You can not blame the fuel only for pinging. If the engine is not serviced correctly, correctly adjusted, valves, points, timing, airflow through the air filter and adjusted carburetor, the engines working temp is increased from little to heavy.
This in conjunction with low octane fuel will cause the fuel to ignite to early and you get pinging. Distorting the timing point will lead to increased working temp and should not be done to overcome pinging. The timing should be spot on 8 degrees TDC regardless of octane level. All our 2cvs are running on French octane 95 bought at Leclerc, Super U and wherever we fill up. We have no pinging in any of our 2cvs. We are running with pistons compression ration 8.5:1 and 9.0:1

Jono runs his on diesel, I am sure he will tell you the economics of that.

Have used French 95 [good name for a perfume me thinks] in our 2cv's without any problems.

This web site will give you day to day prices accros France, 95 is currently 1Euro 20c at our local.

http://www.prix-carburants.gouv.fr/

No, you can't.

But if an engine that doesn't pink at all on UK 95 pinks badly on French 95, with nothing else having changed, it's a fair bet that the difference in the fuel is the cause. Especially when it then doesn't pink on French 98, nor does it pink when it's back on UK 95 again.



General consensus in the UK is to time by ear - advance until they pink slightly, then back off slightly until they don't.



Because you've set them up to not pink when fed French 95.



For the sake of a couple of cents a litre, why not set the 9.0:1 up for 98, and benefit from the extra power?

Have noticed how many people are using the term pinging. When I was a lad [lonnng time ago] the term was pinking. Have just googled it and it seems over the years the term has indeed changed from pinking to pinging.

Is this political correctness.

No, it's a creeping americanisation...

It does pink a bit on diesel, I must admit.

However, as far as I can recall, my Dyane has never ever pinked in the time I've owned it - regardless of whether it's hot, cold, on 95, on 98, laiden, going up an alpine pass, or whatever. And no, the timing's not retarded to the Victorian era! It's just set up well, and it's a proper good 'un.

No I don't set them to French 95. I service these cars daily and I set them exactly to Citroëns specifications no more no less, regardless of compression ratio.
If they still ping after that, I replace the advance weights and all problems are gone.

Oh! Mr Chapman!
i thought the general consensus BTWK (by those who know) is to set it dynamically, or at least its getting there.
Viking (and others not familiar with the UK "debate"), Setting an engine to "exactly 8*" i presume that you mean setting it statically with the peg in the hole? There is scope for engine dammage as this takes no account of any wear in the advance weight stops and the factory tolerance for the max advance acceptable range was pretty generous when new ( maxing out at 40* IIRC). This setting running on modern unleaded will have the pistons like swiss cheese in minutes. 123 and similar dont help, while they do away with the advance weights the advance curve will still be advancing the ignition way past the point of max advance on the points set up, this too could cause pinking.

The work around would be to use the dealer spring balance gizmo to set the advance weight stops.

Or you can set the timing dynamically using a strobe the advantage being you set your engine to work with the optimal iggy timing at full load rather than optimising the timing for idle( where there is slim chance of engine dammage). down side is you might have a lumpy idle but hey ho who wants to sit at idle all day

Im SCOTTISH!

Sean

Even where modern 95 is not only much more volatile than the fuels when the car was new, but significantly lower octane?

None of my own or customers cars has ever blown a piston. I adjust the timing to 8 degrees every time and it is static. Never used a timing gun on a 2cv. Most people do not pay attention to the advance weights. Agree that electronic devices are not a cure but is often used as a quick fix.
Changing the advance weights with new and setting the timing correctly, I’m prepared to put my pretty head on the block and state that you have no pinging on octane 95