misfire/safc
12-11-04, 02:18 PM
#1
misfire/safc
in the upper gears at WOT my car misfires BADLY after being WOT for a while, especially.
Anyone know what can be wrong here?
boost is maybe 13PSI, mods are in sig, 720s, s-afc set at about +8% correction, peak airflow is around 74%, which as I understand is probably pretty near the limit of the AFM, if it isn't.
NO idea on what the a/f ratios are, I wish I could find out but I don't have $$$ for dyno time or a wideband right now.
Also: timing is retarded 2deg, but it did this before I messed with the timing, and also: the turbo gloes red hot after light cruises.
Anyone know what can be wrong here?
boost is maybe 13PSI, mods are in sig, 720s, s-afc set at about +8% correction, peak airflow is around 74%, which as I understand is probably pretty near the limit of the AFM, if it isn't.
NO idea on what the a/f ratios are, I wish I could find out but I don't have $$$ for dyno time or a wideband right now.
Also: timing is retarded 2deg, but it did this before I messed with the timing, and also: the turbo gloes red hot after light cruises.
12-11-04, 03:58 PM
#3
the wires are almost new
I dunno about the plugs though, they're probably less than 60%
I'm going to replace them in the very near future.
I ALWAYS have problems with cars, but I don't care, it's fun fixing them
it pisses me off in this case though because I had finally got the car running PERFECT (ABSOLUTELY perfect) the day I blew the motor, so now I'm starting off from the bottom again.
I dunno about the plugs though, they're probably less than 60%
I'm going to replace them in the very near future.
I ALWAYS have problems with cars, but I don't care, it's fun fixing them
it pisses me off in this case though because I had finally got the car running PERFECT (ABSOLUTELY perfect) the day I blew the motor, so now I'm starting off from the bottom again.
12-12-04, 03:17 PM
#7
HAILERS
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Originally Posted by Terrh
I had it at +15 before 
I need a wideband...
I need a wideband...
What's that phrase they used to use all the time.........RIGHT ON!.....yeah, that phrase.
Minus 15 would be more appropriate. Get a wideband or go to a dyno shop. But your right with your last post.
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12-13-04, 04:41 AM
#8
I'm a boost creep...
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Originally Posted by Terrh
...720s, s-afc set at about +8% correction...
Your 720cc/min secondaries injectors (assuming it's just the secondaries) have increased >3800rpm fuel flow by ~15%, and then you're increasing that by another 8%, meaning ~25% more fuel than normal is being added! No wonder it runs badly.Try setting the >3800rpm corrections nearer to -10% (that's minus, not plus). It'll still probably be richer than it needs to, but it'll run a lot better. You need to get onto a dyno. If you can't afford dyno time you really shouldn't be doing mods that require it.
Last edited by NZConvertible; 12-13-04 at 04:44 AM.
12-13-04, 07:55 AM
#9
DONT FEED THE NOOBS
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why isnt this in the SAFC section...? probably why that part of the forum is dead now. i just got my safc2 and hooked it up im about 1% from maxxing the duty cycle on stock injectors. 36% correction according the posted stock duty cycles of 58-63 % (63X.36) 85.6 percent duty cycle .. thats max i need some 680/720s I would think you should have negative corrections to your air flow ... you car must be snail slow becuase of it.. nice firework show coming out the back im sure.
Last edited by gxlbiscuit; 12-13-04 at 07:58 AM.
12-13-04, 08:05 AM
#10
"If you can't afford dyno time you really shouldn't be doing mods that require it."
This is one of my main reasons I never tell people to buy a SAFC. Usually they are looking for a cheaper way out but with rotary's they are so sensitive you end up popping your motor and paying for a rebuild. I never understand why people ask for other peoples settings. Yes they are great to use for a baseline to get you to a dyno but then try and use them on the car? I don't know but I think NZconvertible hit it right on the head.
This is one of my main reasons I never tell people to buy a SAFC. Usually they are looking for a cheaper way out but with rotary's they are so sensitive you end up popping your motor and paying for a rebuild. I never understand why people ask for other peoples settings. Yes they are great to use for a baseline to get you to a dyno but then try and use them on the car? I don't know but I think NZconvertible hit it right on the head.
12-13-04, 08:09 AM
#11
I allready did pop a motor...
luckily for all of us, used motors are cheap and plentiful.
I COULD afford dyno time, but then my girlfriend lost her job, so now I'm the only one paying the rent/bills... I actually had some scheduled for 2 weeks ago.
when I had the old 550CC injectors in I had the +3800 correction set to ~+30% and it wasn't rich enough.. they were probably beyond maxed....
luckily for all of us, used motors are cheap and plentiful.
I COULD afford dyno time, but then my girlfriend lost her job, so now I'm the only one paying the rent/bills... I actually had some scheduled for 2 weeks ago.
when I had the old 550CC injectors in I had the +3800 correction set to ~+30% and it wasn't rich enough.. they were probably beyond maxed....
12-13-04, 02:47 PM
#16
FC Revolution
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My car used to misfire when it was worming up, but now that I installed some magnacor 10mm wires , no more missfire. I recomend new wires and spark plugs.
gil.
gil.
12-17-04, 04:19 PM
#20
Engine, Not Motor
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What boost pressure? Did you use a wideband or any other accurate A/F gauge? How cold is it in Windsor right now?
Not to be an ***, but somehow I doubt that a 3% change in your S-AFC settings blew your engine.
Not to be an ***, but somehow I doubt that a 3% change in your S-AFC settings blew your engine.
12-18-04, 10:54 AM
#24
Engine, Not Motor
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Damn....Partial throttle? Do you remember what map your S-AFC was on?
This is the Achilles heal with an S-AFC set up as TPS referenced. You can be under boost, yet still on your "low throttle" map.
This is the Achilles heal with an S-AFC set up as TPS referenced. You can be under boost, yet still on your "low throttle" map.
12-18-04, 11:28 AM
#25
Eats, Sleeps, Dreams Rotary
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You're running 550 primaries, correct? If you were running 550s with partial throttle, @ ~3500rpm with 10psi with just the primaries when the ECU is expecting 2-3psi. We all know the ECU doesn't drive the primaries particularly hard at full throttle at that point, would it be reasonable to assume the same is true under partial throttle? How did you have your S-AFC set under 3800RPM?
Regarding the "1 ping death" I also wonder if the cutting out that you described before resulted in repeated detonation that you couldn't hear. It stands to reason that in such situations the control system would be oscillating out of stable operation and that the ECU/sensors are not particularly able to reign it in quickly. Thoughts?
Also, are you running the S4 or S5 ECU?
Regarding the "1 ping death" I also wonder if the cutting out that you described before resulted in repeated detonation that you couldn't hear. It stands to reason that in such situations the control system would be oscillating out of stable operation and that the ECU/sensors are not particularly able to reign it in quickly. Thoughts?
Also, are you running the S4 or S5 ECU?