Beneficial? or not? Just curious thoughts on the subject, most everything i read was concerning FI motors. Looking for ideas/thoughts/etc.

 

what do you need?

 

You lost me at "beneficial".

 

He's talking about ignition timing guys. I think some of the older 70's cars ran zero split, not sure of the details.

 

I assume mazda knew what they were doing when they set the timing split to 15-20*, but I've also heard that a few run zero timing split (note: getting any ignition info from knowledgable tuners is tough..... getting them to explain the principles behind it..... down right impossible).

As far as I understand it, timing split seems to help complete the burn, but that it dosen't affect power that much. It can affect misfire rate and threshold of detonation I would think -- the sooner the flame reached the endgas by the apex seals the less likely that those endgases will detonate.

 

You lost me at "assume"

 

 

So no split would mean the leading and trailing acting as one big spark? Why would you want that? Like you said, obviously Mazda changed it for a reason, but maybe it was just for emissions?

~T.J.

 

The leading plug is doing most of the work. Trailing plugs help in completing the burn. The 79-80 models had them setup so the trailing only sparked part of the time. All the later ones had the split leading/trailling firing all the time. The trailing is mainly for emissions, but does help marginally in power. Yaw had a write up on the best split and is slightly different between 13b or 12a, to get best power you DO want a correct delay.

I don't know if one would want to run zero split, because if there is two flame fronts from each spark plug at the same time will run into each other and possibly cause conditions favarable to detonation. Were as if there is a delay when the trailing fires, the flame front will already be getting close to the trailing plug so when it sparks, it will just assure the charge is completely burned in a smooth flame front which is what you want. Some mazda race rotaries have 3 spark plugs, and have 3 different times they fire the spark.

 

I looked on the theory about the two flame fronts coming together and creating a detoantion spot when they 'hit' each other, but everything I saw was that it doesnt happen and few saw a problem, other than some lower rpm issues. It appears that as rpms increase reducing the split(or lockign it out if you dont have a tuning(EMS) method of doing so), increased power. everyone I read that had tried the 0* split gained power, on a single turbo brew motor some people saw 15-40hp due to reducing(removing the split)

Ill try and dig up the thread up that im talkign about

AFASIK the split all has to do with emissions.

But I am wary of running 0* due to the combustion 'pocket' on the earlier rotors. IIRC it is dished on the Leading side

Just tossing in some ideas on getting some more power


EDIT:
https://www.rx7club.com/forum/showth...t&pagenumber=1