I accidentally ran 5* positive split timing in all vacume areas for a couple of days. Now I know people have said the rx8 runs positive split timing in vacume, but no one has specified how much or in what specific areas. Question is, what kind of damage could this have caused? Car still idles fine and pulls 17in hg @ 850rpm.

 

There is a thread somewhere around here with pfc maps showing someone running crazy positive split under high, mediem and even low vac (like 15* iirc)

the leading, trailling, and split sheets are all posted, i think they were by howard colman

 

did he have a reason why? and did any damage result?

 

tuned for it, kept egt's high under vac, said transision into boost was much quicker

i just searched for it but couldnt find it. i have the maps printed out, ill find em and scan em tommorow

 

You cannot damage the engine under vacuum.


-Ted

 

I run about 20° of positive split in vacuum. In light-throttle cruise, I might see trailing timing as high as 60° BTDC. This is on a Renesis, BTW.
The theory states that positive split improves efficiency by keeping the charge moving forward faster than the rotor moves. The trailing area lights off, pushing the charge towards the leading plug, resulting in more complete combustion.
It does seem to improve mid-throttle to full-throttle transition, but I don't notice any significant fuel savings or any other effects.