80mm MAF Sensor for SOHC V6

[2000StreetRod]

Before I spoke to James, I had purchased a 90mm LMAF, that has never left the box it came in....
He told me about an 80mm, from, if I remember right, '96-'02 4.6L Mustang GT or Cobra. It's still a 6 wire, with the integrated IAT sensor. I actually got one out of a V10 Triton equipped Econoline van ( thanks to the Hollander interchange) This is plug-and play, from a wire harness stand point, but obviously tuning will be required when I install it.

I received my Lightning 90mm MAF and as expected it has the 4 wire (no IAT) connector. I've decided to use my stock MAFsensor/IAT in the Lightning housing. I've started my design of a small (2x3x1 inch) adjustable gain linear amplifier that hopefully will make the 90mm (or any other housing diameter) combination look like a stock unit to the PCM. That way performance/fuel economy changes will be entirely a result of MAF and associated intake diameter changes. While a new "tune" would no doubt be very beneficial, it would introduce an additional set of variables.

I'll have to determine the stock MAF voltage output vs airflow. I can monitor the stock output voltage while changing the engine RPM but initially I won't be able to do the same with the 90mm. After stock voltage vs RPM is measured, testing will be done for each unit connected to a test power supply. The airflow will be provided by an electric duct fan (500 cfm) and a small electric 2 speed leaf blower. The three data points provided by the fan and blower should allow me to set the approximate gain of the amplifier for the 90mm. Then it should run well enough in the vehicle to measure output vs RPM and perform fine tuning.

All of the above is going to take a while but it has been many years since I've designed and built a printed circuit amplifier and I'm enjoying it thoroughly! One advantage of being retired is having a lot of spare time.

 

[CDW6212R]

I am glad that you are enjoying the project, that should make it worth while. Contact James when you can and discuss you project plans. He can suggest to you which things will help the most for the money, and what to do first.

The SOHC should make over 175hp stock, and many trucks here are just over 200hp with the tuner and several modifications. You should be close to that soon also.

 

[techieman33]

While you may think it a challenge to do it your way, it's the wrong way, and won't help nearly as much as a tune written with no other changes other than fixing the size of the MAF. Doing it your way is just going to give your problems.

 

[Carguy3J]

While you may think it a challenge to do it your way, it's the wrong way, and won't help nearly as much as a tune written with no other changes other than fixing the size of the MAF. Doing it your way is just going to give your problems.

You are 100% correct. I wasn't even going to say anything, since I wasn't sure where to start with how wrong :thumbdwn:this plan is. But, since you sum'd it up nicely, I figured I'd 2nd the motion.

 

[2000StreetRod]

The SOHC should make over 175hp stock, and many trucks here are just over 200hp with the tuner and several modifications. You should be close to that soon also.

The combination of throttle cable and racing air filter modifications increased my rwhp from 150 to 175. I just finished replacing my left lower control arm and camber adjusters. In a few days I'll get an alignment. Next week my wife and I are babysitting grandchildren so I won't be able to get gas mileage results for about two weeks.

 

[2000StreetRod]

While you may think it a challenge to do it your way, it's the wrong way, and won't help nearly as much as a tune written with no other changes other than fixing the size of the MAF. Doing it your way is just going to give your problems.

As suggested by Carguy3J I'm actually planning to purchase an SCT XCAL w/ the ProRacer Software and learn how to do my own tuning. Then I'll flash MAF size only changes and compare the results to my MAFSAmp results. I'm actually not as stubborn as some of you think!

 

[CDW6212R]

Ah, so you have had it to a dyno? Well then you were down a bit from the typical SOHC, It thought they ran about 175hp in normal trim/tune.

 

[2000StreetRod]

Stock MAF Output

I made some preliminary measurements on the stock MAF voltage output vs RPM for the transmission in Park. I had to stop at 4000 RPM because of a transmission oil leak at the radiator cooler outlet. Here is the data read with an analog multimeter.

RPM Voltage
550 0.8
1000 1.0
1500 1.25
2000 1.4
2500 1.55
3000 1.65
3500 1.9
4000 2.1

The average increase in voltage per 1000 RPM is .37 volts. If I assume that the output is linear then the voltage at 6000 RPM would only be 2.8 volts. I assume that the airflow at 6000 RPM while accelerating in drive would be much greater than in park. I've read that the MAF will "peg" (voltage stops increasing) at high airflows and that the max MAF output voltage programmed in a stock PCM is around 4.7 volts.

