Tell me how much mass does 0 volume of air have?
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Tell me how much mass does 0 volume of air have?
How is the EGR flow calculated? is there like another MAF or a pressure sensor in the exhaust?Schurkey wrote: ↑Mon May 29, 2023 11:15 pm SOME sensors provide "gross" inputs for the computer to calculate fuel delivery: For example, engine coolant temp, throttle position, MAP, MAF.
The O2 sensor provides a method to "fine-tune" the fuel delivery, some amount of self-learning via the short- and long-term fuel trims.
EGR displaces incoming air. The computer knows when the EGR is operational, the "gross" fueling changes are already incorporated into those fuel tables. Again, the O2 provides "fine tuning" of the fuel delivery.
O2 sensor(s) are essential for closed-loop operation.
SOME applications have an EGR position sensor. Lots of older stuff does not. There's no precise method of calculating EGR flow on those, and even the ones with a position sensor rely on the passages being clear--not coked-up with carbon.
The maf can tell the ECU how much air is entering, and even modulate fuel accordingly, but it can't tell you if that fuel is being burned completely, or if you have a misfire. As others have said.. it's a system no single sensor dominates what the ECU is doing at any point in time, if that were true we'd have a tps and alpha n systems still
My guess is when the OEM gets each engine platform certified for car, light truck, heavy duty, export etc it is days spent on an engine Dyno, then chassis Dyno dialing it in for each engine, transmission, vehicle combination. If you take a look at the tune file of the same engine, same year, but different application/chassis/exhaust system.. you will see significantly different EGR system settings. At least this is true for late 80's, early 90's gm sbc stuff. Camshaft used will also significantly impact the EGR system settings.ELS wrote: ↑Mon May 29, 2023 11:42 pmHow is the EGR flow calculated? is there like another MAF or a pressure sensor in the exhaust?Schurkey wrote: ↑Mon May 29, 2023 11:15 pm SOME sensors provide "gross" inputs for the computer to calculate fuel delivery: For example, engine coolant temp, throttle position, MAP, MAF.
The O2 sensor provides a method to "fine-tune" the fuel delivery, some amount of self-learning via the short- and long-term fuel trims.
EGR displaces incoming air. The computer knows when the EGR is operational, the "gross" fueling changes are already incorporated into those fuel tables. Again, the O2 provides "fine tuning" of the fuel delivery.
O2 sensor(s) are essential for closed-loop operation.
dannobee wrote: ↑Tue May 30, 2023 11:09 am EGR is inert, that is, it won't burn again. It lacks both fuel and oxygen. As such, the egr flow doesn't affect the O2 sensor reading. And sure, someone will say a bad/burned gasket can allow air into the system, and sure, that's true, but in a properly functioning system, an open egr valve will have little or no effect on the oxygen sensor reading. The various sensors used to monitor egr over the years (valve position sensor, egr temp sensor, etc) proves that statement; if it was possible to monitor egr volume by using the O2 sensor, the OEM's would have done it.
And remember, EGR was around long before oxygen sensors. And with carburetors, no less.
This isn't so. EGR from lean combustion contains O2, and bonus, it is hot O2, so the hot exhaust gas will not only improve vaporization it will improve combustion.
yeahTuner wrote: ↑Tue May 30, 2023 1:00 pmdannobee wrote: ↑Tue May 30, 2023 11:09 am EGR is inert, that is, it won't burn again. It lacks both fuel and oxygen. As such, the egr flow doesn't affect the O2 sensor reading. And sure, someone will say a bad/burned gasket can allow air into the system, and sure, that's true, but in a properly functioning system, an open egr valve will have little or no effect on the oxygen sensor reading. The various sensors used to monitor egr over the years (valve position sensor, egr temp sensor, etc) proves that statement; if it was possible to monitor egr volume by using the O2 sensor, the OEM's would have done it.
And remember, EGR was around long before oxygen sensors. And with carburetors, no less.This isn't so. EGR from lean combustion contains O2, and bonus, it is hot O2, so the hot exhaust gas will not only improve vaporization it will improve combustion.
The first EGR systems in '73 were crude and the emissions calibration engineers hadn't figured out how to use the hot exhaust to advantage, so nearly all new cars ran better when EGR was disabled. This created the situation of misguided urban lore and prejudice against EGR which is now going on 50 years old.
In '78 and '79 the emissions engineers started getting EGR figured out and some engines started appearing that didn't respond favorably at all to disconnecting or blocking the EGR. Disconnecting the EGR on some Pontiac 455 and Olds 403 engines would almost double fuel consumption. 302 Ford was another that liked its EGR at part-throttle, but the mileage deal was not as dramatic as the Olds and Pontiac.
Some engines with radical cams that have a lot of valve timing overlap will respond to lean A/F in high vacuum cruising conditions for the same reason, hot oxygen in high vacuum exhaust reversion improves combustion. Exhaust system resonance has large influence on whether or not and to the degree this favorable phenomenon occurs. Just changing the muffler(s) can have a huge influence on carb calibration in high vacuum cruising conditions. Vacuum advance calibration is also important and can be sensitive to small changes in advance per inch Hg. If you don't think clean plugs and minimum fuel consumption are important, don't bother.
