MAF sensor resistor
 

Hey guys, just wondering if anyone could explain to me exactly where you solder the resistor into for the MAF sensor resistor mod or if there's a write-up on it somewhere on the website and I missed when I did my search. Thanks guys. :)

waste of time and 10 cents.

Why are you reying to reduce power? Coz that's all you'll achieve...

If it reduced power and didn't do anything, then why would Mark and other people on here say that it slightly increases power?

https://www.rx7club.com/forum/showth...light=RESISTOR

What city do you live in and what altitude is that city. Do a SEARCH on google for your citys altitude. In other words, there is a possible way to add fuel across the board other than that resistor IF you have a series four car.

EDIT: Never mind, I looked at http://geonames.usgs.gov/pls/gnispub...9739900::NO:::

It's 607 ft over sealevel. So, if this is a series four car, pull the plug off the Atmospheric Pressure Sensor inside the car. IF you have a wideband, you would be able to see a difference in the AFR at idle from prior to pulling the plug to after you pull the plug. A bit richer.

Nowhere above did I say it helps to run a non turbo richer. Just the opposite needs to be done in my very humble opinion.

EDIT: It will run richer because pulling the plug off the ATP makes the ECU default the altitude to sealevel. At sealevel the mixture will be richer. It seems to me, if someone took the right variable resistor and had a clue what he was doing, he could in put an altitude higher than where he lives, which would make the mixture leaner throughout the rpm range.

My S5 has a air temp sensor built into the MAF, I don't recall if the S4 does as well. A resistor on that circuit, I would think, would send a message to the control unit that the ambient temp were lower than actual, perhaps causing a slightly richer fuel map. The control unit probably makes more corrections from the air temp sensor near the throttle than it would from the MAF's temp sensor, just a guess.

On a side note, I have on several occasions installed a resistor on the cylinder head temp sensor circuit of a Datsun 280Z to force a richer fuel map. Those engines were common for carbon buildup on the intake valves and hesitation problems. The resistor trick would make them run like a striped-assed ape!

I was recently told by Steve what the air temp sensor in the AFM is used for

I was talking to him about his AFM to MAF conversion and was wondering what that IAT is really used for since we have one on the manifold.

The S4s do have a IAT in the AFM

if you want it to run rich you could unplug the o2 sensor. i actually recall seeing Mark say it didnt work. look in the FAQ thread.

On most vehicles, when you unplug the o2 sensor and read sensor data with a scan tool, you will see the o2 signal "fixed" at around 450mv, the middle of the sensor's range. Obviously there is no fuel correction based on the o2 input with it unplugged.

OOPS. Actually it won't help much if any if your at 607 ft above sealevel IF you want to be richer. BUT if you want to be leaner you could input a variable resistor that would create a higher altitude.

I can do this with a RTEK2.0. I'm at about 650ft altitude. If I make the altitude on the RTEK say 3500 ft, then the afr goes from the 13.0afr to 14.0 afr plus and or if I set the altitude to four thousand ft plus I can get the idle afr to the 15.0 ft range. It should and will effect the afr across the board to be leaner by making the ECU see a higher altitude.

If one wanter richer, he'd almost have to live at 8000 ft and then unplug the ATP so it would default to sealevel.

Well, I thought that's what the resistor did was lean out the AFR. If it wasn't a good mod, then why would Mark say anything about it? I know that non-turbos need to be leaned out because they run rich stock and yes, I do have a S4.

Quick aside: I believe the ATP needs to be replaced with a voltage source instead of a resistor (so a voltage divider or regulator). I'm at ~300' and mine outputs ~3.9V

Sooooo? You didn't read this thread? Three pages? https://www.rx7club.com/forum/showth...light=RESISTOR

The temp sensor only has one wire going to the ECU. Hard to miss. See wiring diagrams in the free, online, FSM for your car. They even give a value for the resistor in that thread.

https://www.rx7club.com/showthread.p...55#post5131155

scroll al little over halfway down and you'll find this...

Do those cheap eBay "speed chips" or "mod chips" work?
No, they do not. In fact they're not even a "chip" (integrated circuit) but simply a 2 cent resistor in a fancy case. The theory is that by putting this resistor in series with the IAT (Intake Air Temperature) sensor you can fool the car into adding more fuel by making the intake seem colder then it really is. In reality we all know that more fuel is not equal to more power and by messing with the IAT sensor the car will run too rich and lose power. Also the price is a total ripoff considering that anyone could go out and buy the same resistor for less then 5 cents.

