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Car Forum / MINI / February 2006Dwell Angle
Anyone know if the dwell angle changes with rpm? Martin 1986 998cc Mayfair > Anyone know if the dwell angle changes with rpm? > > Martin > 1986 998cc Mayfair There is a very slight variation due to rev's, but nothing to cause a problem,when the heel on the points wears down this causes the dwell angle to alter, and in turn this causes your ignition timing to alter, Fitzy Fizzy Thanks, I thought it might be you to reply first or Steve68s, The reason I ask it that I can get the car to idle quite nicely then for no reason the revs will drop and she stalls. Dwell angle will be 53.9 when cold and on choke then drop to 51ish when fully warmed up and the stalling occurs. I know I need to get this up to 54 ish when hot by closing the contact breaker gap a little, but suspect my problem might be a dodgy coil or other HT component, Any thoughts? Martin >> Anyone know if the dwell angle changes with rpm? >> [quoted text clipped - 5 lines] > angle to alter, and in turn this causes your ignition timing to alter, > Fitzy >Anyone know if the dwell angle changes with rpm? > >Martin >1986 998cc Mayfair If you're talking about a conventional mechanical distributor, then no, it's a function of the shape of the cam and the geometry of the points. If you're talking about an electronic distributor, then it does vary deliberately, reducing the dwell at low rpm and increasing it at high rpm.  SignatureChris Morriss Normal Dizzy with Mechanical points as fitted to a std Mayfair 1986 998cc thanks >>Anyone know if the dwell angle changes with rpm? >> [quoted text clipped - 5 lines] > you're talking about an electronic distributor, then it does vary > deliberately, reducing the dwell at low rpm and increasing it at high rpm. > Normal Dizzy with Mechanical points as fitted to a std Mayfair 1986 998cc > thanks [quoted text clipped - 9 lines] >> deliberately, reducing the dwell at low rpm and increasing it at high >> rpm. Depending on what distributor is fitted,, Lucas or Ducellier, The average Dwell setting is 57 plus or minus 5, also remember ,, the wider the angle the narrower the gap, the narrower the angle = the wider the gap, always set the dwell to the narrowest angle, When the heel on the points begins to wear, (effectively closing the points), the dwell should still be within spec, HTH Fitzy >>Normal Dizzy with Mechanical points as fitted to a std Mayfair 1986 998cc >>thanks [quoted text clipped - 21 lines] > Fitzy > On a 4 cylinder car the dwell angle is not so critical as it is with 6 or 8 cylinder cars. As the capacitor has far more time to recharge compared to the 8 cylinder distributor. Normally for any 4 cyl car just make sure the point gap is correct. Although checking the dwell will indicate a worn or bent internals and this should be within 3 degree (this degree of variation is about the amount the timing will vary on each cylinder). I usually setup a distributor on the bench. Check to make sure the mechanical advance is working. The point gap on each lobe checked with feeler gauge. I agree with Rob, with this addition. I measure dwell when I can't take time to remove the distributor cap to check the point gap. I measure the point gap when the distributor cap is off and I don't want to put it on to check the dwell. Cheers, Kelley >On a 4 cylinder car the dwell angle is not so critical as it is with 6 >or 8 cylinder cars. As the capacitor has far more time to recharge [quoted text clipped - 8 lines] >mechanical advance is working. The point gap on each lobe checked with >feeler gauge. |
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