Sonny

Hi All:

Sorry if this has been asked before....

I'm trying to find out why it is bad to end up in a situation where you have the trailing plug firing first. Being that this is my first rotary engine, I've never had to deal with firing 2 plugs.

Let's say the split between the leading and trailing plugs is 6 degrees. You detect detonation and retard the leading plug by 10 degrees.

So, essentially, the trailing plug will fire first and then shortly after that, the leading plug fires.

What happens inside the motor that makes this situation bad?

Thanks,
Sonny

reza

There is inherent 15 degrees difference between leading and trailing plug location.
If they were to fire together (is this 0 split?), with leading plug at TDC for example, the trailing will be at 15 degrees retard of TDC.

I think if you have trailing fire first, it maybe bad because the rotor may want to go the other way....

rdavidsrx7

^ you got it atleast about the combustion pushing the wrong way... and i also believe about the 0 split

Sonny

So one of the main criticisms of the J&S Safeguard is that the timing is pulled only from the leading plugs. Since the J&S has the ability to pull A LOT of timing, you can end up with negative split.

If it could be setup such that it pulled equal amounts of timing from BOTH leading and trailing plugs, that would be better, no?

The J&S has been an incredibly useful tool for me when street tuning Hondas. I'd basically continue to advance the timing until I got knock and then I would roll the timing back 2-3 degrees in that cell. In the cars that I have done this to, I gained little to no power at the dyno. I just used the dyno to tune my a/f curve.

The whole "split" issue makes this a little more tricky with the RX-7.

Sonny