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Setting base timing - BMW M50/M52

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Hi All, Im struggling on setting the base timing on the Link Fury. First off the recommended settings for this engine is either 30 or -328. Last year I was running a DTA ECU and it was set at -339. None of those settings work and found that it is quite happy at -282, then checking the base timing I locked it at 0 (as that's all I can see on the pulley) and cant get it near that mark with the timing light. The closest I can get is -295 before its unhappy, by the looks of things it would need to be about -310 to be on my locked 0 mark.

I have pulled the rocker cover off and double check the chain timing and all is ok.

One other thing that I have noticed is that when I blip the throttle around the 80 - 100 kpa it bogs down , accelerating slowly is fine. I know once I get the base timing right this might correct itself but thought it might be a clue.

I have also added my scope pattern.

I hope its something simple I have missed, Thanks.

Attached Files

I would check the polarity of the magnetic crank sensor. Perhaps there is a setting in the Link ECU for the edge to trigger on (should be falling edge), but you could reverse the polarity of the sensor then I believe the signal would be rising edge.

I did check the crank sensor polarity more than once and is all good (not sure about flipping it tho). As for checking the rising and falling edge...not sure??? I know the cam sensor setting and have attached another photo of the settings.

I was having another play with it tonight and with -282 setting and locked at 0 degrees, (and to reach my 0 degree mark with a timing light it would be about -310) I changed the first section in the main table to 10 degrees. It was much happier. I then changed it to 0 degrees and still happy and with the timing light it showed roughly 30 degrees BTDC. Now I thought when I locked the Ignition Timing to a point that was visible (my engine has a 0 degree mark) it ignored what was in the main table and everything else and just allowed you to calibrate it?

Attached Files

If you're in the calibrate menu and you've clicked on the 'set base timing' option, the timing will be locked at whatever you have in the 'Lock Ignition Timing...' box. The ECU will ignore the table values.

You can use the trigger scope function to confirm the polarity of the sensors and confirm they are set up as a falling edge trigger. It's useful to attempt to rev the engine with the timing fixed and make sure the timing shown with the timing light doesn't drift. If it drifts then this is a sign the polarity is wrong.

How are you getting a trigger for your timing light? Is it a basic inductive light or a more complex dial-back style? If I have doubt that the timing is correct, often I'll remove a coil and temporarily run an ignition lead from the coil to the spark plug so I have something I can clip the timing light on.

Beyond these aspects I'd be worried about the crank pulley/timing marks being inaccurate.

I have got a basic timing light with no dial back. I have unbolted the coil and fitted a HT lead. Sounds like I'm doing everything right, will need to go over it all again.

So if I Lock the timing to 0 degrees I should be able to change my -282 past TDC and back?

(another photo attached)

Attached Files

So I spent the day going back and forth over and over and ended up buying new M52 sensors (instead of the M50 ones I had) re wired them and still no good.

I have just found this from the Link help section under Incorrect Trigger Wheel Design. I copied it below.

This happens to be my crank pulley. (pictures didn't paste)

Does anyone know what happens when its a plug and play ECU? Do you also need a new crank pulley?

Design of the toothed wheels used for crank and cam angle measurement is critical. It is not uncommon for installers to machine or modify wheels.

Design of the "Gap"

One or more missing teeth are often used to indicate a reference position. One of the most common problems encounter on after-market wheels and in fact on some OEM (eg BMW) wheels is incorrect design of the teeth and gap. Some important points regarding the issue shown below:

· This is only a problem when there are teeth missing.

· This is usually only a problem on high tooth count wheels (eg 60-2).

· This problem gets worse at higher RPM.

· This problem is usually only encountered using Reluctor Sensors. Hall Effect sensors usually do not suffer from this phenomenon.

Incorrect design of the teeth around the gap can lead to a distortion of the sensors signal. There are a variety of contributing factors to this problem (electronic, magnetic), most of which can not be adjusted. The following pictures show a correctly designed wheel and the signal from that wheel at approx 7200 RPM.

GoodReluctorGap

Correctly designed gap

And the signal from the same wheel. Point A shows the arming voltage on the rising edge of the tooth after the gap. Point B shows the zero crossing. Point B is where the ECU sees the signal and uses it for engine position tracking. Note how the signal after point B goes well below zero volts.

GoodReluctorGap

Signal from correctly designed gap

However, it is more common in after market wheels and even some OEM wheels to have an incorrectly designed gap. This causes a problem at very high RPM . The following pictures show an incorrectly designed wheel and the signal from that wheel at approx 7200 RPM.

BadReluctorGap

Incorrectly designed gap

The signal from this incorrectly designed gap show a problem with the tooth after the gap. This signal was taken at approximately 7200 RPM.

BadReluctorGap

Note the excessive amplitude of the signal as the sensor enters and exits the gap. But, more importantly notice what is happening at point B. As RPM increases the negative voltage of the tooth after the gap is reducing. In the picture the signal is just OK as it still passes through zero volts. However, at around 7500 RPM this signals negative amplitude at point B was above zero volts and the tooth was missed all together. This causes the next tooth to be the one seen after the gap resulting in a loss of tracking of engine position. In this case resulting in a six degrees advance in timing to all cylinders!

Have you checked the factory timing marks are in fact correct?

Surely the factory pick-up & sensors must be able to be configured to work reliably?

Yes I have checked the factory timing marks with a dial gauge down cylinder 1 and the crank pulley mark lines up spot on. I had the rocker cover off a few days ago to check the chain timing also spot on. I have made a crank pulley with one large tooth instead of the 2 missing teeth and yes the scope pattern does improve. I'm in the middle of making an aftermarket hall sensor to fit the camshaft hole.

I agree I should just be able to use the factory sensors and pick up as I did last year with a DTA, that's what is giving me a headache.

I have managed to get it timed up. I made a camshaft sensor and it works for now. And still have no idea why the BMW sensors don't work which ever way I wire them up. Does anyone know if this will do the distance? I'm not sure about it being covered in oil and the heat. I have attached a photo.