mods please sticky this, as any information on doing this mod was straight up impossable to find. everything i did was collected from other mods people did for different reasons.

*purpose: this mod is for using a sohc s13 ka24e maf with a s14 sr20det, and not having it bog and run insanly rich.

*cost: like three bucks at radio shack, plus what ever you pick up your SOHC ka maf.

*what you will need: a sohc ka24e maf off an s13 with clip, a linear taper 50k OHM potentiometer from radio shack, mine is rated at .5w and the part number is 2711716. make sure you use a 50K ohm not a 50 ohm, big difference. solder, soldering iron, electrical tape, volt meter.

*purpose: ok, the s14 sr20det mafs are rather expensive and almost no swaps come with them. z32 mafs are a better alternative, but require a safc or some other piggyback to run correctly. considering how expensive and restrictive the sr mafs are, i opted for a cheeper and more expendable alternative that i can easly throw in the trash when i decide to upgrade.

i found out some time ago that you can use a sohc s13 maf with the sr, but when i wired everything up the car ran extreamly rich and would not break over 5500 rpms at full throttle, or anywhere close. i had better luck with the combination of an emanage leaned all the way out and the same maf but i've since sold my emanage, baught a s13 and put the motor in there.

*some things to consider: ok the s13 maf output reads around 1.56 to 1.8v at idle after warm up. this is the white wire on the maf plug. the s14 sr20det fsm says it should read around .8v to 1.5v

*procedure: if you are running a brand new harness, you'll need to extend your maf wire, this should have already been part of your swap as it is common knowledge that stock maf wires on sr harnesses will not reach. wire in the clip for the s13, all the colors match up exactly to the s14 sr harness.

*note: when extending your sr harness, use shielded wire like the harness already has, just solder the shield togather

white to white, black to black, and black with white stripe to black with white stripe

you need to cut the white wire and place the potentiometer on there and solder in place. here is a nifty diagram to explain everything.



after everything is wired up, take your multimeter and test the ohms resistance between the two parts of the white wire. test on a 200K ohm setting if there is one.

rotate the potentiometer clock wise to make sure it sweaps to somewhere around 50 ohms, then counter clockwise to zero. leave it at zero.

start the car and give it a quick rev to make sure the computer will let it rev past 3000 rpms (if not then you have the wrong maf or the wiring is wrong and the car is in limp mode)

you can also drive it like this, but like i said, it wont break past 5500 rpms under heavy throttle and run rich.

what you need to do next is take your multimeter and test the voltage first comming out of the maf (via white wire), it should read somewhere around 1.5v to 1.8v depending on if the car is warmed up or not. (you should do this with the car warm)

now, take the potentiometer and rotate it clock wise. at the same time test the voltage on the white output wire GOING TO THE ECU. you should see a slow voltage drop as you rotate the nob. shoot for around 1-1.2v starting out and see if that fixes the problem. if it still bogs around 5500 rpms, then rotate a LITTLE more. mine is set around half way and runs perfect.

WARNING! WARNING! WARNING!!!you now have a very easy way to lean your motor out. i'll admit the s13 maf makes the car run way rich, but you also have the potential to run the motor lean and detonate and blow your sr. this mod is at your own risk and i take no responsability for what you do to your sh#$.

you should be fine so long as you dont max the knob out, i didnt check to see how low it would go, but i'd imagine anything lower then .8v is detonation level.

wrap everything up, the white wire is an exposed power wire and will need electrical tape so it doesnt contact the chassi.

now go for a spin.
Modified by clovers525e at 7:28 PM 3/24/2009

Just curious but have you put a wide band on this to see what your a/f ratio is in different parts of the rpm range? I'm not sure exactly how this would effect it but it is possible that it's not a linear offset. If everything works out fine, what is the final resistance that you measured as you could just as easily solder in a resistor and not have to work about it turning or getting other junk in it.

well, in the past day or two I’ve come to like around 20k ohm, the input voltage sits around 1.6-1.7 and the output around 1.4 at 950 rpm, cold block, it still runs rich but my boost is up around 15 so I don’t mind. On stock boost levels something a little lower might be better suited as I have a sneaky suspicion my car still shoots flames every once in a while.

