MAF vs SD for dummies
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From: Virginia
MAF vs SD for dummies
Hey, what exactly is MAF and SD, and how are they different? I am new to EFI, so I thought EFI was EFI. Does anyone know of a good article/webpage that could sort of fill me in? Or, if anyone has some time, just give me a quick intro for dummies.
Thanks
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Postmaster
Joined: Oct 2006
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From: Davis & Newcastle, CA
Yes sir, MAF = Mass Air Flow and SD = Speed Density.
The basic idea is that a MAF truck uses an MAF sensor (along with other things) in the intake to tell the computer what kind of airflow it is getting, allowing the computer to adjust the A/F ratio in realtime, while the SD system simply uses a pre-programmed table that it refers to when adjusting it's A/F ratio.
The problem with SD is that if you modify your engine in a way that the pre-programmed table is no longer accurate to your engine spec, it's going to throw things out of whack, while the MAF will find the changes and adjust for them
Long story short, MAF is better for most applications This is merely my EXTREMLY basic understanding of the subject...
The basic idea is that a MAF truck uses an MAF sensor (along with other things) in the intake to tell the computer what kind of airflow it is getting, allowing the computer to adjust the A/F ratio in realtime, while the SD system simply uses a pre-programmed table that it refers to when adjusting it's A/F ratio.
The problem with SD is that if you modify your engine in a way that the pre-programmed table is no longer accurate to your engine spec, it's going to throw things out of whack, while the MAF will find the changes and adjust for them
Long story short, MAF is better for most applications
This is merely my EXTREMLY basic understanding of the subject...
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Speed Density is heavily reliant upon engine vacuum in order to function normally. What burns a few people is they'll put a hotter cam in their truck that won't run well with a speed density and their normal engine vacuum of say.... 20in Hg goes to 14in Hg (just an example) and in turn the computer starts giving you the finger and trying to correct for it when it really can't.
With a MAF setup you can run a bigger variety of cams and it won't hurt anything. There are pro's and con's to each though.
With a MAF setup you can run a bigger variety of cams and it won't hurt anything. There are pro's and con's to each though.
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Postmaster
Joined: Oct 2006
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From: Davis & Newcastle, CA
Originally Posted by tomtoc
and a semi-related question: does MAF = OBD2 and SD = OBD1
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From: The dark carnival
SD has to be reprogrammed to match changes in volumetric efficiency, vacuum etc. where as MAF will adjust itself to those changes (within a certain limit). But, the SD will perform arguably better if programmed by the right person than a MAF that has adjusted itself. Even engine wear can throw off vacuum enough to where the SD wont run the motor....but at that point the motor is probably plenty tired anyways.
Plenty of OBD1s had MAF.
Most of the time MAF has SFI which is nice where as SD usually has batch fire which is arguably not as nice of a system.
Plenty of OBD1s had MAF.
Most of the time MAF has SFI which is nice where as SD usually has batch fire which is arguably not as nice of a system.
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From: The dark carnival
Originally Posted by dagray3
yeah, I know that 88 was the first year for EFI to be standard, but do I have SD or MAF?
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From: The dark carnival
Originally Posted by Lead Head
Does a Mass Air system still use a MAP sensor for things like boost, etc..?
It is basically a MAP sensor with the vacuum line left off.
