David Todd

Well, I hope you have a surprise outfit. I already had two twin-channel ignitors; so I just wired them up to run four brand new ignition coils I bought so I could swap over to direct spark and absolve myself of blowing flames out the wrong end of the motor. Well, it didn't work. I left the throttle stop set at about 5% and played with the settings/throttle inside the car; after I couldn't get it to clear up any I just took a 50Hz log for the better part of ten minutes. When you look at/analyze this log, just look for the IAT spikes, it's unmistakable. Over the duration of the log the TP% will vary as I'm keeping it far open by foot, instead of constantly adjusting the stop screw. I should note that it seemed that the further the throttle plate was open, in comparison to a low idle speed (~1500rpms) the more often an intake backfire event occurs. I could be wrong, or backwards, but it just seemed that way when I was messing with it. So I'm looking for answers; I don't think I'm running too much ignition timing... I've tried adaptive vs constant.. the only thing that seemed to help was a throttle opening around 10-12 percent and an idle limit of 1200 rpms. Hoping you can help, I go racing sunday and as it is I'm leaving the antilag off, afraid I might do damage on cyclical idle. David

well, it definitely is a firing event. my IAT spikes and I see a jump in intake pressures when I hear the pop; so it's definitely a fire event. I changed my plugs right before the race that weekend and drove it, softening up the cyclic idle so that it came out of idle easier and into anti-lag. At the transition point I got lots of pops back through the intake. Car is running pig rich, and I'm getting ignition events so I don't think it's the engine missing and firing the other plug during an intake event. I might try swapping to a coil on plug setup and see if it disappears.

Ah, I forgot to mention, this setup is a wasted spark setup. I'm not entirely sure if what I'm hearing is an actual ignition event happening in the intake; but I thought I'd mention it anyway.

I've got a 1991 Subaru Legacy with an EJ-22 Turbo swap (motor is the entire closed deck variant) no mods, stock injectors.. I'm running the throttle body at 18% open with cyclical idle keeping the revs around 1800; I've tried playing around with the settings some, I've got it setup to where it's pretty rough. Every now and then I'll get a muffled pop sound back through the intake, it's loudest at the filter. I'm not exactly sure what's going on, but it sounds like a lean idle pop. I know that at that point on the fuel map (around where the engine is idling on cyclical idle) I'm seeing AFR's of 13.5. Unfortunately I can't check the AFRs while on cyclical idle since the sensor just reads far lean. I've never seen any flames, nor is it a loud bang; it sounds like it's happening in the runners. At cyclical idle I'm seeing -10kPa to 2kPa manifold gauge pressures, and the entire car smells rich; which isn't really new to my car. I just want to make sure what's going on isn't a serious problem? Maybe it's too much ignition advance? (about 23 degrees) or I need to change the injector timing? (375 degrees) Also, on cyclical idle, is it a fuel cut? ignition cut? both?