"Borrowing" a wheel decoder from MS3

[Monzsta]

I'm getting prepared to turbo my 2000 Jeep Grand Cherokee 4.7l. It uses the early version of the 4.7l which has a JTEC pcm. I believe this 16t wheel is covered under the "Jeep 2002" in the MS3. Is it possible to cut/paste what I need into MS2's code?

[Monzsta]

Here's a few logs of the MS2 piggybacked on the 4.7's sensors.

[jsmcortina]

It wouldn't be a direct cut/paste, but also no. Code written for the MS3 is just that. It is not licensed for back-porting.

James

[Monzsta]

With a working cam sensor the MS2 appears to have accurate rpm under the "toothed wheel/dual wheel" mode. I'll have to set up a test light/timing light to see if it is indeed synced to the engine and that #1 firing is repeatable and correct. Looking forward to implementing fuel and spark.

[Monzsta]

Alright. I've got the injectors wired and with filtering enabled MS2 is managing to run smoothly. I'm trying to discern exactly what the megasquirt is locking onto for a trigger. The crank pattern is 16 teeth, with an alternating long tooth and long gap.



The cam wheel has a 1-2-3-3-2-1-3-1 pattern. I'm just trying to make sense of it.

[MegaHelp]

Please correct me if I am wrong.
But MegaSquirt is looking for change of material.
Either the beginning of the tooth, or the end.
You can select raising edge (beginning of tooth) or falling edge (end of tooth).
Now this also depends on the polarity of the VR sensor.
The MegaSquirt itself sees a waveform from the sensor.
It triggers when the voltage goes trough zero volt (zero crossing).
It does not see the length of the tooth. It just sees the change in material.

So if the start of all tooth are even spaced but one is longer then another, it sees it as a standard 16 tooth wheel.
If you have a cam sensor with a single pulse per 2 revolutions, you could use dual wheel mode.
If you have multiple triggers on the cam I don't think it is going to work.
If you have a missing tooth on the crank wheel, you could get away with that using the "polling" mode.

From what I see, is the triggerwheel you have very simple. Why not just have a 36-1 or 60-2 cut out by a lasercutter.
That would save you a lot of trouble.

You will have to be careful with this wheel.
If the starts or ends of the tooth have varieties in spacing, your ignition timing will shift.
You might damage your engine as timing can be shifting as much as 10 degrees.
You really need to check this when the car is idling. In the tooth logger, all tooth must be seen with the same amount of time between them.

[Monzsta]

Please correct me if I am wrong.
But MegaSquirt is looking for change of material.
Either the beginning of the tooth, or the end.
You can select raising edge (beginning of tooth) or falling edge (end of tooth).
Now this also depends on the polarity of the VR sensor.
The MegaSquirt itself sees a waveform from the sensor.
It triggers when the voltage goes trough zero volt (zero crossing).
It does not see the length of the tooth. It just sees the change in material.

So if the start of all tooth are even spaced but one is longer then another, it sees it as a standard 16 tooth wheel.
If you have a cam sensor with a single pulse per 2 revolutions, you could use dual wheel mode.
If you have multiple triggers on the cam I don't think it is going to work.
If you have a missing tooth on the crank wheel, you could get away with that using the "polling" mode.

From what I see, is the triggerwheel you have very simple. Why not just have a 36-1 or 60-2 cut out by a lasercutter.
That would save you a lot of trouble.

You will have to be careful with this wheel.
If the starts or ends of the tooth have varieties in spacing, your ignition timing will shift.
You might damage your engine as timing can be shifting as much as 10 degrees.
You really need to check this when the car is idling. In the tooth logger, all tooth must be seen with the same amount of time between them.

Thank you for your reply. The sensors are hall effect and the megasquirt is piggybacked directly onto the factory pcm lines. Tomorrow I'll get some logs up in tooth logger mode. Running a separate trigger wheel would be problematic as space is extremely limited in the front of the engine. Fitting a separate cam sensor with a simple pattern might be better but after having a look through the code i believe I might be able tailor one to my needs once I get a good understanding of what is happening. That's why I'd like to understand better what the megasquirt is currently seeing as a good pattern.