From: Kurt Rottner [kurt.rottner@gmx.net] Sent: Friday, March 02, 2001 7:40 AM To: 928 Subject: [928] RE: How does the brain learn? (long) Bill, >So my question is, does driving style really affect >the way the brain learns? If I disconnect the battery >and dive it hard, will it be even better? Or is it just >a matter of getting the full range of throttle under >some variety of conditions? it a pretty complicated system and there is quite some confusion around about what it does and what not. Here comes what I collected from the factory manuals, the owner's manual and various Bosch fuel injection literature: The brain stores different types of parameters with some of them continuously updated, some not. The latter are the parameters for the adaptive idle control. Erasing these can (but need not) cause the car to idle very rough after start-up. There are two possibilities to get these figures back: the quick one is to carry out a system adaptation. That takes about two minutes but you need to have the Bosch hammer. The second possibility is to let the car idle for a while to give the brain the chance to collect the necessary figures. Then there is another set of data which is not affected by the Bosch hammer but forms the basis of the adaptive system: For each parameter there is a set of pre-programmed values and second set of "variable" correction figures for this base set to adapt to match the settings to the individual engine (but not to your driving style) These correction figures are learned during normal operation using sensors (e.g. knock sensors) and closed-loop control. The problem with closed-loop control is that it typically takes many iterations to reach the optimum point, so the better the figures to start with, the faster optimum will be reached. One example is the max ignition advance, right before knocking occurs. During acceleration where the engine runs up quickly through the rev band, it is hardly possible to use the knock sensors for closed-loop optimization, due to the quickly changing conditions. Instead the brain uses the correction figures it found to work in the past and start from there. If knocking occurs, the ignition is retarded, if not, it gets advanced a little more and a new correction value is stored for the respective engine condition. If these figures are erased, you might find your car to knock a little or be down on power until you have "probed" the full rev band for a couple of times. Then there is a third set of parameters which also gets continuously updated but to match the engine to your driving style. They are updated with a time constant of about 10 minutes. The brains try to optimize the settings for the operating conditions: if you use only little power, it tunes the settings for max economy, if you open it up, it is tuned for max power. E.g. if you leisurely cruise around town for a while and then decide to drive a little more spirited, it will take about 10 minutes until the car reaches it's full performance again. So after disconnecting the battery you should expect the car to idle rough and be a little lower on power for the first miles. If you can't drive it spirited during the first outing, don't worry, sooner of later you will have the chance and all should be back to normal again. Hope that helps Kurt 90 S4 Auto schwarzmetallic 928 OC, PCA Germany Region From: Jim Bailey [jim@928intl.com] Sent: Tuesday, March 06, 2001 1:43 PM To: 928 Subject: [928] Re: LH jetronic brain / adaptive ???? Tom Middleton posted ............"And as a final note I did my first runs (four in a row) and then disconnected my battery for 10 minutes to "reset the brain". Then I ran two more times. The numbers showed a slight GAIN after disconnecting. " ...................... Tom tested the learning theory for the L H Brain .... According to Bosche only the Motronic Brains with the designation M L .3 are adaptive no 928 has Motronic ........So the assometer dyno strikes again so much for the ten minutes of "spirited driving" our L H Jetronic Brains are not that smart.............or reliable ... there is so much miss-information being repeated as FACT ...But politics would indicate that if you repeat something enough times it must be true . From: Kurt Rottner [kurt.rottner@gmx.net] Sent: Wednesday, March 07, 2001 3:24 AM To: 928 Subject: [928] Re: LH jetronic brain / adaptive ???? Jim >.... According to Bosche ... no 928 has Motronic ...... Where do you get this from ? According to BOSCH "Motronic" designates an engine management system (incl all sensors) that integrates air/ fuel delivery with fully electronic ignition. The system calculates the engine load as leading parameter; going from there it determines the optimum ignition advance and injector opening duration taking into account engine temperature, lambda signal and other optional signals (e.g. knock sensors). That is exactly what happens in the 928. It does not say on how many boards or in how many boxes this system has to reside in. >..But politics would indicate that if you repeat > something enough times