want weird hose size adapters there's an outfit in Australia that has those (could look it up). I'm sure Others have 'em too.
Ahhh...the Provent. Hobo chinese copies everywhere.
Again, as Cdn, gravity, arathol & those who've had relative comparison on DI carbon buildup observed, the SkyactivG doesn't seem to be nearly as affected. It wasn't all just talk...Mazda has been good on their word. Why fix what ain't broke...or mod what's been good?


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Based on the documentation Mazda solved the carbon deposit problem by configuring the engine so the intake valves will get hot enough to burn off the carbon deposits, so drive your car hard with some regularity to sufficiently super heat your intake valves and burn off the carbon.
Also, depending on the the setup of the catch-can it can cause its' own problems (too much pressure building up in the crank case).
 

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Based on the documentation Mazda solved the carbon deposit problem by configuring the engine so the intake valves will get hot enough to burn off the carbon deposits, so drive your car hard with some regularity to sufficiently super heat your intake valves and burn off the carbon.
Also, depending on the the setup of the catch-can it can cause its' own problems (too much pressure building up in the crank case).
That's a clever solution, I like that Mazda addresses these problems as they pop up. External catch can may also end up causing more fail points long term with hoses collapsing/kinking or vacuum leaks.

I've been through some of these posts on the older engines and was surprised that there's little mention of methanol injection. Aside from its usual uses, its the best possible way to keep squeaky-clean intake runners and valves.
 

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I've been through some of these posts on the older engines and was surprised that there's little mention of methanol injection. Aside from its usual uses, its the best possible way to keep squeaky-clean intake runners and valves.
I've been thinking of Water/Meth injection as it would clean intake valves, and you could tune for more aggressive timing for more power particularly on our ultra high compression engines...
 

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I view meth inj. on an n/a purely for cleaning & engine health. You could tune for more timing, but from what I'm learning about these ECUs & the fact that it's n/a, there's not much performance gain, and potentially worse performance if the tune relied on methanol.

Besides meth allowing for minimal timing advance on n/a, I believe these ECUs switch between octane maps based on [knock retard] KR (someone please feel free to correct me if I'm wrong there), so you might lose higher octane advance if, for example, the ECU is looking to advance with 93 + meth and its pinging KR due to methanol not spraying under the right conditions. It'd drop to an 87 table [or retard however the KR decides to handle it] and lose the benefit of the tune. Or... if it's tuned for only 91/93 + meth, that could mean bad things for the motor if there's ever something wrong with the spray.

I'd just look at the added benefits of cooling & cleaning (the exception is nitrous). It's certainly not going to hurt anything with a check valve & proper size jet. If the maintenance is getting bad, it's worth looking into...more so if someone is limited to 87 octane low tier gas in their area.
 

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I view meth inj. on an n/a purely for cleaning & engine health. You could tune for more timing, but from what I'm learning about these ECUs & the fact that it's n/a, there's not much performance gain, and potentially worse performance if the tune relied on methanol.

Besides meth allowing for minimal timing advance on n/a, I believe these ECUs switch between octane maps based on [knock retard] KR (someone please feel free to correct me if I'm wrong there), so you might lose higher octane advance if, for example, the ECU is looking to advance with 93 + meth and its pinging KR due to methanol not spraying under the right conditions. It'd drop to an 87 table [or retard however the KR decides to handle it] and lose the benefit of the tune. Or... if it's tuned for only 91/93 + meth, that could mean bad things for the motor if there's ever something wrong with the spray.

I'd just look at the added benefits of cooling & cleaning (the exception is nitrous). It's certainly not going to hurt anything with a check valve & proper size jet. If the maintenance is getting bad, it's worth looking into...more so if someone is limited to 87 octane low tier gas in their area.
Meth injection, gotcha covered

 

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lol yup
277939



... But really methanol inj. can be safer on an n/a than a forced induction motor. Some progressive controllers allow an additional MAP sensor, which can be plumbed to read & operate at certain crankcase vacuum rather than intake/manifold for an extra layer of safety. That sensor on a boosted motor would very likely be used for intake pressure instead.
 
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