964 DME fault code - help needed
06-30-2003, 02:53 AM
#16
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Thread Starter
Correction:
There are shielded wires on the 964 DME harness that go to the hall sensor, the knock sensors, and the flyhweel sensors. The hall sensor one looks sort of like twisted pair wire. I only noticed that while fixing my connector today. Shielding is used since the signal levels on those sensors are much smaller than 12V. When I rewrapped my harness with new cloth tape a couple of month ago I didn't pay close attention to this.
LorenFB, from your web site it seems you work with automotive electronics. Allow me a couple of comments (without being offended):
- When I read about later model Porsche DME's not allowing for more agressive ignition timings due to the knock sensors I was a little surprised. The stock timing maps for WOT and closed loop operation on the 964 are nowhere close to knocking but very conservative. Depending on the fuel quality used there is certainly room for improvement before the knock sensors kicks in. As a matter of fact a stock 964 chip has 4 timing maps that get choosen based on the region code plug. This is to accomodate different pump fuel qualities available in different regions of the world.
- On the 993 DME's knock control is adaptive and makes things a little more complicated. The DME "learns" and retains that information until it is reset.
- The Bosch DMEs have pretty well protected in/outputs suitable for the comparably rough automotive environment. As long as you don't disconnect the battery while the engine is running or kill ground they seem to be very "forgiving"
On the Bosch 1.5 Motronic (964) the hall sensor is used to identify which cylinder is firing. The crank sensor alone only sees 360 degrees. This information is used in combination with the two knock sensors (one on each bank) to allow to retard individual cylinders for knock control.
But then again I am only a self-educated hobby wrench trying to have some fun on weekends.
Question: How would I have noticed on a stock 964 that it is in limp mode? It can't be the check engine light since I did not get that with the disconnected hall sensor. And the average 964 owner probably does not read out his/her fault codes him/herself either...
The factory WS manual does not say much about what happenes without the hall sensor working.
Peace,
Ingo
There are shielded wires on the 964 DME harness that go to the hall sensor, the knock sensors, and the flyhweel sensors. The hall sensor one looks sort of like twisted pair wire. I only noticed that while fixing my connector today. Shielding is used since the signal levels on those sensors are much smaller than 12V. When I rewrapped my harness with new cloth tape a couple of month ago I didn't pay close attention to this.
LorenFB, from your web site it seems you work with automotive electronics. Allow me a couple of comments (without being offended):
- When I read about later model Porsche DME's not allowing for more agressive ignition timings due to the knock sensors I was a little surprised. The stock timing maps for WOT and closed loop operation on the 964 are nowhere close to knocking but very conservative. Depending on the fuel quality used there is certainly room for improvement before the knock sensors kicks in. As a matter of fact a stock 964 chip has 4 timing maps that get choosen based on the region code plug. This is to accomodate different pump fuel qualities available in different regions of the world.
- On the 993 DME's knock control is adaptive and makes things a little more complicated. The DME "learns" and retains that information until it is reset.
- The Bosch DMEs have pretty well protected in/outputs suitable for the comparably rough automotive environment. As long as you don't disconnect the battery while the engine is running or kill ground they seem to be very "forgiving"
On the Bosch 1.5 Motronic (964) the hall sensor is used to identify which cylinder is firing. The crank sensor alone only sees 360 degrees. This information is used in combination with the two knock sensors (one on each bank) to allow to retard individual cylinders for knock control.
But then again I am only a self-educated hobby wrench trying to have some fun on weekends.
Question: How would I have noticed on a stock 964 that it is in limp mode? It can't be the check engine light since I did not get that with the disconnected hall sensor. And the average 964 owner probably does not read out his/her fault codes him/herself either...
The factory WS manual does not say much about what happenes without the hall sensor working.
Peace,
Ingo
06-30-2003, 03:09 AM
#17
Ingo wrote: "But then again I am only a self-educated hobby wrench trying to have some fun on weekends"
I'd like to add to that by saying you're doing a damn good job understanding your hobby!!!
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
I'd like to add to that by saying you're doing a damn good job understanding your hobby!!!
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
06-30-2003, 03:58 AM
#18
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Thread Starter
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Lorenfb:
<strong> If this were
a real 964 the problem would be much easier. The
3.2 retro is somtimes a problem, but the 964
retro is a much greater problem.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Huh, How so? This 3.6 is very real and smokes real 964's even in limp mode with 280HP, 2300 pounds and a 7:31 ring and pinion.
