Headers/integrator delay

[dyeager535]

Highly dependent on engine, exhaust, and O2 placement, but is there a "starting point" difference to notice changes? Stock delay is in the 2-300ms range, so is +/- 50ms typically enough to "feel" if the delay change is the right approach?

Doing this by SOTP since I don't have wideband (I know, I know), but the off-idle problem is enough that I will know immediately if it is helping. No matter what the BLM is at idle (whether rich or 128) stabbing the throttle results in an immediate jump to a lean condition, which I can't get rid of with just AE.

I've never dealt with this one before. I know some settings a minute change makes a huge difference, and others it takes massive changes to see/feel a difference. I'm thinking 50ms is a fairly large change

I don't have a Camaro manifold to get a baseline distance to where it is now, but the (heated) O2 is in the collector on long tubes, so I'm guessing it's three feet beyond stock. Using an arbitrary 5" from last exhaust port to 36" to O2 now, 50ms added to 300ms would be nearly perfect as a percentage. I assume however that the theoretical increase in exhaust velocity from headers will skew the results.

[EagleMark]

Use the INT/STFT for comparison when doing this. But I've found much larger then 50ms needed? Maybe someone can figure out math needed? If it's 300ms for time delay from injector pw change to O2 sensor, then moving O2 sensor 3 feet seems like much more time is needed.

I've been using 100ms per foot when testing and seems to work. In your case almost double, which is what I end up with.... If you overshoot at least the O2 sensor sample for next fueling adjustment is getting exhaust reading from corrected fuel and not before creating the yo yo effect....

[dyeager535]

What is STFT? I searched, came up with short time fourier transform.

Is it an abbreviation for swearing? THAT would be applicable in my case. lol

[EagleMark]

Short Term Fuel Trim is what the INT/Intergrater is.

[dyeager535]

So am I understanding correctly to watch the STFT and see if stabilizes? SOMETIMES I get the up/down oscillation in idle, but I got rid of a bunch of it by decaying AE faster.

Yet another thing to test! Thanks. :)

[one92rs]

well I can give you some measurments. mine was a tbi in a 92 Camaro but perty darn close to the tpi. with the stock manifold my 02 sensor was 3" below exhaust flange cyl #7. with shorty headers it is 7" below exhaust flange. with the longtubes if it were in the collector it is ( following the tube not a straight shot) it would be 21" below exhaust flange. truck headers are going to be longer so it would be about 28" to 32". would a heated 02 sensor help you any?

[dyeager535]

Already running a heated O2, just trying to nail down this off-idle stumble. I have other issues, but I figure I might as well nail this one down since I can work on it in the driveway. When I'm starting to affect it, I'll know.

Thanks for the info! :)