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MS2 timing advancing with RPMs in fixed mode

FROSTED_BVTTS

FROSTED_BVTTS

Member
Joined
May 21, 2020
Location
Eagle Rock, MO
Working on MSing my 245 and I've run into an issue. Ignition timing is advancing as RPMs increase with the advance set to fixed mode. I'm using MS2 V3.0, LH2.2 distributor hall sensor for crank signal, Bosch 124 ignition module, and the stock coil. I'm using the resistor method for spark output through D14 as described in the hardware manual here. I've tried setting spark mode to basic trigger and trigger return and input capture as rising edge and falling edge, no difference. Spark Output is set to going high, I get no spark when set to going low. Crank signal seems good, don't think I've had any sync errors.

Anybody run into something like this before? Hoping I'm just an idiot and did something wrong, cause I'm pretty well stumped.
 
Is it a relatively new MS2 V3.0 build? IIRC, some of the really old ones used some filter caps that were way too big. Are you using the adjustable VR circuits or the opto-isolator circuits for tach?

If you use the wrong edge with a VR sensor, you'll certainly see this issue, but it's a VR-only issue that won't happen with the LH2.2 hall sensor.

Edit: what are you using for a pullup resistor? ???ohms to ???voltage
 
bobxyz said:
Is it a relatively new MS2 V3.0 build? IIRC, some of the really old ones used some filter caps that were way too big. Are you using the adjustable VR circuits or the opto-isolator circuits for tach?

If you use the wrong edge with a VR sensor, you'll certainly see this issue, but it's a VR-only issue that won't happen with the LH2.2 hall sensor.

Edit: what are you using for a pullup resistor? ???ohms to ???voltage
Click to expand...

Brand new DIYAutotune kit from a month or two ago. I used the opto circuits.

I saw the VR thing mentioned in some threads on the MSExtra forums and it kind of went over my head, but from what I understood I didn't think it would apply to the hall sensor.

Couldn't remember what I did for a pullup, had to run out and grab the ECU and have a look. I have... a 1k from 5v near the proto area with a jumper to tachselect. Did I mix up the instructions for opto and VR input? I assembled the board using the Megamanual assembly guide and then found the MSExtra documentation as I was finishing up... I have a suspicion that may have been a mistake.
 
On the PCB, there are opto-isolator circuits and VR circuits available to condition the tach pulse. The opto circuits can be used with a direct coil connection (for a fuel-only MS setup), or with a hall sensor. The VR circuits can be used with a hall sensor or a VR sensor.

The older megamanual instructions use the opto circuits if you have a hall sensor; the newer msextra instructions use the VR circuits for both hall and VR sensors. Either set of instructions should work fine with a hall sensor, just don't mix-and-match between the instruction sets.

When you see timing advance in fixed mode, how much is it advancing? ???deg at idle versus ???deg at ???rpm Verified with a strobe light versus pulley timing mark, correct?

When using the opto circuits, D1 and D2 should be wire jumpered. Per the schematics, C30 should be 0.22uf, R12 should be 390 ohms, C12 is empty, R13 is 4.7Kohms, C11 is 0.01uf (but your BOM may have changed the values slightly). If these values are off significantly, the circuit may cause the timing shift. A 1Kohm pullup to +5v is fine.

If everything looks OK, it might be easiest to change to use the VR circuit (move the tachselect&tsel jumpers, adjust the potentiometers per msextra instuctions), and see if fixed timing is then stable.
 
I had this problem, although not with a hall sensor.
Could be noise issues?
Make sure your rpm signal cable is routed away from other cables which could cause noise, such as ignition wires of high current wires.
I used the stock Volvo VR sensor with shielded wiring. Shield was grounded at the engine first. Then I grounded it at the ECU side. Only ground this at the ECU side!

Also, I have blow 2 h?co ignition modules because my ECU output channel was set to "Going low". This setting should depend on the transistor type in the ignition module. Using the wrong option results in a hot ignition module which might eventually die. I have to mention that in addition to changing the shield ground location, i changed from "Going high" to "Going low", although I am not sure if this contributed to the solution.

