Thread: D2 V8 operating temps

I’ve got a D1 with a 4.6 in it. I have installed oxy sensors in it and have a jaycar gauge in the cabin for each sensor so I can watch the led’s flash up and down so at least I know it’s working. it appears that once you start the car the fuel mixture gets managed by the feedback from the maf and other sensors. Once you touch the accelerator pedal (even when cold) the 14cux uses the feedback from the oxygen sensors to manage fuelling levels. When driving, for a millisecond it takes the pre emptive signal from the other sensors but falls back to lambda 1.0 instantly.

i mention this as I assume the D2 V8 has oxygen sensors from the factory and would possibly use the same logic as a 14cux using oxygen sensors. So if you change to a cooler thermostat would the D2 ecu still trim fuel to lambda 1.0 or will it use the ecu temp signal, which believes the engine is not at operating temp yet, to over ride the fuel mixture setting of lambda 1.0?

on the 14cux (with lambda feedback) achieving lambda 1.0 is the priority even driving with motor cold. So please don’t quote me on it – but running a cooler thermostat would not affect fuelling levels??? And so I was thinking is this the same in Pedro’s situation with a D2 (with lambda feedback)??

i'll finish off my comment. i was in the library and had 15 seconds left on the session. anyways...

I had a look in RAVE for the thor motor (I think that’s what pedro has) and here’s what is says on what it does with the feedback from the ECT sensor :

Engine Coolant Temperature (ECT) sensor - (from
99MY)

The ECM uses the information received from the ECT
sensor to make adjustments to the engine operating
conditions. The ECM ensures a richer air:fuel mixture
is available at lower block temperatures for good
quality starts and smooth running. The mixture is then
made leaner as the engine temperature rises to
maintain low emissions and good performance.


If the sensor fails, the ECM uses a substitute software
routine that changes default value during warm up,
based on the signal from the inlet air temperature
sensor. When the software model reaches a coolant
temperature of 6°C (14°F) the ECM implements a
fixed default value of 8°C (18°F). The ECM coolant
model also forms part of the diagnostics that is
performed for detecting a temperature sensor fault, as
well as open and short circuit tests.
Temperature Voltage
-5°C 5V
-2°C 4.8V
1°C 4.2V
4°C 2.8V
7°C 1.4V
10°C 0.6V
13°C 0.2V
NOTE: All voltages listed are approximate.



It doesn’t actually say how it achieves a rich mixture as narrow band sensors are made to measure a stoich mixture which is lambda 1.0. when the ect sensor fails the default set of values it works from stop at 60 deg c and over that it uses 85 deg c. Maybe what this is saying is that once your engine is around 60 deg c based on the readings from a healthy ect sensor then coolant temp/engine temp plays no role in fuelling. Only guessing as I could not see it written explicitly.

so maybe a cooler thermostat will not effect things from an electronic engine management point of view. someone would know the exact ect temperature where the ECM disregards the coolant temp in its fuelling calcs?