Skyactiv Intake Valve carbon build up - Anyone taken a look at intake valves?
- Thread starter johnygfunk
- Start date
oh oh...
Well, there goes the argument that there are no documented cases of carbon build up on skyactiv engines..
http://oemdtc.com/21965/check-engin...0301-p0302-p0303-andor-p0304-2012-2013-mazda3
Well, there goes the argument that there are no documented cases of carbon build up on skyactiv engines..
- :
- San Antonio, Texas
- :
- '15 CX-5 Miata AWD
Wonder which procedure they use
Not so fast, amigo. We are not discussing all Skyactiv engines here and the most important difference between the 2.0L in the Mazda 3 and the 2.0L and 2.5L CX-5 engines is that the Mazda 3 did not have the physical space in the engine bay to use the 4-2-1 Skyactiv scavenging header exhaust.
The function of the extra long 4-2-1 scavenging header is to scavenge exhaust gases from the manifold so they cannot go back into the cylinder. During fully warmed up operation this can cause hot spots (heated by the exhaust gases backing up) and during cold starts it can cause deposits.
This is not evidence the CX-5 is susceptible to this (and even if it were, venting the crankcase to the atmosphere wouldn't do a thing to alleviate it).
you can look at the other pages of the TSB on that site.
Looks like they take off the intake manifold, set the engine at a specific rotation and soak the valves in chemicals for a couple hours before wiping them down with a shop towel/vacuuming. Doesn't seem very difficult to do..
The repair is simple and is covered under the federal emissions warranty (8yr/80k).
All the skyactiv engines are very similar. If one has the problem it's a far stretch to think that the others are immune to it because of the 4-2-1 exhaust header.
I do agree that venting the crankcase to the atmosphere most likely won't solve anything.
One other relevant note:
This service procedure is not applicable to Mazda 3's newer than the 2012-2013 introductory models. The later models came with different warm-up calibration software to prevent this problem. And the repair procedure is not completed until the latest calibration software is installed to prevent further occurrences.
Modern fully computerized engines have adopted an entirely different approach to engine management than existed with even early EFI engines. The difference is that the most modern systems (especially with fully controllable valve timing like our Skyactiv engines) rely upon the computer to monitor every possible condition that can occur and take appropriate steps to address the issue. It's not always simply an adjustment to the ignition timing or fuel mixture that is updated to prevent a particular issue. The precise timing of the direct injection can be altered or the valves can be adjusted to open a little earlier or later to prevent the condition identified.
This is why it's so important to keep this type of engine in stock condition. Otherwise, small changes that might seem inconsequential to the uninformed car enthusiast can cause conditions that fall outside the range of conditions encountered in testing and development. Even a slightly different exhaust back-pressure or intake vacuum may cause a hidden issue in the longer term even if it appears to be running fine from all outward appearances. And, as the above linked service procedure illustrates, even unmodified engines can encounter climatic conditions or variances in fuel that were not anticipated during initial testing and hence require a tweak to the programming to avoid adverse consequences. This is especially likely early in the release cycle but can easily happen, even to an engine with more mature calibrations, especially if the owner intentionally makes a fundamental change to the operation of the engine that the system is not designed to look for. And achieving perfect, clean running is complicated enough without having to design the system to adapt to modifications when owners try to "make it even better". It is not designed to adapt to non-OEM configurations.
That is why I always recommend new vehicles are purchased with the power required, not modified later in a lame attempt to make a bit more.
This service procedure is not applicable to Mazda 3's newer than the 2012-2013 introductory models. The later models came with different warm-up calibration software to prevent this problem. And the repair procedure is not completed until the latest calibration software is installed to prevent further occurrences.
Modern fully computerized engines have adopted an entirely different approach to engine management than existed with even early EFI engines. The difference is that the most modern systems (especially with fully controllable valve timing like our Skyactiv engines) rely upon the computer to monitor every possible condition that can occur and take appropriate steps to address the issue. It's not always simply an adjustment to the ignition timing or fuel mixture that is updated to prevent a particular issue. The precise timing of the direct injection can be altered or the valves can be adjusted to open a little earlier or later to prevent the condition identified.
This is why it's so important to keep this type of engine in stock condition. Otherwise, small changes that might seem inconsequential to the uninformed car enthusiast can cause conditions that fall outside the range of conditions encountered in testing and development. Even a slightly different exhaust back-pressure or intake vacuum may cause a hidden issue in the longer term even if it appears to be running fine from all outward appearances. And, as the above linked service procedure illustrates, even unmodified engines can encounter climatic conditions or variances in fuel that were not anticipated during initial testing and hence require a tweak to the programming to avoid adverse consequences. This is especially likely early in the release cycle but can easily happen, even to an engine with more mature calibrations, especially if the owner intentionally makes a fundamental change to the operation of the engine that the system is not designed to look for. And achieving perfect, clean running is complicated enough without having to design the system to adapt to modifications when owners try to "make it even better". It is not designed to adapt to non-OEM configurations.
