John Morrison Posted October 17, 2015 Report Share Posted October 17, 2015 Hi all, Dwell angle on a 4 cylinder TR, I use a band of 53 -57 degrees. Am I correct? John. Quote Link to post Share on other sites
mike3md Posted October 18, 2015 Report Share Posted October 18, 2015 Hi John, I think so, I set mine at 57deg and all is well. Are you now having doubts? http://www.tr-register.co.uk/forums/index.php?/topic/11188-dwell/ Mike Quote Link to post Share on other sites
Guest ntc Posted October 18, 2015 Report Share Posted October 18, 2015 50 is about right. Quote Link to post Share on other sites
RogerH Posted October 18, 2015 Report Share Posted October 18, 2015 Hi Folks, exactly what is dwell angle, how is it set and what does it do???? Roger Quote Link to post Share on other sites
Fireman049 Posted October 18, 2015 Report Share Posted October 18, 2015 Roger, I was about to ask the same question! Tom. Quote Link to post Share on other sites
RobH Posted October 18, 2015 Report Share Posted October 18, 2015 (edited) Its the time that the distributor points are closed for. By measuring the dwell angle you get a more accurate setting than just setting the gap, but you need a meter to do it with. http://www.howacarworks.com/ignition-system/checking-the-dwell-angle Edited October 18, 2015 by RobH Quote Link to post Share on other sites
Guest ntc Posted October 18, 2015 Report Share Posted October 18, 2015 You should not set the dwell as above with the engine running only cranking and the meter must be set to the variations in voltage before you begin Quote Link to post Share on other sites
Fireman049 Posted October 18, 2015 Report Share Posted October 18, 2015 Does this apply to the Albertronic 123 electronic distributor? Tom. Quote Link to post Share on other sites
peejay4A Posted October 18, 2015 Report Share Posted October 18, 2015 (edited) I think all electronic ignitions (that don't use the points) have the dwell "designed in" although I suppose it would be possible to vary it on a programmable system. Does it really make any difference if it's a degree or two out after setting the points with a feeler gauge? Is the difference detectable? If not it seems a bit of a faff having to measure, alter, measure, alter etc until you get a dwell that you're happy with. I suppose it could be useful as a quick check that the gap is OK. Edited October 18, 2015 by peejay4A Quote Link to post Share on other sites
Guest ntc Posted October 18, 2015 Report Share Posted October 18, 2015 Pete Yep your right but? the life of points is far better. Quote Link to post Share on other sites
mike3md Posted October 18, 2015 Report Share Posted October 18, 2015 As Neil says (I think), setting the dwell can be done by cranking the engine with the plugs out and coil disconnected. If you can arrange for someone to activate the starter motor (or have a remote starter control), just watch the meter and adjust the points to achieve your desired dwell whilst spinning the engine. Mike Quote Link to post Share on other sites
Eddie Cairns Posted October 18, 2015 Report Share Posted October 18, 2015 It seems to me you set the points gap and then measure the dwell angle. If the dwell angle is not to spec you set the points gap to a different value and measure the dwell angle. Unless the dwell angle is miles out, the point setting is the one to go by. If there is a problem with the dwell angle it shows you have a worn distributor. The dwell is a guide to distributor wear for the home mechanic nothing more than that. On some other makes of distributor you can adjust the points gap while the engine is running but not the Lucas ones I have used. In that case you can set the dwell angle with one of these distributors. Quote Link to post Share on other sites
Ian Vincent Posted October 19, 2015 Report Share Posted October 19, 2015 In my view setting the dwell is better than setting the points gap because it will accommodate slightly pitted points and if the dwell is uneven it indicates a worn distributor. The dwell should be set within a range dependent on the the number of cylinders and the profile of the cam. It is possible to manually check the dwell with the distributor out of the car by connecting an AVO across the points and rotating the distributor to measure the number of degrees when the points are closed. (Note this won't tell you if the dizzy is worn, you need the engine running for that). A 123 or similar does not have an adjustable dwell. Rgds Ian Quote Link to post Share on other sites
peejay4A Posted October 19, 2015 Report Share Posted October 19, 2015 I understand that some electronic systems can vary the dwell to allow the coil to build up energy better at high rpm. Quote Link to post Share on other sites
TriumphV8 Posted October 19, 2015 Report Share Posted October 19, 2015 (edited) It is just a point from where you view: If you are "old school" you look at the dwell in degree or percent what in practice is nonsense and comes from the times where only this could be measured. It was a progress compared to the feeler gauge method because the points tend to build a little hill on one contact and a valley on the other side preventing to set up the used points properly. But this method is not good if looking at the physics where a time is needed to load the coil to make it ready to fire when the points open. This time is about 2ms with modern coils. This should be kept constant. Can be compared to order a beer, if you give it half the time you will not get a full beer but more froth....... Unfortunately with different revs the time to load the coil differs because the earlier mentioned 53-57 degrees (should be percent?) will be finished faster or later depending on the rpm. 123ignition advertises "variable dwell" but that only means that it is a constant time at 2ms! As we have the "wrong" measurement of degree instead of milliseconds we see that variable dwell. Not to confuse us more than needed 123 advertises this constant dwell time as variable degree dwell. Somewhat funny when fully understood I think! By the way: The 4 cylinder TR4 is not critical concerning dwell and points gap. The fun starts with the TR6 that already needs a high power coil with short dwell. Also it should be kept in mind that with different gap or degree setup the position where the finger points towards the takeoff for the cylinder varies but also that is not critical on the TR4 and starts to become tricky with the 8 cylinder engines. Anyway if strange behaviour is found a last remedy can be to cut a window out of the distributor cap and idle the engine and look at that cylinder with a strobe. I found that some electronic points for our cars require significant turning of distributor and bring the take off away from the perfect position. Edited October 19, 2015 by TriumphV8 Quote Link to post Share on other sites
John Morrison Posted October 19, 2015 Author Report Share Posted October 19, 2015 Thanks all, I asked the question because although I had a note of 53 - 57 degrees, I couldn't find where it came from. I've used a target 55 degrees for years, and without problem. I started looking for confirmation because I'm having difficulty setting up a 'Spare' contact plate complete with gapped points and condensor, I always carry one in case of problems on the road, and having given my good known spare to a fellow group mermber can't get this new one to run much above 3000 revs or 60ish mph. This after two sets of points and two condensors, So the only common item is the actual contact plate carrier, and I fail to see how this could be my problem. One point arising from the above comments, dwell has to be at least as accurate as a feeler guage, and probobly more so. You do not need to bother with the phaff of setting points, putting everything back together, and then checking dwell, and then repeating etc. Top Tip, (Not Mine) fit the points, just nip then on the retaining screw, and with a dwell meter connected, have someone crank the starter. Simple then to adjust the points to perfect, by moving the points whilst reading the meter, set to about 52 degrees, (To allow for slow cranking speed) and when it is all back together check again when running, it will be within one degree! Never fails. Thanks again. John. Quote Link to post Share on other sites
peejay4A Posted October 19, 2015 Report Share Posted October 19, 2015 Just asking but how accurate is the average dwell meter? I'd imagine it's a simple RC circuit so dependent upon component tolerances. Quote Link to post Share on other sites
Eddie Cairns Posted October 19, 2015 Report Share Posted October 19, 2015 The only reason for the discussion to an extent is that inexpensive dwell angle meters are available. I have yet to be convinced that the are needed but tend to check any points job I do for no other reason than I have the meter. I have not seen test of powere etc against say readings of dwell from say 50 dgrees to 60 degrees in 1 degree stepps. Quote Link to post Share on other sites
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