[TR] TR4 - Dwell v Points Gap

[Jeff Scarbrough]

At 01:46 PM 6/2/2008, Jim Muller wrote:
>If it just measures on-time or off-time and
>normalizes that against a firing interval then it would depend on how
>it "knew" the firing interval.

A dwell meter needs to know how many cylinders there are, either by 
switch or by scale.  My Mac pro meter has separate scales for 4, 6 
and 8 cylinders.

The dwell angle is the amount of distributor rotation ~per cylinder~ 
where the points are closed.  Typically, that number should be half 
of the total rotation per cylinder.  Bentley sez for TR6, dwell is 
35*, open angle is 25* for a total of 60*.  60 x 6 = 360.  For the 
Spitfire, dwell is 51*, open angle is 39* for a total of 90*  90 x 4 = 360.

That's why I said that the spec of 60* dwell was suspicious...that 
only leaves 30* or less for an open angle where the coil 
charges.  Doesn't sound like enough to me...


Jeff Scarbrough      75 TR6 x 1, 76 1500 x 2, 78 1500 x 1, 80 1500 x 0.5
http://www.fishplate.org/vehicles/
Athens, Georgia         #354