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MS Questions: LH VR sensor, and dwell settings

Sjeng

Sjeng

Member
Joined
Sep 3, 2017
Hello,

I am changing to MS2 on my 940.

I will be using the stock redblock VR sensor, which has 3 pins. one VR+, one VR- and a shield (ground).

afewq0.jpg


1. Which pin corresponds to which connection? IIRC Pin 2 is VR-, what about 1 and 3?

2. Is it necessary/recommended to use a shielded wire from sensor connector to the ECU?

3: I will be using wasted spark and the Bosch motorsport 2x2 coil and BR7ES plugs. Does
anyone have a good suggestion for the nominal dwell setting and the cranking dwell
setting?

Many thanks in advance.
 
I can't remember exactly how I wired up the LH2.4 sensor, but I did use shielded wire, and a 5k ohm resister across vr+ and vr-. You need the resistor if you plan on revving over 4k rpm.
 
Perfect JW, just what I was looking for.

I understand why you want to go to an aftermarket management.
I got LH2.4 running fairly well. But for some reason, LH is not constant in how it performs. Even with lambda feedback disabled. (at least in my case)
Also, burning chips every time you want to change something, and the inability to log gets tiring fast. :lol:
Money for an ostrich can also be spend on a newer EMS.

BTW the reason I ever bought a RWD brick is that back in 2010 or 2011 you gave me a ride in your 240 and I was impressed.

grt,

Frank
 
culberro said:
I can't remember exactly how I wired up the LH2.4 sensor, but I did use shielded wire, and a 5k ohm resister across vr+ and vr-. You need the resistor if you plan on revving over 4k rpm.
Click to expand...

Thanks, I will look into this.
 
Sjeng said:
Hello,

I am changing to MS2 on my 940.

I will be using the stock redblock VR sensor, which has 3 pins. one VR+, one VR- and a shield (ground).

1. Which pin corresponds to which connection? IIRC Pin 2 is VR-, what about 1 and 3?

2. Is it necessary/recommended to use a shielded wire from sensor connector to the ECU?

3: I will be using wasted spark and the Bosch motorsport 2x2 coil and BR7ES plugs. Does
anyone have a good suggestion for the nominal dwell setting and the cranking dwell
setting?

Many thanks in advance.
Click to expand...

I don't have my notes here, but the polarity does matter (or at least if you want to copy a standard MS setup). You want the polarity and the MS trigger edge setup so that the MS triggers on the falling edge of the first tooth after the missing tooth region. (I think I posted an oscilloscope picture of this a couple years ago in a thread about a non-working custom 60-2 flywheel.) If you change the polarity, you'll shift timing by ~3degrees and can have additional noise and lost_sync problems.

Yes, use shielded cable (DIYautotune sells some). The VR signal is pretty weak and electrical noise from nearby wires in the harness can cause problems.

You can find a bosch datasheet for the 2x2 coil that lists recommended standard dwell. For cranking, you can increase it by, I don't know, say 30% to 50%.

The MS2 VR circuit needs the pots adjusted for the 60-2 wheel with VR pickup. The reports are that this works OK. With a MicroSquirt, there's a long thread about sync loss at higher RPM. Some folks fixed this by adding a shunt resistor across the VR+/- wires to the MicroSquirt.
 
Sjeng said:
Perfect JW, just what I was looking for.

I understand why you want to go to an aftermarket management.
I got LH2.4 running fairly well. But for some reason, LH is not constant in how it performs. Even with lambda feedback disabled. (at least in my case)
Also, burning chips every time you want to change something, and the inability to log gets tiring fast. :lol:
Money for an ostrich can also be spend on a newer EMS.

BTW the reason I ever bought a RWD brick is that back in 2010 or 2011 you gave me a ride in your 240 and I was impressed.

grt,

Frank
Click to expand...

Hi Frank, nice to hear! Was that during one of the N?rburgring meets or am I mixing things up haha.

