a/f spikes...any ideas why?
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From: Columbia, SC
a/f spikes...any ideas why?
Ok, first my mods on this s2000:
Comptech SC, 4.25" pulley upgrade (front mount intercooler)
Comptech headers/testpipe and then a single exhaust.
V-AFC.
Last situation before problem occured. I took the car to the dyno for the winter to see what kind of power I was getting, we added a little more fuel from the fpr to be safe (a quarter turn I'd say). Subtracted a little with the v-afc at 4500 and 8000 rpms to even out the curve.
Now, cruising down the road at a constant, let's say, 50mph...the car will feel like it bogs down...exhaust gets deep, and then goes back to normal. It all lasts maybe a second or two. I can't ever look down at the wideband quick enough to see my a/f at the moment of it bogging down. I'm guessing it gets real rich. Other times, always from a dead stop, the car starts jerking violently like the first day I tried to drive a stick many years ago. I've glanced at the wideband twice now to see it reading low 30's! and dwindling back down to safety. 30's!!!!! I really have no idea what is going on. Back to the dyno we go and do 10 runs...a/f looks good through the whole spectrum. No spikes...no nothing. Their wideband is reading almost identical numbers as my wideband. Does anyone have ANY idea what might be going on? I also noticed a few times, when I started the car, the a/f will drop to 9.0 for about 5 seconds (makes the low exhaust tone as mentioned in the first situation above) and then rise back up. Any ideas would be greatly appreciated! I've had all these mods for over a year now, and never had these problems. I changed the oil about a month ago and had driven I'd say 800 miles before this started happening. It all started about 3 days after I took it to the dyno. But we did such minute changes, I can't see it doing this. We've been tuning this car for a year now...whenever I add something to it, or to compare my wideband readings to theirs. If no one has any ideas, I guess I'll take the fuel back out with the fpr, zero the v-afc, and start over.
As a sidenote, I turn the car on and let the wideband warm up completely, and then crank it and let it sit until it gets 3 bars. And all of the above incidents (minus the 9.0 readings when I crank it) happen after driving for at least 5 minutes. They never happen right away.
Much thanks in advance,
Dave
Comptech SC, 4.25" pulley upgrade (front mount intercooler)
Comptech headers/testpipe and then a single exhaust.
V-AFC.
Last situation before problem occured. I took the car to the dyno for the winter to see what kind of power I was getting, we added a little more fuel from the fpr to be safe (a quarter turn I'd say). Subtracted a little with the v-afc at 4500 and 8000 rpms to even out the curve.
Now, cruising down the road at a constant, let's say, 50mph...the car will feel like it bogs down...exhaust gets deep, and then goes back to normal. It all lasts maybe a second or two. I can't ever look down at the wideband quick enough to see my a/f at the moment of it bogging down. I'm guessing it gets real rich. Other times, always from a dead stop, the car starts jerking violently like the first day I tried to drive a stick many years ago. I've glanced at the wideband twice now to see it reading low 30's! and dwindling back down to safety. 30's!!!!! I really have no idea what is going on. Back to the dyno we go and do 10 runs...a/f looks good through the whole spectrum. No spikes...no nothing. Their wideband is reading almost identical numbers as my wideband. Does anyone have ANY idea what might be going on? I also noticed a few times, when I started the car, the a/f will drop to 9.0 for about 5 seconds (makes the low exhaust tone as mentioned in the first situation above) and then rise back up. Any ideas would be greatly appreciated! I've had all these mods for over a year now, and never had these problems. I changed the oil about a month ago and had driven I'd say 800 miles before this started happening. It all started about 3 days after I took it to the dyno. But we did such minute changes, I can't see it doing this. We've been tuning this car for a year now...whenever I add something to it, or to compare my wideband readings to theirs. If no one has any ideas, I guess I'll take the fuel back out with the fpr, zero the v-afc, and start over.
As a sidenote, I turn the car on and let the wideband warm up completely, and then crank it and let it sit until it gets 3 bars. And all of the above incidents (minus the 9.0 readings when I crank it) happen after driving for at least 5 minutes. They never happen right away.
Much thanks in advance,
Dave
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