Newbie Speed Density vs. MAF
Thread Starter
Joined: Feb 2008
Posts: 1,265
Likes: 18
From: Bolton Masshole
Newbie Speed Density vs. MAF So we all know that our cars (except for 93) run using a MAF sensor right before the throttle body. However, when going forced induction, i see alot of people converting to 2 bar or 3 bar map sensors. I know that a "bar" is 14.5psi or whatever, but how exactly does the computer know how to make fuel adjustments and such using a MAP sensor? With a MAF, the sensor reads how much air is flowing past it and gives reading to the computer to make fuel adjustments etc. So how does a MAP sensor work? Also, why is it advantageous to run a 2 or 3 bar map sensor? Thanks guys
A MAP sensor measures the air pressure. It also uses the IAT or intake air temperature. When the computer knows the pressure and the temperature, if can calculate the density. From there it knows how much fuel to inject, and that's about it.
1 bar is 14.7psi which is what we have at atmospheric level. You would need a 2 bar sensor for 0 to 14.7 psi of boost and a 3 bar sensor for 0 to 29.4 psi of boost.
1 bar is 14.7psi which is what we have at atmospheric level. You would need a 2 bar sensor for 0 to 14.7 psi of boost and a 3 bar sensor for 0 to 29.4 psi of boost.
A MAP sensor measures the air pressure. It also uses the IAT or intake air temperature. When the computer knows the pressure and the temperature, if can calculate the density. From there it knows how much fuel to inject, and that's about it.
1 bar is 14.7psi which is what we have at atmospheric level. You would need a 2 bar sensor for 0 to 14.7 psi of boost and a 3 bar sensor for 0 to 29.4 psi of boost.
1 bar is 14.7psi which is what we have at atmospheric level. You would need a 2 bar sensor for 0 to 14.7 psi of boost and a 3 bar sensor for 0 to 29.4 psi of boost.
TECH Enthusiast
Joined: Feb 2009
Posts: 538
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not hijacking the thread, but my car is getting a speed density tune with the turbo setup in 2 weeks....with speed density, once the tune is set, when i want to turn up the boost (manual controler for now), do i need a new tune or does it just compensate?
you'll need a new tune.
because you pushing more air into the motor, the PCM has to compensate by adding more fuel. Atleast w/ a turbo setup you can control the boost better than a S/C. When ever it gets cold out the air is denser and you can see the boost levels go up.
Last summer mine was making 10# and on a cool Nov night, I was seeing 12-13#.
because you pushing more air into the motor, the PCM has to compensate by adding more fuel. Atleast w/ a turbo setup you can control the boost better than a S/C. When ever it gets cold out the air is denser and you can see the boost levels go up.
Last summer mine was making 10# and on a cool Nov night, I was seeing 12-13#.
you'll need a new tune.
because you pushing more air into the motor, the PCM has to compensate by adding more fuel. Atleast w/ a turbo setup you can control the boost better than a S/C. When ever it gets cold out the air is denser and you can see the boost levels go up.
Last summer mine was making 10# and on a cool Nov night, I was seeing 12-13#.
because you pushing more air into the motor, the PCM has to compensate by adding more fuel. Atleast w/ a turbo setup you can control the boost better than a S/C. When ever it gets cold out the air is denser and you can see the boost levels go up.
Last summer mine was making 10# and on a cool Nov night, I was seeing 12-13#.
To be safe though, get it checked and tuned if necessary.
Just make sure when its tuned that while on the dyno you get it to put down the max it can so it can be taken into consideration. I can gain 2#'s of boost by just taking off my airlid but I dont drive with it off on the street. Since SD is boost referenced it will know how much air you are pushing into the motor.
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On The Tree
Joined: Oct 2007
Posts: 198
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From: DA SUCK,
I had my tuner back my timing way off and in conjunction with my BAP, and meth I can move between 10-15lbs of boost without any drastic changes in afr's (11.0-11.8) on pump gas. This is on one tune btw
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