 

[CDW6212R]

Very good, progress.

 

[2000StreetRod]

MAFSAmp Update

Well it turns out it was much more difficult than I anticipated to design and build an amplifier to make my Lightning 90mm MAF housing with my stock sensor look like my stock 55mm MAF housing and sensor. The problem was obtaining an adequate settable voltage gain range (0.5 to 3.0) with a minimum voltage output of 0.8 volts. After numerous redesigns and reworks I now have a three stage transistorized prototype to evaluate. I am setting up my bench test fixture (blower and associated ductwork) and will begin by testing the output of the unmodified Lightning 90mm MAF. That way if my MAFSAmp destroys the MAF sensor, I will only have lost a sensor (4 wire with no IAT) that I don't need. I wish that I had a spare 6 wire harness connector so I wouldn't have to cut the one that is in my Sport.

As many of you have suggested, I have contacted James Henson via e-mail about buying an SCT SF3 and custom tunes. I expect that in the not too distant future I will also purchase the SCT Ford Custom Tuning Advantage III software so I can modify engine control parameters at my whim.

 

[CDW6212R]

Have you tried to take the wires out of the connectors? Ford makes just about all of them such that you can swap wires if needed. I plan to do that when I install my six wire 90mm SCT MAF. I don't yet know if the IAT wires are long enough or have the same end terminals. Keep at it,

 

[2000StreetRod]

Have you tried to take the wires out of the connectors? Ford makes just about all of them such that you can swap wires if needed. I plan to do that when I install my six wire 90mm SCT MAF. I don't yet know if the IAT wires are long enough or have the same end terminals. Keep at it,

Thanks for the tip about extracting the wires from the connector. I was able to test the voltage outputs of the Lightning 90mm MAF and my stock 55mm MAF without cutting the wiring harness. I wire wrapped the male pins on the MAF sensors for testing. My electric leaf blower in high speed drove the 55mm MAF output to 5.25 volts. The corresponding output of the 90mm MAF was only 3.2 volts. That means my MAFSAmp voltage gain only needs to be around 1.6. Previously I had computed a required voltage gain of 2.7 based strictly on the different cross sectional areas.

I made a disappointing discovery when I attempted to install the 55mm 6 wire sensor assembly into the 90mm housing. The physical mounting configurations (screw locations) are not interchangeable. I'll have to obtain a separate IAT and pigtail connector. Hopefully, you'll have better luck with your 6 wire 90mm SCT MAF!

 

[CDW6212R]

Well shoot, it sounds like you have an earlier Lightning MAF with different electronics(mounting). I hadn't thought of that when I was deciding on a MAF. You might ask Jon(Turdle) about what he did with his LMAF when he wired that up. His is a 98 Mountaineer like mine with the IAT in the inlet pipe.

 

[2000StreetRod]

Adding Separate IAT Sensor

Obtaining a separate IAT sensor will not be a problem since that seems to be the most common configuration. Hopefully the electrical characteristics (ohms vs temp) will be the same as my integrated IAT/MAF sensor. It shouldn't be too difficult to obtain a mating connector with pigtails. I've already started checking with my online Explorer salvage yard contacts.

In my planned intake system I only have a 4 inch long section of aluminum tube to accommodate the IAC tube, the PCV tube and now an IAT sensor. I didn't plan on locating any of those items in the silicone hoses.

Here's a photo of my 90mm test fixture and a closeup of the 3 stage transistorized MAFSAmp.

The duct fan is on the left (connects to MAF outlet) and the leaf blower is on the right (connects to MAF inlet).

The 3 micropotentiometers shown will eventually be replaced with fixed value resistors or 10 turn micropotentiometers to eliminate changes in value due to vibration.

 

[2000StreetRod]

I bought a used 1997 Escort air intake hose with IAT sensor and mating connector with pigtail for $.99 on eBay. The IAT sensor part number is supposed to be the same as used on Explorers with separate IAT and MAF sensors. It's been shipped and I should have it in a few days.

I'm very close to getting the gain of the MAFSAmp adjusted to alter the signal output of the 90mm MAF to act like my stock 55mm MAF output. Soon I'll be replacing the 3 fast change micropotentiometers with either fixed value resistors or 10 turn micropotentiometers.

