Please advise how to set ignition timing properly using the timing lamp - I never did it before! My car is 635 CSi 1980; M90 motor with breakerless distributor with double action vacuum box (2 hoses for advance and retard).
The inductive clamp of the lamp has to be on the spark plugs' wire of the first cylinder - isn't it?
Next - shall I remove both vacuum pipes from the distributor and plug them?
At what engine speed shall I check the timing? What is the advance angle for this speed?
I've read somewhere that after adjustment it's recommended to connect vacuum hoses back to the distributor and check the timing again at idle. Is it right? What if strobe would show differently than during adjustment at control RPM?
I found the control window on the clutch housing near the starter. How to estimate if tab on housing is just in front of ball on flywheel? Looking from the top I see them aligned but in fact they are moved one to each other due to the angle I give a look. If the real offset is about 2,5 mm (1/10") this means mistake of 1°.
Ignition timing setting
Moderators: GRNSHRK, ron, bfons
this is all described in some detail in the workshop manual. Exact settings vary with model, fuel quality, and exact distributor fitted, so be careful to use the correct settings.
Also, do note that the timing marks are not as other cars; they are marked in German initials, not English.
cheers
Also, do note that the timing marks are not as other cars; they are marked in German initials, not English.
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Looking for the values of ignition advance to be set in my car I found 22°@1800 rpm. It's for Bosch distributor 0 267 302 008, measurement with both vacum hoses disconnected.
The rest of information about distributor is:
Centrifugal advance - begins @1000 rpm; ends @4500 rpm; max control range 33° at crankshaft
Vacuum advance - begins @180 mbar; ends @307 mbar; max control range 10° at crankshaft
Vacuum retard - begins @153 mbar; ends @280 mbar; max control range 10° at crankshaft
It's according to owner's manual. Great.
But life is not easy - I've got the ignition advance curve from Bosch for this distributor - see the drawing. It makes me confused - nothing corresponds to manual. The advance (2) and shaft speed (1) values on the chart refers to cam shaft revolutions so we have to multiply them by 2 to have motor's rpm and advance on crankshaft. Could anybody explain:
1. Why there are two lines for each parameter ?
2. Upper curves refers to centrifugal advace - isn't it?
3. There is max advance of 22° on the chart - there's 33° mentioned in manual as max range. What's going on?
4. Why advance drops down between 3000 and 6000 rpm? The centrifugal weights rotates faster and faster so they should stop on the stops in the distributor.
The rest of information about distributor is:
Centrifugal advance - begins @1000 rpm; ends @4500 rpm; max control range 33° at crankshaft
Vacuum advance - begins @180 mbar; ends @307 mbar; max control range 10° at crankshaft
Vacuum retard - begins @153 mbar; ends @280 mbar; max control range 10° at crankshaft
It's according to owner's manual. Great.
But life is not easy - I've got the ignition advance curve from Bosch for this distributor - see the drawing. It makes me confused - nothing corresponds to manual. The advance (2) and shaft speed (1) values on the chart refers to cam shaft revolutions so we have to multiply them by 2 to have motor's rpm and advance on crankshaft. Could anybody explain:
1. Why there are two lines for each parameter ?
2. Upper curves refers to centrifugal advace - isn't it?
3. There is max advance of 22° on the chart - there's 33° mentioned in manual as max range. What's going on?
4. Why advance drops down between 3000 and 6000 rpm? The centrifugal weights rotates faster and faster so they should stop on the stops in the distributor.
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- Bosch 0 237 302 008.jpg (291.93 KiB) Viewed 5567 times
You did well to find that chart! But I'm not sure how helpful it is in the real world.
I think that those curves are meant for use as a comparison chart when you are testing your distributor in a distributor testing machine. This means that the angles are half crank angles and the speeds are half crank speeds. It also shows you what happens if you test each vacuum circuit separately. The double lines are to show the allowable range. If you are just wanting to set the distributor up in the car and test function I highly recommend that you do not use this chart; you are just gonna confuse yourself.
