FV Ignition Timing
Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo
Re: FV Ignition Timing
I occasionally run my 1936 Marston OJ in a tank, and it has variable timing. The difference from advanced to retarded is pretty minor, and if I had had the job done I wouldn't regard it as money well spent. However I'm not using the thing for hours at a time on a Scottish Loch!
Re: FV Ignition Timing
I have just got around to checking the dynamic ignition timing of an FV.
I used a strobe light in conjunction with painting marks every 10 degrees from TDC on the cover plate, and a pointer clamped to the tank mounting. I used FV1867T (which has the points set to the standard .020) in a test tank.
This showed that the spark occurred at approx. 50 degrees BTDC.
This surprised me as apparently the 'standard' setting is 23.5 degrees.
I spent a bit of time adjusting the angle, but unsure of the result except that possibly 30 to 40 degrees appeared 'better'.
However, this work, even with the older smaller Seagulls, must have been carried out by experts many times over the last 65 years. Has anybody got the results of this work?
It is possibly rash to jump to conclusions following one test on one engine, but there is a big difference between 50 and 23.5 degrees.
Would somebody else like to carry out this check?
Wouldn't starting be easier at 30 degrees compared to 50?
I think that I might well try a trial run on a dinghy with a 30 degree setting.
Jeremy
I used a strobe light in conjunction with painting marks every 10 degrees from TDC on the cover plate, and a pointer clamped to the tank mounting. I used FV1867T (which has the points set to the standard .020) in a test tank.
This showed that the spark occurred at approx. 50 degrees BTDC.
This surprised me as apparently the 'standard' setting is 23.5 degrees.
I spent a bit of time adjusting the angle, but unsure of the result except that possibly 30 to 40 degrees appeared 'better'.
However, this work, even with the older smaller Seagulls, must have been carried out by experts many times over the last 65 years. Has anybody got the results of this work?
It is possibly rash to jump to conclusions following one test on one engine, but there is a big difference between 50 and 23.5 degrees.
Would somebody else like to carry out this check?
Wouldn't starting be easier at 30 degrees compared to 50?
I think that I might well try a trial run on a dinghy with a 30 degree setting.
Jeremy
Re: FV Ignition Timing
I have a digital display strobe, so I will only have to put a TDC mark on the flywheel. I will give it a go on my FVP tomorrow.
Re: FV Ignition Timing
Gave It a try, on very low tick over I was getting Around 48 degrees BTDC, I did notice I have got the throttle stop on this motors carburettor.
Re: FV Ignition Timing
Thanks for doing that Keith. In effect the same value as I got, so one can begin to assume that 48 degrees could be the standard setting.
How does this square with 23.5 degrees thought to be the standard setting. We need a few more results.
I would be interested in the position of the base plate securing bolt. Is it on the TDC/BDC centreline or offset 5/10 degrees to one side? My FVs have it to one side which increases the advance.
I don't think it is significant what the rotational speed is. The angular advance will be the same for all speeds.
Jeremy
How does this square with 23.5 degrees thought to be the standard setting. We need a few more results.
I would be interested in the position of the base plate securing bolt. Is it on the TDC/BDC centreline or offset 5/10 degrees to one side? My FVs have it to one side which increases the advance.
I don't think it is significant what the rotational speed is. The angular advance will be the same for all speeds.
Jeremy
Re: FV Ignition Timing
I gave FV1867T a run on my small dinghy, having previously moved the base plate to give an advance of 30/35 degrees.
It started well (first pull) from cold and ran quite smoothly. At full throttle the power was, to quote another British icon, 'sufficient' - one could add 'just'!
Another cold start produced the same result, as did a few warm starts. This is not untypical of how it was previously.
I was pleased with the starting performance, as on my small dinghy the engine is immersed quite deeply when I am in the stern starting it, and there is nobody to sit in the bow to put the boat on an even keel. My electric start FV project will resolve this problem.
To sum up:- With this very subjective test there is no positive conclusion as to whether 50 or 30/35 degrees is better. However I think I am going to leave it at its present setting, although I am extremely reluctant to make any change from BS's original specification in this or any other matter.
However I am very curious as to how we have got to this situation.
Can somebody comment as to whether modern fuels burn quicker and require less advance?
Also what is the actual setting for other Forty series engines?
Keith's later FVP had an advance of 48 degrees. Can anybody provide information on any other FV/FVP?
Jeremy
It started well (first pull) from cold and ran quite smoothly. At full throttle the power was, to quote another British icon, 'sufficient' - one could add 'just'!
Another cold start produced the same result, as did a few warm starts. This is not untypical of how it was previously.
I was pleased with the starting performance, as on my small dinghy the engine is immersed quite deeply when I am in the stern starting it, and there is nobody to sit in the bow to put the boat on an even keel. My electric start FV project will resolve this problem.
