So I got off the phone with Rotaryshack, and Rob told me something interesting:

Apparently since I am not running anything on the trailing, I can advance my timing on the leading much more, like 15*.

I have done some searching, but cannot find anything on it. The amount of people who ditch their trailing are very few to begin with, and the people who advance it are pretty much Nil...


EDIT: Come to think of it, I never told him that I had it advanced already to Yaw's recommendation. I don't know if that is what he is saying to advance to, or if I can advance more from that. I would assume the latter as I will not have to worry about a trailing spark preigniting the next combustion event, but I like my engine too much to detonate it!

 

i've never run without trailing, so i don't have any concrete answers, except that without trailing, you don't need to worry about crossfires or miss triggering or anything like that, so its a little safer.

2. the trailing changes the combustion, so without, you may indeed need to change the timing.

 

I don't know man, sounds kinda fishy. I think there may have been a disconnect in your communication, or maybe he was drinking a lot?

The trailing fires (obviously) after the ignition event caused by the leading. So, eliminating something that happens after an event, couldn't have an effect on the event itself. Right? I mean, unless it could time travel or something.

I dunno, and I personally have been drinking tonight. So don't trust my judgement. lol. But something seems basically, primally, wrong with that idea. If I'm wrong, then I hope someone can help me understand how that is possible.

 

At least your verbiage makes sense and is phoenetically correct while you are drunk.....better than some of the folks here...

 

Keep in mind that leading and trailing will both shift when you set leading, due to dizzy design. Trailing can be adjusted separately, but every leading change will effect trailing until you readjust it.

There's a minimum amount of separation you can get between the two, but I've never tested to find out what it is. Maybe this has something to do with that. I still can't quite see what, though.

And I haven't had time to be drinking yet.

 

Trailing doesn't matter to me, I can have trailing fire before leading and still be fine. I have removed my trailing completely. I have a video of it running on youtube, I will get the link after I am done with the reformat.

 

http://www.youtube.com/watch?v=cON1DU_5oDU

 

I meant that maybe Robert's statement had something to do with being able to advance more since trailing was no longer an issue for you.

In other words, maybe the inability to adjust trailing enough is one of the things that prevents a stock motor from using more advance. Since you don't have trailing anymore, you're no longer limited by it?

I still don't see it, though. Me no unnastan Robert's assertion. Need beer to comprehend, maybe?

 

So what do you have your timing set to now?

 

Timing is set stock right now. My timing gun broke. That thing was awesome, built in the 60's.



I guess I get to cut the wires off and dress up for halloween now:

 

this would have been answer if j9fd3s had not posted first.

however, why don't you just call him (Robert) back sometime and have him explain? he'd be the best person to give "his" reasons and train of thought.

 

It is true, you can safely run more leading timing with a larger split (or no trailing at all in your case). There are some threads about it in the single-turbo section, but seems like the NA guys rarely experiment with timing (plus, detonation isn't usually an issue for NA rotaries).

 

Holy **** that really does look like a old school Star Trek gun! Wait so you're gonna dress us as capn' Kirk?

As for the timing thing, ask Robert again, this just sounds way to weird to be right ya know?

 

OK - being an electrical neophyte - and NEVER having (yet) adjusted my timing, I "thought" I'd read that certain SAs (CA? US?), the trailing STOPPED firing after a certain point, by design (after warm-up; after certain RPM?) - sorry I can't find the reference to this...
Anybody heard this?

Stu Aull
80GS
Alaska

 

Yes, you are correct. I believe all SA's had part time trailing, but don't quote me on that. But I do know that at least some of them did/do.

 

I run 27* BTDC at full advance with 87 octane and 2 stroke premix which drops octane even lower. I found I made the most power here. Some people have put in higher octane and ran like 35*, but I tried it one day with 93 and adjusted up about 2-3* per pull and didn't see a gain of not even 1whp above 27*. however at 20* I was about 10whp down from 27*. I run directfire FC coil on the leading powered by a Crane HI6R, and the trailing is a crane HI-6 w/ a LX92 coil running through the cap.

