Tom Fansher asked...
>I sent the last request to the digest since I'm digest only. However, I got no
>replies.
>I'll try again. I know there are two aftermarket electronic ignition systems
>available,
>but can't remember which is "better." I seem to remember from earlier
>discussions that
>one mounts inside the distributor cap and one mounts on the firewall/inner
>fender with
>wires to the distributor. Which is which? Also, do they use the standard
>coil? Also,
>how do they mount to the distributor, to the base plate? I have a good base
>plate, but the
>wires inside the distributor fried last weekend. ALso, I guess that they are
>available in
>neg or pos ground. I was going to convert to negative ground anyway. Thanks
>in advance
Tom:
I can't say one is better, as I am only familiar with the Crane (or Allison)
unit.
I have two Crane units on two LBC: one 1500 cc Spitfire and one 1500 cc Midget.
Both have
given pretty good service (with some provisos--read on). To make it short, I
highly
recommend the Crane unit. This unit does have a small electronic module (about
2 in. by
3 in by 1.5 in, from memory) that you mount on the firewall, or somewhere
convenient, and
connect by cables to the distributor photodiode sensors and to the power
supply. It is not
obtrusive, but it will stand out in an otherwise stock TR-3/4 engine bay.
I had two failures with the Crane unit early on. It has (or had at the time) a
lifetime
warranty, both were covered. In the second failure, I discovered that I was
driving it
at 12 V, rather than at 6 because of a DPO "adjustment" of the wiring to the
ballast resistor.
This caused it to run very hot to the touch, and it only lasted about 5 months.
The model
sold for the 1500 cc engine implies it is supposed to be used with the ballast
resistor in place,
but the instructions are a bit ambiguous--it doesn't say it should be driven at
6 V (except at
starting it sees 12 V). When I connected its' replacement up to the 6V source,
I couldn't
tell the difference from the 12 V; both make it perform very well, but 12 V
will kill it,
eventually (other models may be designed for 12 V, I can't say, but I think the
same part number
is sold for late Midgets with ballast resistor and other 4 -cylinder cars that
may not have ballast
resistors.)
While my two units have been trouble free for several years now, the downside
is they can fail,
and it is not always easy to determine whether the fault is in the unit or
somewhere else. If you
can afford a spare, I think it would be a good investment to have two (or as I
do, have
two identical units on two cars) to facilitate swap-out diagnosis and repair.
Alternatively,
you should keep all the needed parts to convert back to conventional points,
and be able
to get back on the road quickly if the unit croaks.
If you buy one, be very careful to try to determine whether it wants 6 or 12
Volts input,
and make sure your supply is appropriate. I don't think there is any reason
you couldn't
use a hotter coil than standard--if the coil needs 12, but a ballast resistor
is in the circuit,
you could wire the coil to the 12 V side of the ballast resistor and wire the
electronic
igintion to the 6V side, I guess (but this sounds like a Dan Masters question).
Probably,
from looking at your list of cars (TR3-TR4), you don't have any ballast
resistor to worry
about, so all this is moot (just be sure the unit you install likes 12V input.)
Rule of thumb
(I think)--if the heat sink on the electronic ignition unit is too hot to touch
while running,
it probably wants a lower excitation voltage. Mine, anyway, do much better on
6V.
Good luck with your conversion, if you decide to do it.
Ray
-------------------------------------
Ray W. James, P.E., Ph.D.
Civil Engineering Department
Texas A&M University
College Station, TX 77843
Phone (409)845-7436; Fax (409)845-3410
E-mail: r-james@tamu.edu
Date: 2/12/99 Time: 4:17:04 PM
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