Realistically, on the car the check you do is typically to check the integrity of the vacuum lines and the capsule, and check that the centrifugal springs are present and not broken. Then you
a) set the timing (vacuum disconnected) at the recommended 'knee' speed.
b) check the centrifugal advance works as described at different speeds
c) check the vacuum advance (static)
d) check that the centrifugal +vacuum works as described at different speeds.
This procedure will allow the system to be checked and set accurately enough for most folk, and any large errors will become apparent. It is well described in (say) the E12 Haynes manual.
There is much confusion re this model of distributor because it is described as having a 'vacuum retard' on it. It has no such thing. It simply has two vacuum tappings so that it measures the differential pressure across the TB, (in contrast to simpler distributors that measure the relative inlet vacuum w.r.t. to atmospheric pressure). The system allows for the pressure drop in the AFM and also the consequences of a blocked air filter.
If you test both parts of the vacuum system separately, it appears that it is possible for the distributor to retard the ignition timing in response to a vacuum. In reality it never does this because there is always a bigger vacuum on the other tube and this always results in net advance with more vacuum, never net retard.
[edit; remember that this is a hall effect distributor and there is also a certain amount of capacitance on the output. Both these things result in a short time delay between the phase of the rotor and the trigger point of the ignition output. I think that this is the reason that the ignition timing appears to retard itself slightly at higher speeds; a fixed delay would have this effect when plotted in those parameters]
hth
cheers
I think that those curves are meant for use as a comparison chart when you are testing your distributor in a distributor testing machine. This means that the angles are half crank angles and the speeds are half crank speeds. It also shows you what happens if you test each vacuum circuit separately. The double lines are to show the allowable range. If you are just wanting to set the distributor up in the car and test function I highly recommend that you do not use this chart; you are just gonna confuse yourself.
Realistically, on the car the check you do is typically to check the integrity of the vacuum lines and the capsule, and check that the centrifugal springs are present and not broken. Then you
a) set the timing (vacuum disconnected) at the recommended 'knee' speed.
b) check the centrifugal advance works as described at different speeds
c) check the vacuum advance (static)
d) check that the centrifugal +vacuum works as described at different speeds.
This procedure will allow the system to be checked and set accurately enough for most folk, and any large errors will become apparent. It is well described in (say) the E12 Haynes manual.
There is much confusion re this model of distributor because it is described as having a 'vacuum retard' on it. It has no such thing. It simply has two vacuum tappings so that it measures the differential pressure across the TB, (in contrast to simpler distributors that measure the relative inlet vacuum w.r.t. to atmospheric pressure). The system allows for the pressure drop in the AFM and also the consequences of a blocked air filter.
If you test both parts of the vacuum system separately, it appears that it is possible for the distributor to retard the ignition timing in response to a vacuum. In reality it never does this because there is always a bigger vacuum on the other tube and this always results in net advance with more vacuum, never net retard.
[edit; remember that this is a hall effect distributor and there is also a certain amount of capacitance on the output. Both these things result in a short time delay between the phase of the rotor and the trigger point of the ignition output. I think that this is the reason that the ignition timing appears to retard itself slightly at higher speeds; a fixed delay would have this effect when plotted in those parameters]
hth
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Thank you Brucey. Absolutelly great explanation about descending curve at higher rpms. Timing curve by Bosch I received by case and quickly found it was not to be very usefull - interesting to examine the distributor could be a curve of advance angles with summarized centrifugal and vacuum effect. I still try to find the reason my 6 is lazy to accelerate from idle up to about 2500 rpm. I started from the easiest to check - the ignition.
Is somewhere pdf version of E12 Haynes manual available in the net to find the procedure You've described in a)-d)?
Is somewhere pdf version of E12 Haynes manual available in the net to find the procedure You've described in a)-d)?
I don't know of an online version of that manual. I'd suggest looking on the firstfives website for this kind of thing because they (of course) use the exact same setup.
I didn't mention this before but the front pulley is where the timing marks are easiest to see with a strobe light. However because the front pulley is a bonded rubber assy there is always a chance that the parts of the pulley assy have moved and the marks are no longer accurate.
