As some of you know I have been running zero timing split from time to time with good results (ie no blow motor). Before I commit to it full time I was hoping someone would answer my final question.

Assuming that both plugs fire at the same time, how come the dual flame fronts don't compress the air between them enough to cause detonation?

 

So is anyone going to jump in this conversation?

 

Sorry Carson, I can't help you out man. If its one thing I don't do myself its tune and mess around with stuff like that. Maybe someday when I get a job again I'll mess around with that stuff but I've got enough power for now and my $hit runs good like.
Laterz

 

the reason they have the split seems to have something to do with the physical distance between the spark plugs. i have kenichi yamamoto's rotary engine book and he kinda glosses over the subject. what he refers to split as the distance between the plugs, and that the timing split changed with that.

mike

 

Would RiceRacing or Anthony Rodrigues care to jump in here?

 

Hey spyfish, I jumped on the reduced split bandwagon last night.
I reduced all my split above 2000 rpm, down to 3 degrees, but kept it 15 split in the low rpm/high vacuum ranges(such as low speed cruise part throttle), the car felt stronger, so out came the G-tech, and the HP readings are up by 35 hp. I noticed I have boost a few hundred rpm sooner as well.. But not brave enough for zero split yet.... But I have observed the factory ecu's running zero split at times, so it must be for some good reason I would think..Max

 

this is why the 4rotors run zero split also more power.
split is good for emmisions

 

If that's the case, how would running zero or little split increase hp? The plot thickens...
Michel

 

Wouldnt that be on the waist spark side that they are seperated by the apex seal? On the combustion side wouldnt the indention be covering both plugs during spark???

Am I getting confused and not thinking of this right? I'm at work and my head is hurting haha

STEPHEN

 

Maxthe7man - just out of curiosity, how much split did you have above 2000rpm before you jumped the "reduced split bandwagon". and have you tried only reducing the split by 1/2 of what it was (plus 3) and measuring the gains.

ie how much reduced split did it require to make that ~35rwhp gain. I'm also wondering if the gains are linear to reduction in split or if there is a "sweetspot" that once you get to to a certain "low" (few degrees) split that there aren't significant gains worth the risk of running no split, OR if there is a ramp in gained HP as you approach 0 split.

K

 

This is just wrong. If that was the case then the trailing plug would be firing into the incoming mixture. This is also the exact reason why you can't run wasted spark on the trailing side.

 

Am I right by saying that the split on a 2nd gen car would be different because of the different locations of the spark plugs opposted to a 3rd gen car?

 

my rotary engine book says exactly that.

mike

 

The T2 engines have there spark plugs in a different location than the later FD/Cosmo enigines? How much farther up or down are they on the rotor housings?

 

Im not sure how much different they are but im sure its enough not to be able to alter the split timing as much as a 3rd gen owner would be able to.

 

Hey nocab, at somepoints there was 18-20 degrees of split above 2000 rpm, at first I just knocked it down to 15 for a about a 5hpgain, then after reading alot on the zero split, decided to go down towards zero, but not all the way, I am so far pleased with the results, better than I would have expected.
I really felt the difference in the car, I usually don't bother g-teching until there is a definite seat o the pants pull factor, I knew the car was pulling harder, I think with the g-tech, the rpm at which you spool can really play with the hp number, and given that it made the turbo spool that little bt quicker, thats largely responsible for the increase.
By the way thats one of the largest hp increases I have ever seen from any tuning change I have done on my rx-7's.
Now getting back to the factory strategy, has anyone mapped an FD trailing ignition?
I can vouch for the n/a Fc's running zero split from 15% throttle or so up. It was one of the things I didn't check though prior to gutting my TII of the stock ecu, I made notes of the closed loop cut off points, the idle a/f part throttles and wot a/f's and initial timing, but I should have check the actions of the ecu under boost..doh..nex time I guess..Max

 

Hey Maxthe7man: at what boost levels are you feeling this hp increase?

only in 89-later engines did Mazda lower their leading spark plug opening ~1/4" down...89-91 turbo II are on the same location as FD's and later engines. It does nothing for timing !!!! it simply places it in a better location.

I know NA's do run better with them firing together and looking at PowerFC maps which are close to OEM maps they too run NO split while engine is in vaccum. Once it sees boost they add split as boost goes up....to 10-12 degrees.

Interesting topic !!!! to split or not to split!!!!

I know on the PowerFc it's easy to do this...just make identical maps for both leading and trailing :-)

 

I know this is a really stupid question but I don't have any rotary annimation in front of me at the moment. If you're looking at the engine from the front (intake ports are on the left), which way is engine rotating? Clockwise or counter clockwise?

Would there be any issues with more stress being placed on the coils/charging system by running zero or low split?
Michel

 

I hope everyone has seen this by now, but just in case - pretty good animation here:

http://www.howstuffworks.com/rotary-engine4.htm

k

 

Best place to go is:
http://www.rotaryengineillustrated.com/index.html.


Run the animations by mouse control and stop it when you want to. 15 degree crank rotation is only 5 degree rotor rotation!

**********************************
CARSON,

Just finished a second round of chemo, this stuff is worse than pulling stock turbos by yourself!!!!
I do drive my "7" when I have the chance. Nothing
like a fast drive in the "7" to cheer one up.

Love and speed.

Chuck

 

Boostn7, I am running a preschoolish 12 psi right now on my T04e, I am gonna turn up the wick tonight to 15 psi(1bar)...Max

 

Chuck,

We'll have to get you a single turbo so life will be easier! I'd hate to see you pull stock turbos by yourself .... might as well pull the motor!

Anyway after talking to my stepdad I'm going all out with the zero split. I'm putting in two dual post coils and race plugs with no ignition amp. Wish me luck!

 

SPY-007-- Garfinkle is running low rpm 4 deg split , it pulls very well ,he was running 8 deg min split ,both are good on the street.He wonts to know if his 1600 cc and rail are working good. also he needs your help wilh the computer.

 

Just a little side note to everyone on the subject: Not all ECU's have the ignition accuracy to control a very close split, or zero split, so be careful when doing this. I know that the Factory ECU(Don't laugh, it's very accurate), Power FC, Electromotive(Tec1,2,3), and Motec can control these splits properly due to these units having really good ignition accuracy, and the speed of at which their processors handle the ignition system. Just my 2 cents.

 

Why not just run each rotor off of a single dual-ended coil? That way you KNOW the leading and trailing will fire at the same time, because they're being fired by the same coil.

Of course you'd need an aftermarket ECU running in four-cylinder waste-spark mode in order to do this...