Setting timing using elanscan

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Setting timing using elanscan

Postby Rocklobster » Fri 15.03.2019, 18:09

I've connected a switch in that allows me to switch to service/diagnostic mode without having to crawl around in the passenger footwell. This leaves the plug free, so I can attach and run elanscan and switch the car into service mode at the same time. Question is, is the elanscan data for spark advance accurate and is there any reason why this can't now be used when setting the ignition timing?
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Re: Setting timing using elanscan

Postby Brit-Car-Nut » Fri 15.03.2019, 18:25

I believe the ElanScan is "seeing" the ECM version while you NEED to disable the ECM to set the timing the old fashion way. If you do that once and then read the idle timing with ElanScan, then that that should be a number you could use with the ECM engaged and looking at ElanScan.

Hopefully, someone will confirm that my logic is correct.
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Re: Setting timing using elanscan

Postby Giniw » Fri 15.03.2019, 19:03

Hi,
Elanscan will tell you what the ECU is requesting the engine to be at. But the ECU isn't reading anything from the engine: it commands the timing, only assuming it's mechanically properly set at its reference. There is no feedback.
So if the ECU is in diagnostic mode and you can read the ECU requested timing through Elanscan at the same time (not sure if it's possible?), I highly suspect ElanScan will tell you 16° for any CAS rotational value. Because the diag mode locks the ECU requested value to 16°.

So you really need to check the ignition ignites the spark at 16° when the ECU is asking for 16°. That is the point of the CAS adjustment.
Last edited by Giniw on Fri 15.03.2019, 19:52, edited 1 time in total.
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Re: Setting timing using elanscan

Postby Fredjohn » Fri 15.03.2019, 19:42

Simple answer, you can't set the timing using elanscan.
You have to use a strobe light in the old fashioned way, but in service mode.
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Re: Setting timing using elanscan

Postby Rocklobster » Fri 15.03.2019, 19:54

Thanks all, I suspected it would be too good to be true. Wheel off it is then...
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Re: Setting timing using elanscan

Postby Simon_P » Sat 16.03.2019, 11:21

Hopefully a little more (or perhaps clearer) explanation.

For the time being forget any thought of ignition timing that is not directly what you are setting.

The Cam Angle Sensor has within it two passive sensors 1. the Hall sensor provides a reference sync-pulse for angular (rotational) position 2. A magnetic sensor which provides pulses used for position and engine speed. The pulses will always be generated at the same angular position of the CAS

The CAS is adjustable relative to the engine, hence the reference pulse is adjustable to Crankshaft angular position.
The ECU is expecting position pulses from the CAS to happen at certain angular positions of the crank (which is fixed relative to the camshaft).
Putting the ECU into service mode fixes the spark timing to 16° BTDC
But the ECU relies on the CAS to produce a pulse to know when 16°BTDC is.
You use the strobe to set the position of the CAS such that it produces a pulse that results in a spark that you are measuring to be at 16° BTDC
You now fix the position of the CAS and it always produces pulses at the same angular positions of the engine. ie it now knows when the engine is at TDC or any other position.

Now exit service mode and think of Ignition timing.
The Ignition Control Module and the ECU take the sync pulse, position pulse, and speed pulses from the CAS together with sensor parameters and depending on operating conditions calculate the desired ignition timing which is then triggered as an offset to the CAS pulse.

The ignition timing is calculated and variable and related to the CAS pulse. The CAS pulses are always in the exact same position.

So back to the question
"is the Elanscan data for spark advance accurate"
Yes, but only as accurate as you set the base timing.

"and is there any reason why this can't now be used when setting the ignition timing?"
Yes! You are not setting the ignition timing, you are calibrating the Base Timing from which ignition timing and injector timing are derived. What if anything you see for Ignition timing in Elanscan has nothing to do with setting the base timing. And the 16°BTDC ignition timing quoted is only relevant to setting base timing.
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Re: Setting timing using elanscan

Postby Rocklobster » Sat 16.03.2019, 12:24

Thanks Simon. I couldn't have explained it better myself....or at all actually.
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Re: Setting timing using elanscan

Postby Brit-Car-Nut » Sat 16.03.2019, 13:26

Likewise, THANKS Simon. That made things understandable.
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