Anyone tried firing leading and trailing plugs at the same time, PFC or other ECU?

[royal]

I\'ve been looking at DIY ECUs specifically Megasquirt which supports seperate leading and trailing sparks, but would prefer to use VEMs. VEMs doesn\'t support seperate leading and trailing plugs and I wondered if firing both at the same time is an option as I could do this ok? any help appreciated :Ladys-man
On the subject, also if anyone has ever used these ECUs?

[Prof]

After looking at the ignition timing on the datalogs from the Emanage, I\'ve even seen Trailing fire before Leading !
 
This so called \'Negative Split\' was in the \'cruise\' part of the map - never under boost, and was only 1 or 2 degrees difference.
 
That\'s on a chipped ECU - but apparently Mazda do it on the stock maps for the RX8.

[royal]

I read about trailing before leading whilst in vacuum on rx7club, odd stuff! still wondering if firing both at the same time throughout the map is a viable option?

[Nik da Greek]

Surely at high rpms they\'re firing to all intents and purposes simultaneously anyway, aren\'t they, given how quickly each cycle will take? Must be talking about tiny fractions of a second difference? So by extrapolation, it can\'t be too bad a thing... I think :3Confused

[Prof]

I read about trailing before leading whilst in vacuum on rx7club, odd stuff! still wondering if firing both at the same time throughout the map is a viable option?

I think you really want some split at the top end to resist detonation - the whole point of the 2 plugs was to clean up emissions and also create 2 flame fronts so you didn\'t end up with a load of unburnt charge detting when the flame front (with increasing pressure behind it) caught up with it.  The combustion chamber shape is less than ideal - which is why the scallops are there in the rotors to try and \'fatten\' the otherwise long and thin chamber that results.
 
From what I\'ve read (again mostly on RX7club, but also on teamfc3s.org and more recently on Rx8club as well), you get some gains by eliminating split in the vacuum part of the map, but then need to bring it back in again as you reach peak torque.  You can reduce the split slightly again after that.
 
Mazda seem to have done a lot of research into the timing on the RX8 - some of the new tricks there seem to be adapatable to the older 7\'s.

[Carl]

No split under boost is a big no no for a rotary as it will lead to det.
Infact a wider split is better.
Regards
Carl

[royal]

Thanks Prof and Carl, VEMs isn\'t looking viable at the moment!

[BlitzBoy]

also a lot of rotary race cars, track and drag do not ran a trailing spark at all and just ran on the leading (economy not being a concern)

[BlitzBoy]

here is a link with some info on it
http://www.rx7club.com/showthread.php?t=325400

[antnicuk]

just out interest,  would these non rotary ecu\'s be able to run primary and secondary injectors?

[royal]

Can run up to 8 seperate injectors but I\'m not sure how it would work with secondary injectors that were only coming on in higher revs, still doing my homework!

[BlitzBoy]

I stick with the Apexi to be honest matey instead of trying out something different not much to be gained

[royal]

Its not so much that I\'m bothered about gains, I\'m purposefully dropping 100bhp on the new setup to stop killing other areas like the gearbox. I just like the idea of these things for the DIY aspect and learning about it all. If I\'ve got to spend money on the datalogit and wideband for the Apexi I\'m tempted to spend it on something a bit more flexible.

[BlitzBoy]

Hows spending your money on a cheaper EMS more flexiable then the Apexi PFC, the Apexi has lots of good features that some EMS dont have?

You are going to have buy a wideband regardless on what EMS you go for.

Decent EMS that offer more flexiability then the Apexi tend to start off from £600 upwards and soon add up when you add custom loom sensors etc etc

[mx1311]

just buy the pro chip ed is selling on fduk then apexi will more than suit your needs and you can still tinker with dataloggit as there are lots of forums on rx7club to give you pointers