Seriously, a 964 only adds the diagnosis port. Other than that my retro is much simpler than a 964 with all its other control units.
Ingo
<strong> If this were
a real 964 the problem would be much easier. The
3.2 retro is somtimes a problem, but the 964
retro is a much greater problem.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Huh, How so? This 3.6 is very real and smokes real 964's even in limp mode with 280HP, 2300 pounds and a 7:31 ring and pinion.
Seriously, a 964 only adds the diagnosis port. Other than that my retro is much simpler than a 964 with all its other control units.
Ingo
06-30-2003, 05:27 AM
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As you said the spark cal is quite conservative so losing knock control probably won't cost you many ponies. The other reason for knowing which phase you are on (the only thing the dizzy sensor tells you) is to provide sequential injection. This is mainly an emissions thing, to avoid injecting onto an open inlet valve which causes high HC's.
So not having this sensor working isn't a big deal really.
So not having this sensor working isn't a big deal really.
06-30-2003, 06:47 AM
#20
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The Bosch 964 system and the 1994 and 1995 993s is the Bosch 2.1 Motronic. 1996 and up is the Bosch 5.1 system.
The hall sensor tells the DME when No 1 piston is at TDC. According to the factory this is quite an important function. The hall sensor input is part of the timing function not fuel injection function. However there is some disagreement about the importance as can be seen by certain posts on this thread and other thread. I am reliably informed that if the hall sensor has actually failed and providing no real input to the DME that the engine should not start or keep running. Others tell me that they have started their 964s with the hall sensor disconnected. Not something I would recommend.
Limp home mode is just that. You will know when you are it. You have no power and very few rpms to work with. Speed is limited to circa 80 kph (50 mph). It is very rare for somebody to actually enter limp home mode.
Ciao,
Adrian
911C4
The hall sensor tells the DME when No 1 piston is at TDC. According to the factory this is quite an important function. The hall sensor input is part of the timing function not fuel injection function. However there is some disagreement about the importance as can be seen by certain posts on this thread and other thread. I am reliably informed that if the hall sensor has actually failed and providing no real input to the DME that the engine should not start or keep running. Others tell me that they have started their 964s with the hall sensor disconnected. Not something I would recommend.
Limp home mode is just that. You will know when you are it. You have no power and very few rpms to work with. Speed is limited to circa 80 kph (50 mph). It is very rare for somebody to actually enter limp home mode.
Ciao,
Adrian
911C4
06-30-2003, 01:35 PM
#21
Instructor
Thread Starter
Hm Adrian,
my hall sensor was for sure disconnected for at least a couple of weeks. As I said all wires were ripped clean inside the rubber boot. The engine ran fine and it was by no means limping. It was fast like hell. I smoked a 993 Strossek who was afraid of paint chips during a back-road driving event.
According to some other write-up the hall sensor is needed to identify which cylinder is knocking.
I thought 964's have a multipoint injection where all injectors fire at the same time.
Ingo
my hall sensor was for sure disconnected for at least a couple of weeks. As I said all wires were ripped clean inside the rubber boot. The engine ran fine and it was by no means limping. It was fast like hell. I smoked a 993 Strossek who was afraid of paint chips during a back-road driving event.
According to some other write-up the hall sensor is needed to identify which cylinder is knocking.
I thought 964's have a multipoint injection where all injectors fire at the same time.
Ingo
06-30-2003, 03:05 PM
#22
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Dear Ingo,
I cannot see how a halls ensor mounted in the primary distributor is going to tell the DME which cylinder is knocking. That is what the knock sensors are for.
How can all the injectors fire at the same time. Pretty silly pumping fuel into the cylinder on the exhaust stroke. They are pulse injectors and are opened to inject fuel to mix with the air for ignition. Once the fuel is injected they close. Boy I wish Bentley would hurry up with my book.
Ciao,
Adrian
911C4
I cannot see how a halls ensor mounted in the primary distributor is going to tell the DME which cylinder is knocking. That is what the knock sensors are for.
How can all the injectors fire at the same time. Pretty silly pumping fuel into the cylinder on the exhaust stroke. They are pulse injectors and are opened to inject fuel to mix with the air for ignition. Once the fuel is injected they close. Boy I wish Bentley would hurry up with my book.
