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MAP Sensor Adjustment Install
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Hydro Tacoma Offline
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Post: #1
MAP Sensor Adjustment Install
Hi all,

I am trying to get my 95 Toyota Tacoma to get results. I have a the Hydro Super 2 installed and also a EIFE. It appears that my computer is ignoring the data from the O2 sensor that the EIFE is working on and is relying on the other sensors to adjust fuel-air ratio because it is compairing the data from the o2 sensor and other sensors and over-riding the data from the o2 sensor and relying on other inputs. Results of this: NO MILAGE GAIN. I talked with Ken from Hydro Fuel Solutions and he is stating that I need to start by adjusting the MAF.

I took a look at the tuning for milage document and I see the instructions for building a trim pot to do the adjustment. I am not a electronics person so I don't want to go to radio shack and get a circut board and build something to add the 15 ohm's of resistance. Nor do I understand much in the building instructions. Does anyone know of a trim pot that will adjust 0-100 ohms that I could buy?

Also, has anyone hooked up a trim pot to a MAF? I have 3 wires going from my MAF. 1 goes to the ECM and grounds 2. is 12 V power and 3 is 1 to 1.5V wire going to the ECM. (this is according to my wiring diagram for the truck) I am guessing that I add the resistance to the 1-1.5V wire going to the ECM?

Thanks for your help!
07-14-2008 04:34 PM
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PanamaRik Offline
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Post: #2
RE: MAP Sensor Adjustment Install
I don't have a MAF on my Chevy, just a Map sensor, but I believe they operate in a similar fashion.

I used a 50ohm pot, in the ground wire. That way the 5v supply voltage from the ECM is still the same, at 5.06 volts in my case, but the output back to the ECM is lowered to approx 4.8v.

Another point to watch out for with MAP sensors, they measure barometric pressure at switch on and the ECM compensates for that. If you reduce the voltage at switch on the ECM thinks you are at a different altitude and sets the whole internal fuel map for those conditions. To solve that I have all my sensor mods fed through a 4 pole relay which is only energised when the HHO generator is switched on. When the relay is off all sensors revert to stock settings. Start on just gas and then switch on the HHO and sensor systems.

Currently getting 47mpg tank to tank from mixed highway/city driving in a 2.2l chevy cavalier (33mpg before starting this project)


Hydro Tacoma Wrote:Hi all,

I am trying to get my 95 Toyota Tacoma to get results. I have a the Hydro Super 2 installed and also a EIFE. It appears that my computer is ignoring the data from the O2 sensor that the EIFE is working on and is relying on the other sensors to adjust fuel-air ratio because it is compairing the data from the o2 sensor and other sensors and over-riding the data from the o2 sensor and relying on other inputs. Results of this: NO MILAGE GAIN. I talked with Ken from Hydro Fuel Solutions and he is stating that I need to start by adjusting the MAF.

I took a look at the tuning for milage document and I see the instructions for building a trim pot to do the adjustment. I am not a electronics person so I don't want to go to radio shack and get a circut board and build something to add the 15 ohm's of resistance. Nor do I understand much in the building instructions. Does anyone know of a trim pot that will adjust 0-100 ohms that I could buy?

Also, has anyone hooked up a trim pot to a MAF? I have 3 wires going from my MAF. 1 goes to the ECM and grounds 2. is 12 V power and 3 is 1 to 1.5V wire going to the ECM. (this is according to my wiring diagram for the truck) I am guessing that I add the resistance to the 1-1.5V wire going to the ECM?

Thanks for your help!
07-14-2008 06:54 PM
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CraigBMM Offline
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Post: #3
RE: MAP Sensor Adjustment Install
PanamaRik Wrote:I don't have a MAF on my Chevy, just a Map sensor, but I believe they operate in a similar fashion.

I used a 50ohm pot, in the ground wire. That way the 5v supply voltage from the ECM is still the same, at 5.06 volts in my case, but the output back to the ECM is lowered to approx 4.8v.

Another point to watch out for with MAP sensors, they measure barometric pressure at switch on and the ECM compensates for that. If you reduce the voltage at switch on the ECM thinks you are at a different altitude and sets the whole internal fuel map for those conditions. To solve that I have all my sensor mods fed through a 4 pole relay which is only energised when the HHO generator is switched on. When the relay is off all sensors revert to stock settings. Start on just gas and then switch on the HHO and sensor systems.

Currently getting 47mpg tank to tank from mixed highway/city driving in a 2.2l chevy cavalier (33mpg before starting this project)


Hydro Tacoma Wrote:Hi all,

I am trying to get my 95 Toyota Tacoma to get results. I have a the Hydro Super 2 installed and also a EIFE. It appears that my computer is ignoring the data from the O2 sensor that the EIFE is working on and is relying on the other sensors to adjust fuel-air ratio because it is compairing the data from the o2 sensor and other sensors and over-riding the data from the o2 sensor and relying on other inputs. Results of this: NO MILAGE GAIN. I talked with Ken from Hydro Fuel Solutions and he is stating that I need to start by adjusting the MAF.

