My 1995 civic dosnt have a MAF, yet these hondas are known to have great fuel economy and emissions. I wonder what makes the difference when the car company chooses to have a MAF or not. Is it necessary, and does it provide a benefit? I would think the O2 sensor could adjust if there was too much or too little air.
Why do some cars not have MAF's?
- Thread starter robnitro
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Patman
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If they don't have a MAF they use something called "speed density" which takes info from many different sensors and estimates how much air is coming in. It's not as precise a method as using a mass air meter though, which knows exactly how much air is getting in.
Pretty much all cars with a MAF also have a manifold absolute pressure sensor as well. MAP sensor based systems are not good at coping with extreme changes in airflow.
With due respect
Bosch D Jetronic = MAP. (First electronic injection, 1968)
Bosch L Jetronic = MAF with moving flap in airflow
Bosch LH Jetronic = Hot wire MAF (in my 87 Volvo)
Megasquirt = MAP (build your own EFI)
Early 90's GM used a MAP only,I think
My 98 Lumina has both.
Maybe only newer cars with EFI have both. I guess my age is showing!!
me and robnitro were talking about this last night. then i was thinking why do accords and civics dont have this MAF feature. well i failed to realize that the accord has a MAP sensor and a IAC sensor (intake idle control). i guess those substitute....
still i wonder why...isnt a MAF sensor more reliable?
still i wonder why...isnt a MAF sensor more reliable?
MAF sensors are delicate affairs, a thin light bulb filament type thing in the full force of incoming air. MAP sensors hide behind a diaphragm at the long end of a piece of vacuum hose.
MAFs are great (more responsive/precise than MAPs) until you clog them with paper lint or K&N oil and they start seeing less air. The part is more expensive (and IMHO, less reliable) than a MAP which is why we still see MAPs in economy cars like that civic.
MAFs are great (more responsive/precise than MAPs) until you clog them with paper lint or K&N oil and they start seeing less air. The part is more expensive (and IMHO, less reliable) than a MAP which is why we still see MAPs in economy cars like that civic.
MAP and MAF they measure different parameters,
MAP: absolute pressure or actually intake vacuum
MAF: air flow volume or mass
MAP: absolute pressure or actually intake vacuum
MAF: air flow volume or mass
My car (98 Grand Prix GTP) has both map and MAF.
One good Reason why most Maf cars use a MAP is this.
when an obd2 car sees a problem with the maf it will switch over to Speed density and guess its way from there (after setting your ses light).
example:
If I modify my L67 (supercharged series 2 3800) to the point that it flows more air than the maf tables in the computer can compute the car switches to speed density.
Only problem is that the speed density is not as accurate or quick to changes in air/ fuel mixture requirements and has a tendency to pop pistons in my application. The backup speed density computations are designed to "limp home".
One good Reason why most Maf cars use a MAP is this.
when an obd2 car sees a problem with the maf it will switch over to Speed density and guess its way from there (after setting your ses light).
example:
If I modify my L67 (supercharged series 2 3800) to the point that it flows more air than the maf tables in the computer can compute the car switches to speed density.
Only problem is that the speed density is not as accurate or quick to changes in air/ fuel mixture requirements and has a tendency to pop pistons in my application. The backup speed density computations are designed to "limp home".
Using a MAF costs a few HP compared to a speed-density system. I read a good article comparing the two, if I can dig it up I'll post the link.
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