After this solid timing was achieved.

What does your tooth logging look like?
Hope you get it sorted soon.
 
bobxyz said:
When you see timing advance in fixed mode, how much is it advancing? ???deg at idle versus ???deg at ???rpm Verified with a strobe light versus pulley timing mark, correct?.
Click to expand...

I have it set at 10 deg advance at a high idle so it's stable enough to get a reading. It runs off past the 20deg mark on the cover by 2500 rpm or so. Checking with a digital timing light on the crank pulley, yup. Not using the light's advance function, just keeping it set at 0 and checking the mark on the pulley against the cover. The pulley is good, before I installed it I checked that the mark was aligned at TDC, then made paint marks from the inside to the outside so I'll know if it spins.

Sjeng said:
Could be noise issues?
Make sure your rpm signal cable is routed away from other cables which could cause noise, such as ignition wires of high current wires.
Click to expand...

I have the hall sensor wires ran alongside my bastardized LH harness from the passenger footwell where the ECU is to the side of the block, so it's not the most isolated.

Also, I have blow 2 h?co ignition modules because my ECU output channel was set to "Going low". This setting should depend on the transistor type in the ignition module. Using the wrong option results in a hot ignition module which might eventually die. I have to mention that in addition to changing the shield ground location, i changed from "Going high" to "Going low", although I am not sure if this contributed to the solution.
Click to expand...

I switched it to going low briefly just to see if it would make a difference, but when it wouldn't make spark with that setting I decided it probably wasn't a good idea to keep trying it :lol:

What does your tooth logging look like?
Hope you get it sorted soon.
Click to expand...

Thanks! Tooth log looks about as stable as my idle, so I'd say crappy but reasonable. I can't say for certain that I'd recognize an issue if it wasn't blatantly obvious, but it seems consistent with what the engine's doing.

linuxman51 said:
if you're using a distributor, make sure you don't have spark latency values set
Click to expand...

Set at 0



I'll look everything over and make sure I've got the opto circuit assembled correctly, then if I can't find anything wrong I'll switch to the VR circuit and see if that changes anything.
 
Wow, that's a big shift (10deg to 20+deg from idle to 2500rpm). I forget if you need to do a power-cycle after setting MS to Fixed timing mode. Maybe post your .msq, or a screenshot of the fixed timing setup page to see if something else is mis-configured.

Are you running the B&G firmware or the latest MSextra firmware?

Also, double check your pullup resistor: 1K brown-black-red = Good, 10K brown-black-orange = Bad

Edit: I just realized that the reported timing shift is Advanced. If there were electrical problems, it would delay the spark, i.e. the shift would be Retarded.

New guess is that somehow it isn't actually going into fixed timing mode. You could temporarily rewrite your entire timing table to 10deg and see what happens.
 
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bobxyz said:
Wow, that's a big shift (10deg to 20+deg from idle to 2500rpm). I forget if you need to do a power-cycle after setting MS to Fixed timing mode. Maybe post your .msq, or a screenshot of the fixed timing setup page to see if something else is mis-configured.

Are you running the B&G firmware or the latest MSextra firmware?

Also, double check your pullup resistor: 1K brown-black-red = Good, 10K brown-black-orange = Bad

Edit: I just realized that the reported timing shift is Advanced. If there were electrical problems, it would delay the spark, i.e. the shift would be Retarded.

New guess is that somehow it isn't actually going into fixed timing mode. You could temporarily rewrite your entire timing table to 10deg and see what happens.
Click to expand...

Can't post attachments, but here's links to .msq and a tooth log (both from after I switched to VR, to be clear)

Firmware is MS2/Extra 3.4.3 Release 20191126

Checked the resistor and it is a 1k

I looked over the circuit and everything was installed correctly. The manuals differ from your post in that they specify that C30 should be omitted though, so that's what I did. Since everything seemed fine, I switched from opto to VR, but no dice. Same thing is happening. Guess next step is to try rewriting the whole table as you've suggested.
 