^ Those are not used on the AFM IAT. Only on the manifold IAT. Talking about our cars not others.

Yea, I just read through those threads, and Mark does mention using a resistor to get a 2 HP gain after soldering it into the AFM IIRC. He said he used a 4.7k Ohm at 1/4 watt resistor, and I PM'd him about it too. So which sensor is the AFM then and where is it located? That's not the one on the back of the dynamic chamber is it?

Just a thought, but 2HP is an immeasurable gain. Even two dyno runs back to back in exactly the same conditions could show a 2HP variance.

Probably an astute thought!

The AFM is attached to your air filter. You might spend some time perusing the training manual to familiarize yourself with various sensors first. There are some other links that may be of interest in the CSM:
http://howto.globalvicinity.com/gv_w...=118&co=1&vi=1

The temp sensor is internal to the AFM. If you demate the AFM from the airbox, you'll see it. A jpg is attached showing it a couple of ways.

The AFM has a rectangular connector. One of the wires is Green with an Orange stripe. That is the wire you'd cut and install a resistor in.

By the way, in case you missed it. I don't recommend doing that at all. It's be a waste of time and effort.

I only butted in this thread to take note that the mixture can be fiddled with by messing with the ATP sensor located above the passengers feet. And then I even backtracked a bit and noted it'd ohly be useful for making a engine leaner, not richer (unless you live in the mountains around 8,000 ft altitude).

I've now jpg'd every part of the car but the Engine Fail Box. humor

Alright, so it is the AFM sensor then that you solder the resistor into and not the MAF or the one on the back of the dynamic chamber. Maybe I'll try messing with that ATP sensor too. I'm definitely looking to try and lean out the AFR, because it does seem like my car runs a little rich, and IIRC, N/A's are known for this, moreso the S4 models. Thanks for posting the pictures and that How-To page, there's tons of useful information on there that I could use in the next couple days!

Like Steve was saying. You should read the training service manual and you should learn what parts are what and what they do. Reason is, a AFM (Air Flow Meter) and MAF (Mass Air Flow) are 2 completly difference animals and we only have an AFM. We do not have a MAF.

If you believe those stories on Ebay about installing a variable resistor on the IAT sensor to make the ECU think you are getting colder or hotter air then to gain 10+ hp then PLEASE do not go any further and search around and learn the characteristics of our engines. Making the engine run leaner you may gain some power but the AFR is usually all over the place to begin with, so leaning the AFR out, you may get lean spots and loose power in certain spots of the RPM band. Same deal with making it richer.

You really should get your self data logging wideband so that you know exactly where your AFR is and where you should make adjustments. Then get a SAFC or similar.

You will be very disappointed if you go the route you going.

Yea, I don't recall the FC having a MAF, so that's why I was confused about it. I don't believe those eBay chip things, but I do know that if your engine is running rich and you lean it out a bit, it's going to give it a bit more power, and I'm pretty sure my engine is running a bit rich. I'm not wanting to spend a lot of money on something that I won't be using much. This car is currently my daily driver, and I'm trying to get the best gas mileage and performance from the car without spending a lot of money on it, or making it not streetable.

Don't waste time with resistors (as several other people have mentioned). If you want to dune the fuel curve, get an S-AFC.

I get about 23-25mpg while driving over 50mph. I don't do a lot of city driving.
But you can take a look at Getting the most MPG

Like I said before, you may get lean spots. If your engine is running rich, its not a solid 11:1 or 12:1 across the board. It varies greatly. In some spots you may see 12:1 and in others, 13.8 and in others 14.2. If you install the resistor mod, you may put the 13.8 or 14.2 spots even leaner, loosing power which means, in our minds, we need to step on the gas more to get the car moving which only means putting in more fuel since you are getting more air and giving more throttle input.

Please see the link I provided because a lot of owners miss diagnose their engine troubles and think that manipulating the ECU is the only way of fixing the problem.

You could try advancing your timing a few degrees to allow for a more complete burn which could, depending on your motor, increase the power of your engine meaning you may not have to give it as much throttle for it to do the same amount of work. Example, when you give your engine 35% throttle (full range), and you possibly get more power by advancing your time, you may only have to give 28-30% throttle to do the same amount of work. I have noticed this on one to many occasions.

If your TPS is out of adjustment, you could also feel a lose of power at a given throttle point because the AFR at that point and a give rpm will be richer or leaner then it should be.

