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sport1901966

1.9 Mi16 Flywheel Reference Tooth To Tdc Sync

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sport1901966

I am in the process of investigating aftermarket management setup for my Mi16 (1.9 XU9J4) and when it comes to specifying the reference tooth position in the ECU calibration research on here has suggested a number of different positions of the flywheel teeth relative to the crank angle sensor position. I decided the best thing to do was to confirm it for myself and thought that I'd post the results here for peoples future reference.

 

I aimed to establish what tooth was under the CAS (and the exact position of the tooth) when piston 1 (and hence 4) is at TDC. From this the position of the reference tooth, as specified by the ECU being used can be individually calculated. In my case the reference tooth is the second tooth following the gap formed by the 2 missing teeth.

 

To accurately ascertain what tooth on the flywheel, counting clockwise from the first tooth after the gap, was under the CAS with piston 1 at TDC an oscilloscope was used. On the signal trace further down the first channel, blue, was the signal output from the CAS, the second channel, green, represents the position of piston 1. The data for the piston position was obtained using an AFM, where the flap was actuated by a probe on piston 1, placed through the spark plug hole (see below).

 

AFMProbe.jpg

 

CASConnection.jpg

 

With this instrumentation set up, when the engine was turned on the starter, the signal traces below were recorded from the CAS and AFM potentiometer. It can be seen by drawing a line parallel to the y-axis at the peak value of the AFM voltage, and hence where the piston is at TDC, what tooth is under the CAS.

 

CASandPistonTrace.jpg

 

CASandPistonTraceNumbered.jpg

 

The numbers labelled on the signal plot above are at the start of each tooth, and knowing that the positive peak is the rising edge of each tooth, it is seen that the top of the 20th tooth is under the CAS when piston 1 is at TDC.

 

This means in my case, as the reference tooth is number 2, it passes the CAS at; (20-2) teeth *6 deg = 108 deg BTDC. It is multiplied by 6 deg as the Mi16 flywheel is a 60-2 tooth trigger wheel, therefore the tooth spacing is 6 deg. Usually ECU's require the reference tooth position as an ATDC figure, therefore in my case the ref tooth is at 252deg ATDC.

 

Hope this is of help to people!

 

Geoff

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M@tt

ingenious use of an AFM to monitor TDC!!!

 

great bit of investigating :) well done

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[L'e$kro]

Thanks, very useful topic!

The value I'm using is 114deg, so 1 tooth off

 

Nico

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sport1901966

ingenious use of an AFM to monitor TDC!!!

 

great bit of investigating :) well done

 

Haha thanks, was originally planning to use a TPS but only had the switching types. The AFM actually ended up being the better choice as I could use the four bolts in the housing to level it and ensure it was directly inline with the piston motion!

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rallysteve

Excellent Idea.

 

Im very interested in the Picoscope you are using as I am looking to buy one myself. I was wondering what experience you have of using it and how you find it?

 

 

I take it is the Picoscope 2000 series, is it the 2203, 04 or 05?

 

 

Cheers Steve

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sport1901966

I think they are excellent tools. This one is a 2204 but I have used a 2203 and there is very little practical difference between the two, other than the signal out channel on the 2204. They are capable of silly sample rates, more than most would ever need. I was using the 2203 to log pressure fluctuations on an FS intake during each engine cycle at 16000 rpm which requires a pretty high sample rate!

 

They are excellent for vehicle diagnostics. The picotech.com site has loads of case studies and example waveforms - well worth a look.

 

Geoff

 

Excellent Idea.

 

Im very interested in the Picoscope you are using as I am looking to buy one myself. I was wondering what experience you have of using it and how you find it?

 

 

I take it is the Picoscope 2000 series, is it the 2203, 04 or 05?

 

 

Cheers Steve

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rallysteve

Cheers, I will check them out :)

 

 

 

Steve

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madspikes

I like it, great idea! Just like something I would come with!!

 

MAd :rolleyes:

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