Descreening a MAF??
12-08-2005, 10:20 AM
#16
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,825
Re: Descreening a MAF??
You can't just swap them back and forth at the track, and expect to get a reasonable comparison. The calibration affects the long term fuel corrections, so it takes time for the PCM to react to the changes in the calibration that result from removing the screen, or any other changes to the meter.
The "ported" sensors, and the aftermarket sensors rely on the fact that they may lean out the stock "target" A/F ratio at WOT. That's good for up to 15HP. But hacking up the MAF sensor, and hoping the results work that way is not the correct way to tune an engine. Just have the PE tables leaned out for the same 15HP. Don't screw up a precision sensor and hope it works.
I've been arguing this pont here (and on other boards) for about 7 years now. Based on the posts I've read, it seems that its pretty much split up 1/3-1/3-1/3. 1/3 of the people report miraculous ET gains at the track, 1/3 feel nothing, and 1/3 have problems like stumbling, surging and lost fuel mileage. Inj the earlier models, its easy to just pull the snap ring out, remove the screen without damaging it, and drive around with it that way for a couple weeks to see how it works on your car. If you feel it helped, leave it out. If you see no difference, or feel it hurts something, put it back in. The problem is the later year cars, where you can only remove it by destroying it. If you don't like the results, your sort of screwed.
The "ported" sensors, and the aftermarket sensors rely on the fact that they may lean out the stock "target" A/F ratio at WOT. That's good for up to 15HP. But hacking up the MAF sensor, and hoping the results work that way is not the correct way to tune an engine. Just have the PE tables leaned out for the same 15HP. Don't screw up a precision sensor and hope it works.
I've been arguing this pont here (and on other boards) for about 7 years now. Based on the posts I've read, it seems that its pretty much split up 1/3-1/3-1/3. 1/3 of the people report miraculous ET gains at the track, 1/3 feel nothing, and 1/3 have problems like stumbling, surging and lost fuel mileage. Inj the earlier models, its easy to just pull the snap ring out, remove the screen without damaging it, and drive around with it that way for a couple weeks to see how it works on your car. If you feel it helped, leave it out. If you see no difference, or feel it hurts something, put it back in. The problem is the later year cars, where you can only remove it by destroying it. If you don't like the results, your sort of screwed.
12-08-2005, 12:17 PM
#17
Registered User
Join Date: May 2001
Location: fort worth/burleson Tx
Posts: 1,511
Re: Descreening a MAF??
Originally Posted by Injuneer
You can't just swap them back and forth at the track, and expect to get a reasonable comparison. The calibration affects the long term fuel corrections, so it takes time for the PCM to react to the changes in the calibration that result from removing the screen, or any other changes to the meter.
The "ported" sensors, and the aftermarket sensors rely on the fact that they may lean out the stock "target" A/F ratio at WOT. That's good for up to 15HP. But hacking up the MAF sensor, and hoping the results work that way is not the correct way to tune an engine. Just have the PE tables leaned out for the same 15HP. Don't screw up a precision sensor and hope it works.
I've been arguing this pont here (and on other boards) for about 7 years now. Based on the posts I've read, it seems that its pretty much split up 1/3-1/3-1/3. 1/3 of the people report miraculous ET gains at the track, 1/3 feel nothing, and 1/3 have problems like stumbling, surging and lost fuel mileage. Inj the earlier models, its easy to just pull the snap ring out, remove the screen without damaging it, and drive around with it that way for a couple weeks to see how it works on your car. If you feel it helped, leave it out. If you see no difference, or feel it hurts something, put it back in. The problem is the later year cars, where you can only remove it by destroying it. If you don't like the results, your sort of screwed.
The "ported" sensors, and the aftermarket sensors rely on the fact that they may lean out the stock "target" A/F ratio at WOT. That's good for up to 15HP. But hacking up the MAF sensor, and hoping the results work that way is not the correct way to tune an engine. Just have the PE tables leaned out for the same 15HP. Don't screw up a precision sensor and hope it works.
