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MG TD TF 1500 - Resistor Sparking Plugs for TD

Does anybody have experience using resistor type sparking plugs? I usually buy Champion L82C, but have just bought a set of RL82C and am wondering it there would be any problems. Resistor type plugs have a 5Kohm resistor in the plug body, it is there to supress Radio Frequency
Interference(RFI), but in our case it "may" reduce the voltage to the spark. Any effect would be most noticeable on the original coil and breaker ignition, and less on an upgraded system (sports coil & electronic breaker).

John
John Scragg

John -- I have done s series of experiments on spark coils and plugs. I used an oscilloscope and high voltage probe and printed out pictures of the voltage across the spark plug. As a result I am using resistor plugs with a wide gap 0.035". Seems to work real well, quick starts and good at high revs.
Cheers,
Bob
R. K. (Bob) Jeffers

bob, what plug (mfg & number) are you using? thanks. tom
tm peterson

Bob, Thanks for the information. Do you have any special coil or is it standard, mine is not original but is a Lucas replacement.
Also do you have standard breaker points or electronically assisted ignition.

John
John Scragg

Tom and John Scragg --- Had to go out to the garage and remove plugs to be sure I am telling you the true facts.

TF NGK BR6ES plugs, the coil is the standard HA 12 by Lucas. Ran it several years with points now a pertronix.

TD NGK BR6HS plugs, I have had an original "Q" coil, an HA 12 and an SA 12 is now on it. The TD has run the same plugs with regular breaker points, a Crane XR700 electronic ignition and now a Pertronix module. The biggest change noticed was the electronic modules give quicker starts. Also had one dist. rotor short. Still can't see anything wrong with it but the car won't run with it. Too high a voltage for todays replacement parts?

BTW those experiments showed that Pertronix does not put a capacitor in their module! They use a diode (got to be rated at 1000 volts). Their module is not big enough for a capacitor to fit inside anyway.

Is this the info you wanted?
Cheers,
Bob
R. K. (Bob) Jeffers

Forgot to mention that the compression on both engines has been raised. TF about 9.3-9.5 and TD about 10.
Cheers,
Bob
R. K. (Bob) Jeffers


Does that necessarily indicate you would get better ignition, having a larger voltage over a larger gap?

For example, you could have a smaller voltage, but a narrower gap, and have a larger overall field strength which I would think might be better...

Scott
Scott

Scott -- I'm not sure I understand the concept of field strength in this senario. Bob
R. K. (Bob) Jeffers

If you use resistor type plugs, it may be worth checking that you don't end up with three resistors in each HT line; the plugs, the plug caps and the actual leads.
Roger Wilson

I'm quite pleased with the performance of NGK non-resistor plugs. I use their BP6ES gapped to .035" in Lazarus with a Pertronix ignition, Lucas Sport coil, solid ignition wires and 9.1 compression. If the RFI is bothering anyone's radio, they haven't complained yet.
Bud Krueger

This thread was discussed between 23/05/2006 and 24/05/2006

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.