To sum up:- With this very subjective test there is no positive conclusion as to whether 50 or 30/35 degrees is better. However I think I am going to leave it at its present setting, although I am extremely reluctant to make any change from BS's original specification in this or any other matter.
However I am very curious as to how we have got to this situation.
Can somebody comment as to whether modern fuels burn quicker and require less advance?
Also what is the actual setting for other Forty series engines?
Keith's later FVP had an advance of 48 degrees. Can anybody provide information on any other FV/FVP?
Jeremy
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Stylo Seagull
- Posts: 15
- Joined: Thu Aug 15, 2013 12:28 pm
- Location: Norwich
Re: FV Ignition Timing
from someone who tinkers with vintage scooters, I have to say that 50 degrees BTDC sounds like a mahoosive amount of advance to me....
i'm not disputing it at all in anyway, but with the lesser quality of modern fuels (and much higher states of tune), most scooter engines get timed to 16-18 degrees BTDC! Run even a bog standard lambretta engine at the old innocenti figures of 21-23 degrees and they really won't be too happy.
I'm guessing the good cooling properties of the engine help to deal with the heat produced by such an advanced spark, but am surpirsed the engines don't pink more than they do with that much advance... Or could this be because they are fed with an overly rich mixture as standard?
Interesting stuff.
i'm not disputing it at all in anyway, but with the lesser quality of modern fuels (and much higher states of tune), most scooter engines get timed to 16-18 degrees BTDC! Run even a bog standard lambretta engine at the old innocenti figures of 21-23 degrees and they really won't be too happy.
I'm guessing the good cooling properties of the engine help to deal with the heat produced by such an advanced spark, but am surpirsed the engines don't pink more than they do with that much advance... Or could this be because they are fed with an overly rich mixture as standard?
Interesting stuff.
FP416G2
Re: FV Ignition Timing
Thanks Stylo,
As you say interesting stuff.
Thanks for your comments. I keep thinking that I have made a complete hash of the measurement, so I was glad that Keith with a broadly same age Seagull, got the same result.
I would very much like other owners to do the measurement. Dynamically with a strobe is possibly the best method, but determining when the points open would, I think, be satisfactory. This could be done visually or with a meter connected across the points.
Do you have a Seagull on which you could measure the advance?
You state 'the lesser quality of modern fuels'. Presumably you are referring to 'old' fuels of the 1980s which had plenty of lead and other differences that I don't know anything about.
I was suggesting that fuel of the early 1950s was different to present day fuel. Is the difference mainly in the quicker flame/burn speed of modern fuels?
Jeremy
As you say interesting stuff.
Thanks for your comments. I keep thinking that I have made a complete hash of the measurement, so I was glad that Keith with a broadly same age Seagull, got the same result.
I would very much like other owners to do the measurement. Dynamically with a strobe is possibly the best method, but determining when the points open would, I think, be satisfactory. This could be done visually or with a meter connected across the points.
Do you have a Seagull on which you could measure the advance?
You state 'the lesser quality of modern fuels'. Presumably you are referring to 'old' fuels of the 1980s which had plenty of lead and other differences that I don't know anything about.
I was suggesting that fuel of the early 1950s was different to present day fuel. Is the difference mainly in the quicker flame/burn speed of modern fuels?
Jeremy
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Stelios_Rjk
- Posts: 1458
- Joined: Sun Jun 17, 2012 10:15 pm
- Location: Athens - Greece
Re: FV Ignition Timing
Hi guys,
In order to be able more members to follow this topic could anyone shed some light?
How could I "see" the zero degree angle or how could I specify 20 or 23.5 degrees BTDC?
In order to be able more members to follow this topic could anyone shed some light?
How could I "see" the zero degree angle or how could I specify 20 or 23.5 degrees BTDC?
I love the 10600/145 turns!!!
Re: FV Ignition Timing
Hi Stelios,
Fix a small pointer to the engine so that it is points to or just above the flywheel or cover plate.
Turn the engine to TDC.
Put a mark on the flywheel or cover plate opposite the pointer.
With a protractor draw marks on the flywheel or cover plate at 10, 20, 30 40 etc degrees with 0 degrees at TDC.
Stylo,
Do Lambrettas have a timing which varies with engine speed?
If they do, then starting at 17 degrees, what is the actual advance at top engine speed? Would it be near, say, 50 degrees?
Jeremy
Fix a small pointer to the engine so that it is points to or just above the flywheel or cover plate.
Turn the engine to TDC.
Put a mark on the flywheel or cover plate opposite the pointer.
With a protractor draw marks on the flywheel or cover plate at 10, 20, 30 40 etc degrees with 0 degrees at TDC.
Stylo,
Do Lambrettas have a timing which varies with engine speed?
If they do, then starting at 17 degrees, what is the actual advance at top engine speed? Would it be near, say, 50 degrees?
Jeremy
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Charles uk
- Posts: 4972
- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: FV Ignition Timing
How are you fixing where TDC is?
