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"When switched on, a random cylinder ignition cut was employed using a simple circuit consisting of a 555 timer and a power tranny shorting the coil (heavily heat-sinked!). The passed mixture was ignited using a spark plug that was tapped into the exhaust manifold, and was driven by an EHT circuit (I think it was the Jacobs Ladder power supply from memory). But we had pretty severe cracking problems that occurred due to the thermal stresses incurred by dissimilar metals placed together. I think that the spark plug expanded more. The carby was jetted so that it ran pretty rich too. The circuit switched itself off after the engine RPM hit 2500 (using the shift light circuit), and was switched off after the car reached third gear (micro-switch).
Once switched on, the combustion WAS controlled, and sounded like a bloody great V8 with only 6 cylinders firing. The exhaust manifold glows a pretty colour after about 30 seconds though (as did the turbo)! On launch, the car spat a 2-3 foot yellow-blue flame that was only really visible at night. For the best launch, the car was revved up to 2000rpm at the lights (keeping an eye on the boost, letting it build up to 7psi, and letting the wastegate do the work) then either a slip or a dump of the clutch. There were problems though. Once, on take off, the spark plug lead fell off and the car was pumping raw fuel into the manifold. It ignited, and blew burning fuel out the tailpipe all over the front grille of the car behind us. OOPS!
The engine ran like [shizzle] when the system was running - really lumpy - so the revs had to be kept up or it would stall. Mind you, the mixture wasn't exactly stoichiometric!
We were also experimenting with propane injection into the manifold. We actually had more success with this method - the explosions were more powerful thus making it more effective - but as the exhaust manifold finally blew itself to bits, we decided that it really wasn't worth the effort. But the main disadvantage of this ignition-cut only system was that the fuel charge would cool the manifold (we believed) causing thermal stress = cracking manifold. Air injection would still be a wise thing to try, we also tried pure oxygen injected into the manifold with limited success..."

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