MAF Adjustment Screw
Oct 20, 2003, 09:57 AM
#1
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MAF Adjustment Screw
On the 3rd Gen Eclipse there is an adjustment screw in the bottom of the MAF. I have been told that this is used to initally tune the maf to make sure that the volume of air that is being flowed is true to the value supplied to the ECU. In the third gen eclipse, they came pig rich from teh factory just like the EVO, and a simple way to lean things out (though only a small amount) was to back that screw out.
The way that this works is that the screw goes through the MAF body and places an approx half inch wide by 3/8 inch high blockage into the bottom of the airflow area. This plug is outside of the flow area where the sensor setermines the airflow value, and though it does nothing to change th value being sent to the ecu, it does alter the actual amount of air that is flowing through the MAF.
In the eclipse, backing that screw out until the plug on the inside of the MAF was flush with the exterior, helped to lean things out slightly. It is never a cure for the seriously rich condition that mitsubishi ships it's cars in, but it did help some.
I was curious if any evo tuners or other users had tried backing this screw out as an interim way to lean things out a little bit until a re-flash/piggyback could be installed. Like I said, it does not change the electrical signal sent to the ECU, but rather just allows more air to flow through the MAF for any given value sent to the ecu, thereby leaning things out a bit.
The way that this works is that the screw goes through the MAF body and places an approx half inch wide by 3/8 inch high blockage into the bottom of the airflow area. This plug is outside of the flow area where the sensor setermines the airflow value, and though it does nothing to change th value being sent to the ecu, it does alter the actual amount of air that is flowing through the MAF.
In the eclipse, backing that screw out until the plug on the inside of the MAF was flush with the exterior, helped to lean things out slightly. It is never a cure for the seriously rich condition that mitsubishi ships it's cars in, but it did help some.
I was curious if any evo tuners or other users had tried backing this screw out as an interim way to lean things out a little bit until a re-flash/piggyback could be installed. Like I said, it does not change the electrical signal sent to the ECU, but rather just allows more air to flow through the MAF for any given value sent to the ecu, thereby leaning things out a bit.
Oct 20, 2003, 10:26 AM
#2
we did it the beginning of this summer on the dyno in combo with a BR mas pipe and filter, safc, and mbc and actually SAW a 4.5 or so hp diff when we did this, I about crapped, granted there are variables between dyno runs that can affect power, but this is all we did in between 2 runs while allowing the same cool down time every time, Chris Wertz said it was an old trick for a little more air flow over the maf, it worked and I haven't had any problems yet, anyone else do this?
Oct 20, 2003, 10:56 AM
#6
ok if you take out the maf or just feel underneath it you will see/feel a silicone kind of soft spot on the under side of the unit, if you scrape that silicone off there will be about a 1/2 inch diameter hard plastic screw, you want to remove the maf unit so you will be able to tell how far up the screw is protruding on the inside and then give a few turns until it is sitting flush on the inside of the maf housing, I think most people see that silicone covered spot and are thinking it is a drain hole for the maf unit, it's not, just scrape it away with a flathead screwdriver or whatever and you will see the screw underneath.
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Oct 20, 2003, 10:57 AM
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Ah that's what that was, ok I'll check it out, thanks for the explanation. I had it off when I installed my HKS RS but figured it was some "sensitive" part of the MAF itself.
Oct 20, 2003, 10:59 AM
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I will try to post pictures later since I am taking all that stuff apart tonight to paint the housing. I know it doesn't make it any faster, But it does look a lot nicer when you open the hood.
Oct 20, 2003, 11:12 AM
#10
haha, yeah I was all scared to touch it when I first got my car, installed the BR filter like the 2nd week I had my car and was still super scared to mess with anything, funny that it just turned out to be Mitsu trying to be all stealth, like stated above, I've had mine like this ever since June 10th and no problems I can see, have had it on the dyno since then as well and no apparent problems, just freeed up some air, anyone out there know of any negative affects of this as long as air/fuel control such as safc is used?
Oct 20, 2003, 11:33 AM
#13
don't know if it would or not, like I said I did this on a dyno so I would be able to tell what was going on, it was beneficial, all you have to do is take the maf off and look at the inside where the screw come up and just unscrew it until it sits flush on the inside, then you're done.
Oct 20, 2003, 11:34 AM
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Originally posted by w2pac12345
I have the works reflash- would turning the screw help any?
I have the works reflash- would turning the screw help any?
Maybe david or someone at works can comment on how this might affect the flash, both P1 and P2. Also he can correct me if I am wrong on the compenation factor. Since you are not changing what the ecu sees, just allowing in more air than it thinks is there.