On a standard Century the piston moves 0.004" between TDC & 5 degrees ATDC, & it's less than that on a FV with it's shorter stroke.
On a standard Century the piston moves 0.004" between TDC & 5 degrees ATDC, & it's less than that on a FV with it's shorter stroke.
Make it idiot proof and someone will make a better idiot.
Re: FV Ignition Timing
Charles,
I am using a Dial Indicator Gauge, but still find it a little bit difficult to judge it precisely.
I would expect that by the time I have made a TDC mark on the flywheel and transferred this mark to the cover plate the error could be +/- 5 degrees.
Then using a protractor, I have put white paint marks every 10 degrees on the cover plate. Probably accuracy of this operation is within +/- 3 degrees.
Then interpretating the position of the strobe light on the white paint marks with respect to the pointer could have an error of +/- 5 degrees.
Total error would be within +/- 13 degrees. The actual error might be, if we are lucky, nearly zero, but is probably about 5 degrees.
Charles,
What's your view on this issue? What advance do you set on your engines? How do you measure it?
The most important question - does it really matter?
Jeremy
I am using a Dial Indicator Gauge, but still find it a little bit difficult to judge it precisely.
I would expect that by the time I have made a TDC mark on the flywheel and transferred this mark to the cover plate the error could be +/- 5 degrees.
Then using a protractor, I have put white paint marks every 10 degrees on the cover plate. Probably accuracy of this operation is within +/- 3 degrees.
Then interpretating the position of the strobe light on the white paint marks with respect to the pointer could have an error of +/- 5 degrees.
Total error would be within +/- 13 degrees. The actual error might be, if we are lucky, nearly zero, but is probably about 5 degrees.
Charles,
What's your view on this issue? What advance do you set on your engines? How do you measure it?
The most important question - does it really matter?
Jeremy
Re: FV Ignition Timing
If I'm the Charles you're referring to (rather than the older and less good looking one) then I have consistently relied on British Seagull's dimple to provide me with the right timing.
Apart from once when I made the cringingly embarrassing mistake of putting a Century crankshaft into a Forty Plus, and wondered why it didn't work!
I have never had a problem with timing, and as far as I'm concerned all the magnetos are interchangeable once you get past the early domed ones.
So I work on the principle that if the motor doesn't fire then it ain't the timing that's wrong.
Apart from once when I made the cringingly embarrassing mistake of putting a Century crankshaft into a Forty Plus, and wondered why it didn't work!
I have never had a problem with timing, and as far as I'm concerned all the magnetos are interchangeable once you get past the early domed ones.
So I work on the principle that if the motor doesn't fire then it ain't the timing that's wrong.
Re: FV Ignition Timing
Charles P. I am not going to upset the other Charles by agreeing that you are the young handsome one, in case by implication ......
The motor fires and runs, and therefore you would say the timing isn't 'wrong'.
However, if we weren't curious about these old outboards, we wouldn't be interested in them. I know curiosity killed etc etc, but why does the timing appear to be approx 48 degrees BTDC instead of the stated 23ish degrees? Or is this difference just relevant to the FV/FVPs? Or is it a measurement problem?
I think it is reasonable to consider and understand whether or not BS's specification for the timing advance needs to change with modern different fuels; in the same way that the oil to petrol ratio has changed with the different oils now used.
Thanks for confirming that magnetos are interchangeable.
Jeremy
The motor fires and runs, and therefore you would say the timing isn't 'wrong'.
However, if we weren't curious about these old outboards, we wouldn't be interested in them. I know curiosity killed etc etc, but why does the timing appear to be approx 48 degrees BTDC instead of the stated 23ish degrees? Or is this difference just relevant to the FV/FVPs? Or is it a measurement problem?
I think it is reasonable to consider and understand whether or not BS's specification for the timing advance needs to change with modern different fuels; in the same way that the oil to petrol ratio has changed with the different oils now used.
Thanks for confirming that magnetos are interchangeable.
Jeremy
Re: FV Ignition Timing
I understand your wish to not upset the other Charles, at his age people get sensitive..
Yes it's a fascinating subject, ignition timing, and I wish I had studied the whole issue more closely. I am sure that your comment about different fuels is a pertinent one; I understand that the stuff we put in opur 'petrol' or 'gas' tank varies tremendously with time and, of course, country. I have one Seagull tank which refers to a different oil mix for 'Benzol' based fuels, and it makes sense that some differences may exist.
I will be interested to see the issue bottomed out.
Yes it's a fascinating subject, ignition timing, and I wish I had studied the whole issue more closely. I am sure that your comment about different fuels is a pertinent one; I understand that the stuff we put in opur 'petrol' or 'gas' tank varies tremendously with time and, of course, country. I have one Seagull tank which refers to a different oil mix for 'Benzol' based fuels, and it makes sense that some differences may exist.
I will be interested to see the issue bottomed out.