If in doubt you can check the relationship of the flywheel marks with the front pulley marks, or verify TDC with a dial indicator.
BTW if the car has a hesitation below 2500rpm I'd suggest that the fuelling is the first port of call. You don't say if you are running open loop or closed loop but in either case there is plenty of scope for poor running.
Some common faults are;
- air leaks
- worn AFM
IIRC the later Bosch EFI systems were fundamentally different in several respects, in particular the whole sense of the AFM output is different. I think this was to give more reliable fuelling should there be any kind of glitch in the AFM output.
cheers
I didn't mention this before but the front pulley is where the timing marks are easiest to see with a strobe light. However because the front pulley is a bonded rubber assy there is always a chance that the parts of the pulley assy have moved and the marks are no longer accurate.
If in doubt you can check the relationship of the flywheel marks with the front pulley marks, or verify TDC with a dial indicator.
BTW if the car has a hesitation below 2500rpm I'd suggest that the fuelling is the first port of call. You don't say if you are running open loop or closed loop but in either case there is plenty of scope for poor running.
Some common faults are;
- air leaks
- worn AFM
IIRC the later Bosch EFI systems were fundamentally different in several respects, in particular the whole sense of the AFM output is different. I think this was to give more reliable fuelling should there be any kind of glitch in the AFM output.
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Answering Brucey’s question I run open loop. Many years ago car was upgraded with G-Kat with lambda probe and some electronic device cut-in to the main control unit harness. I had switched it off and observed ANY difference afterwords.
I’ve checked real distributor’s characteristic with timing lamp. I measured advance in different RPMs for vacuum connected and disconnected. See chart below for two different distributors. Generally Brucey’s remark that factory chart by Bosch is unuseful in real life is perfect true.
DISTRIBUTOR 1 (red lines)
This one was originally in my car. First thing I noticed in strobe light was jumping reference mark on the flywheel in between 600-1000 rpm range. This partly explains not smooth idle – the irregular “flashâ€
I’ve checked real distributor’s characteristic with timing lamp. I measured advance in different RPMs for vacuum connected and disconnected. See chart below for two different distributors. Generally Brucey’s remark that factory chart by Bosch is unuseful in real life is perfect true.
DISTRIBUTOR 1 (red lines)
This one was originally in my car. First thing I noticed in strobe light was jumping reference mark on the flywheel in between 600-1000 rpm range. This partly explains not smooth idle – the irregular “flashâ€
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- Bosch 0 237 302 008_adv.curve.jpg (545.94 KiB) Viewed 5451 times
that is some nice detective work there!
It looks like the Distributor #1 had some problems. I suspect that the first centrifugal spring was a little worn, and that the vacuum mechanism may have been sticky (or worse).
I have seen some remarkable improvements in engine power and responsiveness with changes in ignition timing too.
If you would like a slightly mad project, it might be worth looking at using the ignition computer from a later LE jetronic system, as fitted to the 2.8litre M30 engine.
This uses a distributor (with vacuum and centrifugal advance as normal) to provide the primary timing signal for the whole system (fuel and spark) and similarly an ignition amplifier is used to drive the coil. AFM, TPS, and CTS functions are as per other Jetronic systems (although the compenents are different in detail).
However on LE jetronic there is an additional box of tricks; an ignition computer. This accepts both fuel signal (from the main ECU that drives the injectors) and the distributor signal. Within the box there is essentially a mapped ignition system which alters the ignition timing beyond what the distributor manages alone, by using the injector signal as a third axis to a map. [You can find a potted version of these workings in the Bosch Auto electronics handbook from the 1990s BTW]
Now, in fairness, I don't think this additional element is intended to give more power; I think it is intended to give better fuel economy. However it might be possible to graft it into an earlier L-Jet system like yours....
I have an M90 engine build underway in which I have adapted the entire 2.8 LE-Jet engine management to run the short stroke 3.5litre motor. Initial impressions from a short test run of the engine are very good.
cheers
It looks like the Distributor #1 had some problems. I suspect that the first centrifugal spring was a little worn, and that the vacuum mechanism may have been sticky (or worse).