That is why I always recommend new vehicles are purchased with the power required, not modified later in a lame attempt to make a bit more.
Last edited:
LOL! Well, sorry if I'm laughing but that is such a laughable statement, it's hard not to (laugh).
First off, I never claimed any engine was immune from any potential issue, I said that one engine with one early software version that has an issue, is not evidence that another engine with a different header and different software will have the same problem. Very difficult to prove immunity from something, even if that something never was known to manifest. In fact, I'm sure you could make a modification to the CX-5 engines that would guarantee they would all have that problem. It's called software. Engines cannot be looked at as purely mechanical devices, they are as much sensors and software as they are metal and oil. And from where I'm sitting this is the most beneficial advance in internal combustion engines in my lifetime. It's incredible!
The different engines have custom calibrations developed independently for each engine. And the 2.0L Mazda 3 will have different calibrations and different maps than the CX-5 2.0L, primarily because of the different headers with vastly different characteristics. Characteristics that would tend to prevent exhaust gases from backing up into the cylinders to begin with but valve timing, ignition timing, fuel timing all have proper roles to play to insure the desired behavior given other variables involved.
Well, it's obvious it would not prevent the issue identified on the early Mazda 3. And there is no evidence the CX-5 has this issue.
Does anyone even know if the Skyactiv engines have an EGR valve? With advanced variable valve timing it may not even be needed or even work with such a low pressure exhaust header. The whole purpose of the EGR valve back in its heyday was to help cool the combustion process with inert gasses and thus reduce NOX emissions.
I've never heard that it has one and, I agree, with fully variable valve timing and other clean burn technologies, it probably doesn't need one. I disagree the header would prevent one from working as long as it was designed properly and tapped into an appropriate location. The low pressure in a scavenging header is temporal, timed with the engine stroke, it still has an overall positive pressure.
Not seeing a reference for an EGR valve in FSM... unless Mazda is calling it something else.
Extracted from WikiPedia on EGR:
"Usually, an engine recirculates exhaust gas by piping it from the exhaust manifold to the inlet manifold. This design is called external EGR. A control valve (EGR Valve) within the circuit regulates and times the gas flow. Some engines incorporate a camshaft with relatively large overlap during which both the intake valve and the exhaust valve are open, thus trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke. A form of internal EGR is used in the rotary Atkinson cycle engine."
SkyActiv IS an Atkinson cycle engine (although not rotary) so that does make sense. Also part of Mazda's claims for the SA-G design is it's increased inherent thermal efficiency which is the desired effect of EGR: reducing the peak temp's of combustion to reduce NOx emissions, not by COOLING the mixture but by tempering the combustion process with the introduction of inert gasses.
Also, if there is carbon build-up on the intakes occurring and the source of that carbon is the oil vapor in the crankcase vent stream it makes all the sense in the world that venting it to atmosphere would solve it. Not that it wouldn't introduce a whole host of other problems, which it probably would. It would also have to grant the propositions that 1)there IS carbon buildup on the latest generation 2.0 and 2.5 SA-G engines and 2) the vent gasses indeed are the source of the carbon for that build-up, both very much uncertain for the time being.
Last edited:
This is the part that has me wondering what the concern is with carbon build-up. They are designed to go hundreds of thousands of miles without de-carbonization necessary. And in light of no evidence to the contrary, why is this even a concern?
It would be like purchasing a new pair of brand X jeans and immediately triple-stitching the crotch to prevent blow-out, even though there were no reports from others that brand X jeans were blowing out at the crotch.
It's baffling.
Right. That analogy is also like Mazda Moly vs. other quality 0W-20 synthetic oils that have gotten many vehicles past 200,000 miles without issue. If the others meet the requirement with no measurable penalty, then why all the fuss?
I'm not sure what you're speaking of when you say "all the fuss".
- :
- RDX Aspec Adv.
What's even MORE baffling is that people who don't even know whether or not it has an EGR valve are wanting to change s*** around. It's like worrying about blowing out the crotch of the jeans without even knowing if there is a seam there, lol!
That's nice to know. This is my first GDI engine and I'm glad I waited a bit for the technology to mature.
I think you've missed a few key points: the SkyActiv engine merely uses GDI as one component of a whole host of technical enhancements many which, whether by design or serendipity, overcome limitations imposed by others. Each of them individually may be pretty mature (even Atkinson cycle which has been used over a decade in hybrids) but I don't think I'm wrong in saying Mazda's application of everything is itself at least fairly novel in production automobile engines.
And of course it's obvious why: mfr's have to develop means to meet ever tighter emission and fuel economy regulations. Others are using tiny motors and turbo's; Mazda is using SkyActiv.
The upshot of all this is it's actually very new technology.
Last edited:
I think Mazda used Atkinson Cycle engine back in the mid '90s in the Millenia sedan
mazdadude
ZOOOOOOOOOM ZOOOOOOOOOM
- :
- '16.5 Mazda CX-5 Touring
It was actually a MILLER - CYCLE engine used in the Amati/Millenia Sedan.
