Classic Audi Ľ Technical Ľ Mech/Tech Ľ Engine » Ignition timing question

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Old 08-04-20, 09:02 PM   #1
Sie!
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Default Ignition timing question

Evening all,

Time for a daft question from me, Iím looking for some assistance/guidance with the ignition timing on the 80. Itís the 4cyl DS (carb 1781).

To cut a long story short Iím about to take the distributor off to change the hall sender, but before I do that I wanted to check the ignition timing before I start, Iím new to this so have just bought a timing gun to assist.

So, from reading the haynes, my understanding is that when I take the vacuum feed off the dizzy, with the car at idle and warm, the ignition timing for the number one cylinder should be when the mark aligns with the pointer on the flywheel...the flywheel has two marks, one Ď0í which I believe is TDC, and one Ď|í, which I believe to be the ignition timing mark - is that correct?

So that when I replace the distributor, I set the static timing, then start the car and turn the dizzy until the gun flashes when the pointer aligns with the | mark - is that right...?

If I am right in what I say above, then when I checked the timing on the car today something strange is afoot, if I take the vacuum line off with the car warm, the gun fires and I cannot see anything on the flywheel, if I leave the advance attached, the gun flashes and the timing mark is about 3 teeth out, on the side of advanced.

Can the timing on the car be out by that much? MPG is great, power is fine, idles nice... and I've driven it over 50k and the timing has never been touched.

Sorry to babble on, I just donít want to take the thing to bits and not be sure on how to reset anything.

Many thanks for any advice you may have.

Stay safe!


Sie!
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Old 08-04-20, 09:52 PM   #2
mikes2
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Does your timing light have advance built in ?

They are a lot easier to use as they allow you to use the 0 mark for timing adjustment because the light does advance for you

The chances are your car will run a different advance for unleaded petrol. When these cars were new, standard 4 star was the norm.

What you should do is find the timing 0 mark on the flywheel and on the distributor make sure the rotor arm is aligned on cyl 1. You should have a mark on the distributor body and it will be close to this. Also check the front cam pulley mark is aligned. I'd recommend some tipex or white marker on the flywheel 0 mark.

This is the static timing and it allows you to remove the distributor. Consider taking a photo of your distributor and rotor arm position.

The | mark may not be useful due to the change to timing for UL.

When you refit the distributor, you'll need to offset the rotor arm so that when it engages with the camshaft splines, it should revert close to how the original was. You won't get it exact.

You need to get the car warm before making adjustments. If the vacuum advance needs to be disconnected, you'll need to plug it off. Cover the spout on the distributor and also block the vacuum line.

It sounds like on your car that with no vacuum advance , it's outside the range of the bellhousing window.

On my car I wanted roughly 5 degrees btdc. This is when timing lights with advance are good because you set the advance on the light to the required 5 deg and with the engine running, you can rotate the distributor until the 0 mark lines up with the bellhousing mark.

What's the normal timing for that engine ?

You will need to retard about 4-5 degrees for unleaded.

Hope this is of help - feel free to ask more questions
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Old 09-04-20, 08:41 AM   #3
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Thanks that’s very helpful, I never thought about a change in timing to compensate for different fuel... thought I was going loopy!

On the basis of what you say above, if I were to acquire a timing light with advance setting (I don’t currently have one), I guess I would be able to block the vac lines, then use the light and the TDC mark to dial in and find the current setting?

That way I would be able to simply retime the engine once I’ve refitted it to what it currently is.
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Old 09-04-20, 12:09 PM   #4
Sie!
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Actually on second thoughts, the comment above maybe a stupid statement, I thought you may be able to dial back on the advance timing gun, then look to align the flash with the TDC mark, but it appears not.

I believe the engine should be 18deg BTDC, but I’m even questioning that now, as I can’t find it in the blooming manual, I had just hoped to use the flywheel mark.

Last edited by Sie!; 09-04-20 at 12:18 PM.
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Old 09-04-20, 02:46 PM   #5
mikes2
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The timing light I got was the Innova 3568.

You can dial in the advance and use the tdc flywheel mark.

This might help for the DS engine

http://www.sealtd.net/quattro/ishamr...ervice_20.html
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Old 09-04-20, 03:22 PM   #6
tractor Dave
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I have b2 and b3 Haynes manual but can't find a DS engine in either?
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Old 09-04-20, 04:31 PM   #7
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Timing should indeed be 18 degrees retarded to 10 for unleaded. In practice the less you have to retard it the better (from a performance point). Historically it used to be possible to set the timing to around 12 -14. The main thing to look out for is Ďpinkingí if it does pink knock it back another degree or two.
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Old 11-04-20, 08:09 PM   #8
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Cracking advice, and thanks to all.

I finally managed to find it in the Haynes, itís in the supplement, and it does state 18deg BTDC with the vacuum connected - which tallies with what I was seeing on the flywheel... oddly it must be advanced a degree or two extra in my case.

Iíll whip the dizzy off early next week and retime the engine to specs with the new gun and the TDC mark and see where weíre at.

Just to confirm, if I hear it pink/ping/knock, I need to retard the timing a degree or two?

Thanks again for your patience guys, I really do appreciate it!
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Old 26-05-20, 09:32 AM   #9
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All done - thank for all your help!

Was much easier than I was thinking, not sure what I was bothered about! Managed to get it running at 14 BTDC on unleaded, with no pinking.

Thanks again gents!
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