Classic cars forum & vehicle restoration.

[nickjaxe]

Hi all was hoping somebody may be able to shed some light on something I have come across with my 1960s vehicle...its a motorcycle but wondering in general terms how owners of various types of vehicle find ignition static ignition timing with modern petrol with ethanol

So have any of you guys have had to move away from manufacturers book static ignition timing.

My 1969 2 stroke BSA Bantam when it was built had a book static timing of 16.5deg btdc....the timing is not adjustable on the move.

It doesn't like the 16.5 deg setting these days and needs to be around 15 deg BTDC.

I was wondering if anybody else has found the same.

I am thinking its down to the ethanol in our petrol...some say it has a slightly slower but rate some say a faster burn rate.

Love to hear your comments.
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http://www.youtube.com/watch?v=KbBlfYO46mI

My other hobby.

[alastairq]

Hi..you have asked the same question in your post above.

Yes, timing has to be adjusted...as does mixture. Nothing To do directly with ethanol in petrol...everything to do with the rest of the stuff that makes up petrol.

Ethanol has been around in fuel for a long time....and, historically, was old under the Cleveland Discol banner right up until the late 1970's.....

For years now quite a lot of petrol has contained up to 5% ethanol.

The ethanol issue has become a bandwagon which the banal [ie, not serious?] media have cottoned onto.

You have a link I posted in your other thread.....to a publication of results conducted by Manchester University, into the effects of modern petrols, and old technology engines.

They are quite an eye opener....and dispel much of the boswellox and urban myth surrounding ethanol, promoted by the casual press & media.

Worth a good read....3 or 4 times....and should be in there along with the Highway Code, for any sort of motoring enthusiast.....
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Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
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Ford Pop chassis, Ashley 1172 bodyshell, in pieces.

[peter scott]

My understanding (for what it's worth) is that modern fuels have an octane rating rather lower than we had back in the 1960s so engines with higher compression ratios from back then will tend to detonation.

I suspect retarding the ignition might not fully resolve the problem and putting a compression plate sandwich in place of the head gasket might be better.

My own old vehicle is pre-war and has a CR of 7.6:1 so it doesn't have a problem and it is particularly insensitive to ignition timing anyway.

BTW I do like your other hobby and the ELO music (You must get YouTube complaining about copyright though.)

Peter
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http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[alastairq]

[peter scott]

I know I didn't express it very well but I just meant that hundred and what ever octane petrol is no longer available on the average forecourt. No avgas.

Peter
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http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[alastairq]

Aaaah...different story then? But..as far as I can recall, the highest generally available octane rating back i the 1960's was 100 octane [what used to be known as 5 star petrol?]

If one has an engine which can only use 100 octane fuel....then one has some choices.
First, use 98 octane [so-called super unleaded, ]... If the engine pinks on that, then add some octane booster each fill-up?
Second choice, is to convert to LPG fuelling [which is, over 100 octane].

Third choice is to buy one of the specialist [racing] fuels, at around £4 a litre, and use that. these can be had with a variety of octane ratings.

Of course, one's engine has to be free of other influences which can cause pinking..for example, like attempting to reduce cyclic variation...[the timing of the burn of the mix].

Not many engine in regular use that require 100 octane fuels....

Personally, Id find some 98 octane petrol with 10% ethanol in it.
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.

[petelang]

Beginning to look like Alastair's pension fund is allied to book publishers...
Can anyone post the salient extracts as I shouldn't think there will be enough copies to go round..
Peter

[Miken]

Is the answer to get your old car or bike set up on a rolling road?

[Ray White]

[alastairq]

[ukdave2002]