Motronic - long, & not for the uninitiated.

[George M]

hehehe...I love your style Winfred!

[MarkD]

Where did you find information that the computer ignores the O2 readout at WOT? As I understand it from riding in cars w/ A/F meters, thats the only time that you can actually read the gauge accurately, as at partial throttle it jumps all over the place. Not saying that the ECM doesn't ignore it, just wondering where you read that.

Good luck

The DME can't use the O2 sensor at WOT because the sensor output is very non-linear. (it's not a wideband O2 sensor) Since the WOT a/f ratio is not close to stoichiometric (and the narrowband sensor wants to see an excursion through this point) the DME runs open-loop in WOT. Some new cars have wideband sensors that allow sampling the O2 sensor at WOT also. The New Beetle, some Porsches, and Cadillacs have wideband O2 sensors.

(edited after posting) : I forgot to mention that the reason you see the narrowband afr meter display juming all over the place is because the O2 sensor is switching between roughly .2V and .8V about 20 times a second. These two voltages indicate lean and rich, and .5V indicates lambda = 1.0

When running WOT, the a/f ratio will stay around 12.5 to 13.6 : 1


Mark

[DanDombrowski]

Interesting. BTW mark, I still have 2 of those chips at home from the group buy if you want me to send them somewhere or back to you.

The DME can't use the O2 sensor at WOT because the sensor output is very non-linear. (it's not a wideband O2 sensor) Since the WOT a/f ratio is not close to stoichiometric (and the narrowband sensor wants to see an excursion through this point) the DME runs open-loop in WOT. Some new cars have wideband sensors that allow sampling the O2 sensor at WOT also. The New Beetle, some Porsches, and Cadillacs have wideband O2 sensors.

Mark

[MarkD]

Interesting. BTW mark, I still have 2 of those chips at home from the group buy if you want me to send them somewhere or back to you.

Dan,

don't send them back here, please keep them in case someone wants them in the USA. If you were going to the Chicago meet I'd say take them there in case anyone is looking for one, but I don't think you'll be driving that far.

Mark

[DanDombrowski]

I'd love to go to the Chicago meet but no, thats too long to drive. Perhaps a South Florida meet if I'm in town when one goes on. I'll hang on to them in my office until whenever, its no big deal.

Dan,

don't send them back here, please keep them in case someone wants them in the USA. If you were going to the Chicago meet I'd say take them there in case anyone is looking for one, but I don't think you'll be driving that far.

Mark

[Bellicose Right Winger]

This is a fabulous discussion on the operation of the DME, thanks for taking the time Robin.

On the WOT issue, it's important to recognize that an engine produces maximum torque at 85-90% of lambda, where lambda is the ideal A/F Ratio. This is 10-15% richer then stoichiometric. The DME tries to achieve this and emissions are secondary, as they should be, when you're making a pass on a two lane road.

I was unaware of wide band O2 sensors, being a stuck in the '80s kinda of a guy. Although I can't imagine why anyone would want to monitor much less control emissions at WOT. Must be a regulation. Thanks for the insight.

....O2 sensor switching...? Mark, I suspect you mean the O2 sensor output varies .2-.8v as a result of exhaust gas composition change caused by the PID loop the DME uses to continuously vary injector durations. All this in a effort to keep O2 sensor output in the desired range.

Anyone know where to get the latest version (1999, I think) of the Bosch Technical Instruction - Motronic"? It seems to be out of print and should be required reading for all board members. I've got a early '80's version I think I can email.

Paul Shovestul

The DME can't use the O2 sensor at WOT because the sensor output is very non-linear. (it's not a wideband O2 sensor) Since the WOT a/f ratio is not close to stoichiometric (and the narrowband sensor wants to see an excursion through this point) the DME runs open-loop in WOT. Some new cars have wideband sensors that allow sampling the O2 sensor at WOT also. The New Beetle, some Porsches, and Cadillacs have wideband O2 sensors.

