Zyrano

Hey guys,

Let's talk trailing ignition, i was told that the trailing ignition doesn't fire all the time, this leads me to three concerns.

1. When exactly does the trailing fire? I'm guessing it's controlled by the ecu, but under what condition and what rpm does trailing ignition work?

2. My shift light (as well as a lot of people's tach) gets the signal from the trailing coil, and i've read that it was ok, but if the trailing shuts off, how is it ok? I probably should switch it to the leading coil. and maybe that's why i never notice the shift light coming on?

3. I'm researching getting an msd 6al to take advantage of the rev limiter (and extra spark), but i was told that since the trailing MAY be firing, the motor might keep going...

please enlighten me in this subject!

Thanks,

Alvin

j9fd3s

iTrader: (3)

on the 79-80's (maybe only the 80, i dont remember) they shut off the trailings under some conditions. the 81-85 cars always fire the leading and trailing.

steve84GS TII

Correct,the trailing ignition was cut to feed the thermal reactor extra fuel in order to keep its temps up.This feature wasnt needed once catylists took over for the reactors.(in 81)

Trailing isnt a big concern over the stock configuration.Keep the wires,plugs and timing at, or near stock and you should be fine.
I tried the direct fire leading ignition and found it to be superb when run with Blaster coils and an MSD6A.
I saw no increase in power or economy afterwards when I ran the trailing through the leading ports of the cap(to eliminate an airgap) and running an MSD box on the trailing ignition side.Theres just not much left to glean from the trailing,especially after the big boost that direct fire/wasted spark leading ignition gives you.

Zyrano

Thanks guys, that solves one problem, so then will I be able to regulate my rpm (ie limit the rev) with just 1 6al box? will the trailing be able to keep increasing the engine rpm because it is unregulated per a second msd box? anyone have encountered this problem? I just don't want to do all this work and end up blowing the engine anyway from overreving...

Alvin

BMS2004

Don't know, just start the car and unhook the leading and see if it still revs or if its a dog.

SparkienSuggah

with the trailing ignition being so weak, the motor will likely hit a squishy brick wall when you misfire the leading ignition.. you should have more than enough time to back off and shift when this happens.. if the MSD6 had an output for a secondary cut, then yould be in solid brick wall territory, but i dont suspect this is the case.

i personally want to do experiments with advancing the trailing ignition timing to some point where it become more effective..

wecycle

Why is the trailing fired later than the leading? Some posts have indicated that both plugs for a given rotor could be fired at the same time. What are the consequences of this? I. E. pro's and con's?

SparkienSuggah

trailing is fired later because it trails the leading... thus trailing. *evil grin*

ive read stuff about it "cleaning up" the hydrocarbons that are lagging on the rotor face up near the trailing apex seal...

perhaps if the trailing ignition were advanced to fire before the leading (t and L would then stand for "top" and "lower") and the leading were retarded to compensate (marginally) better performance could be gleaned..
if it wasnt so cold outside, and i didnt have to put in my mothers kitchen, i would definitly try this on the ol' butt dyno