Motec-wide band lambda control

Has anyone ever contemplated a true and proper density calculation as an alternative?

 

efioz, i'm not following you where there is a contradiction. The corrections are in the form of logged short and long term trims. sorry I wasn't clear on that.

What is a "true and proper" density calculation? MAP/EMAP?

 

aircon,
the type of O2 sensor dictates the closed loop mode, i.e. wide or narrow band. You cannot use wide band mode with a narrow band sensor.

to answer your question, yes, light throttle in closed loop mode should target lambda of 1.0. If you don't have cats, you could run richer or leaner as desired. If the car has cats, then running rich has its obvious risks.

 

100% certain. This is the most important component of the 'adaptive' ECU software that self corrects to changes in the motor. This is why, for example if you ut a higher flow exhaust system, within the constraints of the traget values the ECU is seeking, you will see perfromance gains, without any manual ECU reprogramming required and the car will maintain (after the adjustment period) the constant target values, as long as the changes are not so large as to take them out of correction range.

 

Does that make sense? If it's a MAF system, the additional flow is captured by the sensor, no correction is required.

That makes sense for a MAP system, I guess, but I didn't realize anyone but racers were still using that and I just don't see how they are get values they can tune with from the narrow band senor. I've used them to rough in the maps, but all the action is in the .85v-.95v range and not very predictable sensor to sensor....I just don't see how they are making any sense of it.

 

That is what I do on my car and it seems to work quite well. But you need the right type senor as superx pointed out.

 

Hi guys, I worked for MoTeC for 12 years and maybe I can shed some light on the Lambda values vs. A/F. Start with a 14.7 perfect burn on gasoline (can vary depending on the specific gravity of the fuel that day, but not much). If the Lambda value reads .88 than the A/F would be (.88*14.7) or 12.936 A/F. A good NA engine will make good power and survive at .90-.92 Lambda or 13.5 A/F ratio and turbo, high boosted (over 1.2 bar boost) need to be more at .82-.85 Lambda or 12.0 A/F ratio. Remember an easy rule of thumb, double the atmosphere (boost) double the fuel (and be sure to pull back that timing or you'll find your pistons coming out your exhaust tips... ) Hope this helps!

 

Stephen, a quick question, my 355C has the 2.7 OBD1 this motronic doesn't have that adaptive capability does it? I'm not wanting to change anything with 2.7 system just trying to understand how and what the sensors do. As I understand Bosch's info, which is limited, my 02 sensors only supply info to the ECU during idle and steady state throttle postion and MAF sensor is the source for info at WOT. Sorry for getting off topic here. Regards, Vern

 

You still need to correct AFR's via the O2 sensors, additionally the Merc super and turbo charged motors, along with the M3 CSL(I think) use throttle position and manifold pressure rather than flow for the intake side. Better exhaust side breathing does not increase intake flows, just promotes better evacuation of spent gases from the cylinder, meaning a cleaner/less diluted charge, which needs more fuel to maintain the target air/fuel mix.

 

Vern
That's my understanding. I did a quick Google and couldn't find any reference to adaptive fuelling capabilites for this ECU.

 

Is it the standard Ferrari one?

 

Yes, it has to be in the software set-up, but I'm not familary with motec, hopefully someone else can answer.

I've never thought that was a good idea since it can cause a very lean condition. I use the ignition to rev limit, but I might just be paranoid

 

I think Peter is referring to engine braking rather than rev limiting. All modern cars do this AFAIK to help with fuel economy numbers.

 

2.7 does "learn".

Excellent thread gentlemen...

Best,
Rob

 

Engines advertised as "lean burn" like Honda Civic Cx do use a version of wide band sensor, one of the reasons reasonable quality wide band sensors are going down in cost and more development is going into this area. You'll see wide band installed OE more often as feedback controls become more robust and emissions/ fuel economy standards become tougher to achieve.

Just wait until in-cylinder pressure sensors come down in size and cost, that will give you a tuning aid and immediate feedback...

Best,
Rob

 

Yes, catalyst equiped vehicles use injection to limit rpm... don't want to send unburned fuel to the catalyst. This technique is also used for traction control, stability control, cylinder de-activation, etc.

