That's a silly idea. Without extensive test equipment there is no way to verify if it's better or worse. And it's probably worse.
Skyactiv Intake Valve carbon build up - Anyone taken a look at intake valves?
- Thread starter johnygfunk
- Start date
That's a silly idea. Without extensive test equipment there is no way to verify if it's better or worse. And it's probably worse.
Why do you say that it's probably worse ? I did dyno test but forgot to also mention I also did a compression test. All four cylinders where with in factory spec and also very important the numbers were pretty much the same on all four cylinders. The compression test was done because a bad miss shift I did at the track not because I was testing it for venting to atmosphere at that time. I do accept that test as part of venting because I was running it that way for thousands of miles. I think it was in the low 30k miles and was venting since the car had 700 miles or so . I believe 30k is enough time to be able to detect at least see some minor adverse affects when doing compression testing. But it was spot on.
To me dyno test and compression test is good enough.
These are my reasons from experience. Unless the 2.5 skyactiv motor is designed specifically in such a way that requires vacuum , then that's a different story. But I strongly believe it's recirculating to the intake for emissions .
One more thing to add. On the sky active it recirculates after the maf sensor . The ecu will most likely make the minor corrections in the fuel trims to compensate for plugging the unaccounted air/fumes if needed. Evo was the same and data logs showed no major changes in fuel trims. I just plugged the intake as I have done to the cx-5.
The SRT-4 however was slightly different than the evo and skyactiv as it did not have a maf and was using map sensor with o2 sensor (o2 only used during "closed loop" aka normal driving ) .
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- San Antonio, Texas
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- '15 CX-5 Miata AWD
Not sure how you can decide that a tuned car (which usually doesn't run as rich as stock) will have more deposits than a stock by default since tunes vary as do fuels, driving habits, air quality, and many other factors that play into it. Two stock motors with the same miles could easily be apart in terms of soot build up. A stock, well running motor leaves soot on the exhausts anyways, not like it blows out clean air. I could say my transmission should be in worse shape or my brakes should be in worse shape yet people with stock cars and low miles have had a transmission replaced, or brake components replaced.
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- San Antonio, Texas
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- '15 CX-5 Miata AWD
Connect it to a BOV for s**** lol.
I just want to clarify , venting only keeps the intake pipe and intake manifold clean similar to running a really well designed catch can that would trap 100% of all oil vapors while still running the intake vacuum line. There are no other power gains unless something is clogged in the line and venting frees it from that clog or bottle neck . I just don't like recirculating even with a really good catch can with baffles and stainless wire mesh inside.
FYI I tuned the evo at 18k mile mark . But regardless tuning the car only effects Wide open throttle (open loop). It does nothing to normal driving unless you change the injectors and you just need to tell the ecu the flow rate of the new injectors. When your in closed loop the o2 sensor and maf work together to ensure 14.9 air fuel ratio. So tuned or not your always running and ecu trying to achieve the 14.9 air fuel ratio during normal driving , cruising , accelerating and idling. When you go WOT or over a certain load that is near wot then it follows the tables in the open loop.
There a little more factors involved as but to keep things short , I did not upgrade the cams. If I did then in that case I would need to mess around with timing (mivec and some other areas) during closed loop low loads area for smoother idle.
The tune changes the timing of the valves opening and closing without ever checking how those changes impact potential deposit formation.
With a rich running tune and different valve timing it's possible that unburnt carbon gets pushed back into the intake during periods of valve overlap.
The only major downside of this is the extra pollution that you're releasing into the air, likely with no real benefit.
The PCV valve on the CX-5 is attached to an oil separator. Obviously not all the oil will be caught by it, but I trust that enough will.
btw..
Do you still have the PCV valve in place? The valve depends on a little pressure difference to vent properly, so the pressure in your crankcase might be a little bit higher without the vacuum.
johnygfunk
Member
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- Car
Glad I could start a discussion here. I have no mods in place was just concerned as I've seen first hand how bad it can get on early VW gdi engines and I just thought about mine after 45,000 miles.
I never checked or looked at the valves.
The tune only effects timing if you change the timing tables during low loads aka normal driving. Other wise the ECU follows what ever factory values there are for certain conditions. If you dont touch those in the low load normal driving fields, in which 98% of all tunes do not, then it will be left unchanged. Most people only tune from certain higher loads aka WOT. I did also mess with the timing tables in low loads around when I had 40k miles but that was when I was testing timing and mpgs during closed loop. Regardless, PCV venting or not is totally different when it comes to tuning the car. Only thing that would ever changes is the ECU compensating for the lack of extra fumes that are no longer coming in after the maf. The o2 sensor will read that ever so slight difference and the ecu will adjust to reach the 14.7 a/f ratio. My previous posts i mentioned 14.9 but its actually 14.7 , sorry about that. If the ECU keeps struggling and is unable to achieve 14.7 then the CEL will probably come on.
FYI I just looked at the valve cover and there arent any valves or oil separators. Its just tubing running straight from the valve cover to the intake pipe. I even applied air pressure as well as vacuum and there werent any restrictions like a check valve or anything. Its just open tubing from valve cover to the intake pipe.
