Good evening guys,
Today in France, it was a sunny day ! A good time to have a ride with the SP250 currently into my workshop.
The ride was a real pleasure, the engine, recently and completely rebuilt, seems to run perfectly. Once back at my workshop, just by professional consciousness, I decided to check up the dynamic ignition timing and the Dwell angle. For that purpose, I use a Gunson G4123 Supastrobe Professional.
10°BTDC at 750 rev/mn : perfect. But concerning the Dwell angle, 98% !!! Can any engine run with a such Dwell angle ?!? The data given by the official handbook is 32% !! Should I incriminate my device or should I adjust my contact points gaps ?
Thank you,
Julian
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SP250 Dwell angle
Re: SP250 Dwell angle
Don't you halve the reading for an 8 cylinder engine?
Re: SP250 Dwell angle
When the Dwell angle is given in %, no matter the number of cylinders. I think...
Re: SP250 Dwell angle
Just my 2c
For an eight cylinder engine the distributor needs to trigger eight sparks in one revolution of the distributor shaft.
This leaves a mere 45° degrees of revolution for each spark.
The dwell angle therefore should be at about 33°.
I guess the figure given in the handbook is correct
Hans
- dwell angle too small ==> ignition coil will not deliver it’s maximum power
- dwell angel too big ==> ignition coil will overheat
For an eight cylinder engine the distributor needs to trigger eight sparks in one revolution of the distributor shaft.
This leaves a mere 45° degrees of revolution for each spark.
The dwell angle therefore should be at about 33°.
I guess the figure given in the handbook is correct
Hans
owner since 2015
https://www.wyhe.ch/
https://www.wyhe.ch/
Re: SP250 Dwell angle
Page 2 of the instructions.
For an 8 cylinder engine: Dwell % = Dwello / 0.45 assuming a single distributor and a single set of points.
The data sheet for my dwell angle meter quotes 31o- 37o for a Lucas 20D8 distributor on a Daimler V8. That would be 70% - 82%. Your gap is slightly off at about 44o. The gap needs to be increased slightly.
If all else fails, read the instructions!
For an 8 cylinder engine: Dwell % = Dwello / 0.45 assuming a single distributor and a single set of points.
The data sheet for my dwell angle meter quotes 31o- 37o for a Lucas 20D8 distributor on a Daimler V8. That would be 70% - 82%. Your gap is slightly off at about 44o. The gap needs to be increased slightly.
If all else fails, read the instructions!
Re: SP250 Dwell angle
Chris,
Are you saying that the value of 32 given by my SP250 Handbook is a degrees and not a percentage ?
In this case, I would understand...
Julian
Are you saying that the value of 32 given by my SP250 Handbook is a degrees and not a percentage ?
In this case, I would understand...
Julian
Re: SP250 Dwell angle
Does the fact that there are two sets of points make a difference ?
Also how much wobble is in the shaft ? If it is considerable then it will exacerbate the findings.
That said if it is running sweet then leave it well alone.
Also how much wobble is in the shaft ? If it is considerable then it will exacerbate the findings.
That said if it is running sweet then leave it well alone.
Colin,
I may be slow but I’m rough as well !
I may be slow but I’m rough as well !
Re: SP250 Dwell angle
If there are two sets of points each set is tested separately with no connection between them.