Originally Posted by 6SPD_FTW Ya know, I rather take a bit of offense to you saying I am spreading incorrect information because I am not. You are. Blow-by is what
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02-07-2011, 11:56 PM | #9 (permalink) | |
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70% of the blowby gasses (which is a small amount to start with) gets sucked back into the intake tract. Want to guess how much %-wise this unburnt hydrocarbon mixture is vs amount of fuel injected into the cylinder during combustion? Basically negligible. The ECM has NO WAY of measuring this. Your mass airflow sensor tells the engine how much air is getting in through the intake and thats ALL the ECM injects for. So yes I am saying that NISSAN does not account for blowby gasses in the AFR equations. I can also tell you for certain that Subaru does NOT account for blowby gasses in their modern ECM's as well. I have a fair bit of experience working with Opensource tuning on the Subaru's and have seen the effects of running crankecase breathers set to VTA on aggressive and daily driver vehicles. In short there are no problems (at least with AFR anyway...emissions is another story). I'm not as familiar with Mitsubishi, but I'm pretty sure they don't account for it either. The ECU's AFR correction is also not 3D. Its 2D. Think of it like this. (just guessing on the actual g/s values) MAF sensor g/s ECU correction % 0-10 x% 11-30 y% 30-50 z% 50+ a% Oil contamination is not really a concern. The oil gets really hot and the fuel is vaporized. Even with just VTA crankcase breathers, you should really be fine unless you never let your engine get up to operating temps. If anyone is really that concerned about fuel dilution then get an oil analysis done after your first oil change of running VTA breathers. Also an AFR and an O2 sensor are one in the same. In fact there is no such thing as an AFR sensor. The O2 sensor just measures the ratio of oxygen in the exhaust tract to that of the ambient air. Then calculates the air fuel ratio based on that data. Additionally your comments about the air filter and the manifold not delivering the same amount of air is meaningless. Only air that makes it past the air filter will be measured by the ECM (which then tells the injectors how much to inject), and all of that air will go into the engine to be burned. Perfect air-Cylinder distribution is inconsequential because there is not an O2 sensor at each cylinder. The system's O2 sensor is only being read far enough downstream that cylinder exhaust will be mixed. I would agree that air-cylinder distribution is important, but its not adjusted for in the ECM. I'm glad you've had good luck with your setup. I'm not saying all of what you said was miss-information, just the part about the ECM using blowby as part of the air fuel equation. |
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