Lost Sync on Low RPM < 1000

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JohnWick
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Lost Sync on Low RPM < 1000

Post by JohnWick »

Hi guys, I have no RPM reading at low engine speeds, sub 950 I'm using a MS2 with v3.0 PCB. Firmware is 3.4.2.
Car: Peugeot 206 s16 (GTI 136hp) Engine code EW10J4
Trigger wheel: 60-2
Crank Sensor: I'm honestly not sure whether it's Hall or VR sensor.
MS is running parallel with stock Magnetti Marelli ECU. Currently MS is not controlling anything, I'm just trying to get RPM.
I'm using the optoinput as I couldn't get any signal, tooth log, composite log, anything with vr circuit. I've tried all possible software and jumper configurations.

The problem seems to be at lower RPM. Once I rev the engine past 1000 rpm it works perfectly all the way to 6000.

This is the composite log with the engine at about 1500 RPM
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And this is the tooth log with engine idling (about 750-800 RPM)
Image
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grom_e30
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Re: Lost Sync on Low RPM < 1000

Post by grom_e30 »

can you post the tooth logs of the engine running
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
hybrid
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Re: Lost Sync on Low RPM < 1000

Post by hybrid »

2 wires = VR
3 wires = hall
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prof315
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Re: Lost Sync on Low RPM < 1000

Post by prof315 »

hybrid wrote:2 wires = VR
3 wires = hall
While this is generally true be careful. Some VR sensors have built in shielding . Bosch in particular likes to do that and so there are 3 wire VR sensors
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Paul_VR6
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Re: Lost Sync on Low RPM < 1000

Post by Paul_VR6 »

If opto is working at all I would be surprised its a vr sensor.

Easy check:
Sensor has power: hall
Any two wires read 250-1k ohm: vr
-Paul
1992 Corrado SLC 3.6 VR6 11.38@120 - MS3 Pro Ultimate - Microsquirt I/O - Can EGT - Racepak IQ3s
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hybrid
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Re: Lost Sync on Low RPM < 1000

Post by hybrid »

prof315 wrote:
hybrid wrote:2 wires = VR
3 wires = hall
While this is generally true be careful. Some VR sensors have built in shielding . Bosch in particular likes to do that and so there are 3 wire VR sensors
That's not really a signal wire though is it?
Do not load someone elses tune and expect it to work for you!
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JohnWick
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Re: Lost Sync on Low RPM < 1000

Post by JohnWick »

Update: still using the optoin circuit, I shielded the signal wires with aluminium kitchen foil and connected to megasquirt shielded wire loom. I seem to be getting rpm even at 700 RPM. The sensor does have only 2 wires... I'm still confused as AFAIK it should be a vr sensor but optoin reads perfect rpm 1000+
hybrid
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Re: Lost Sync on Low RPM < 1000

Post by hybrid »

You really need to switch to the VR input.
Do not load someone elses tune and expect it to work for you!
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prof315
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Re: Lost Sync on Low RPM < 1000

Post by prof315 »

hybrid wrote:
prof315 wrote:
hybrid wrote:2 wires = VR
3 wires = hall
While this is generally true be careful. Some VR sensors have built in shielding . Bosch in particular likes to do that and so there are 3 wire VR sensors
That's not really a signal wire though is it?
No it's not, but it sure does have a 3 wire connector and if you assume that all 3 wire crank sensors are hall you're gonna be beating your head against the wall when you run into one. VW and Audi are notorious for using a shielded 3 wire VR and since the wire colors are often green red and black it's easy to be confused. If you aren't sure its always best to check the factory wiring diagram
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Re: Lost Sync on Low RPM < 1000

Post by jsmcortina »

hybrid wrote:You really need to switch to the VR input.
Absolutely.
Using the Opto input circuit with a VR sensor will give unreliable operation and almost certainly inconsistent timing.

James
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142 guy
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Re: Lost Sync on Low RPM < 1000

Post by 142 guy »

At the risk of responding to a post that may already be resolved, in the absence of a part # or wiring diagram probably the easiest way to identify a Hall versus reluctance type sensor on a toothed wheel application is to power up the system (with the fuel pump and coils disabled) and manually rotate the engine with a voltmeter or scope connected between the signal line and signal ground. A Hall sensor will give a nice clean transition between less than 1 volt (VCE sat on the output transistor) and +5 or +12 volts (depends on the pull up arrangement on the native system) as the crankshaft is rotated. The transition voltages will be unaffected by the cranking speed.

Reluctance sensors generate a signal voltage that is a function of the speed at which the tooth transition passes by the sensor. Rotating a crankshaft by hand may result in a voltage that is barely noticeable on a digital voltmeter. With sufficient engine speed a reluctance sensor may generate enough voltage to cause the opto isolator to energize which could explain operation at higher RPM and loss of the signal at lower RPMs. As noted, a reluctance sensor on an opto input will be hit and miss and chances are that at cranking speeds it may not generate enough voltage to switch the opto isolator on and off.
JohnWick
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Re: Lost Sync on Low RPM < 1000

Post by JohnWick »

142 guy wrote:At the risk of responding to a post that may already be resolved, in the absence of a part # or wiring diagram probably the easiest way to identify a Hall versus reluctance type sensor on a toothed wheel application is to power up the system (with the fuel pump and coils disabled) and manually rotate the engine with a voltmeter or scope connected between the signal line and signal ground. A Hall sensor will give a nice clean transition between less than 1 volt (VCE sat on the output transistor) and +5 or +12 volts (depends on the pull up arrangement on the native system) as the crankshaft is rotated. The transition voltages will be unaffected by the cranking speed.

Reluctance sensors generate a signal voltage that is a function of the speed at which the tooth transition passes by the sensor. Rotating a crankshaft by hand may result in a voltage that is barely noticeable on a digital voltmeter. With sufficient engine speed a reluctance sensor may generate enough voltage to cause the opto isolator to energize which could explain operation at higher RPM and loss of the signal at lower RPMs. As noted, a reluctance sensor on an opto input will be hit and miss and chances are that at cranking speeds it may not generate enough voltage to switch the opto isolator on and off.
Thank you very much, I also thought that in case of vr it might not generate enough voltage. In the meantime I've inspected the vrinput circuit and found a cold solder on comparator input which caused the vr circuit malfunction. I'm gonna try and get the vr circuit to read thr input now, regardless if it's hall or vr it should read it much better than optoin.
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