Hey all -

Im not sure if Im the first to have suggested this, but I think this might be helpful to some people.

I had home ported a spare MAF to see if my car liked it or not. Being an '02 car, of course, my car did not. It ran extremely lean and would ping at high RPM. Even using a MAFT would not completely fix my LTFTs of +21 to +23.

I did some research to find out how exactly MAFS work, and found that they basically measure the current necessary to keep a heating coil at a constant temperature. The more air that flows past, the faster the heating coil cools, which means the MAF needs more current to keep them hot. The idea is that if you can trick the MAF into thinking that its using slightly more current, you can report the extra air the ported MAF is actually flowing.

After experimenting with some test leads and dozens of resistors I found the best value to be a 1K ohm 1/2 watt resistor. This resistor spanning between the two longer bars inside the sensor gave me a MAF frequency of 2500, right where my unported one was at idle. I then soldered the resistor in, and buttoned everything back up, and set my MAFT back to zero. After 100 miles of driving, my LTFTs are -4 to +2 across the board, which is much better than +21 to +23 across the board.

The mod:

Take a 1K ohm 1/2 watt resistor and solder it so that it spans across the two longer bars inside the MAF sensor (as if it were another heating element). Thats it. Button everything back up and go driving.

If youre really feeling experimental, and you have ATAP and a voltmeter, you can make it somewhat adjustable by drilling a hole in the side of the MAF housing, close to the base so you can run wires out through it. Solder two pieces of wire - one to each of the long bars inside the MAF and run the wires out through the hole. Epoxy the hole closed so you dont get any leaks. Now take the wires on the outside of the MAF sensor and connect one to a 680 ohm 1/2 watt resistor, and connect the resistor to a 500 ohm potentiometer, and connect the pot back to the other wire. (MAF bar > wire > resistor > pot > wire > bar) Make sure you have the pot all the way closed. Check this with your multimeter by turning the pot all the way one way or the other till you see the highest resistance. Button it back up and go drive. After learning your new trims, ATAP and make small adjustments with the pot until you get to where you want. Make your changes slowly if you do it with the engine running otherwise you could potentially stall the engine. Let me know what you think.

-Tony

Special thanks to John @ TeamZR1 for the help

 

do any other values work??? like to make it a little lean or a little rich??? and is there any point in being a little lean or a little rich

 

The way its described above, It can only richen you up. If youre already running lean from MAF ends or ported MAF, then yes, you cna change the resistance value to adjust just how much you richen it back up. I found between 600 and 1800 ohms to make meaningful changes. Too far below 600 ohms will draw too much current and probably report too high a freq. Anything above 1800 ohms and it dosnt change the MAF freq very much at all. I did a hell of a port job and removed the whole airfoil, and the black support crossmember inside the MAF sensor. If you didnt port that much, you may want to use a resistor around 1200 ohms rather than 1000. I experimented with 2 foot test leads (aligator clips) hooked onto the two bars and run forward and out under the airlid. This way I could clip on different value resistors until I found one that worked well. I decided on the 1K ohm resistor and soldered it in.

As far as there being an advantage to being lean or rich, Id say for the average person, getting the LTFT's down to 0 is probably best. (not lean or rich.)

Thanks,
-T

 

nice info...

 

Very neat thread!

 

This is what SLP does on their aftermarket MAFs
to make the truck 85mm match LS-1 calibration.
Only they use a fixed resistor. I measured it once
but forget its value now. I think I posted it at
the time though.

http://community.webshots.com/photo/...62585024hfdzqE

 

Awesome info, man! I did the same thing and I was wondering if I was running lean, but I thought there was nothing I could do about it. Now I'll check my LTFT's and adjust accordingly. Thanks

 

jimmyblue -
Yes someone over at ls1.com had brough that to my attention when I explained what I was doing (budget GMAF). TeamZR1 here on LS1tech informed me that the resistance between the bars was around 130 ohms, however that is not the value of the resistor itself, but of the resistor and heating element(s) in parallel. One other difference is that the resistor for the stock 75mm MAF needs to be placed inbetween the two longer bars, not the center one and the shorter one. Placing a resistor there (as on the SLP MAF) would only further lean out the car (on an LS1 MAF. Im not sure if they have the heating coil and thermistor placement swapped on the 85mm MAFs.

-Tony

 

OK enlighten me here. Doesn't the stock unported MAF flow more than the T/B? The purpose of porting the MAF is to fool the PCM that the car is under less load with the same amount of air passing through it, theoretically giving you more timing and leaning the fuel a little. By porting the MAF and then recalibrating it, I don't see that you are gaining anything. The bottleneck is still the T/B and the opening in the intake. I was under the impression thet the stock MAF will flow enough air to support around 450 hp. There is a tuner in Tulsa that swears by leaving the MAF stock. (he told me personally)

 

a "tuner" is trying to get your air/fuel dead on...not lean...not rich.... too lean and you have my problem(knock and ping at high rmp) which defeats the purpose when it retards the timing anyways....so if you port it you get more air...and the pcm doesnt know that...so you use the resistor to help tell it that its getting more air...and it dumps in more fuel....more air and more fuel=more horsepower!!! and no ping or knock=no timing retard=more consistent pulls=get the point...I did...and I did the resistor at 1k ohm....Fixed my problem....and kept my power I gainde from porting....no special tuning needed...but I will get tuning in the future.