Yea, I was looking at that article about getting the most MPG, and I completely forgot about changing the O2 sensor. I'm going to be changing that and the fuel filter here pretty soon. Also, I'm gonna pick up some LED's and spade connectors to check the TPS. I think it's actually a bit off, but I do know it is functioning correctly because if I work it with my hand, the car revs up and down. Strangely, I'm able to pull 28 MPG average out of my car without CC, but I'd love if I could get up to 30. :)

What I'm thinking is that I can try soldering this resistor in and see what happens with the car. It's not like it'll take very long to do it, and I've got some free time today to try it out and maybe put a resistor on that one that HAILERS was talking about. If it messes with the car, I can always remove them and resolder the wire back. I did use the CSM to adjust the idle air screw and the variable resistor and got the car idling pretty smoothly at 750 RPM. Just a quick question. What's the point of using the jumper wire? It really didn't seem to do anything.

I already advanced my timing to 10 degrees advanced ATDC when idling at 750 RPM, which I was told is the farthest you can go safely without possibly having detonation issues. I did notice it takes a little less pedal effort now though.

Well, I soldered in the resistor today and noticed it did give the car just a slight bit more power from what I can tell. I know it did something because now the car doesn't tell me to shift up as soon anymore from what I can tell. Also, after adjusting the idle using the variable resistor and intake screw, the car idles almost perfectly. When I step on the brakes now, the car doesn't try to stall out anymore at all. It constantly maintains a 750 RPM idle with just a very slight bit up surging up and down, 50 RPM's at the most. I was really surprised how much of a difference it made.

What exactly would you have to do to adjust the ATP sensor that HAILERS was talking about? Would it be another resistor type deal or is it actually adjustable somehow? Also, RotaMan99, do you have any pictures on how the LED/spade terminal setup goes together? I'm having trouble understanding how you set it up and hooked it into the test connector from reading the CSM.

It's really simple.

Adding a resistor to the AFM temp sensor makes the ECU think the air is colder. If the air is colder it's denser, so more fuel is needed for the same AFR. The ECU therefore injects more fuel. But the air is not actually denser so the AFR goes up (i.e. richer). Richer mixtures result in LESS POWER! This has been proven over and over again. Any improvement in power are in your head.

The idle improved because you made it richer, both with the added resistor and (properly) messing with the variable resistor. This probably means it was too lean before due to a vac leak.

About the ATP in the series four engine. Your at about the same altitude as in Ft Worth, so not much will happen on the rich side. I only saw a few tenths richer afr when I put it at sealevel using a RTEK2.0.

You can do the same just by removing the plug from the ATP. The ECU defaults to sealevel if you do that. So not much change doing that.

I know you can make the mixture leaner by inputing a higher altitude coming out of the ATP to the ECU. I've done that using a RTEK2.0 and inputing various altitudes. I live at about 650ft altitude. I can input a three thousand ft altitude and make the afr change close to a full AFR point. Such as from 13.2 AFR to 14AFR while sitting at idle. Looking at a wideband as I adjust the altitude.

If I didn't have a RTEK2.0 I would have to do it another way. STEVENA88 above gives a clue as to how. I have no need to do so.

The location of the ATP in a series four is shown in the FSM. It's in the interior on the passengers side foot well.

I don't have the RTEK set at an altitude above 650 ft on a regular basis. I just noticed this function of the RTEK after I bought the unit , and then realized that if someone set his altitude to a figure above where he really lives, then the change will lean out the mixture throughout the full rpm range. It's just a thought. Something to play with and ammuse me.

So about this ATP sensor, how would I possibly make it run leaner? Would it be another resistor type experiment? From what it seems like, the resistor in the AFM sensor seemed to give the car a little more power, but nothing serious.

With a fuel controller...

Did you read my post above (#28)? Your butt dyno is reading in the wrong direction.

Hey NZ where ya been? Take a look at the howto below "wiring an electric fan" and scroll down to where I typed up about the SVS. Let me know what ya think.

I don't but you can look at the link below and it runs you through on how to wire up the LEDs and also gives you a list of error codes.

http://teamfc3s.org/info/articles/errorcodes/main.html

You buy a 100K Trim Pot from Radio Shack.

One leg to the Green/Yellow wire coming to the pin 2H of the ECU. What you do is depin the wire at the ECU and attach it to the pot leg.

The other leg of the pot goes to ground.

