Warren,
Detonation at full throttle meant that we had to severely retard the timing, but in doing so it caused the engine to run hot. On the dyno, the engine raced to 100C before we could get a maximum power reading. With the engine temp at 100C and climbing, a reading at 6,400-6,800rpm would have probably shown an increase of only 5-10bhp; we couldn't get ahead of the dyno, if you know what I mean.
I'm going to be upgrading to a radiator-style cooler, but if we leave the engine alone, it would have a negligible cooling effect given how much we have to retard the timing to stop the pre-ignition.
Adam,
I'm surprised, too! But, a standard RS Touring is still a pretty quick car.
Now we know why I had trouble keeping up with the front-runners during our convoy! I didn't think shot front shockers would make the car
that much slower!
Bill,
It's the pre-ignition that makes another tear-down unavoidable.
Cam,
Reducing the CR to 9.5:1 should do the trick, and will be cheaper than twin plugging it. Man, if only I had more cash to take advantage of this free tear-down!
Matt Holcomb
1974 911 Carrera 2.7 RoW
1975 Mercedes-Benz 280SE
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