Same here, LH is working good. But not consistent. Missing some elegance. Right now I need bigger AMM, some form of boost control, new wideband, etc.
 
bobxyz said:
I don't have my notes here, but the polarity does matter (or at least if you want to copy a standard MS setup). You want the polarity and the MS trigger edge setup so that the MS triggers on the falling edge of the first tooth after the missing tooth region. (I think I posted an oscilloscope picture of this a couple years ago in a thread about a non-working custom 60-2 flywheel.) If you change the polarity, you'll shift timing by ~3degrees and can have additional noise and lost_sync problems.

Yes, use shielded cable (DIYautotune sells some). The VR signal is pretty weak and electrical noise from nearby wires in the harness can cause problems.

You can find a bosch datasheet for the 2x2 coil that lists recommended standard dwell. For cranking, you can increase it by, I don't know, say 30% to 50%.

The MS2 VR circuit needs the pots adjusted for the 60-2 wheel with VR pickup. The reports are that this works OK. With a MicroSquirt, there's a long thread about sync loss at higher RPM. Some folks fixed this by adding a shunt resistor across the VR+/- wires to the MicroSquirt.
Click to expand...

Thank you very much for your detailed post and recommendations. I will first give it a try in it's current form, and see if sync losses occur at higher engine speeds. Apparently most people add a 10K resistor inline if this happens on MS2 but I guess it will take some experimenting.

JW240 said:
Hi Frank, nice to hear! Was that during one of the N?rburgring meets or am I mixing things up haha.
Click to expand...

Back when we were in engineering class you gave me a ride.
If you're interested I have a good 012 available as soon as I get my car running on MS.
 
Here's some additional info:

For the CPS, I couldn't find my notes showing "standard" polarity. If you're working off of someone else's MS setup, make sure that you have the same wiring (CPS pin 1 or pin 2 to TachIn), and same MS "Ignition input capture" edge (rising or falling).

Alternately, you can wire it up either way (pin 1 or pin 2 to MS TachIn), but you'll need to check that the timing doesn't drift with rpm -- set MS to fixed timing (say 10deg) and rev the engine with a timing light on the crank. If it drifts, change the MS "Ignition input capture" edge (rising or falling) and try again. IIRC, the MicroSquirt edge setting may not be the same as the MegaSquirt2 edge setting (but that might just be for the MS2 OptoIsolator circuit and not the VR circuit). See this post for additional (painful) details on VR edge selection: http://forums.turbobricks.com/showpost.php?p=5342736&postcount=39

For the long thread on MicroSquirt issues with 60-2 wheel, see:
https://forums.tbforums.com/showthread.php?t=306770

It was harder than I remember to find the specs for the Bosch 2x2 double fire coil. I did a search for "Bosch Motorsport Double Fire Coil 2x2 0 221 503 407" and found this doc still around, but not directly from Bosch: https://www.finjector.com/documents/550bedaf32fb6/Double_Fire_Coil_2x2_Datasheet_0221503407.pdf
From the dwell tables, I'd try 3.0ms Nominal Dwell (should give ~7Amps at 13.5volts), 2.0ms spark duration, and 4.5ms Cranking Dwell (should give ~8Amp at ~11.5volts cranking). You might need to back off on the duration setting for max spark at higher RPMs (I'm not sure how MS uses this duration number).

I've setup my '85 245 wagon to allow either LH2.4 or MS. For now, I'll start with LH2.4 to break in the new engine (unheated garage and back willing). I did go through all the details of how to crosswire the LH2.4/EZK-116 connectors to MS or microsquirt, but haven't yet tried it out - https://forums.turbobricks.com/showthread.php?t=338742

Cheers,
Bob
 
Hello Bob, thanks again for taking the time to write your detailed answer. I really appreciate it.

Kind regards Frank
 
Stiggy Pop; said:
I’ve got a 4.7k ohm resistor between + and - on the stock VR sensor with a microsquirt
Click to expand...

I'm sitting at 5k on the uS. The engine will rev to 8k with a clean signal, and no sync issues with starting.
~5k ohm seems to be the ticket.
 
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