(edited after posting) : I forgot to mention that the reason you see the narrowband afr meter display juming all over the place is because the O2 sensor is switching between roughly .2V and .8V about 20 times a second. These two voltages indicate lean and rich, and .5V indicates lambda = 1.0

When running WOT, the a/f ratio will stay around 12.5 to 13.6 : 1


Mark

[Robin-535im]

Hi Robin,
what you posted is basically correct but there is still more that could be added. (such as timing CORRECTION MAPS that retard timing based on IAT and coolant temperature)

Also, the WOT maps are trimmed based on the value that the software sees it has to trim the Part Throttle (PT maps) by. Part Throttle mode is what you call "warm running". The DME switches between PT and WOT mode by looking at for the WOT switch on the TPS to close. This usually happens at around 75% of the gas pedal depression.

Since the software trims the WOT fuel maps, increasing fuel pressure or using bigger injectors does not work as well as could be expected, unless you adjust the WOT fuel maps in the chip to supply more fuel also.


Mark

So there is a timing correction map that retards the timing set by the PT map by looking up the inlet air and head temperatures... Is that adaptive or programmed in ROM?

Also - the WOT map trimmed by the accumulated pulse duration offset map from the lambda control just like the PT map. So all you have to do is program the WOT map higher by the ratio you want the WOT a/f ratio higher than the PT ratio? I.e., if your WOT fuel map is 10% richer than the PT map, the car will still run 10% richer at WOT even after the trim map is applied, right?

Good info!

[Robin-535im]

This is a fabulous discussion on the operation of the DME, thanks for taking the time Robin.

On the WOT issue, it's important to recognize that an engine produces maximum torque at 85-90% of lambda, where lambda is the ideal A/F Ratio. This is 10-15% richer then stoichiometric. The DME tries to achieve this and emissions are secondary, as they should be, when you're making a pass on a two lane road.

I was unaware of wide band O2 sensors, being a stuck in the '80s kinda of a guy. Although I can't imagine why anyone would want to monitor much less control emissions at WOT. Must be a regulation. Thanks for the insight.

....O2 sensor switching...? Mark, I suspect you mean the O2 sensor output varies .2-.8v as a result of exhaust gas composition change caused by the PID loop the DME uses to continuously vary injector durations. All this in a effort to keep O2 sensor output in the desired range.

Anyone know where to get the latest version (1999, I think) of the Bosch Technical Instruction - Motronic"? It seems to be out of print and should be required reading for all board members. I've got a early '80's version I think I can email.

Paul Shovestul

I'm at robin(nospam).ritter@ngc.com w/o the (nospam)

[Bill R.]

any confusion. Lambda is Stoichiometric, this is the ideal point where combustion is the closest to complete, the 10 to 15% richer that Paul is talking about is the air to fuel ratio that maximum power is produced at.

This is a fabulous discussion on the operation of the DME, thanks for taking the time Robin.

On the WOT issue, it's important to recognize that an engine produces maximum torque at 85-90% of lambda, where lambda is the ideal A/F Ratio. This is 10-15% richer then stoichiometric. The DME tries to achieve this and emissions are secondary, as they should be, when you're making a pass on a two lane road.

I was unaware of wide band O2 sensors, being a stuck in the '80s kinda of a guy. Although I can't imagine why anyone would want to monitor much less control emissions at WOT. Must be a regulation. Thanks for the insight.

....O2 sensor switching...? Mark, I suspect you mean the O2 sensor output varies .2-.8v as a result of exhaust gas composition change caused by the PID loop the DME uses to continuously vary injector durations. All this in a effort to keep O2 sensor output in the desired range.

Anyone know where to get the latest version (1999, I think) of the Bosch Technical Instruction - Motronic"? It seems to be out of print and should be required reading for all board members. I've got a early '80's version I think I can email.

Paul Shovestul

[winfred]

i use to be a parts runner for a euro shop a long time ago and the shop car was a 240 diesel volvo wagon with a 4 speed od stick, oh that was fun painting a tailgaters hood and grill black, it's that bosch ve injection pump (same as 524 td) lotsa power lotsa smoke at high rpm 4-5k, turbos with this pump are even better

hehehe...I love your style Winfred!