Someone might want to try something around a 35k ohm on stock level.

My mods are typical, full straight through 3” exhaust, turbo elbow, front mount, intake, 15psi, t28, kouki sr. typically I run rich at lower rpms but at full boost and high rpms the motor is not starved for gas what so ever.

I’ll take a multimeter or two with me on a ride tomorrow to make sure the voltage drop doesn’t fluctuate at all. But ya, a wideband would be nice, but im in collage and this worked ill see if my buddy will let me borrow his. everyone i know has aem eugos, so its like a big thing.

My S14 SR MAF died recently and my mechanic decided to see if this would work for us. He couldn't get the car to start with the potentiometer attached. When he finally got it to start, he still couldn't get it to work right. He worked on it this past weekend, but I have a feeling that I'll be looking to by a new (used) MAF very soon.

EDIT: Nevermind! He got it working. But even he wasn't sure what he did differently... Seems to be running just fine now.
Modified by dragonboy240sx at 8:05 AM 6/5/2009

OP would you mind posting pix of your maf as it sits in your engine bay.

I'll take some pics of mine this weekend and post it up for you.

thx, laying in wait

Here ya go, you can see the potentiometer mounted just to the right of the filter. This is on an S14 SR and works fine.

so dragon, thanks a ton for this visual

my harness is extended

so do i splice wires from the MAF [b.w, b, w] to the potentiometer then mount it like yours?

thoughtless wrote:so dragon, thanks a ton for this visual

my harness is extended

so do i splice wires from the MAF [b.w, b, w] to the potentiometer then mount it like yours?

Yep, I think I had to adjust the throttle cable and the Camshaft position sensor to get it to run smoothly.

LIIIIKE this?

Nope just cut the white wire and connect one to either pin of the pot.

SO

BLACK ->maf
BLACK/w ->maf
WHITE ->either prong on the POT.

edit: im st00pid.

white wire cut, then place the pot. in series with the white wire.

sorry to bring this thread back from the dead, however i have a question, can you guys think of any reason why this wouldn't work with a z32 maf?
the general consensus on z32 maf output is usually in the 1.2v ish - 5.12v ish range, wouldn't a potentiometer work for the z32 in the same way it works for the sohc ka maf?

Bad idea, Z32 MAFS has a different airflow vs. voltage curve. The S13 SOHC MAFS curve is close enough to work ok, though still a bad idea IMO.

Seishuku wrote:Bad idea, Z32 MAFS has a different airflow vs. voltage curve. The S13 SOHC MAFS curve is close enough to work ok, though still a bad idea IMO.

the poteniometer is a great tool to get your SR running. although running isnt the same as performing. once i got the motor running 'right' with the pot. then i 'tuned' it with a SAFC and a dyno.

just $0.02

This is assn awsome find for me! I have a base tune that is on the very rich side and is tuned for the z32 maf. A 10k or 15k resistor may do me some good! I'll do some data logging and see what happens.

compactfean wrote:This is assn awsome find for me! I have a base tune that is on the very rich side and is tuned for the z32 maf. A 10k or 15k resistor may do me some good! I'll do some data logging and see what happens.

What's your fuel pressure at? You'd be amazed how much richer my car runs with an extra .5 lbs of fuel pressure.

I've dropped my fuel pressure all the way to 25 with no affect.

How's your ignition system? Is it breaking up any during 3/4 throttle or full throttle?

No, but I have splitfire ignition. Pulls hard with no hicups all the way to redline...... Just rich.

compactfean wrote:No, but I have splitfire ignition. Pulls hard with no hicups all the way to redline...... Just rich.

Can you smell how rich it is? It should be 11.5 under boost, but other than that, it shouldn't be able to be smelled... It might be worth using another wideband just to verify that it is actually rich. Most widebands require free-air calibration.

Its like 10.5 under boost. I have the lm1 wideband which does require a free air calibration which I have done. When im under partial throttle cruising I have good afrs. Just my wot and idle afr is rich.