Ignition cut-off may respond faster though.

Best,
Rob

 

I'm starting to get a bit confused about how much “learning or adapting” is actually going on….particularly since I’ve never found the slightest need for anything of the sort in any tuning I’ve ever tried to do….maybe shift points on an automatic, but I generally don’t mess with automatics so it’s never really been relevant.

To the best of my knowledge, all EFI ferraris are MAF systems, use a narrowband O2, and are closed loop only at low throttle positions. I think the newer ECUs do adapt somewhat based on the O2 readings, but only at low throttle positions where the O2 is active because they simply can't read AFRs much off 14.7 accurately with a narrow band O2, which are specifically designed to respond at 14.7 and are very accurate. But that makes AFRs of 0-14 all lumped in a 0.2v response window and there’s variability from sensor to sensor on top of that. I've never seen anyone claim they are able to make use of that information in any definitive way.

On a MAF system, any change that's made to the engine, exhaust system, or intake system is corrected for by the MAF, unless the change it to the MAF sensor itself because it’s reading the air mass flow directly. There is no need to adjust anything except at low power/flow rates where the MAF sensor is less accurate and tight control is required for emissions compliance.

On cars equipped with a MAP system, any change to the engine, intake or exhaust systems require the ECU to be re-mapped because the system has no way to know the air mass flow rate has changed. The common work-a-round has been an adjustable fuel pressure regulator that ups the fuel pressure and therefore the fuel flow rate and then just let the O2 sensor pull the mixture back down at low power. I’ve never seen a MAP equipped car that could self-correct for changes made…but that might just mean I lead a sheltered life.

 

That makes sense. I guess with full sequentail injection the software can cut an entire fuel cycle and that would be perfectly safe. I was thinking muli-point injection, so at the beginning and end of the fuel cut, some cylinders whould see a partail injection and a very lean condition.

 

I did not know that....but I still can't think of any reason why they would need a wide band senor? ...never mind, by lean burn they mean they are going higher than 14.7 were a narrow band sensor can't read.

Are they using the sensor to keep the engine in closed loop at high power or just higher than they could with a narrow band sensor?

 

Hey, great thread guys and very pertinent to my last year.

I ended up having to swap out both turbos on my Ghibli Open Cup racer (track debris/vermin as in a Viper took them out). The originals were stupid money from Maserati so we went with a pair of newer albeit somewhat larger turbos. I had someone who tunes these cars for the aftermarket give me what I thought would be an appropriate chip. It was supposedly designed for this exact setup. But on the dyno it ended up so rich all the time (11-12) that the engine seemed bogged and very dull except at full boost. It felt the same on the track. I worked with some guys in PA, Seventh Street Speed for the dyno testing but the chips were from Germany.

Now nothing else was changed on the car except the larger turbos same boost at first so maybe new chips weren't needed?

In any event I installed a data logging system from PLXDEVICES and it seems to bear out that the original chips are working fine. 12.5-12.75/99 at 18 lbs and then much leaner at idle or when when the throttle is closed.
It even works fine up to 20lbs.

It's the Weber Marelli map based system.

Has anyone else used the PLXDEVICES data acquisition system yet?

Bob S.

 

aircon-
you can easilly tell the sensor type by counting the number of wires on the O2 sensor. If it has 5 wires, it is a wideband sensor. If there are less than 4 wires, it is a narroband. If there are 4 wires, it could be either. The reason is, the motec m48 uses a special narrow band sensor for wide band capture, this is the bosch lm-11 and has 4 wires. The only real way to tell between the run-of-the-mill 4 wire narrowband and the special lm-11 "wide band" is to tell by the part number on the sensor. Hope that all makes sense. It would be helpful if you specified which ecu is installed. The m800 cannot use the lm-11.

If you are running lambda at 1, and richer at WOT, everything sounds normal.

yes, cutting fuel for RPM limiting is best for sequential systems. Cutting ignition only can cause unburnt fuel to collect and backfire, or stress the cats. The ecu will randomly cut cylinders so it is a soft limit. There is a second threshold for a hard limit, where all fuel can be cut.