There might be a baffle under the valve cover to reduce oil spray and vapors coming out (the evo had it as well) but I know it will not block 100%. Hence, why I want to vent. And you are correct venting will not pass visual emissions testing in most states.
I followed the OVTuned thread on the Mazda 6 club forums and as I understand the tuning is done both under partial load and under WOT. I doubt that a tune will cause carbon deposits to form, but as MikeM posted, it has the potential to.
I recommend you check out the 2013 factory service manual. (the mazda links no longer work, but the dropbox is still available) http://www.mazdas247.com/forum/showthread.php?123825111-Full-Service-Manuals-PDF
The Service Highlights section has interesting stuff:
I'm sure the oil separator doesn't catch 100% of the oil, but it probably catches enough of it.
Ok now I see what your talking about. Thanks for that link. The hose I was referring to that I vented to atmosphere is the one labeled as "Ventilation Hose". The one your referring to is the one labeled "Check Valve”. I havent looked into those lines yet and missed it completely. I’ll have to check it out when i get a chance.
Ok, went and took a quick. I started the motor first time after disconnecting it and inspected it. Instead of air blowing out from the "Ventilation Line” there was actually a slight vacuum. This leads me to think that there is air drawing out from the crank case from else where. And this Ventilation Line is a source of filtered air to ventilate fresh air under the valve cover.
I will later look into more details on how this works on the CX-5. Its possible the Mazda engineers have designed something that will keep emissions happy, relieve pressure from the crank and also keep the intake oil free at the same time. But I got to look further into it later when I have time. For now back to stock as venting that part only, is not going to do what I want.
Thanks for posting that link.
I will later look into more details on how this works on the CX-5. Its possible the Mazda engineers have designed something that will keep emissions happy, relieve pressure from the crank and also keep the intake oil free at the same time. But I got to look further into it later when I have time. For now back to stock as venting that part only, is not going to do what I want.
Thanks for posting that link.
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If you vent the vacuum line to outside to eliminate a dirty intake you are likely making a dirtier crankcase. The vacuum pull out of the crankcase removes fumes from the crankcase as it is a continuous flow. This reduces the fume buildup in the crankcase compared to an open vent with no natural flow so the open vent will build up fumes and likely precipitate more junk into your oil pan.
The CX-5 is designed to reduce the manifold vacuums pumping loss for efficiency by controlling engine speed by keeping the intake valves open during the compression stroke. They close them only with the volume of air in the cylinder needed for the current power demand and fuel injector flow instead of using a throttle plate that creates a high vacuum behind it. Perhaps the exception is when you are off throttle looking for engine braking. So, there may be a vacuum pump in the loop to keep the crankcase clean as I think is used on the vacuum brake assist...
The CX-5 is designed to reduce the manifold vacuums pumping loss for efficiency by controlling engine speed by keeping the intake valves open during the compression stroke. They close them only with the volume of air in the cylinder needed for the current power demand and fuel injector flow instead of using a throttle plate that creates a high vacuum behind it. Perhaps the exception is when you are off throttle looking for engine braking. So, there may be a vacuum pump in the loop to keep the crankcase clean as I think is used on the vacuum brake assist...
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- RDX Aspec Adv.
I'd not go screwing around with this motor. It' not a rock-simple thing like a Chevy 350.
Agreed. It makes even less sense to start changing things around when there is zero evidence that a problem exists in the first place.
Just took a quick walk through the service manual and saw no mention of an EGR. Cars with VVT really don't need it. Hyundai stopped using it.
The vacuum from the PCV valve helps create negative pressure inside the engine. Without it you'll have positive pressure buildup inside the engine just from the ring blow by gases. Even just slight positive pressure can cause oil leaks to develope in time.
Not necessarily. Thats only if the ports that it is supposed to vent from are clogged or are not large enough handle the amount of pressure that needs to be relieved or moved.
I remember in the past forums people always argued that you need to ventilate the valve cover to reduce contamination in the oil etc... But Black Stone oil analysis proved that theory incorrect (i didnt test the oil someone else did). In addition, think what happens when the car is turned off? Nothing ventilates the valve cover, the blow-by from the crank case goes straight up and fills the valve cover area.
Its possible that something could be different on the Mazda, some new technology. But most modern motors are all the similar, especially emissions related parts.
A slight vacuum will reduce potential leakage of valve cover, oil pan cover, main bearing seal etc. GM uses this theory on the differential of my C5 Corvette. The gear case vent has a one way valve so that after it heats up and air escapes it seals and creates a slight vacuum as it cools and sits so the seals on the wheel drive shafts do not leak. My 2000 C5 started leaking and after reading a lot of forums I replaced the vent valve and that stopped it, saved me from pulling the rear end, tearing it down and replacing the seals...
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- RDX Aspec Adv.
Why on earth are people even debating the merits of this. Next thing you know, someone will have a carburetor conversion kit for the CX-5.
