MGB & GT Forum
Can Dwell be adjusted on an Electronic Ignition
Posted by Back2Bs
Topic Creator (OP)
Jul 3, 2015 08:11 PM
Joined 17 years ago
491 Posts
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Hello all,
I have an electronic ignition (Petronic I think ) in my 64 B- after being outside all winter covered only with a tarp I tried it after I got the snow off & it started and ran ok so I just covered it up and waited for some good weather. Fast fwd. a few months I come back & I try it again - it run but poorly under load. - life goes on I get back to it put in new wires pulgs & distb. cap - Same problem - I check compression its ok 170 -185 I test the dwell for the hell of it & it read @ 25 or so. Thought it was going to be @ 30 (or 60 depending on your meter)
any way I know I must have a few problems here but just wondered about the dwell-? can it even be adjusted or does it do it on its own..
any ideas?
I have an electronic ignition (Petronic I think ) in my 64 B- after being outside all winter covered only with a tarp I tried it after I got the snow off & it started and ran ok so I just covered it up and waited for some good weather. Fast fwd. a few months I come back & I try it again - it run but poorly under load. - life goes on I get back to it put in new wires pulgs & distb. cap - Same problem - I check compression its ok 170 -185 I test the dwell for the hell of it & it read @ 25 or so. Thought it was going to be @ 30 (or 60 depending on your meter)
any way I know I must have a few problems here but just wondered about the dwell-? can it even be adjusted or does it do it on its own..
any ideas?
Van-island-mgb thanked Back2Bs for this post
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Jul 3, 2015 09:20 PM
Top Contributor
Joined 18 years ago
24,294 Posts
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30 or 60...depending on meter. NOT. Depending on your reading instructions for your meter. These instructions should tell you for a 4cyl engine to multiply value seen by 2.
And if you want to fuss with the gap (dwell), go ahead and waste your time.
Nothing to be gained.
1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
Edited 1 time(s). Last edit at 2015-07-03 09:22 PM by mac townsend.
And if you want to fuss with the gap (dwell), go ahead and waste your time.
Nothing to be gained.
1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
Edited 1 time(s). Last edit at 2015-07-03 09:22 PM by mac townsend.
calsunshine
Paul R
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Jul 3, 2015 09:23 PM
Top Contributor
Joined 13 years ago
1,077 Posts
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Topic Creator (OP)
Jul 3, 2015 11:11 PM
Joined 17 years ago
491 Posts
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In reply to # 3028965 by mac townsend
30 or 60...depending on meter. NOT. Depending on your reading instructions for your meter. These instructions should tell you for a 4cyl engine to multiply value seen by 2.
And if you want to fuss with the gap (dwell), go ahead and waste your time.
Nothing to be gained.
And if you want to fuss with the gap (dwell), go ahead and waste your time.
Nothing to be gained.
Topic Creator (OP)
Jul 3, 2015 11:30 PM
Joined 17 years ago
491 Posts
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Well thanks for that Mac - yeah I have read my instructions & I have more than 1 meter The bottom line remains the same the dwell is off... & it would seem according to Paul that there are programmable electronic ignitions . Well I guess you forgot the question. Thanks for the reply...
Paul thanks for your input as I thought there were some that could be tweeked.
Paul thanks for your input as I thought there were some that could be tweeked.
In reply to # 3028965 by mac townsend
30 or 60...depending on meter. NOT. Depending on your reading instructions for your meter. These instructions should tell you for a 4cyl engine to multiply value seen by 2.
And if you want to fuss with the gap (dwell), go ahead and waste your time.
Nothing to be gained.
And if you want to fuss with the gap (dwell), go ahead and waste your time.
Nothing to be gained.
Jul 4, 2015 01:09 AM
Top Contributor
Joined 12 years ago
19,523 Posts
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I think the point (ha) Mac was trying to make is that dwell is not your problem and that trying to set or analyse your timing by it is an exercise in futility.
The dwell on simple points eliminating systems like the Pertronix and others is predetermined by the profile of the magnetic rotor so unlike with points where you can adjust it with those you can't.
To set your timing optimally throw away your dwell meter(s) and advance it until the engine starts to pink on heavy load then back it off a fraction until it doesn't.
The dwell on simple points eliminating systems like the Pertronix and others is predetermined by the profile of the magnetic rotor so unlike with points where you can adjust it with those you can't.
To set your timing optimally throw away your dwell meter(s) and advance it until the engine starts to pink on heavy load then back it off a fraction until it doesn't.
Jul 4, 2015 02:20 AM
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Joined 13 years ago
15,830 Posts
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Hi
Dwell is something that only needs to concern you with points, and is usually set by the point gap..
It is the measure of points closed vs points open, which in a mechanical system is fixed and a compromise. At low revs the dwell allows the coil to over energize and at high revs it under energizes.
With electronic systems the electronics measure the coil current and turn the current off when it has reached optimal.
If you measure dwell, on an electronic system and change the revs you will see that the dwell changes.
The coil needs a certain time to reach optimum current, after which there is no further advantage, and a bit of a disadvantage.
If you were to measure the time that the coil is ON, with your electronic system, you would find that that time is fairly constant.
Herb
Dwell is something that only needs to concern you with points, and is usually set by the point gap..
It is the measure of points closed vs points open, which in a mechanical system is fixed and a compromise. At low revs the dwell allows the coil to over energize and at high revs it under energizes.
With electronic systems the electronics measure the coil current and turn the current off when it has reached optimal.
If you measure dwell, on an electronic system and change the revs you will see that the dwell changes.
The coil needs a certain time to reach optimum current, after which there is no further advantage, and a bit of a disadvantage.
If you were to measure the time that the coil is ON, with your electronic system, you would find that that time is fairly constant.
Herb
tvrgeek
Scott S
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Jul 4, 2015 04:07 AM
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Joined 8 years ago
15,011 Posts
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Tim,
As mentioned, DWELL is not relevant to electronic ignition at all, as it controlled by the electronics. But what is making your car run poorly? What might have happened while it sat for months? Gunk in carbs? How do the plugs look? Vacuum leak?
I would run a bottle of Redline gas treatment through it first. Look for vac leaks. Be sure the vac advance and mechanical advance are working. Be sure your carb dashpots are free. Check the valve lash. All the usual stuff.
Cogito ergo sum periculoso
As mentioned, DWELL is not relevant to electronic ignition at all, as it controlled by the electronics. But what is making your car run poorly? What might have happened while it sat for months? Gunk in carbs? How do the plugs look? Vacuum leak?
I would run a bottle of Redline gas treatment through it first. Look for vac leaks. Be sure the vac advance and mechanical advance are working. Be sure your carb dashpots are free. Check the valve lash. All the usual stuff.
Cogito ergo sum periculoso
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