Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

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Mckorkins
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Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Mckorkins »

Filled "Daisy" up with E5 97-98 Super Unleaded petrol for the first time today (was using E5 95) and she "pinked" a bit when under load, having previously had no trouble with the latter. My natural assumption was that the ignition dizzy ought be be retarded just a tad, but on reading the following post on the Web to confirm, this is what I found:

http://classicmechanic.blogspot.com/201 ... fuels.html


It is worth noting that once set, the engine must be run on the same grade of fuel used during the test thereafter. Modern, computer-controlled engines are capable of making dynamic adjustments to engine timing to compensate for higher or lower grade fuels, but these adjustments must be made manually in an older vehicle.
If you are running standard 95 RON unleaded, and decide to change to 97-98 RON super unleaded, the ignition timing should be advanced to achieve peak performance. If you are running super unleaded and wish to change to standard, the timing MUST be retarded to avoid damaging pinking.


The last para suggests I should be ADVANCING the ignition, not retarding it. I'm now confused so, where do I stand? Any clues would be appreciated. Of course, there is always the trial and error method!

"Daisy" is a 1962 convertible with 1098cc engine.
liammonty
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by liammonty »

The symptoms you report are the opposite to what I would expect - higher octane fuel is less prone to causing pinking at a given timing setting than a lower octane fuel, so you should be able to run slightly more advance. My cars will pink far more readily on 95RON than they do on ‘Super’, whether that be 97 or 99RON. Could your issue be a red herring, actually caused by something else, or perhaps you’re noticing it more as people are thinking about the potential issues with E10?
liammonty
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by liammonty »

To add - what you read is correct, but if your engine really is pinking, advancing the timing will make it worse. So the advice you read is sound, but your situation is the opposite to what you would expect :D
Mckorkins
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Mckorkins »

Thanks for your reply. Of course I'm aware of every extreneuos sound the car makes - even a squeaking door - but my wife noticed the pinking sound as soon as we filled up with super unleaded! It's not a classic high-pitched tinkle, but more of a low note when under load, so only pinking slightly in my opinion. Will try to advance ignition a touch to see if that cures it. It's definitely nothing like a loose tappet or a failing bearing in the engine.
Mckorkins
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Mckorkins »

Just had a thought: could it be the clutch thrust bearing slapping, I wonder? Will investigate, even if unlikely! :wink:
myoldjalopy
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by myoldjalopy »

I have been forced to use Super E5 over the last month or two without any pinking or other issues........except paying more to fill up! :(
Mckorkins
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Mckorkins »

Good to hear it's not pinking on super unleaded, even if it hurts your pocket! :)
simmitc
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by simmitc »

I'm just envious that you found somewhere that you could fill up. All the nice sensible people who do not believe in panic buying must have moved away from this area, leaving the few remaining of us with a choice: companies that have not reported a shortage of drivers have still run dry, thus option (a) is a closed petrol station; whilst option (b) is a supermarket with queues literally right round the entire car park, and a wait of almost an hour to reach the pump. :cry:
les
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by les »

When authorities say don't panic, guess what is inevitable? If nothing had been mentioned I’m pretty sure things would have been fine.
Classiccars
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Classiccars »

That's why they keep quiet about water shortages.People use more when they are asked to use less.What do you think of the civilised society.Sensible people buy a moggie
Mckorkins
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Mckorkins »

A friend just rang to say he can't get any diesel in and around Peterborough at the moment, so maybe won't be able to pay a scheduled visit to us in Somerset over the next few days. I said what about cycling down! Stony silence... :D
les
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by les »

Classiccars wrote: Sat Sep 25, 2021 5:14 pm .Sensible people buy a moggie
I’m not too sure about that !
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Classiccars »

Same here thinking about it Ha Ha
Mckorkins
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by Mckorkins »

A bit of fiddling with "Daisy" this afternoon. First of all, adjusted the clutch release bearing to 3/4" free movement of the pedal (was 1 1/2"), so eliminated that as a potential problem. Engine knocking still occured under load on a test run, so out with the stethoscope with probe and listened to the small ends when revving up (whilst static, of course!). No.3 just a tiny bit noisy, but not too bad at all. I reset the ignition, having found that it was probably a little bit too advanced and retarded it just a tad (I had set it for max rpm at tick over). Took it for another test run and found there was not so much knocking as before, so may have solved it. However, it's still a little noisy when under load, but I think that's general wear and tear and sloppiness of the engine, which has some 65,000 miles on the clock. I can learn to live with that. Rebuild this winter? Maybe. We'll see. :roll:
liammonty
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Re: Ignition timing using E5 97-98 Super Unleaded fuel - now pinking!

Post by liammonty »

Good to hear that you've potentially resolved your issue - I would be inclined to try another tank of fuel though, as the notion that you've had to retard the timing to cope with higher octane fuel just doesn't make sense - I wonder if it could have been a bad batch of fuel. Additionally, it's worth getting a strobe light on the engine and seeing how the distributor is actually advancing - they wear out and the advance curve can be all over the place. If you're getting much more than 30 degrees of maximum advance (i.e. at revs) then there's an issue - could be the distributor has started to advance unpredictably?

Re the clutch free-play - if your car's a 1098, the original inch and a half of play wasn't far off what it should be - the 3/4" is for 948 cars. Not that it will make any odds to the noise you are looking to eliminate, but I thought it worth mentioning :-)
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