Ciao,
Adrian
911C4
06-30-2003, 04:25 PM
#23
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Thread Starter
Adrian,
think about it: The crank sensor only has a 360 degree marker (missing a couple of teeth). It has no way of knowing if cyl 1 is on the compression stroke at TDC or the exhaust stroke. The dizzy is running at half crank speed and this signal will allow the DME to "know" which stroke cyl 1 on is at TDC.
This information allows the DME to retard the spark on an individual cylinder when knocking is detected.
I will check about the sequential vs. multipoint injection and come back on that topic.
Ingo
think about it: The crank sensor only has a 360 degree marker (missing a couple of teeth). It has no way of knowing if cyl 1 is on the compression stroke at TDC or the exhaust stroke. The dizzy is running at half crank speed and this signal will allow the DME to "know" which stroke cyl 1 on is at TDC.
This information allows the DME to retard the spark on an individual cylinder when knocking is detected.
I will check about the sequential vs. multipoint injection and come back on that topic.
Ingo
06-30-2003, 05:36 PM
#24
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Adrian wrote </font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> How can all the injectors fire at the same time. Pretty silly pumping fuel into the cylinder on the exhaust stroke. ... Boy I wish Bentley would hurry up with my book. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">No reason the injectors cannot all fire at the same time, because they don't inject directly into the cylinder. They inject into the intake runners just upstream of the intake valves, and of course the intake valve is generally closed on the exhaust stroke. We have "port injection", not "direct injection".
Air-cooled piston engines made by Lycoming & Continental for airplanes have continuous port fuel injection where the injectors spray fuel continuously. Also the "CIS" in Bosch CIS (e.g. used on the 911SC?) stands for Continuous Injection System, doesn't it?
I too wish Bentley would hurry up with your book! I want one. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
-Dave
Air-cooled piston engines made by Lycoming & Continental for airplanes have continuous port fuel injection where the injectors spray fuel continuously. Also the "CIS" in Bosch CIS (e.g. used on the 911SC?) stands for Continuous Injection System, doesn't it?
I too wish Bentley would hurry up with your book! I want one. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
-Dave
06-30-2003, 09:43 PM
#25
Yes, I think everybody is waiting for Adrian's book....hint, hint....
The 964 uses sequential fuel injection, which is why the cylinder number is on the wire harness.
The previous 911 3.2 and also the 928 use "bank injection" where a number of injectors fire at the same time.
According to the Porsche 964 intro book; the hall sender is used to sense the position of cylinder #1 and for assignment of the knock sensors, by using the engine firing order. The knock sensor system adjusts timing for selected cylinders.
The 964 uses sequential fuel injection, which is why the cylinder number is on the wire harness.
The previous 911 3.2 and also the 928 use "bank injection" where a number of injectors fire at the same time.
According to the Porsche 964 intro book; the hall sender is used to sense the position of cylinder #1 and for assignment of the knock sensors, by using the engine firing order. The knock sensor system adjusts timing for selected cylinders.
07-01-2003, 02:28 AM
#26
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Thread Starter
My 964 engine sure idles better now that the hall sensor issue is fixed. I also notice less back fire on decel and cold engine.
I first thought my lighter flywheel/clutch combo(in comparison to the stock dual mass setup) was the main cause for having a hard time to catch decel events properly. When the engine was cold idle was really unstable, too and hunting. I know there are chips with modified idle programs (Cyntex, Authority, etc). I use a RUF chip once in a while but my version does not seem to have the light flywheel mod.
Maybe the engine was not using sequential injection without the hall sensor. That would explain things.
Ingo
I first thought my lighter flywheel/clutch combo(in comparison to the stock dual mass setup) was the main cause for having a hard time to catch decel events properly. When the engine was cold idle was really unstable, too and hunting. I know there are chips with modified idle programs (Cyntex, Authority, etc). I use a RUF chip once in a while but my version does not seem to have the light flywheel mod.
Maybe the engine was not using sequential injection without the hall sensor. That would explain things.
Ingo
07-01-2003, 10:27 AM
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Absolutely right Ingo, sequential injection would give you more stable combustion improving your idle quality and reducing combustion in the exhaust.
