Quote:
Originally Posted by hat_man
This has been an interesting read for me. Even though I don't understand the specifics (pumping losses:throttle opening etc.) I get the main understanding. Warm air is less dense and means less fuel.
I am not a mechanic by any stretch of the imagination. Just a guy who likes to tinker with his truck and squeeze as much as I can get out of it. I do have two questions that I hope someone can explain for me without going into too much techspeak. (I ain't got much fer smarts)
1) Why does this not seem to work with a MAF but does with a MAP? And what is the difference in these two doo-hickeys anyhow?
2) I have heard of the ZX2's using a resistor to "trick" the computer into thinking the intake air is colder than it really is. I realize it is to help advance the timing (I know what that physically means but don't know why it works), but doesn't it use more fuel to compensate for what it thinks is colder/higher density air?
I'm sure these questions seem trivial for the most of you, but I'm always trying to learn something new.
p.s. I made a what I think is a "poor man's WAI" but I don't know how to re-size my pictures to get them posted here. They are about twice as big as the site allows. Any help there would be appreciated also.
Thanks.
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MAF (MASS AIR FLOW) sensors are mostly fine wire that is heated by an electrical current. As the air flows past the wire the voltage differential, across that wire, is measured by the computer and this voltage signal is used to control injector cycling duration.
MAP (MANIFOLD ABSOLUTE PRESSURE) sensors read the amount of atmospheric pressure that is actually available to the cylinders. This pressure is equal to the atmospheric pressure minus the negative pressure created by flow restrictions. Otherwise know as manifold vacuum. MAP is the opposite of manifold vacuum. Take atmospheric pressure subtract MAP and you have manifold vacuum, the reverse is true.
Both MAP and MAF give the ECU a load signal and the ECU can calculate the amount of fuel to deliver to the cylinders knowing either MAP or MAF. This, combined with RPM, provides a amount of fuel which is then adjusted further by the feedback from the oxygen sensor which measures the content of the oxygen in the exhaust after combustion is complete.
MAP and MAF tell the ECU to deliver X amount of fuel. The oxygen sensor tells the ECU to trim the delivery of fuel slightly to achieve the ideal amount of residual oxygen in the exhaust when it leaves the combustion chamber.
Hope this helps and I hope the explanation is understandable. If not let me know what is still fuzzy and I will try to explain it further.
regards
Mech