Does anyone know how much impact a disconnected IAT sensor has on a SOHC? I assume that the PCM will flag the disconnected IAT sensor as failed and revert to a default value for intake air temperature.

 

[CDW6212R]

I'd ask James about it, I'd also guess that it would be minor and have a default value.

 

[2000StreetRod]

Dual Mode MAF Enhancer

I just read aldive's thread http://www.explorerforum.co om/forums/showthread.php?t=219445 about his Dual Mode MAP/MAF Enhancer and realized I could expand on the capability with my MAFSAmp.

My first fuel injected vehicle was a 1973 Volvo 142E with Bosch port injection. When I rebuilt the engine I had the cylinders bored to increase the displacement from 2 liters to 2.2 liters. To accommodate the 10% increase I needed to modify the fuel control unit which was an analog computer located under the front passenger seat. I purchased a modified controller from ipd Volvo that had a remote potentiometer to control the richness. I could vary the stock richness from 15% lean to 25% rich just by turning a knob at a convenient location.

Since aldive's Dual Mode MAP/MAF Enhancer is based on a voltage divider it can only reduce the richness from stock. My MAFSAmp can be adjusted to increase the MAF output voltage.

I have decided to set the MAFSAmp gain to increase it's output to 20% more than stock. The output will be routed to a potentiometer controlled voltage divider easily accessible to the driver. The output of the voltage divider will be routed to the PCM and range from 20% more to 20% less than stock. One limitation of this implementation will be that even though the PCM MAF input voltage can be as large as 6 volts, the richness will never exceed that for 5 volts - the maximum voltage that the PCM utilizes. In other words, there will be no performance increase at maximum MAF airflow.

 

[2000StreetRod]

MAFSAmp Prototype

The photo below shows the male and female 6 pin connectors I inserted between the MAF sensor and the wiring harness that goes to the PCM.

To test the MAFSAmp I disconnect the above connectors and insert a wiring harness with mating connectors and the MAFSAmp. The wiring harness is shown in the photo below.

The connector in the upper right with the pink shrink wrap is the socket for the IAT sensor. The connector at the top left mates with the wiring harness for the richness potentiometer that will be located next to the air/fuel ratio gauge on the pillar pod. The other two connectors mate with those installed between the MAF sensor and the PCM.
During part throttle I suspect that the richness potentiometer will only have an effect when the load on the engine as reported by the MAFS is changing. After a few seconds of constant load the PCM will probably rely on the O2 sensors and adjust the richness to lambda. During wide open throttle (WOT) the richness potentiometer may have an effect because the PCM runs open loop during WOT.
Below is a slightly blurry photo of the 3 stage circuit board mounted in a plastic box.

The blue rectangular items are vibration resistant 15 turn adjustable potentiometers that determine the amplifier gain.
I will be ready for my first engine start and run in Park test as soon as I finish the wiring harness for the richness potentiometer.

 

[CDW6212R]

That wiring looks very good Dale, and I hope it works for you.

 

[2000StreetRod]

Test 1 - Ultimate Kluge

Last night the suspense of whether or not my MAFSAmp would work finally got to me. I quickly wired the richness potentiometer wiring harness and temporarily connected the harness to the potentiometer. This morning using what was available I pieced together a temporary test set up as shown below.

The IAT sensor is on the throw rug at the left. The richness potentiometer is in the middle. I just kept the stock 55mm MAF in place along with the stock intake tube since I don't have all the air plumbing (pcv, IAC & IAT) for the 4 inch intake done. The results were encouraging. The engine started fine from a cold start and idled normally (better than with my stock MAF and racing air filter). An IAT low input code was set so I must have a bad connection somewhere. I set the idle MAFSAmp voltage to the PCM to 0.8 volts (same as stock) which was midrange on the richness potentiometer. As the engine warmed up and the idle speed dropped to 550 rpm the MAFSAmp dropped below 0.8 volts and the idle speed became unstable. Increasing the richness improved the idle stability. I will have to increase the gain at idle to keep the voltage above 0.8. The engine ran very strong and responsively when accelerating in PARK. However, I was able to "blip" the throttle and detect some hesitation. For now its back to the test bench to locate the IAT sensor problem and correct it.