I've been arguing this pont here (and on other boards) for about 7 years now. Based on the posts I've read, it seems that its pretty much split up 1/3-1/3-1/3. 1/3 of the people report miraculous ET gains at the track, 1/3 feel nothing, and 1/3 have problems like stumbling, surging and lost fuel mileage. Inj the earlier models, its easy to just pull the snap ring out, remove the screen without damaging it, and drive around with it that way for a couple weeks to see how it works on your car. If you feel it helped, leave it out. If you see no difference, or feel it hurts something, put it back in. The problem is the later year cars, where you can only remove it by destroying it. If you don't like the results, your sort of screwed.
12-08-2005, 12:46 PM
#18
Registered User
Join Date: Aug 2002
Location: BC
Posts: 2,325
Re: Descreening a MAF??
Even if you do hack your MAF, you'll be plauged with the "Is my car running as good as it should be because of my MAF job a few years back??"
With the internal computer we want all the sensor readings to be as accurate as possible. Although a sensor may be off by a bit (IE after hacking the maf) you may not notice a thing wrong, but what you don't know is that your other cars internal sensors have adjusted to compensate for the miscalibrated MAF. The long term fuel correction readings will be off a bit in the computer... So cruising and driving normally may correct iteself "fine".
BUT situations where you snap or let go of the throttle may also give a "not quite accurate" reading of the Air passing by... this means too little or too much fuel may be added during transitions like this. Your more likely to get driveability problems near shift pts or on quick throttle responses with a hacked maf... because the computer is more dependant on accurate readings during those times.
The right way (as posted above) - Lean out the PE tables, leave the MAF as is - getting the most accurate readings.
You'll thank yourself later when you start messing with your car more and you run into issues which may/may not be MAF related... at least you won't have to worry that your MAF is screwing things up because of a hack job 3 years ago
With the internal computer we want all the sensor readings to be as accurate as possible. Although a sensor may be off by a bit (IE after hacking the maf) you may not notice a thing wrong, but what you don't know is that your other cars internal sensors have adjusted to compensate for the miscalibrated MAF. The long term fuel correction readings will be off a bit in the computer... So cruising and driving normally may correct iteself "fine".
BUT situations where you snap or let go of the throttle may also give a "not quite accurate" reading of the Air passing by... this means too little or too much fuel may be added during transitions like this. Your more likely to get driveability problems near shift pts or on quick throttle responses with a hacked maf... because the computer is more dependant on accurate readings during those times.
The right way (as posted above) - Lean out the PE tables, leave the MAF as is - getting the most accurate readings.
You'll thank yourself later when you start messing with your car more and you run into issues which may/may not be MAF related... at least you won't have to worry that your MAF is screwing things up because of a hack job 3 years ago
12-08-2005, 01:04 PM
#19
Registered User
Join Date: Jul 2005
Posts: 1,783
Re: Descreening a MAF??
Originally Posted by toby360
at least you won't have to worry that your MAF is screwing things up because of a hack job 3 years ago
12-08-2005, 01:04 PM
#20
Registered User
Join Date: Oct 2003
Location: DOVER DE
Posts: 2,140
Re: Descreening a MAF??
This isn't true, according to the book titled "How to Tune & Modify Chevrolet Fuel Injection", the screen is just there to protect the delicate wires. It also says that removing this screen frees up 182 cfm of flow. If it is such a problem, why don't the aftermarket MAF's have a screen in them?
I could tape a nickle to the sensor and not restrict that much airflow. GMHTP did a test last year I think where they compared the Granatelli (or however you spell it) MAF sensor to a stock unit. The car was driven for a few days before testing each unit and the RWHP and track gaines were practically nill. I also placed my stock MAF on a flow bench for the heck of it. I don't know what you would get from porting it, but pulling the screen gets you about 6 CFM.
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