Could anyone explain to me why when running with the trailing split for rotary that the trailing spark outputs don't immediately work when cranking and low initial RPM's.... And if any abnormalities have been detected using the split trailing feature.
2day we were on a dyno trying to setup our first 13BT when at approx 3600 rpm at +/- 100-110 kpa we got a massive backfire... And she didn't want to run properly at idle any more.
Fearing damage to the seals we stoped the dyno and strated checking things....
Luckily No mechanincal damage BUT now everytim we start her we get horrible backfiring from the exhaust and noticed that it only stopped when the trailling spark outputs came online at approx 900 rpm's
Could any one help us out here, we are running MT 2.25 release with 29f firmware, FC trailing type....
All timing is set correctly as we can see... running trailing split of 14 degrees above 100kpa...
Any Help would be appreciated.
Gordon.
Something is wrong with your leading plugs, wires, ignitor, or coil. I'd start checking there.
The trailing ignition is off below 800 rpms because we'd have to rewrite a whole section of code to support trailing at low speeds. At one point or another when I get time, I'm going to add a fixed zero split firing of the plugs at low speeds... but it appears that you have a problem with one or more of the leading ignition parts that I listed above.
Here's some questions that might turn up another clue.
After the event, have you confirmed proper leading and trailing spark and spark timing? Have AFR's changed?
How did you determine the suitable dwell time? I'm not familiar with that VW coilpack, but dwell of 1.3ms is much shorter than average. If you've got a scope, you could check to see what time is needed to reach the current-limiting of the VB921, and set dwell to that value. That'd maximize spark energy while avoiding excessive heating of the VB.
If you have them wired straight to the cpu and not to the negative leads of the LED's, you'd be running inverted spark, and inverted spark is not supported by the rotary code. That could cause some problems.
The rotary code was really only meant to run the stock FC and FD ignition systems.
Also, how are you running leading? are they both running off the same output and firing in wasted-spark form? FD outputs only make the trailing separate, leading will still need to fire together as both the FC and FD run a single wasted spark coil for leading, and we don't support true COP for a rotary at this point.
Assuming you're running the vb921's off the negative leads of the LED's (with pullup resistors), and you're running the leading coils together, and running non-inverted spark outputs, I'd say whatever problem you're having is related to plugs or wires.
However, if you're not doing what I just said above, you may have fried one or more coils, and/or one or more vb921's... probably only on leading from what you're saying.
Have you checked spark yet? Sounds to me like you popped one of the leading ignition components (VB, coil...). Once the trailing coils kick in above 800 rpm, then the rotor with the dead ignition comes alive. Below that, the unburned fuel is dumping out the tailpipe creating the backfires. It's just a guess, but it fits the symptoms.
BTW, there's been many reports of reset and other problems running VB's direct from the cpu. Do a search on 'VB921 reset' and you'll find plenty of hits.
I'm not sure how the firing is set up on quad rotors, but on 3 rotor engines, you should be able to do leading-only by setting it up as a wasted-spark v6 in software, and running each of the 3 spark outputs to a rotor. If the 4 rotor is set up to fire once every 90 degrees, you could do something similar there, set it up as a V8, with 4 outputs.
As for the change in operation...
if you fried a coil or vb921 or another component on the leading ignition system somehow, then below 800 rpms, when leading isn't working quite right, the car will run like crap. Once trailing comes on, it can mask problems with leading. However, if most of the combustion is being done by trailing, there'll be other problems too... You may get knock at places you don't expect it based on the tune and stuff like that. I've seen people knock out their leading plugs without trailing being hurt too.
Rex4Life had some kind of similar problem where the car wouldn't run right without trailing. I can't remember what he did to fix it but I'm pretty sure something was wrong with one of the components in his leading ignition.
Just curious though... why didn't you just install a stock 2nd gen ignition system? They're very simple to install, and well tested with the megasquirt. They also provide very strong spark.
I'm using 2 2nd gen leading ignitors/coils to run wasted spark on a 20 valve 4age because I like those ignitors/coils so much.
When you set them up off the negative leads of the LED's make sure that each LED has a +5v pullup resistor to the negative lead as well.
I would set it back up with the vb921's triggering off the LED's, and turn OFF spark inverted (so spark should be non-inverted). Did you reset your timing after switching to this configuration? (timing should be -5 degrees on a 13b engine).
Then I'd figure out why it pings and such. You might just be running too much advance.
Honestly I'm surprised the code worked at all the way you had it before. I might go home and try it on the scope to see what it does in that situation. Again, the code will likely not work properly in inverted mode and is likely only working by luck.
With it non-inverted it's possible I guess that you might have the two trailing coils backwards (meaning the trailing coils are firing into the wrong rotor at the wrong time).
Also, what are you using for a trigger? ARE you using a stock CAS?
Can we see msq's and logs of the setup?
I know that mike robert had a similar setup working at one point or another with the FD-style outputs.