Getting colder outside - fuel-cut behaviour

[TRI]

It gets around freezing temps here (even gets lower during the winter). I already have a hot air intake. Instead of a radiator block I've installed something like in the picture. Works well and keeps the radiator working if needed (a lot of hills here).

Here's my question: the inside temp was set to 77 Farad, no A/C. Fuel-cut 'stops' at higher speeds working (means that it feeds the engine with fuel earlier) and Auto-stop is far less than in warmer climate. Does the climate control unit take the set inside temp into account and lets the engine runs more often? If yes, any way to cancel it?

[Right Lane Cruiser]

Yes, the thermostat for the HVAC system is taken into account. I just turn off the system when I'm slowing down or stopping and want autostop -- it works at the lowest temperatures I've ever tried as long as the engine and battery are warmed up.

[joecvt]

Originally Posted by TRI

...and Auto-stop is far less than in warmer climate. Does the climate control unit take the set inside temp into account and lets the engine runs more often? If yes, any way to cancel it?

Besides some other factors, AutoStop is also based on the outside temp sensor. In order to get more AutoStops in the winter time, you need to move the sensor to the mid engine compartment.

The sensor is located in the front bumper (behind where the front license plate would attach). The sensor is the only thing with wires that goes to the front bumper mid section so follow the wire trail if you can't locate it.

Without cutting any wires to the sensor, I was able to move the sensor and mount it next to the MAP sensor (near mid engine - left of air cleaner).

I made a bracket for it and used the same 10mm mounting screw that was holding the MAP sensor.

You may have to undo some cable ties to get the wiring to be long enough. I did this mod in 2004 or 2005 and has been working fine since.

My AutoStop even works on some of the coldest days (once the engine completely warms up) and I live in New Hampshire

JoeCVT = Just your average CVT owner

[TRI]

Joe, thanks very much for the hint.
I've already located it and will move it behind the radiator and my version of the grill block and will see.

EDIT: I have another idea. Why not measure the resistance at 68 Farad outside temperature and simulate the value by changing the sensor by a simple resistor? No need to relocate and it's changed within 10 seconds without relocating it.

[N2oExpresS2k]

Think it would probably take a lot less effort to just relocate it. The install might not take long but it'll probably take a while to figure out the resistor you need, and if it doesnt work properly after all that extra effort you'll kick yourself for not just relocating it.

[TRI]

I don't think it's a lot to do. Just take it inside the house, measure the resistance and choose the appropriate one and connect it. I'll give it a try.

[N2oExpresS2k]

I guess what's not hard for you is for me and vice versa.. If you do figure out what the proper resistance is post it up, i'll do the same since i'm taking a road trip up north next month. Getting the car ready for the cold =D.

[joecvt]

Originally Posted by TRI

EDIT: I have another idea. Why not measure the resistance at 68 Farad outside temperature and simulate the value by changing the sensor by a simple resistor? No need to relocate and it's changed within 10 seconds without relocating it.

I guess as long as the climate control does not use the temp reading for anything else, what you suggest may be ok.

The climate control makes part of the decision of AutoStop and that sensor goes to the climate control only.

Moving it to the mid engine area still gives the proper outdoor temperature when cooled down overnight whereas your mod will always report approx. 68F no matter what condition.

JoeCVT = Just your average CVT owner

[TRI]

I've some data from the sensor:

4 degrees C: 5.1 kOhm
13 degrees C: 3.3 kOhm
17 degrees C: 2.7 kOhm
21 degrees C: 2.3 kOhm

I went with a 3.3 kOhm resistor and simulate 13 deg. C or 55 Farad.

[MN Driver]

Farad = Measure of electrical capacitance
Fahrenheit = The measure of temperature developed by Daniel Gabriel Fahrenheit based on the hottest and coldest temperatures he could manage to create reliably in his laboratory by using brine consisting of water, ice, salt, and ammonium chloride. 100 degrees was what he measured the temperature of his wife at.