Robert56
12-15-2009, 02:04 AM
Just some basic information on the MAF de-screening for those reading along. We always want to de-screen the MAF when running dry hits. Why? Well what can happen on a humid day is condensation can collect and freeze on the screen making for a wild a/f ratio. This issue often gets mixed up with statements like, " running dry can cause the MAF to freeze and you will go lean".
That is nonsense, the MAF itself does not freeze up. How on earth could guys in Alaska run their EFI cars when the chill factor is 60° below zero. Also, another point to show how ridiculous that type of statement is this, if by some weird reason the MAF wires did freeze, it would dump all available fuel and go crazy rich not lean. That is the premise of the before the MAF nozzle style dry hits, chill the wires to increase the amount of fuel added. The wires are at a set temp/voltage/current and when the air passes the wires and tries to cool them down it records what it takes to keep them at the set current/temp, or difference. The computer uses advanced algorithms to figure this all out and appropriate tables are adjusted as needed. So when we super chill the wires with nitrous, the computer thinks we are getting massive amounts of very dense cold air and compensates by adding more fuel via the injectors.
Once de-screened we may need to re-map the MAF tables for a slight increase in intake volume. For most, and especially the latest EFI cars, this will not be needed as the small discrepancy can be dealt with via the VE tables. On the LSx platform this can work up to a 20/25% error at any one spot on the fuel table. So the computer can adjust for slightly leaner readings. The guys that have problems usually already have their tunes out of whack enough that they may be already compensating at 20/25% and once we reach that point then the next step is a code will be thrown.
One more thing to point out, the MAF screen is there to straighten up the air flow so the MAF wires get a nice even reading. However, this is only really needed on set-ups that have numerous 90° turns, like the truck plumbing, and this un-straightened air can cause turbulence. What GM did for cost savings was to add the screen to all the MAFs so as to have one part number, so the cars that didn't need the screen got one anyway.
One of the ways that GM upped the HP rating on the '02 thru '04 Z06, from the previous 385bhp to the new 405bhp, was by removing the MAF screen. They opened up the air box and found the MAF screen to hinder flow for best power, so they removed it. That is why you will see a separate, or different, part number for the '02/'04 Z06 MAF, and the '01 part # staying the same as other GM cars. Other than that, they are same as other GM MAFs of that era. Also, the MAF freq range was increased, IIRC, at this time over prior MAFs, partly I believe due to the better flow that increased the range (GM guys should run the Z06 MAF if ya need a replacement). Just thought I would through this info out for any nitrous geeks that might care, LOL.
A copy of this thread has been added to the import section too, as it applies to most all late model EFI cars. Please give your input and ideas, and additional info is welcome, or if someone can explain things a little better that is great.
Robert
That is nonsense, the MAF itself does not freeze up. How on earth could guys in Alaska run their EFI cars when the chill factor is 60° below zero. Also, another point to show how ridiculous that type of statement is this, if by some weird reason the MAF wires did freeze, it would dump all available fuel and go crazy rich not lean. That is the premise of the before the MAF nozzle style dry hits, chill the wires to increase the amount of fuel added. The wires are at a set temp/voltage/current and when the air passes the wires and tries to cool them down it records what it takes to keep them at the set current/temp, or difference. The computer uses advanced algorithms to figure this all out and appropriate tables are adjusted as needed. So when we super chill the wires with nitrous, the computer thinks we are getting massive amounts of very dense cold air and compensates by adding more fuel via the injectors.
Once de-screened we may need to re-map the MAF tables for a slight increase in intake volume. For most, and especially the latest EFI cars, this will not be needed as the small discrepancy can be dealt with via the VE tables. On the LSx platform this can work up to a 20/25% error at any one spot on the fuel table. So the computer can adjust for slightly leaner readings. The guys that have problems usually already have their tunes out of whack enough that they may be already compensating at 20/25% and once we reach that point then the next step is a code will be thrown.
One more thing to point out, the MAF screen is there to straighten up the air flow so the MAF wires get a nice even reading. However, this is only really needed on set-ups that have numerous 90° turns, like the truck plumbing, and this un-straightened air can cause turbulence. What GM did for cost savings was to add the screen to all the MAFs so as to have one part number, so the cars that didn't need the screen got one anyway.
One of the ways that GM upped the HP rating on the '02 thru '04 Z06, from the previous 385bhp to the new 405bhp, was by removing the MAF screen. They opened up the air box and found the MAF screen to hinder flow for best power, so they removed it. That is why you will see a separate, or different, part number for the '02/'04 Z06 MAF, and the '01 part # staying the same as other GM cars. Other than that, they are same as other GM MAFs of that era. Also, the MAF freq range was increased, IIRC, at this time over prior MAFs, partly I believe due to the better flow that increased the range (GM guys should run the Z06 MAF if ya need a replacement). Just thought I would through this info out for any nitrous geeks that might care, LOL.
A copy of this thread has been added to the import section too, as it applies to most all late model EFI cars. Please give your input and ideas, and additional info is welcome, or if someone can explain things a little better that is great.
Robert