boost oriented miss
02-04-2007, 12:53 PM
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boost oriented miss
I've been driving around for over a month on mechanical boost (~8psi) trying sort my EBC issue. Prior to that I'd run on a MBC at ~12-14psi w/o issue. Now I'm back on the MBC w/o any changes to it or anything connected and I'm getting miss (feels like a misfire) right at peak boost. As soon as peak boost is reached I get the miss, and it continues throughout the acceleration at that boost level. If the throttle is backed off and boost drops to around 9psi the miss goes away. I thought maybe it was because I'd widened the plug gap to .040, but that wasn't the case. Installed new plugs at .035 and nothing changed. Next is plug wires. Any other suggestions for checking?
Datalog of the last run linked below of the last run for those interested. Fuel/Inj look steady, I suppose AF is bouncing around from unburnt fuel. - rob
http://ebersol.com/FE3/DL020407a.TXT
or
http://ebersol.com/FE3/DL020407a.TXT.zip
Datalog of the last run linked below of the last run for those interested. Fuel/Inj look steady, I suppose AF is bouncing around from unburnt fuel. - rob
http://ebersol.com/FE3/DL020407a.TXT
or
http://ebersol.com/FE3/DL020407a.TXT.zip
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02-04-2007, 01:07 PM
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Wow man, if it's not one thing, it's another. 
I've not been able to get away with a gap that large at 9 psi, so it may be worthwhile to close em down some and see if the spark isn't getting blown out.
I have a good spare set of wires you can try, but it's not really worth the drive is it. If your wires aren't all that old, I'd think it's maybe the coil, or a bad connection at the coil.
I've not been able to get away with a gap that large at 9 psi, so it may be worthwhile to close em down some and see if the spark isn't getting blown out.
I have a good spare set of wires you can try, but it's not really worth the drive is it. If your wires aren't all that old, I'd think it's maybe the coil, or a bad connection at the coil.
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02-04-2007, 08:11 PM
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I'm running the autolite 3922s- I think they're a 7. My tune is rich now, I know, but I can't see how the cold weather (the only thing that's changed) could cause this. I've got a collection of plug wires I can swap out, coil too. Checked in to the gap, and as mentioned, most run a gap around .025 with boost. I thought I read the AFloyd was running .040- but with ngk iridiums I think. So I can crank down on my gap. And tweak my tune now that I've got a good log.
Ben- This is the second time I've driven my car since I met up with the miata crew!
I hope it's the gap- haven't really had much trouble except for the EBC and that looks like it's actually a component on the ecu, which is going to require some solder work if I can actually find a replacement. Meantime, I'll just stick with the MBC. - rob
Ben- This is the second time I've driven my car since I met up with the miata crew!
I hope it's the gap- haven't really had much trouble except for the EBC and that looks like it's actually a component on the ecu, which is going to require some solder work if I can actually find a replacement. Meantime, I'll just stick with the MBC. - rob
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02-05-2007, 02:18 AM
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I'm running the autolite 3922s- I think they're a 7. My tune is rich now, I know, but I can't see how the cold weather (the only thing that's changed) could cause this. I've got a collection of plug wires I can swap out, coil too. Checked in to the gap, and as mentioned, most run a gap around .025 with boost. I thought I read the AFloyd was running .040- but with ngk iridiums I think. So I can crank down on my gap. And tweak my tune now that I've got a good log.
Ben- This is the second time I've driven my car since I met up with the miata crew!
I hope it's the gap- haven't really had much trouble except for the EBC and that looks like it's actually a component on the ecu, which is going to require some solder work if I can actually find a replacement. Meantime, I'll just stick with the MBC. - rob
Ben- This is the second time I've driven my car since I met up with the miata crew!
I hope it's the gap- haven't really had much trouble except for the EBC and that looks like it's actually a component on the ecu, which is going to require some solder work if I can actually find a replacement. Meantime, I'll just stick with the MBC. - rob
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02-08-2007, 02:19 PM
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Leaned out the fuel near 12psi and swapped out with some other used injector wires and it's 90% better. Hmmm... I need to find out what kind of OE wire setup I can use. I mounted the coil pack at the back of the head, but the engine is just long enough so that one of the wires isn't long enough (the number 4). So I have use two number 3s- which means two sets of Miata plug wires. I'm thinking wires.
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02-09-2007, 12:26 PM
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Not sure if it applies here, but my DSM will missfire at full boost (22psi) if the mixture gets much richer than 10:1.
It's easy to spot when it's that rich since it leaves a smoke trail behind the car.
It's easy to spot when it's that rich since it leaves a smoke trail behind the car.
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