it must be true . OK, let's see what the literature says about it: You seem to be familiar with Charles Probst's book on "Bosch Fuel injection and Engine Management. The application list on page 14 in the overview section lists the 928 S4 as "LH-Motronic" equipped. Might still be a rumour?! So, lets see what Bosch says: Go to: http://www.bosch.de/aad/en/start/index.htm click on "Vehicle ID" click "Go to search menu" Enter data for 928 Select "ignition/fuel air supply" and see how they call the LH brain : "control unit Jetronic/Motronic" Guess it's time to send a letter to Bosch and tell them that what they call MOTRONIC in the 928 is in fact not a Motronic but something else! Kurt From: Wally Plumley [wplumley@bellsouth.net] Sent: Wednesday, March 07, 2001 10:14 AM To: 928 Subject: [928] Re: LH jetronic brain / adaptive ???? At 03:23 AM 3/7/01, Kurt Rottner wrote: >Jim > > >.... According to Bosche ... no 928 has Motronic ...... While you did include the .... in the center, the full quote is: "Tom tested the learning theory for the L H Brain .... According to Bosche only the Motronic Brains with the designation M L .3 are adaptive no 928 has Motronic In the Probst book, page 7 in the overview: "In Bosch 'Motronic' engine-management systems, fuel delivery control and ignition timing controls are combined in one control unit that processes all of the necessary engine information." On page 9 in the Overview: "Bosch engine-management systems are often grouped under the single term 'Motronic'. This can be confusing, because while the original Bosch engine-management system was called Motronic to differentiate it from the Jetronic systems, there are now many different Motronic-type engine-management systems. So when you see a system called 'Motronic', make sure you know what type it is." Does Bosch consider "Jetronic/Motronic" a different system form "Motronic"? >Guess it's time to send a letter to Bosch and tell them that what they call >MOTRONIC in the 928 is in fact not a Motronic but something else! Perhaps a "Jetronic/Motronic"? I think that there is a lack of communication here. A couple of points: The definition of "Motronic" is obviously not very clear, as show by the varying references in the Probst book. I would suspect that Bosch Marketing got involved, and pushed "Motronic" as a new buzz-word. I don't know whether the 928 system, with two separate ECUs would qualify as "Motronic" or not, and really don't care. The real point that Jim was trying to make is that the 928 engine-management system does not learn your driving style, despite the wishful thinking and urban legends of owners. The system does have adaptive control, in that it will correct the engine idle and air/fuel ratio in response to air leaks, A/C on or off, temperature, etc. It appears that it does not decide, "Well, the boss is in a hurry today - I'll change the engine mapping points to give better performance, and screw the fuel economy!" Our engine-management systems were designed in the early 1980's, and never upgraded. They are really pretty primitive compared to today's cars. Wally From: Dan Prantl [dprantl@hotmail.com] Sent: Wednesday, March 07, 2001 10:53 AM To: 928 Subject: [928] Re: LH jetronic brain / adaptive ???? Wally et al, "Motronic" and "Jetronic" are names that really don't matter; you have to look at the version of the system. The Bosch website quotes the 928 5.0 liter as having the LH 2.3 system. In fact, even the 1995 GTS 5.4 liter has LH 2.3. This system, like the LH 2.2 is NOT adaptive. The first adaptive version that Bosch made was the LH 2.4 (which is in my wife's '90 SAAB 9000T with DI). Dan '86 928S 5-spd w/LSD From: Wally Plumley [wplumley@bellsouth.net] Sent: Thursday, March 08, 2001 2:02 PM To: 928 Subject: [928] Re: LH jetronic brain / adaptive ???? At 01:32 PM 3/8/01, Tom Middleton wrote: >I thought it would run rough after reconnecting the power, but the car >fired up normally and the runs were conducted as soon as I got everything >connected and started up....I was really surprised that numbers went up..? > Very interesting ! The LH ECU does adapt to certain conditions for an individual engine. This allow the ECU to compensate for things like false air (vacuum leaks), injector imbalance, etc. It is worth noting that if the engine is in perfect condition, the pre-programmed maps built into the ECU are an exact match for the engine conditions. The more that is wrong with the engine, the more adapting the ECU has to do. The moral might be - If your engine runs/idles poorly immediately after you disconnect/reconnect the battery or ECU, there may be some problems that the ECU has to compensate for. If, on the other hand, your engine runs very well immediately after the battery or ECU have been disconnected/reconnected, there shouldn't be much wrong with it! Wally Plumley 928 Specialists "Hacksaw" - One of a family of cutting tools built on the "Ouija Board Principle". It turns human energy into crooked, unpredictable motion, and the more you attempt to control its course, the worse the results.