I have seen some remarkable improvements in engine power and responsiveness with changes in ignition timing too.
If you would like a slightly mad project, it might be worth looking at using the ignition computer from a later LE jetronic system, as fitted to the 2.8litre M30 engine.
This uses a distributor (with vacuum and centrifugal advance as normal) to provide the primary timing signal for the whole system (fuel and spark) and similarly an ignition amplifier is used to drive the coil. AFM, TPS, and CTS functions are as per other Jetronic systems (although the compenents are different in detail).
However on LE jetronic there is an additional box of tricks; an ignition computer. This accepts both fuel signal (from the main ECU that drives the injectors) and the distributor signal. Within the box there is essentially a mapped ignition system which alters the ignition timing beyond what the distributor manages alone, by using the injector signal as a third axis to a map. [You can find a potted version of these workings in the Bosch Auto electronics handbook from the 1990s BTW]
Now, in fairness, I don't think this additional element is intended to give more power; I think it is intended to give better fuel economy. However it might be possible to graft it into an earlier L-Jet system like yours....
I have an M90 engine build underway in which I have adapted the entire 2.8 LE-Jet engine management to run the short stroke 3.5litre motor. Initial impressions from a short test run of the engine are very good.
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I'm obstinate and have opened my old distributor (no. 1) to check why does it work unproperly.
First I noticed is the differnt coil springs in centrifugal mechanism. They are both mounted in such a way that spring no 1 is angaged as a first one while second one due to a little overlonged aye on right at a photo starts to work appprox. at a half of way of centrifugal mechanism. Spring no 2 is stronger a little bit. Centrifugal forces are proportional to the square of angular velocity. This maybe explains the curve's deflexion and deflexion's angle on the chart at about 1800 rpm.
The distributor is cleaned, greased and mounted again. No significant wear is available. I'm lazy to replace the distributor but couriozity of overhaul's result is strong. If I find something interesting I keep you posted.
NB. The exploded view at BMW part catalogue doesn't contain the centrifuge!
http://bmwfans.info/parts-catalog/E24/E ... gle_parts/
First I noticed is the differnt coil springs in centrifugal mechanism. They are both mounted in such a way that spring no 1 is angaged as a first one while second one due to a little overlonged aye on right at a photo starts to work appprox. at a half of way of centrifugal mechanism. Spring no 2 is stronger a little bit. Centrifugal forces are proportional to the square of angular velocity. This maybe explains the curve's deflexion and deflexion's angle on the chart at about 1800 rpm.
The distributor is cleaned, greased and mounted again. No significant wear is available. I'm lazy to replace the distributor but couriozity of overhaul's result is strong. If I find something interesting I keep you posted.
NB. The exploded view at BMW part catalogue doesn't contain the centrifuge!
http://bmwfans.info/parts-catalog/E24/E ... gle_parts/
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- DISTR 1-SPRINGS.jpg (47.74 KiB) Viewed 5371 times
the springs appear to be as intended.
Thinking about it, the distributor works using a variable reluctance magnetic circuit. This comprises both stator and rotor parts. If one or the other part only is eccentric, and the other is concentric, then the signal should be the same in every case.
However if both parts are eccentric, the signal will not be the same in every case, although it should be the same each time on any given cylinder.
If the timing was erratic using that distributor it might be a mechanical fault causing a genuinely erratic ignition timing, or it might be another unrelated fault causing a slight misfire...?
cheers
Thinking about it, the distributor works using a variable reluctance magnetic circuit. This comprises both stator and rotor parts. If one or the other part only is eccentric, and the other is concentric, then the signal should be the same in every case.
However if both parts are eccentric, the signal will not be the same in every case, although it should be the same each time on any given cylinder.
If the timing was erratic using that distributor it might be a mechanical fault causing a genuinely erratic ignition timing, or it might be another unrelated fault causing a slight misfire...?
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Re: Ignition timing setting
This is an old thread but also I would like to inspect by centrifugal mechanism. I'm this far but hesitate removing the cog wheel. Anyone who knows how to proceed without risk to break the position/timing/alignment? What I see is a locking washer and Allen bolts.
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