Adrian, of course you can fire all the injectors together as engine managemenet systems of old did for years. The fuel just puddles in the inlet manifold until the inlet valve opens and the charge is drawn in. Ideally of course you spray onto the back of the closed valve just before it opens, giving the fuel just enough time to vapourise before being sucked in. But even firing the injector a full 360 degs out gives a pretty minimal difference in torque output.
As there is only one knock sensor per bank the EMS can't which cylinder is knocking unless it knows which cylinder is firing. The only way it can do this is by using the accurate timing information from the crank position sensor (high reslution) and the phase indication from the phase sensor in the dizzy (low resolution - not used for timing). A knock 'window' is then calculated for each cylinder and the sensor output is integrated during this window generating a knock level for each cylinder allowing the system to control each cylinder's spark advance individually.
Losing the dizzy sensor would only lose the phase information (i.e. TDC #1 or #4) and not have any serious effects other than those listed above.
Trust me on this, I write engine management software for a major vehicle manufacturer for a living.
Cheers
Simon
Adrian, of course you can fire all the injectors together as engine managemenet systems of old did for years. The fuel just puddles in the inlet manifold until the inlet valve opens and the charge is drawn in. Ideally of course you spray onto the back of the closed valve just before it opens, giving the fuel just enough time to vapourise before being sucked in. But even firing the injector a full 360 degs out gives a pretty minimal difference in torque output.
As there is only one knock sensor per bank the EMS can't which cylinder is knocking unless it knows which cylinder is firing. The only way it can do this is by using the accurate timing information from the crank position sensor (high reslution) and the phase indication from the phase sensor in the dizzy (low resolution - not used for timing). A knock 'window' is then calculated for each cylinder and the sensor output is integrated during this window generating a knock level for each cylinder allowing the system to control each cylinder's spark advance individually.
Losing the dizzy sensor would only lose the phase information (i.e. TDC #1 or #4) and not have any serious effects other than those listed above.
Trust me on this, I write engine management software for a major vehicle manufacturer for a living.
Cheers
Simon
07-01-2003, 10:57 AM
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What a great thread - like watching a bunch of sharp shooters in an old western...
...LOTS of practical knowledge stuck in you guys heads...glad some of it is getting onto teh board...
Not intending to cause offence, but it is very useful to have the opinions of someon ewho specilaises in Engine management software. Combined with others' specific motronic knowledge, this could all be quite useful.
...LOTS of practical knowledge stuck in you guys heads...glad some of it is getting onto teh board...
Not intending to cause offence, but it is very useful to have the opinions of someon ewho specilaises in Engine management software. Combined with others' specific motronic knowledge, this could all be quite useful.
07-01-2003, 12:00 PM
#30
Yes, the Hall sensor in the distributor/cam is
needed for sequential fuel injection and for
direct ignition systems (DIS).
The Hall is not needed when using an ignition
distributor for spark distribution, but is needed
to run in the sequential fuel injection mode
versus bank injection. The sequential fuel
injection for the 964 provided mostly better
emissions control and smoother running.
You're all assuming the early DMEs (964) used the
knock sensors to control the timing for each
cylinder versus all the cylinders. OBDII ('96)
cars with misfire control do have this capability,
but they use more than two knock sensors. The
knock sensors in the 964 were used mainly to
optimize performance (run at close to max.
advance) and for better emissions control.
The firmware in the 964 DME was a major advance
over the 3.2 Carrera Motronic, but present day
automotive electronic systems have advanced
significantly since the 964 days.
Loren
'88 3.2
Systemsc.com
needed for sequential fuel injection and for
direct ignition systems (DIS).
The Hall is not needed when using an ignition
distributor for spark distribution, but is needed
to run in the sequential fuel injection mode
versus bank injection. The sequential fuel
injection for the 964 provided mostly better
emissions control and smoother running.
You're all assuming the early DMEs (964) used the
knock sensors to control the timing for each
cylinder versus all the cylinders. OBDII ('96)
cars with misfire control do have this capability,
but they use more than two knock sensors. The
knock sensors in the 964 were used mainly to
optimize performance (run at close to max.
advance) and for better emissions control.
The firmware in the 964 DME was a major advance
over the 3.2 Carrera Motronic, but present day
automotive electronic systems have advanced
significantly since the 964 days.
Loren
'88 3.2
Systemsc.com