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Ignition timing for 1911 atmospheric inlet model E

Started by Ian, 07 Dec 2023 at 04:28

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Ian

Hi folks, I am finally getting round to doing some "post first rides" fiddling with my model E. I rode it a couple of days at the Bundaberg rally. My main query is what settings are suitable for an atmospheric motor for ignition timing ? When I was riding it I had to run almost fully retarded on the lever and it went well. I have not yet checked where it is actually set at the moment.  I am thinking it probably doesnt need as much advance as a mechanical valve motor ?

EW-Ron

Quote from: Ian on 07 Dec 2023 at 04:28
I have not yet checked where it is actually set at the moment.

If it runs and rides, I think you have about answered/solved your own question.
Check where it is currently set, and report back !

P.S. Isn't having variable ignition timing at your fingertips a wonderful invention.
Who needs an engine management 'puter to do all the figuring for ye ....

EW-Ron


Ian

Quote from: EW-Ron on 07 Dec 2023 at 04:38
Quote from: Ian on 07 Dec 2023 at 04:28
I have not yet checked where it is actually set at the moment.

If it runs and rides, I think you have about answered/solved your own question.
Check where it is currently set, and report back !

P.S. Isn't having variable ignition timing at your fingertips a wonderful invention.
Who needs an engine management 'puter to do all the figuring for ye ....
Well, I would prefer to know what the normal rule of thumb for these is as a starting point - as mentioned I was running fully restarted - how much more did I need to go ? I would prefer my normal mode to be fully advanced. But if no one has a rule of thumb I will work it out anyway.

Ian

Quote from: EW-Ron on 07 Dec 2023 at 04:45
I know we discussed this before ?, is a 1911 Model E somewhat akin to this Bonhams offering ?

https://images1.bonhams.com/image?src=Images/live/2012-09/21/8647077-1-1.jpg
That is my bike when bonhams sold it in about 2012

cardan

Hi Ian,
Great to hear that the bike is running.
The ignition timing for the FN four of the same period (also multi cylinder with atmospheric inlets) is 30 degrees BTDC fully advanced, so I'd guess that the Model E would be something around that mark. Perhaps you'll find that your current timing is about 30 degrees BTDC at full retard, and you can just advance the mag appropriately to get the stronger fully-advanced spark.
The biggest deal with the FN, and probably the Model E too, is the atmospheric inlet valves. The two things to get right are (1) the spring tension and (2) the maximum allowable valve lift. Not sure what tension is required (keep increasing until it's hard to start, then back off a little), but the amount the valve should be allowed to open is surprisingly small, likely no more than about 3mm. If the valve is allowed to open more than this the inlets can get very fluttery, and in this mode they are prone to run badly and break collets.
Hopefully someone with direct Model E experience can add more.
Cheers
Leon

Ian

Thanks Leon, I will take on board that suggestion re spring tension !

Hutch

Hi Ian,

I don't have any experience with the timing on a 1911 Model E Douglas but here is some information from the 1911 Douglas Booklet.

Hope this helps.

Cheers

Hutch

Hutch

Ian,

Leon makes a very good comment about the inlet valve springs - I had a quick look in the 1911 Booklet and this is what Douglas has to say about them and the exhaust valve springs.

Cheers

Ian

Ian

Thanks for that info. Exactly what I was looking for. Interestingly the ignition timing is set with the exact same method as my 23 TS !

EW-Ron

So it would be interesting to compare what you currently have with what is obtained by this method ?

Can we also infer from that blurb that there is NO valve overlap in the cam timing ? !!
Ah, the age of innocence and innocents ....

cardan

No overlap by definition in the age of atmospheric inlet valves: with no mechanical lift, the inlet valve would only open when the piston was on the down stroke after TDC, when the pressure in the cylinder was less than the atmospheric pressure on the back of the valve.

Early mechanical inlet engines mostly opened the inlet valve 5 or 10 degrees after TDC - it took a while to adopt the obviously ridiculous idea of having both valves open at the same time at TDC!

Of course Douglas had special problems with their atmospheric inlet valves. After some mucking around in the 1890s it was determined that to work properly the valve had to be vertical, and preferable head-down so that in its "resting" state the spring pulling up and the weight of the valve pulling down were just about balanced to give clean opening when the cylinder began to "suck". Easy in vertical cylinders (the inlet was almost always directly above the exhaust, to help cooling), but a bit of a mess when the cylinders were lying down. Perhaps Barter's weird vertical-exhaust-valve design was originally planned to have the valve heads opposite each other, but it doesn't seem the valves even line up in the final design? I don't think I've ever seen an atmospheric inlet Douglas cylinder in the flesh - it's a rare thing.

Leon

Ian

There were two at the national veteran rally Leon !