15k ohms resistor mod

[lancerevo]

Here is the diagram to make a low price, almost no cost at all performance mod. I have tried it myself and it worked. What I did was put a 22k ohms resistor between the iat/vat sensor and the ecu. Here's the diagram. The difference is more torque and power and feels power full in the high rpm range, small increase but noticeable. Right now I am using 22k ohms resistor but I am going to try the 15k resistor soon. Using the 15k resistor is the max resistor you can use because the manual says so. I will try and see what it does.

The vat wire is green and black.

[sam.1956]

So if I understand this, with the fixed value resistor you're attempting to fool the ECU into "believing" the incoming air is cooler than it really is, so it will enrich the fuel/air mixture? Won't the feedback signal from the Oxygen sensor clue the ECU into how to deal with your clever ruse and it will eventually lean the mixture back to normal?

[eurotiva]

I tried one of the cheap ones off ebay and watched it (air/fuel gage) while going down the track....I saw no changes but mine was already turbo and gettin alot more fuel

[lancerevo]

Won't the feedback signal from the Oxygen sensor clue the ECU into how to deal with your clever ruse and it will eventually lean the mixture back to normal?

Yes it will lean it. I am testing it by unplugging the o2 sensor and have the o2 voltage readings and see if I can tune from there.

[FestYboy]

remember that the PCM will input a value if you unplug the O2 and no tuning will be available (other than spark control).

if you wnat to tune, get an adjustable cam gear, a timing light and an A/F gauge. fussing witht he intake air temp sensor is futile as there are other sensors that will suggest to the PCM that the IAT values are false and therefor should be ignored.

[sam.1956]

Seems to me that he would have to get into the PCM code & edit several entries in the table of "limp-home" (inoperative sensor) values for any of the fixed-resistor type mods to really be effective at all.

Interrupting / disabling inputs and/or changing base values in a multi-dependent sensor system (engine computer) sounds risky, if you don't really know the guts of the thing and how one value's limit may affect the operation of the system as a whole.

It may be just easier for him to go the MegaSquirt route & then have complete access & control of literally every parameter & value in that ECU.

[FestYboy]

^yes

[lancerevo]

Disconnecting the o2 sensor worked. I am using a volt meter to measure the o2 sensor. Before when the 02 sensor was plugged the volts go up and down and will not let you know if it is rich or lean. It's like going rich and lean all the time along the rev band. The o2 sensor reads from 0-1volt. Lower than .45volts = lean, .45/.50v = correct ratio, Above .55v = rich. I have tried multiple resistors. I have found that with the 15k resistor is a little rich, volts indicates .70v. Now I have to try some lower resistance.

[FestYboy]

the O2 swings when connected to indicate that the A/F is swinging to keep the cat alive (cats need fuel and o2 to operate properly). only do this for testing please, otherwise you'll be buying a new cat soon.

[lancerevo]

I don't have cats... But I have a little dog.

[sam.1956]

^^LOL! I think FestYboy is trying to advise you to proceed judiciously, else you may end up with a very Big Dog! Best luck with your mods!

I suppose you could wire in a potentiometer that would let you dial, dial, dial until you got the performance you were looking for. Then at that point, measure its resistance & replace it with a precision resistor of that value.