You sure you have a LH2.2 distributor with fixed advance??? I think Europe may have had some Volvo 240 distributors with 3 wires and centrifugal/vacuum advance. If it's not the electronics, and not MS, I don't know what else it could be.

When you set MS to Fixed advance, are you doing a Burn? and maybe a power-cycle?

Can you post a normal log of idle and rev'd up a bit?

(I'm not at home, so I can't look at your previous .msq/tooth log yet)
 
either that, or the lovely "universal input" strikes again. Are you using the opto input? if not, I'd suggest you switch to that and see if it starts behaving
 
Distributor is just a normal LH2.2 distributor to my knowledge. No vacuum advance. Bosch 0237506001, same as the one I pulled off my 86 parts car.

Yep, burn every time, power cycle when required as well as most times when I've changed any timing settings.

Composite log is here

Just realized I forgot to hook up MAP for this one... which explains why it was running chunkier than normal. This was the only time though, I swear! Didn't seem to make any difference with the timing issue anyways though.
 
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Mighty strange....

I looked at your .msq and tooth logs, but nothing seemed bad. :???:

For some reason, my copy of megalogviewer didn't like your composite tooth log, but I was able to view the raw data OK as a spreadsheet.

Can you run a standard log, not a tooth log, of ~20 seconds of startup / idle / reving? It's the "Data Logging" menu at the very top of the screen, not the Diag&HighSpeedLoggers menu. In the log, you want to look at: RPM, Batt V, SPK:SparkAdvance, and the various other SPK:xxxx lines. Maybe something will give a clue why spark timing isn't staying fixed.

When you tried the whole table at 10deg, did you remember to change back from Fixed Timing to Use Table mode too?
 
bobxyz said:
Mighty strange....

I looked at your .msq and tooth logs, but nothing seemed bad. :???:

For some reason, my copy of megalogviewer didn't like your composite tooth log, but I was able to view the raw data OK as a spreadsheet.

Can you run a standard log, not a tooth log, of ~20 seconds of startup / idle / reving? It's the "Data Logging" menu at the very top of the screen, not the Diag&HighSpeedLoggers menu. In the log, you want to look at: RPM, Batt V, SPK:SparkAdvance, and the various other SPK:xxxx lines. Maybe something will give a clue why spark timing isn't staying fixed.

When you tried the whole table at 10deg, did you remember to change back from Fixed Timing to Use Table mode too?
Click to expand...

Ok, log is here

Yeah, I switched it back to use table, but it still did the same thing.
 
Well, I'm stumped. The standard log shows 0deg spark timing from all the contributors for the whole log. Sure looks like MS timing is completely fixed.

Do you have access to a different timing light? Maybe the fancy light is misbehaving or misconfigured?

Summary - please correct if anything is wrong:
- idle timing is set to 10deg, verified with timing light
- MS timing is set to Fixed mode, 0deg
- MS logs show 0deg timing, and seemingly reasonable tooth logs
- timing advances to more than 20deg by 2500rpm, as seen with timing light
- standard LH2.2 distributor and 124 module
- changing between the opto and the VR/"universal" tach circuit didn't change anything
- opto circuit components and pullup resistor are OK
 
bobxyz said:
Well, I'm stumped. The standard log shows 0deg spark timing from all the contributors for the whole log. Sure looks like MS timing is completely fixed.

Do you have access to a different timing light? Maybe the fancy light is misbehaving or misconfigured?

Summary - please correct if anything is wrong:
- idle timing is set to 10deg, verified with timing light
- MS timing is set to Fixed mode, 0deg
- MS logs show 0deg timing, and seemingly reasonable tooth logs
- timing advances to more than 20deg by 2500rpm, as seen with timing light
- standard LH2.2 distributor and 124 module
- changing between the opto and the VR/"universal" tach circuit didn't change anything
- opto circuit components and pullup resistor are OK
Click to expand...

Yeah, that's all accurate. I don't think I know anybody else with a timing light, but I'll find a different one somewhere.
 
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