[TR] TR4 - Dwell v Points Gap

[Jim Muller]

On 2 Jun 2008 at 0:00, Greg Perry wrote:

> If I remember correctly the 4 cylinder scale is double
> the 8 cylinder scale reading.

Good point but it actually depends on how the dwell meter works.  If 
the meter measures the ratio (or the difference) between the on-time 
and the off-time then dwell would be independent of both rpm and the 
number of cylinders.  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.

An obvious way for the meter to know the firing interval is just to 
measure it is.  Of course, this is the same thing as measuring on-
time and off-time, and still means the result is independent of 
number of cylinders.  But if the meter's operating instructions are 
for the user to adjust the engine to a particular rpm using the 
meter's tach display, then the #-of-cylinders setting for the tach 
will affect the rpm display,.  So a wrong setting will mean the user 
is actually measuring dwell at the wrong rpm, thus producing a wrong 
dwell answer too.


-- 
Jim Muller
jimmuller at rcn.com
'80 Spitfire, '70 GT6+