Dwell on this ....

  1. JonathanT

    JonathanT Not normal for Norfolk

    Messages:
    1,075
    Location:
    Wymondham Norfolk
    I managed to pick up a nice Dwell / tuning meter at a car boot sale. I gather the dwell angle on an R4 GTL should be about 56 deg . But at what RPM??? Meter works great but the rpm varies the displayed angle
     
  2. Richnd1974

    Richnd1974 Enthusiast

    Messages:
    250
    Location:
    Bournemouth
    Check out my posts....
     
  3. Richnd1974

    Richnd1974 Enthusiast

    Messages:
    250
    Location:
    Bournemouth
    Search dwell
     
  4. harbourseal

    harbourseal Enthusiast

    Messages:
    473
    Location:
    Breda The Netherlands
    Set the stationary RPM at 750-775 the dwell angle should be round 56° + or - 6°
     
    Cornish4, JdeW and Richnd1974 like this.
  5. AdamWilkes

    AdamWilkes Enthusiast

    Messages:
    120
    Location:
    Poole
    I've always had trouble with dwell - set at 50 deg now with very small points gap (should be about 0.4mm). My points are 0.4mm at about 40 deg dwell, so I have experimented with dwell vs gap & found that more dwell (up to 50 deg) is good for running, but points need keeping clean or engine-starting becomes troublesome as the gap is then only 0.1-0.2mm. Could be my dizzy is knackered but the points are new (twice in two years just in case they were at fault!).
     
    Richnd1974 likes this.
  6. Richnd1974

    Richnd1974 Enthusiast

    Messages:
    250
    Location:
    Bournemouth
    My new accu spark electronic ignition has solved the starting issues but still need to wrestle with the timing as can't quite get it right, the timing marks are confusing me
     
  7. AdamWilkes

    AdamWilkes Enthusiast

    Messages:
    120
    Location:
    Poole
    The ignition timing dictates where in the piston-travel that the petrol mix is ignited in the cylinder, measured in degrees of rotation of the crankshaft away from the top of the piston-travel (zero being 'Top Dead Centre', TDC). Ignition timing set too early and the engine can 'pink' (pre-ignition, timing too advanced); too late and performance is reduced (timing retarded - and sometimes 'backfiring' or 'popping' begins as the resultant unburnt petrol burns in the exhaust pipe). For a R4, some degrees before TDC are normal - mine is said to be 6 degrees, set at the factory.

    Richnd, a strobe-light timing light with adjustable timing may solve your issue. The light timing-adjustment moves the light's flash-point - setting the strobe-light adjusting dial to 6 degrees and pointing it at the flywheel should show alignment between the TDC (zero degrees) mark (the gearbox/bell-housing mark nearest the middle of the engine on the 1108cc) and the single flywheel mark, if the engine timing is currently set at 6 degrees before top dead centre (BTDC).
    Using this method means that the other (confusing) timing marks can be ignored, and just use the strobe-light adjustment dial to read the current timing advance. Timing marks on the bellhousing for the 1108cc engine seem to be in one degree steps - zero to eight degrees, though they are tricky to see - especially with fading eyesight resolution (hence my use of the adjustable timing strobe!).

    Currently mine is running well at 11 degrees BTDC (which would be off the scale if I used the bellhousing markings) - far more than the 6 degrees 1984 'book' value.
    More ignition advance gives the petrol more time to burn fully before being shoved out into the exhaust, but too much advance reduces efficiency as the early petrol burn works more to slow the piston's rise rather than to power it's fall. There will be a sweet spot!
     
    JdeW likes this.
  8. Richnd1974

    Richnd1974 Enthusiast

    Messages:
    250
    Location:
    Bournemouth
    Just timed it up to 8 degs btdc and idles smooth and revs smooth, I will have to test drive tomorrow as burnt my arm on the exhaust like a complete plum....
     
  9. petak

    petak Enthusiast

    Messages:
    1,079
    Location:
    Vodice, Croatia
    I could not read dwell angle when switched to accu spark.

    With plugs i have set it to 54° with 0,4 gap.
     
    Richnd1974 likes this.
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