 

2xls1 -

Personally I dont see the stock TB as being more restrictive than the stock MAF. I feel the MAF, especially with the screen is much more restrictive, although I dont have any hard facts to back this up. Just to be on the safe side I do have a ported TB. One thing to think about is this; even if both the TB and the MAF are similarly restrictive, porting one or the other should help, even if its very minimal, because there less length of restriction. To see an example for yourself, cut a small section of drinking straw, maybe like 1/2 inch. Its fairly free flowing. Now take a full drinking straw of the same diameter and blow through it. The longer straw has more resistance. Eliminating one of many similarly sized restrictions should still help out atleast minimally, IMHO.

As far as the timing - one could go either way on this one. Its kind of a black art. Personally, Id rather tune for zero or negative LTFTs that way the ECM is not adding fuel when you go WOT (based on the last non-WOT ftc).

-Tony

 

My point is if the throttle body only flows x amount of cfm, making something upstream flow more cfm adds nothing. I'm pretty sure the ID of a stock MAF is larger than the ID of the throttle body and intake manifold opening.

 

2xLS1 -

1. IMO, if you have two 600 CFM restrictions back to back, the flow of the whole intake tract will be even less than 600 CFM. However if you have only one 600CFM restriction and the rest of the intake tract can flow 1000 CFM, then you may be able to reach the full 600 CFM through the entire tract. Flow is affected not just by diameter or cross section, but also by the length of the conduit / number of restrictions.

2. Perhaps the ID is larger on the MAF however there are other contributing factors, such as the MAF's airfoil, the bars, the black plastic thats left in the center, etc. All of which disrupt airflow.

If you'd rather play it safe, no one can critisize you for leaving your MAF stock. However if youre willing to risk your MAF or buy a second one to experiment, you may gain from porting it. Some cars respond better than others. Some people swear that theres HP to be freed up by porting a MAF while others disagree.

 

Here's a pic:



-Tony

 

2x 1kohm paralel on the heated resistor
500ohm
1x 1kohm on the first on heated
From a old printer supply
Thanks for your explanation we are greatfull!!
For our merc. A160 w168 automatic 2000

Im not sure if Im the first to have suggested this, but I think this might be helpful to some people.

I had home ported a spare MAF to see if my car liked it or not. Being an '02 car, of course, my car did not. It ran extremely lean and would ping at high RPM. Even using a MAFT would not completely fix my LTFTs of +21 to +23.

I did some research to find out how exactly MAFS work, and found that they basically measure the current necessary to keep a heating coil at a constant temperature. The more air that flows past, the faster the heating coil cools, which means the MAF needs more current to keep them hot. The idea is that if you can trick the MAF into thinking that its using slightly more current, you can report the extra air the ported MAF is actually flowing.

After experimenting with some test leads and dozens of resistors I found the best value to be a 1K ohm 1/2 watt resistor. This resistor spanning between the two longer bars inside the sensor gave me a MAF frequency of 2500, right where my unported one was at idle. I then soldered the resistor in, and buttoned everything back up, and set my MAFT back to zero. After 100 miles of driving, my LTFTs are -4 to +2 across the board, which is much better than +21 to +23 across the board.

The mod:

Take a 1K ohm 1/2 watt resistor and solder it so that it spans across the two longer bars inside the MAF sensor (as if it were another heating element). Thats it. Button everything back up and go driving.

If youre really feeling experimental, and you have ATAP and a voltmeter, you can make it somewhat adjustable by drilling a hole in the side of the MAF housing, close to the base so you can run wires out through it. Solder two pieces of wire - one to each of the long bars inside the MAF and run the wires out through the hole. Epoxy the hole closed so you dont get any leaks. Now take the wires on the outside of the MAF sensor and connect one to a 680 ohm 1/2 watt resistor, and connect the resistor to a 500 ohm potentiometer, and connect the pot back to the other wire. (MAF bar > wire > resistor > pot > wire > bar) Make sure you have the pot all the way closed. Check this with your multimeter by turning the pot all the way one way or the other till you see the highest resistance. Button it back up and go drive. After learning your new trims, ATAP and make small adjustments with the pot until you get to where you want. Make your changes slowly if you do it with the engine running otherwise you could potentially stall the engine. Let me know what you think.

-Tony

Special thanks to John @ TeamZR1 for the help[/QUOTE]

 

Now that's my kind of necro thread...17 years later

 

….and as usual, a first-poster gets the prize...

 

ffs, when did hptuners or efilive come out? where hack jobs like that common?