Resetting the ECU

[Chassis 33]

Something that's just triggered in my mind. What happens why you reset the ECU? Does it remove some of the parameters it has "learnt" since the last time it was reset, I presume the permanent live feed to pin 15 keeps all these learnt parameters in memory.

If this is the case, what effect do these learnt parameters have on the running of the engine? I'm curious because in the racer, the main batter kill switch has to kill all electrical circuits in the car, which also includes the "permanent" feed to the ECU, meaning every time the car is switched off I loose all the learnt info. Could this explain some of the interesting fuel characteristics I get?

Regards
Iain

[paulathome]

Ian,
from what i've read on various ECU's this one doesn't learn much at all.
If however you disconnect the battery, the ECU will loose any fault codes it has stored from any parameters the engine sensors have exceeded.
Then again I might be talking poo.
Paul.

[GreenV8S]

As far as I understand it, the ECU has a single adaptive settings which is set automatically when certain conditions have been met. I would have thought that if the ECU map was perfect then the adaptive setting should set itself at zero. It'll never be perfect, but hopefully the adaptive setting will be very small.

Resetting the ECU will also clear any fault codes that have been raised, and if it had gone into 'limp home' mode due to a serious fault this would bring it back to normal operation (until the faults reappeared).

Although the ECUs seem to be pretty robust, repeatedly connecting and disconnecting it is probably not a good idea as this is when it's most likely to be damaged. If this is going to be a regular occurrence it might be worth looking to see if you can apply any sort of filter or regulator to the supply to protect the ECU. Mark Adams would be the person to talk to about that imo.

[john p]

So does disconnecting the battery reset the ecu,or do you have to actually unplug it?

[GreenV8S]

john p said:

So does disconnecting the battery reset the ecu,or do you have to actually unplug it?

Either of these would reset it.

[Chassis 33]

Cheers Pete. ATM the pressure to revret to either my Weber 500 or one of the bigger Holley's is getting near unbearable...however I will persist for now!!!

Regards
Iain

[Cider Andy]

My understanding is that the ECU 'learns' the range of the ancillary components connected to it. For example, a healthy throttle pot should show a voltage reading off the wiper of between 4.6V and 5V at one end of the track, falling to between 0.26V and 0.36V at the other end. So, the actual one fitted on your car might have a range of 0.3V to 4.8V and I think this is what it 'learns' over a period of driving. Same goes for other equipment, eg. AFM, coolant temperature sensor, etc.

There's room in the 14CUX casing to fit a back-up supply, eg. a battery of CR2032 cells up to 12V, but I don't know what kind of drain the ECU would put on it. You'd also have to fit a diode in the permanent supply to stop the back-up cells trying to power up the whole car when the kill switch was open.

[spend]

FWIW, never seems to be mentioned very often, but the ECU operation is extremely dependent on engine speed sense from the ignition circuit (have you been modding?). Any iffy tolerances in this circuit (the one with a resistor taped on the loom) will produce 'interesting' results.

Dave

[Chassis 33]

Cheers Dave, I'll make sure this is in A1 condition.

Regards
Iain

[GreenV8S]

spend said:

FWIW, never seems to be mentioned very often, but the ECU operation is extremely dependent on engine speed sense from the ignition circuit (have you been modding?). Any iffy tolerances in this circuit (the one with a resistor taped on the loom) will produce 'interesting' results.

Dave

Particularly wrt to the routing of the signal line relative to the nearside HT leads.

[blitzracing]

I thought the only "learning" the ECU could do was tweek the sub 2500 rpm fueling with the feed back from the lambdas. Thats one reason the tickover can be a bit erratic after a power reset untill the mixture becomes stable. This could also be complete rubbish, as with many urban myths associated with the ECU. Your quest grasshopper is to find an ancient parchment or circuit diagram of the 14cux so we would not have to speculate.....

[GreenV8S]

blitzracing said:

I thought the only "learning" the ECU could do was tweek the sub 2500 rpm fueling with the feed back from the lambdas. Thats one reason the tickover can be a bit erratic after a power reset untill the mixture becomes stable.

The lambda feedback system is separate from the adaptive setting I referred to, although the adaptive setting obviously has to derive from the lambda feedback.

[neal1980]

Dont know how correct i am here but dont shoot the messenger. Ive been told by TVR mechanic (what would they know... :-P) that the lucas ecu have no adaptive learning facility at all its just a myth. By unplugging it, it will simply clear the fault codes nothing else. Im inclined to believe him look when it was designed and it was for a landrover/rangerover not TVR. Theres quite a few of us doing megasquirt at the mo, its looking the best way to go for value for money and will give you full control.

[GreenV8S]

You may be right, but my understanding based on comments Mark Adams has made in the past is that the ECU does have an adaptive value which it learns under certain specific conditions. With all due respect to your bloke at the factory, MA is somebody that I know understands the workings of the ECU very well indeed and as far as I'm concerned what he says about the ECU is beyond question. I may have misremembered what he said, but I doubt I made the whole thing up. As I said before, my understanding is that this adaptive setting is quite separate from the real time lambda feedback system.

MegaSquirt does seem to be the way to go for a DIY installation if you are OK with electrics and electronics, I just wish they'd get a move on with the router board so it can replace this OMEX system I've got at the moment.

[peebee]

This link may be of interest for those that haven't seen it before:

http://www.britishv8.org/Articles/Rover-14CUX-EFI....

[Pupp]

peebee said:

This link may be of interest for those that haven't seen it before:

http://www.britishv8.org/Articles/Rover-14CUX-EFI....

That's a really informative article, chhers. Always wondered why I could never find a tune resistor on mine!