This is a bit off the wall, perhaps.

I'm wondering about Lamba and Non-Lambda ECU differences, with respect to pins and connectors

Consider the ECU pins for all functions NOT related to Lambda. Are they in the same locations on all V12 6CU and 16CU ECUs? Illustrations here seem to suggest they are...

LUCAS EFI / AJ6 Engineering

Or, in other words, is the connector from a Lambda ECU compatible with a non-Lambda ECU?

Cheers
DD

 

Doug,

The pin numbering is the same.

The Lambda ECU has the circuits attached to the related pins, and the wires for such are IN the multi pin plug.

Those cars without Lambda, have NO wires in that plug, just empty spaces.

When I fitted the 16CU to my '85, NO Cats etc car, the 16CU came from a 1988 S3 V12 with cats and O2 sensors.

Pre Forum days, so I was dumb to this stuff. Just new that the 16 was better than the 6, and this one was FREE.

Drove to the place with the 16CU available, removed my 6CU in the driveway, plugged in the 16CU, drove home.

After the event, Forum days, I was informed that what I did was NOT possible, and the car CANNOT run. Really, better inform the car of this revelation.

My deducting at the time, and still today is that if there are NO wires in the Multipin plug for whatever the ECU pins go to, that circuit is a dead circuit, as in NO input, NO output.

ALL the ECU's I have played with have a full complement of male pins in the socket, and the chassis loom of the car has whatever wires are deemed needed for that car, and it works.

However, putting a none Lambda ECU in a Lambda car, dunno. Maybe the circuits are already IN the box, coz it got all the pins in the socket, or maybe they are not connected??, just there due to production simplicity of that socket, again, dunno.

 

Thanks, Grant. I was having a hard time translating my thinking into words but you obviously recognized what I was after.

The reason I bring up the subject is to explore options for anyone needing to replace their ECU. I have a spare ECU so I'm probably Ok for life, but one ponders these things over Sunday morning coffee.







Good




And, further, beyond just running or not running, I have confidence that a person such as yourself would be aware of any too-lean or too-rich conditions, if either one existed.


Makes sense to me



Ok, good info.


My gut feeling is the internal circuits are not there even though the pins are. If both the circuits AND pins were in place we wouldn't see different ECU parts numbers for "with catalyst" and "without catalyst".

I'll do more pondering and checking but I'm thinking that someone with a lambda car can use a non-lambda ECU.....with the understanding, obviously, that all lambda functionality will be gone

Thanks, Grant

Cheers
DD

 

Lambda is only a trim and the ECU disables this on startup and heavy throttle and acceleration application. So the ECU only uses O2 trim for idling and cruising.

My guess is the Lambda circuitry may be there in non-L ECU's ( it's probably only a few cents worth of components) and just the ECU programming is different to disable this function.

 

That's my understanding as well


Perfectly plausible

Next item.....if we agree (and I think we do) that all lambda V12s are low compression....

What about different fueling 'maps' for high compression versus low compression? Do they have different maps? How significant would the difference be?

We know from Grant's experience that different mapping, if it exists, is not a problem when using a Lambda ECU in a non-Lambda car. But what about the other way round?

Cheers
DD

 

My car has O2 sensors and is 11.5:1 cr. It runs very rich when cold, like black smoke rich. Once warm it's fine. I have done nothing about this as I have a Mega Squirt (MS2) almost ready to install.

The base fuel map will most likely be the same between L & non-L cars. CR and fuel quality would have the biggest effect on base fueling, but this may not be a big enough difference to warrant a different map, who knows what Jaguar did. When I install the MS2 I will be installing 2 wideband O2 sensors. My plan is to map the stock ECU fueling with these before I remove the 16CU.

 

As expected

The consensus has long been that none of the 12.5 compression cars had Lambda


I suspect the proof will be in the pudding-- someone using a non-Lambda ECU in a Lambda car and then reporting back if they sense (or can confirm) any mixture problems.

Cheers
DD

 

This is correct according to my recollection of a chat with Mr Bywater. He told me that from about 1988 or so ALL V12s were the 11:1 CR regardless of market. The lower CR cars were so made because of the relatively low octane unleaded fuel then sold in the USA. The 12.5:1 Cr on the UK and other countries' cars was to enhance part throttle economy, and had no great effect on power output.

 

The Long Term trim is used to correct open lop fuelling during high load driving.

Non-lambda ECUs usually have some method of adjusting the mixture, usually a potentiometer.

 

Lambda is not used for high load, the ECU disables the O2 sensors on heavy throttle application, this is done so the ECU can apply acceleration enrichment.

The O2 sensors are only used when warmed up and for idling and light/medium throttle cruising.