The middle leg is attached to a wire and goes to socket 2H of the ECU. How you do that is up to you. I have an old harness and just depined a wire from the ECU plugs and cut it off a couple of feet from the ECU. You then install the pin of that wire to the 2H on the ECU and the other end of that wire gets soldered to the middle leg of the 100K pot.

1st jpg is the pot
2nd jpg is the voltage at 3.93
3rd jpg is the voltage at 3.75
4th jpg is the voltage at 2.75
5th jpg is out of order and shows the voltage at 3 vdc.

Adjusting this sensors output effects the afr across the board. Personally I wouldn't screw around doing this unless you have a wideband to look at.

I'll concede the SAFC or whatever is the *right* way to lean things out, BUT this is a low budget method to lean things out, for us po folk or folk who like to just screw around with the car.

Only cheap way to use this sensor to make things richer is to just unplug it and let the ECU default the ATP to sealevel. Sealevel being richer than any??? anything higher.

The output from the ATP on my car read 3.96vdc prior to installing the pot. The fully warmed up car read a AFR of something like 2.8 AFR. This is with a STOCK ECU, not the RTEK2.0.

Then I used the trim screw on the 100K pot (I've mentioned this three times and won't again), to adjust the voltage DOWNWARDS. At quarter volt increments I scanned the Palm that is in turn attached to a Zeitronix Wideband, to record the difference in AFR.

I'm attaching a couple of jpg of the difference in AFR as the trim screw turned the voltage downwards. I started at approx 2.8afr and stopped at 15 something AFR. I could have stalled the car out if I kept on screwing around.

This was on a series four car. Series five??? Got me. I think they have an internal ATP. Internal to the ECU. Maybe. Got me

Thanks for that information HAILERS. You're right about it being a good idea to only do it if you have a Wideband to look at so you get accurate results. From the looks of it though, this would be a cheap way to adjust the AFR instead of getting a SAFC or other system. I think I'm going to take the sensor out of my AFM and see how the car drives to see if I notice a difference. Thanks for the info guys. Is there any other "easy" ways to lean out the AFR? Also, what does a good Wideband run on price nowadays?

*******I'm going to take the sensor out of my AFM and see how the car drives to see if I notice a difference. Thanks for the info guys. Is there any other "easy" ways to ****************

Errrr, ahhhh, there's a misunderstanding here. The ATP on a series four is in the passengers foot well to the right and up. It looks similar to the boost/pressure sensor in the engine bay but has no *nipple* for a vacuum hose.

You'd be hard put to find a cheaper way to lean things out other than what I described.

Widebands cost dough. On THAT car I've a Zeitronix that came with no display, and I use the Palm in the picture using software from Pocketlogger folk. It can display, rpm, AFR, EGT, TPS, Boost/pressue/vacuum and has an analog wideband output to the ECU if needed and takes out the garbage each Wednesday morning.

Actually, on a n/a car you probably could adjust it using a narrow band 02 sensor and not get hurt doing it. Hard to destroy a n/a in my humble opinion.

Or if you have a digital multi meter you can backprobe pin 2D (memory here), and look at the output of the 02 sensor. It'll range from 0000 to approx 1vdc. At idle with no airpump working it'll read around 0.7 -0.8 vdc if memory serves. Driving at a steady speed or cruise it'll display, rapidly, b/t 0.4 to 0.5 if memory serves. I was using a cheap, under fifteen bucks Radio Shack meter when I was doing that a couple of years ago.

Again, hard to hurt a n/a in my Humble opinion.

And while here, let's remember that in just six or so hours from now, Casey Stoner on his Ducati will TROUNCE Valention Rossi at LeMan. Rossi's old and worn out. Talking MOTOGP. https://www.rx7club.com/forum/showth...51#post6958051

Just rambling. This has squat to do with this thread. None at all. Too lazy to put it on the Lounge area.

No no, I meant my AFM sensor. I put a resistor in that sensor and tried it out, but am going to remove it and see how the car runs. I know I could probably tune it with a narrowband, but if memory serves me right, they aren't very accurate since they are just reading voltages and display out in bars on the gauge.

A wideband just reads voltages, and can display is bars if you want. The difference is the completely different output characteristics of the sensor, and the electronics used to interpret the readings.

Alright, thanks for the info. I wouldn't mind getting a wideband, but for the money I could buy a few other things that would be much more important and without a sure fire way to tune the AFR without a wideband and SAFC, it's pretty much pointless. I believe I'm done with this thread.