[panabax]

I have a '96 Bronco with 351W and EECV (AGANF). I recently completed a supercharger install using an Eaton M112 from an '04 Lightning. Tuning has gone well and the truck is running really good now. I have a few lingering issues to run down. One of them is an odd sound that happens sometimes when I let off the throttle or when the truck shifts (E4OD) thus reducing engine load suddenly. It typically involves a transition from small boost to no boost. It sounds like a swoosh or a single rattle from a rattle can. It's really hard for me to describe, but I suspect it may be related to the bypass valve on the SC suddenly opening in the presence of vacuum, but that is just a wild guess. I would really like to nail down the cause to determine if it is benign or needs to be addressed. My "worst case" scenario is that it is some type of transition induced ping or detonation, but I do not notice anything unusual on my wideband sensor. Typically under boost I am running a lambda between .75 and .8. I am right at 1 for cruising with low load.

Any ideas? Any additional info needed to diagnose?

TIA

Baxter

[decipha]

can you isolate the source of the noise?

an engine detonating/ping and a bypass valve venting shouldn't be confused in most cases

[floodking88]

my N/A 302 does the same thing on throttle releases, although very quick. it's an auto, but if it was a manual i bet it would happen on shifts too.

it's not too loud, but it sounds like in between shifts on a turbo nissan 6. a sweet little swoosh. i'm not too worried about it.