I took a look at the tuning for milage document and I see the instructions for building a trim pot to do the adjustment. I am not a electronics person so I don't want to go to radio shack and get a circut board and build something to add the 15 ohm's of resistance. Nor do I understand much in the building instructions. Does anyone know of a trim pot that will adjust 0-100 ohms that I could buy?

Also, has anyone hooked up a trim pot to a MAF? I have 3 wires going from my MAF. 1 goes to the ECM and grounds 2. is 12 V power and 3 is 1 to 1.5V wire going to the ECM. (this is according to my wiring diagram for the truck) I am guessing that I add the resistance to the 1-1.5V wire going to the ECM?

Thanks for your help!

dual setup .. controls both o2 and MAP ..
http://cgi.ebay.com/ebaymotors/ws/eBayIS...ink:top:us
i contacted this guy and he said he would have more available this Thur. up on ebay.

another option (one i bought)
http://cgi.ebay.com/ebaymotors/ws/eBayIS...0247800076
07-14-2008 07:42 PM
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ncmountainmadness Offline
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Post: #4
RE: MAP Sensor Adjustment Install
Tacoma,

Plainly put, ALL sensors will need to be modified to see any positive results. All as in, IAT (Intake air temp) MAF (mass air flow) CTS (coolant temp) and in your case 02 (oxygen). The last you are already trying to do with the efie. Keep in mind if you are running a V6 you will need 1 efie on each side prior to the cat. None are needed after the cat. If you have the 1.8 or 2.4L 4 cyl you will need only 1.

let me state Ive been doing lots of recent research on toyota's as I myself am attempting the same. However, mine is an o5 and yours a 95 but alot should be similar. It is possible that your system is OBD1. You need to know for sure before starting to do tons of research.

If you plan to successfully TUNE your sensor chain, and dont already have one, you will need a device such as or equal to the SCANGUAGE. But then again if you have OBD1 I am not 100% sure if it will work for you or not. either way you need a way of seeing how your adjustments effect the computer.

I suggest that you read the link by MPG Mike, Tuning For Mileage.

In addition, a fellow by the handle of "Colchiro", common here on the boards has an excellent toyota link. http://www.autoshop101.com/autoshop15.html

IAT and CTS , on near all TOY's, regardless of age are very simply done by using on avg a 5kohm variable resitor in parallel with each. parallel means, dont cut any lines, just tap onto the side of the present line (skinned wire) Both place one end of var resistor on the signal wire, and the center tap of the res on the ground for the device. I have found that on Toyota, the IAT and CTS share the same ground common to be found as a brown wire. CTS should aslo have a white wire, and the IAT a yellow with black tracer. On your model the IAT and MAF are two sep units. On the newer ones they are in one package with 5 leads going to it.

On your MAF, If like mine.....MPG Mike states to place a resistance value in Series with the ground as one method there are others. you Need to know what you have prior to tinkering.. On the newer toyotas this only InCreases the MAF reading, opposite from what we want. I have found that to lower the MAF signal, a variable resiter need to be placed between the signal wire and the ground wire. Value of said var resistor to be between 200k and 1Mohm. But as I am not 100% sure of what is on you truck I cannot be sure if this approach will work or not.

as for the actual electronic components.....radio shack offers very limited. I suggest, http://www.jameco.com , Ive been using them for near 20 years and they have just about anything the imagination can think of where electronics supplies is concerned.

YOu have a much easier vehicle to tune than mine. Take the time, study the links, get the scanguage or similar if possible and you should see positive results.

hope this helps
07-15-2008 02:19 PM
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Bwanar Offline
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Post: #5
RE: MAP Sensor Adjustment Install
This is one of the nicest ones I've seen. It is just like the one I made and even has a shutoff for running stock. One of the best prices too!

http://www.hydrogen-water-cars.com/store...18218.html
07-15-2008 02:21 PM
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ncmountainmadness Offline
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Post: #6
RE: MAP Sensor Adjustment Install
Bwanar Wrote:This is one of the nicest ones I've seen. It is just like the one I made and even has a shutoff for running stock. One of the best prices too!

http://www.hydrogen-water-cars.com/store...18218.html

Nice unit and fair price, but states it is desinged to offset a MAP sensor. Not all MAF sensors work the same as MAP sensors. But if I had to guess if they offer such for MAP's then they probalby also offer it for MAF's.
07-15-2008 02:30 PM
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waterboy1 Offline
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Post: #7
RE: MAP Sensor Adjustment Install
I know that it is posted somewhere, but I can't find it. Please help. I have located the MAP sensor and think I have the signal wire identified (will test with voltmeter) but I can not find where it says to cut the wire or to splice into it. My MAP has 3 wires, gray, green, and black. My Haynes manual shows the gray as the 5v wire. Also on the MAP itself, it shows a 5v, gnd and one other right where the wires go in. (I don't want to run down now and take off the aie intake to see.) My question is do I cut or splice??? Thanks
08-03-2008 06:31 AM
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