 

Very interesting to know!! Currently I have no trailing, MSD 6T, 2nd gen leading coil
and plugs. I have it advanced 10* from the stock yellow dot on the pully. I'll bump it
up to 20* and see how she is!

EDIT: I take it by full advance, you did this at 4kRPM?

 

it seems like sideport NA engines like somewhere between 22-27degrees of timing, but that's WITH trailing. although more leading might not work either, just due to the layout/geometry of the engine.

 

uhm, I'm going to be running a Mallory HyFire here soon before i do a stand alone, if you can just run the leading without any power loss/efficiently that would be very beneficial when setting up the ecu... when i get it installed ill have to play with timing some. Those aftermarket CDI ignition systems provide multiple sparks, maybe if done just right it will help complete the burn instead of the trailing doing the job. obviously you still don't get to burn the extra mixture as it comes around the bend. so a low octane level, quick fuel burn might be reasonable... uhm lots of thought...

 

I have done various testing on my own car with different timing setups and and trailing splits and less split is more power (to an extent), for example on my car in the top end it likes about 1 degree difference between leading and trailing. At 2 degrees, i was loosing quite a bit of power.

I have the 2 graphs of 2 degree split and 1 degree split over laid in this thread here for comparison.
https://www.rx7club.com/1st-generation-specific-1979-1985-18/new-dyno-pulls-904766/

Another thing about dialing in the trailing too, is the way the engine gets "freed" up. By that I mean when you stomp on the throttle its a bit more responsive. I remember the one time at the track I ran a map that had a timing varying from 15-10 degrees split, vs another map of 15-0 split(so 15 would be in the low load, and 0 at full load) and it was easier to break traction with the 15-0 split on the exits.

 

How many degrees is your trailing split at 27*? The Yaw recommended 8*?

 

hmm i like the idea of removing the trailing and running the FC dual output leading coil only, direct fire. does anyone have more info on this?

re combustion i would imagine that the waste spark leading from direct fire combusts the mix more fully, although compared to the trailing spark, the leading waste spark occurs a lot later

 

i run leading only direct fire wastespark
( two HEC coils and BIM024 igniters ),
though i do have a stock igniter and FC twin coil in the spare well as my emergency spare
( its got me home once when one of the BIMS gave out )

though in context i run turbo with LPG,, and a very modded ignition curve

but,, having trialled the 4 coil ( LTX8 ) microtech sequential ignition,, and stock and DLIDFIS ( with trailing ) dizzy setups with the LPG fuel
- and many variations of timing curve and relative split

i can vouch pretty much what was hinted at in the OP
-- i run much more timing advance,, and less retard under boost ,, when i have leading only spark


with LPG ( and trailing ignition ) ,, heat soaked inlet manifolds would introduce light deisel/detonation
--even with less timing and more boost retard than i would put into stock petrol rotors

eliminating the trailing = diesel issue gone
allowing me to set more initial and full mech timing than i had gotten away with previously
-- in fact,, even when the boost retard dizzy pot failed and it ran 15 psi no retard,, i had no issue ( and lots of fun ! )
--- more in line with what i would have expected the relatively high octane LPG to behave

PS
i believe non trailing ignitions is more common in methanol fuel cars
-- maybe for reasons of the fixed maximum split being insufficient , or for elimination of potential for cross fire taking out expensive hardware
or just possibly due to inherent slow burn characteristics of the fuel
( me thinks all 3 )

 

I run a wasted spark ignition using GM HEI modules and a Ford TFI coil per leading
plug with no trailing. It works great. I think I need to play with the timing to
see how much more I can get out of it. Right now I'm running about 24 degrees at
4K rpm.


With this ignition I can't tell I have no trailing but thats with the butt dyno

 

LPG is higher octane, but does it burn faster too?

the problem with regular gasoline is that in a NA type engine, over about 5000rpm, the rotors are moving faster than it can burn.

there is only so far you can bump the timing advance, at some point you're in the next chamber!

ive played with no trailing on the PP, and it barely runs, its actually happier running on just the trailing