924Board.org

[cgoldhill]

If you use the msd ignition with boost timing master can it dramatically help reduce detonation or will it just make it a little better?Also, i see this msd boost timing master igniton kit which retards ignition as the boost pressure increases from summit , is this a good setup to use with the porsche 931 and can it also help detonation?

[goturbo]

I have used the boost timing master on my other turbo car and I just sold it on e-bay. The Boost Timing Master works linearly, ie with each incramental increase in boost pressure the timing master retards the timing the 'adjusted' ammount ( it is 1-4 degrees per pound of boost on that unit). I really don't think that particular unit is well suited for turbocharged applications. Linear spark controls work well on supercharged applications, but the dynamics of a turbo engine require more fluctuation in spark control due to the scavenging effects etc. of turbo induction. Every engine wants a little something different for spark control (when to advance and when to retard) and I have not really started playing around with it on the 931, but if you are going to spend the money it would be better spent on a fully programable ignition. As an example my other car has a spark curve that looks like an 'S' shape, that is just what the engine wants and the boost timing master only helped during half of the curve so I went with a fully programmable unit-my gut instinct from the beginning! There are several units out there that have provisions for pressure/RPM controls. There are several discussions on ignition timing on this site. Do a quick search and you will find some real good information pertaining directly to the 931 and what it wants for ignition timing under different levels of tuning.

In MVHO, I would hold off on the Boost Timing Master and check out what some of the creative folks on this site have done