Ice_Wolf

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.

NCross

iTrader: (18)

waste of time and 10 cents.

NZConvertible

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

Ice_Wolf

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

HAILERS

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.

HAILERS

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.

scrip7

iTrader: (6)

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!

RotaMan99

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

NCross

iTrader: (18)

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.

scrip7

iTrader: (6)

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.

HAILERS

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.

Ice_Wolf

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.

stevej88na

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

HAILERS

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.

NCross

iTrader: (18)

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.

RotaMan99

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

Ice_Wolf

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?

Aaron Cake

iTrader: (1)

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.

stevej88na

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

HAILERS

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

Ice_Wolf

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!

RotaMan99

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.

Ice_Wolf

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.

Aaron Cake

iTrader: (1)

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

RotaMan99

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.