Renix 87 4.0 WIring mod

[Marine1Texas]

So we were taking the air cleaner out today and the air temp sensor wire snapped off at base of sensor. So Put the new inline tube air cleaner in and I had to go look at the ECU wiring diagram.

 

It basically same setup as the ECU temp sensor, as the engine heats up lets more ground through the sensor to feed back to ECU, which leans it out. Now it looks like the engine temp ground side goes through the air sensor and then finally meet ground. So for temporary I have wired a loop in the wiring to pass right through where the air temp sensor is.

 

It was cold and it started right up without issue. I have seen posts on here where to get a replacement sensor, will take a few days till I get it.

 

What you think on this will it lean out the engine the most since it is giving full ground?

 

Just got the mind going and was thinking about those sensors and how the ecu works on renix 4.0. If in theory I wired a toggle switch to ground and spliced it to the sensor line by ecu, when switched the toggle on, it would bypass sensor and get a full ground, causing it to lean the engine out all the way the ECU would let it. So if one was on the highway driving in cold or hot weather you would get great mpg.

[omega_rugal]

put a potentiometer for more control...

 

mine is disconnected to fool the ECU to think the air is ice cold, it`s supposed to give some ignition advance...

[Ωhm]

Two (2) things will happen. Fuel trim will compensate (within its range of authority) for your lean condition to the point of going from closed loop to open loop.

[omega_rugal]

A quick look at the manual says

 

185 ohm = 212 f and 100,700 ohm = -40 f

 

don`t ground the pin or else the ECU will assume the sensor is faulty, ignore it and use some preset value...

[Marine1Texas]

I have the temp hooked as normal, however the air temp sensor is direct looped. I will then put a adjustable resistor in place of the loop. I will play with the knob with my analog meter to find best ohm. I think 2,000 ohm is good to start. That is around 85 degree temp. Since it is about that temp right now in Texas. 

[Eagle]

12 hours ago, Noriyori_Kudo said:

Just got the mind going and was thinking about those sensors and how the ecu works on renix 4.0. If in theory I wired a toggle switch to ground and spliced it to the sensor line by ecu, when switched the toggle on, it would bypass sensor and get a full ground, causing it to lean the engine out all the way the ECU would let it. So if one was on the highway driving in cold or hot weather you would get great mpg.

 

It shouldn't lean it out. The oxygen sensor is what controls the mixture in closed loop mode. If that sees a lean condition, it tells the injectors to feed more gas.

 

Several years ago, on a trail ride, one of the guys either broke his exhaust manifold, or lost a couple of manifold bolts. That cause an air leak that fooled the O2 sensor into thinking he was running lean, so it enrichened the mixture to the point that there as raw gas coming out of the cylinders and burning in the manifold. He limped off the trail and, by the time we got to the trailhead, it was getting dark and his exhaust manifold was glowing bright red.

[omega_rugal]

the ECU uses all inputs: coolant temp, air temp and (when in closed loop) the O2 sensor signal...