coax withstanding voltage

IIRC, teflon insulated RG-8 coax will do 30KV, at least.

...Jim Thompson

I recall typical 'working' voltages of 2KV in many cables. I suspect many low-loss solid polythene dielectric cables would probably qualify, though may not be specced for it.

A company called Nology sells grounding sleeves to go over spark plug wires. Be aware that this creates a capacitor that gets charged up by the discharging coil to whatever voltage the plug fires at, which then discharges with a much shorter time constant giving much higher peak currents (same capacitive transfer circuit used in lots of pulsed lasers). Nology claims wonderful amounts of peak power from this scheme, 10-100x what the coil discharge would normally give. What they don't tell you is that if the mixture isn't sufficiently uniform in the chamber you can get lean spots and if one of them is at the plug it won't light off during the now sub-microsecond discharge where the millisecond coil discharge would have allowed time for the mixture to change and light anyway. More important, this gives huge kA current pulses which can wreak havoc with computer sensors (can you say rfi and ground bounce? :-)). Also, the dielectric of normal spark plug wires isn't designed to handle this stress and doesn't last. I'm sure Nology is on the web.

-- Regards, Carl Ijames carl.ijames at verizon.net

marc

Look at aviation ignition leads. Most of these have a shielded 'braid'. Remember though, you also have to work out how to do the ends very carefully indeed. The aviation ones have a ceramic insulator in the plug, and a external thread on the plug, with a clamp nut assembly that grasps the braid, which ends about an inch before the end of the insulator itself.

Best Wishes