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Block mount distributor sensor for sequential injection

DailyDriverMods

DailyDriverMods

Member
Joined
Aug 23, 2020
Location
Netherlands
I came across this set that converts conventional Bosch 009 distributors to electrical ones. I would like to use this as a single pulse cam sensor on my LH2.4 distributor to enable sequential injection on my MS3 setup. Does anyone have any experience with these things?
Ali-link
 
I wasn't the first to do this, but if you take an old hall-equipped dizzy and cut out three out of four blades, then align the one blade left with the sensor at tdc you have half of what you need for sequential ignition. Not sure if MS3 has a chip on the board but I had to build a hall circuit to accommodate the 2nd trigger.

You'd also need something like the crank sensor on the flywheel to complete the package.

Did you rewire your injectors to accommodate sequential injection?
 
740atl said:
I wasn't the first to do this, but if you take an old hall-equipped dizzy and cut out three out of four blades, then align the one blade left with the sensor at tdc you have half of what you need for sequential ignition. Not sure if MS3 has a chip on the board but I had to build a hall circuit to accommodate the 2nd trigger.

You'd also need something like the crank sensor on the flywheel to complete the package.

Did you rewire your injectors to accommodate sequential injection?
Click to expand...

The car came with LH2.4 and has already been swapped to MS3x, so the crank sensor and such is all sorted out. The injectors will also be rewired of course because they are now all running in batch fire on 1 injector channel via the original wiring harness. I have a link in my sig that goes to the msextra forum where i did a little write-up about the ms3x install including the tune file.

I do also have an old dizzy with a hall sensor, not from a LH2.2 system but one with mechanical and vacuum advance with the hall sensor as a points replacement. I could also use that one but just having to install a hall sensor seems easier than locking, modifying and swapping the other dizzy. The MS3x board does have a cam signal input which supports the use of hall sensors and vr sensors including the neccessary adjustments options. So the sensor type won't be an issue either way fortunately.
 
That looks like a Pertronix knock-off. Pertronix was the original company that offered electronic points-replacement kits for all sorts of mechanical distributors. There's a magnet and hall sensor in the replacement module, and a 4 vane metal rotor in the ring, hidden under the plastic. You'd need to figure out how to mount the module to the distributor housing, and how to modify the ring to give one pulse per revolution. (Note: these use the distributor housing as a ground connection to the block - the 2 wires are +12v and sensor out.)

Depending on local availability, it might be easier to find and modify a LH2.2 distributor.
 
bobxyz said:
That looks like a Pertronix knock-off. Pertronix was the original company that offered electronic points-replacement kits for all sorts of mechanical distributors. There's a magnet and hall sensor in the replacement module, and a 4 vane metal rotor in the ring, hidden under the plastic. You'd need to figure out how to mount the module to the distributor housing, and how to modify the ring to give one pulse per revolution. (Note: these use the distributor housing as a ground connection to the block - the 2 wires are +12v and sensor out.)

Depending on local availability, it might be easier to find and modify a LH2.2 distributor.
Click to expand...

Well the unit i have is an interesting one. It's a Bosch TZ-28H and i can't find that much info about it. Here in the Netherlands (and probably other parts of Europe) we didn't really get LH2.2 on the 240 but instead Volvo started to use B230A/K engines with carburettors in combination with this electronic dizzy. The hall sensor, connector and disc look the same as on the LH2.2 dizzy except that its also got the vacuum/mechanical advance. The hall sensor was purely used as a points replacement to get along with the times while still using mechanical ignition timing.

I understood that the module from the aliexpress unit should be hooked up directly to the negative terminal of the coil, it doesn't require any additional electronics. They also have different versions for positive ground and negative ground cars.
 
There's a page in the '85 greenbook, TP30808-1, with the TZ-28H. From the wiring and notes, it's a hall effect sensor in the distributor (+/O/- pins) and the "Control Unit" includes the power transistor coil driver, plus over-dwell protection after 1 second.

I don't know how tolerant MS is of the cam tooth input moving around a little, but I'd try running the TZ-28H with one tooth (if you don't mind destroying it for normal use) and the vaccum unplugged. You'll need a 1K pullup resistor to +5Vref on the "O" output pin (or a 10K to +12v would work too).
 
Are you doing sequential injection and coil on plug (or similar) or are you just doing timing control in MS3 and retaining the conventional coil and distributor?

Something to consider in repurposing an old distributor to provide a cam position signal is wear on the distributor shaft. On my B20E, wear on the distributor shaft contributed to significant timing wander at 3000 crank RPM. Volvo used to sell distributor rebuild kits through GCP which allowed you to re bush the distributor. This worked as long as the distributor shaft itself is not worn, although getting the split pin out of the drive end of the distributor shaft to allow disassembly can be a challenge.

If you are going with coil on plug or a similar arrangement which eliminates the need for the distributor function, consider the Yoshifab adapter to mount an optical cam angle sensor in place of the distributor on OHC redblocks. Gives you both a cam position signal and a medium resolution (12 crank tooth equvalent) tach signal. That was my solution for dealing with a worn distributor shaft although it is significantly more expensive than the $30 Hall sensor. Clearly does not work if you need to retain the spark distribution function.

As bobxyz notes, the Aliexpress part looks like a Pertronix clone. Eliminating the centrifugal and vacuum spark control by locking the breaker plate to do spark timing control via MS3 is trivial. Modifying the plastic collar to give you a single pulse per distributor revolution may be slightly more challenging. If you don't need the distributor function, you are relatively free in figuring out the positioning of the trigger. If you need to retain the spark distribution function of the distributor then life is more complex. I don't know about MS3; but, on MS2 the recommended positioning is to have the cam position signal occur about 60 deg before TDC on #1. Getting that 60 deg timing with an unmodified breaker contact plate and still retaining reasonable alignment of the distributor rotor with the contacts in the distributor cap can be a challenge.
 
