Why do these maf cars run lean/rich?
10-01-2002 | 11:37 AM
#1
Thread Starter
Teching In
Joined: Sep 2002
Posts: 10
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From: Jupiter, FL
Why do these maf cars run lean/rich? I don't understand why these cars run rich or lean with modifications. If I buy a performance maf for an ls1 I am guessing it is calibrated.
I guess I am wondering is if more air comes in shouldn't it be metered (maf sensor reads it) and the ecu react and supply fuel? or does the sensor have a cap on how much flow it can see? maybe then it would flow more than it is reporting to the ecu?
Sorry I am a ls1 noob lol <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
I guess I am wondering is if more air comes in shouldn't it be metered (maf sensor reads it) and the ecu react and supply fuel? or does the sensor have a cap on how much flow it can see? maybe then it would flow more than it is reporting to the ecu?
Sorry I am a ls1 noob lol <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
10-02-2002 | 12:11 AM
#2
Re: Why do these maf cars run lean/rich? There are a couple things that happen when you do modifications to your car.
Intake Modifications: Factory MAF's are callibrated for a specific scenario of air flow. Altering your intake path is going to change air velocity, laminar/turbulent, charateristics of your intake. These changes are going to cause the MAF to operate in conditions that it was not specifically calibrated for. These alterations (ie air lid) typically do not alter the a/f ratio that much.
MAF Modifications: Some people directly goof with the MAF to flow more air into the engine. These altercations to the MAF will desensitize it and cause it to report less air than is actually entering the engine. These modifications can cause some very lean conditions, and are often the cause of LS1's running excessively lean. Modifications that are commonly done to the MAF are MAF ends, porting your MAF, removing the screen, etc...
Exhaust Modifications: Exhaust modifications will alter the percieved reading of the O2 sensors. These sensors directly control the adjustment fueling to your engine. Exhaust modifications that enlarge the piping associated with the O2's, move the O2's, increase exhaust velocity across the O2's, will alter the percieved reading of the O2 sensor. In these cases, your car may actually be running with a fairly decent a/f ratio, but the percieved a/f ratio of O2's is off, and they will adjust the fueling incorrectly causing either a rich or lean condition.
Good Luck,
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Intake Modifications: Factory MAF's are callibrated for a specific scenario of air flow. Altering your intake path is going to change air velocity, laminar/turbulent, charateristics of your intake. These changes are going to cause the MAF to operate in conditions that it was not specifically calibrated for. These alterations (ie air lid) typically do not alter the a/f ratio that much.
MAF Modifications: Some people directly goof with the MAF to flow more air into the engine. These altercations to the MAF will desensitize it and cause it to report less air than is actually entering the engine. These modifications can cause some very lean conditions, and are often the cause of LS1's running excessively lean. Modifications that are commonly done to the MAF are MAF ends, porting your MAF, removing the screen, etc...
Exhaust Modifications: Exhaust modifications will alter the percieved reading of the O2 sensors. These sensors directly control the adjustment fueling to your engine. Exhaust modifications that enlarge the piping associated with the O2's, move the O2's, increase exhaust velocity across the O2's, will alter the percieved reading of the O2 sensor. In these cases, your car may actually be running with a fairly decent a/f ratio, but the percieved a/f ratio of O2's is off, and they will adjust the fueling incorrectly causing either a rich or lean condition.
Good Luck,
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
10-02-2002 | 01:46 PM
#3
Teching In
Joined: Aug 2002
Posts: 45
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From: Dallas, TX
Re: Why do these maf cars run lean/rich? So when you do those exhaust mods what can you do to correct the A/F ratio? Will an aftermarket MAF do? Or should I go with a MAFT? Or if I don't plan on doing any more engine mods go to a dyno shop and get some LSEdit tuning?
TIA
TIA
