Right so ive got my car all mapped and am happy with the way it drives etc, but ive got a small misfire at around 3500rpm. Tried and tested all the usual suspects with no luck, so it was suggested to me to try switching the ignition triggering to rising edge as i was on falling.
So i tried this last night, and its cured the misfire or so it seems. But now the car idles like shit and is lean across the whole map except very low rpm/idle where its rich. I spent some time playing with the map and it now drives better, ive also pulled 5degrees from the whole on boost section of the map for safety. So what i want to know is.

Why would/has this cured my misfire?
What effect has it had on the ignition timing?

 

Hi mate, just got your txt. When using EDIS the trigger settings should be set to rising edge capture. This basically tells the ecu to RPM trigger on the rising edge of the CPS tooth, rather than the falling edge. This should in theory advance your timing slightly. Hence the need to check timing with a strobe, to make sure the advance the ecu see's is the same as the advance the engine see's (no offset).

Im not sure why it would cause a misfire, however looking at your datalogs the misfire you had was very slight, although it may have felt worse. There also wasn't a sync loss count that would be associated with a cps trigger fault.

There have also been very slight misfires caused by stupid things like cps wheel or cps mount jitter (you won't have this problem) but also by lumps of metallic shite stuck to the trigger wheel, however edis is normally very tolerant of thing like this.

Advancing or retarding the timing can have a significant effect of fueling (as you have found), sadly there is nothing for it but to re tune your VE table. On the rollers it isn't uncommon to re visit the VE table 2-3 times ie) after tuning the ignition table the VE table normally needs slight alteration....

You are probably idling like shite as AFR's are out, and timing is well out. Adjust the VE table for around 14.0 (to begin with), then adjust the timing around idle to see if advancing or retarding the timing helps.... this should give some indication as to your CPS trigger offset..... normal CVH's idle well at or around 12deg, if your using like 20deg in your table to get a good idle then something is wrong and your trigger offset.

Does any of that make sense lol? or am I rambling....

Rob,

 

No that sounds good... Im idling at around 20-22degrees and 13.5-14afr!
Im going to have a look at checking the timing again with a strobe and i'll keep you updated!

Cheers m8

 

Yes, in that case keep a copy of your original map and change the trigger offset when you can strobe the timing properly, your VE map shouldn't be as far out then

In theory it shouldn't really matter a toss if you are using rising or falling edge as long as the timing is correct... However the EDIS unit may be relying on rising edge etc... so if that fixes the misfire then happy days

I haven't had the same issue on another car yet using edis, but they are all setup to use rising edge.

If that doesn't fix the miss then a firmware update would be the next step.

Rob,

 

Cheers m8,
I'll keep you posted!

 

Cool, let me know if you need an hand.

Rob,