142 guy said:
Are you doing sequential injection and coil on plug (or similar) or are you just doing timing control in MS3 and retaining the conventional coil and distributor?

Something to consider in repurposing an old distributor to provide a cam position signal is wear on the distributor shaft. On my B20E, wear on the distributor shaft contributed to significant timing wander at 3000 crank RPM. Volvo used to sell distributor rebuild kits through GCP which allowed you to re bush the distributor. This worked as long as the distributor shaft itself is not worn, although getting the split pin out of the drive end of the distributor shaft to allow disassembly can be a challenge.

If you are going with coil on plug or a similar arrangement which eliminates the need for the distributor function, consider the Yoshifab adapter to mount an optical cam angle sensor in place of the distributor on OHC redblocks. Gives you both a cam position signal and a medium resolution (12 crank tooth equvalent) tach signal. That was my solution for dealing with a worn distributor shaft although it is significantly more expensive than the $30 Hall sensor. Clearly does not work if you need to retain the spark distribution function.

As bobxyz notes, the Aliexpress part looks like a Pertronix clone. Eliminating the centrifugal and vacuum spark control by locking the breaker plate to do spark timing control via MS3 is trivial. Modifying the plastic collar to give you a single pulse per distributor revolution may be slightly more challenging. If you don't need the distributor function, you are relatively free in figuring out the positioning of the trigger. If you need to retain the spark distribution function of the distributor then life is more complex. I don't know about MS3; but, on MS2 the recommended positioning is to have the cam position signal occur about 60 deg before TDC on #1. Getting that 60 deg timing with an unmodified breaker contact plate and still retaining reasonable alignment of the distributor rotor with the contacts in the distributor cap can be a challenge.
Click to expand...

I'm currently using the dizzy in combination with an MSD 6AL / Blaster II ignition system which is driven by the megasquirt. The megasquirt uses the crank sensor and an ignition map to determine the timing. The sensor in the dizzy would only be used to sync up the fully sequential mode, the timing itself will be determined via the crank sensor.

I think i'm going to try to make it work with the Volvo hall sensor dizzy. If this doesn't work out with the cam signal timing being too close to TDC, i can always use the Ali express sensor and maybe custom 3D print a new plastic collar.

A full-on cam trigger with a pattern wheel would be a bit overkill for just syncing up the sequential signal i think.
 
I looked at the MS hardware manual under "Missing tooth crank wheel and single tooth cam wheel" and it sounds like MS is pretty forgiving of the Cam wheel behavior. All MS really needs is a Cam sensor edge before tooth #1 on the crank wheel.

I think that MS is simply setting a flag when it sees the Cam tooth edge. On the next crank Tooth #1, if the Cam flag is set, then the engine is nearing TDC #1 on the compression stroke (and MS clears the flag). If the Cam flag isn't set at Tooth #1 time, the engine is nearing TDC #1 on the exhaust stroke. If it really works this way, you don't need to lock down the distributor advance -- MS won't care if it moves around a little as long as the cam/distributor flag is consistently before Tooth #1 on compression stroke.

I forget the exact numbers, but the original 60-2 crank wheel has a tooth #1 (the one just after the gap) angle of ~80degrees BTDC. With a 1-3-4-2 firing order, I think you want to retain the cylinder #2 flag in the distributor and remove the other 3. Look at the MS guide and crank the engine around to confirm this before cutting up anything.

OK, am I making sense? Maybe someone who's modified a disti for the single cam tooth can say which of the 4 disti teeth/flags they retained?
 
bobxyz said:
I looked at the MS hardware manual under "Missing tooth crank wheel and single tooth cam wheel" and it sounds like MS is pretty forgiving of the Cam wheel behavior. All MS really needs is a Cam sensor edge before tooth #1 on the crank wheel.

I think that MS is simply setting a flag when it sees the Cam tooth edge. On the next crank Tooth #1, if the Cam flag is set, then the engine is nearing TDC #1 on the compression stroke (and MS clears the flag). If the Cam flag isn't set at Tooth #1 time, the engine is nearing TDC #1 on the exhaust stroke. If it really works this way, you don't need to lock down the distributor advance -- MS won't care if it moves around a little as long as the cam/distributor flag is consistently before Tooth #1 on compression stroke.

I forget the exact numbers, but the original 60-2 crank wheel has a tooth #1 (the one just after the gap) angle of ~80degrees BTDC. With a 1-3-4-2 firing order, I think you want to retain the cylinder #2 flag in the distributor and remove the other 3. Look at the MS guide and crank the engine around to confirm this before cutting up anything.

OK, am I making sense? Maybe someone who's modified a disti for the single cam tooth can say which of the 4 disti teeth/flags they retained?
Click to expand...

I have checked the MS documentation and it indeed states that it should work this way.

I removed the vacuum advance and locked the base plate in the middle position, kept the mechanical advance and removed the cylinder 1, 3 and 4 triggers on the wheel.

The hall sensor is hooked up to the sensor 5V and ground. The signal wire goes directly to the CAM input of the MS3x board on which i enabled the internal pullup resistor and set up the potentiometers accordingly to the manual for use with a hall sensor.

This all works fine now and the megasquirt is (finally) running in sequential mode, which is really nice for the injection timing and the per-cylinder knock signal adjustment.
 
I think you will also want to lockout the mechanical advance. You want your cam and crank signals to be locked down to engine position, otherwise you wouldn't be able to use timed injection.
 
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