In the case of valve timing overlap combined with intake and exhaust system resonance resulting in a large amount of intake air passing through into the exhaust, the O2 sensor will see O2 that has not been involved in combustion and will report a leaner A/F than the actual combustion A/F. When a radical engine responds favorably to indicated A/F leaner than 17/1 overlap bypass is probably occurring, so the O2 sensor reading must be taken with a grain of salt, but because tuning is a process of judgement calls in seeking best performance, numbers on a gauge are irrelevant for anything but reference anyway.
It is evident you misunderstand what you have seen on the old flathead engines. The exhaust gas only heats the intake manifold for vaporization, it does not actually mix with the intake air.ELS wrote: ↑Tue May 30, 2023 2:08 pmyeahTuner wrote: ↑Tue May 30, 2023 1:00 pmdannobee wrote: ↑Tue May 30, 2023 11:09 am EGR is inert, that is, it won't burn again. It lacks both fuel and oxygen. As such, the egr flow doesn't affect the O2 sensor reading. And sure, someone will say a bad/burned gasket can allow air into the system, and sure, that's true, but in a properly functioning system, an open egr valve will have little or no effect on the oxygen sensor reading. The various sensors used to monitor egr over the years (valve position sensor, egr temp sensor, etc) proves that statement; if it was possible to monitor egr volume by using the O2 sensor, the OEM's would have done it.
And remember, EGR was around long before oxygen sensors. And with carburetors, no less.This isn't so. EGR from lean combustion contains O2, and bonus, it is hot O2, so the hot exhaust gas will not only improve vaporization it will improve combustion.
The first EGR systems in '73 were crude and the emissions calibration engineers hadn't figured out how to use the hot exhaust to advantage, so nearly all new cars ran better when EGR was disabled. This created the situation of misguided urban lore and prejudice against EGR which is now going on 50 years old.
In '78 and '79 the emissions engineers started getting EGR figured out and some engines started appearing that didn't respond favorably at all to disconnecting or blocking the EGR. Disconnecting the EGR on some Pontiac 455 and Olds 403 engines would almost double fuel consumption. 302 Ford was another that liked its EGR at part-throttle, but the mileage deal was not as dramatic as the Olds and Pontiac.
Some engines with radical cams that have a lot of valve timing overlap will respond to lean A/F in high vacuum cruising conditions for the same reason, hot oxygen in high vacuum exhaust reversion improves combustion. Exhaust system resonance has large influence on whether or not and to the degree this favorable phenomenon occurs. Just changing the muffler(s) can have a huge influence on carb calibration in high vacuum cruising conditions. Vacuum advance calibration is also important and can be sensitive to small changes in advance per inch Hg. If you don't think clean plugs and minimum fuel consumption are important, don't bother.
In the case of valve timing overlap combined with intake and exhaust system resonance resulting in a large amount of intake air passing through into the exhaust, the O2 sensor will see O2 that has not been involved in combustion and will report a leaner A/F than the actual combustion A/F. When a radical engine responds favorably to indicated A/F leaner than 17/1 overlap bypass is probably occurring, so the O2 sensor reading must be taken with a grain of salt, but because tuning is a process of judgement calls in seeking best performance, numbers on a gauge are irrelevant for anything but reference anyway.
If EGR being 'innert' means it wont affect the O2 sensor reading. Think of what the O2 sensor is reading... Exhaust Gasses.
It will affect the reading because it "dilutes" the oxygen content so the O2 sensor thinks the engine is running richer than it actually is, because there's exhaust gases that displace the real mixture exhaust gases.
Well I've seen EGR systems on MUCH earlier engines, think of early flat-heat engines where the intake was a log intake right on top of a log exhaust manifold, and would have a sizeable passage going from the exhaust to the intake.
I presume this was done to instead heat the intake mixture for better evaporization, but it is also adding EGR.
This is your basic mistake in logic.
Ok I think you're right that the reading will be the same but not for the reason you described.Schurkey wrote: ↑Tue May 30, 2023 6:39 pmThis is your basic mistake in logic.
Any dilution of the intake charge with inert material is automatically compensated-for via the MAP, MAF, and throttle-position sensors. You're moving the throttle to get the power you need--which affects mass flow, intake pressure, and throttle position.
The inert EGR affects nothing so far as the O2 sensor is concerned. It's still reading the O2 in the exhaust stream, it doesn't know the difference between "fresh" exhaust and "recirculated" exhaust, and it's still fine-tuning the fuel delivery to make the O2 voltage swing from high to low to high, exactly as the engineers intend; therefore the mixture is essentially at the air/fuel ratio the engineers intend.
In the big truck world egr flow is measured and clogged passages sure cause running issues.ELS wrote: ↑Mon May 29, 2023 11:42 pmHow is the EGR flow calculated? is there like another MAF or a pressure sensor in the exhaust?Schurkey wrote: ↑Mon May 29, 2023 11:15 pm SOME sensors provide "gross" inputs for the computer to calculate fuel delivery: For example, engine coolant temp, throttle position, MAP, MAF.
The O2 sensor provides a method to "fine-tune" the fuel delivery, some amount of self-learning via the short- and long-term fuel trims.
EGR displaces incoming air. The computer knows when the EGR is operational, the "gross" fueling changes are already incorporated into those fuel tables. Again, the O2 provides "fine tuning" of the fuel delivery.
O2 sensor(s) are essential for closed-loop operation.