On posts 2-5 on this thread, we briefly addressed how modern engines are reluctant to settle back down to idle...
Ha... I was just thinking how quickly we get off track. I'm not offended or complaining, hey I do it too. But I just came up with a term for it: THE DIGRESS ADRESS. How 'bout that??? This would be a great term to describe a post that jumps off topic.
Anyway, getting back to the subject at hand, I was doing some research on a german car forum where they were addressing this. Apparently the phenomenon I was trying to describe is known as "REV HANG."
The following are just opinions from forum members. I copied and pasted a few of their comments below:
--From what I understand it helps emissions because while it's slowly climbing down in revs it's consuming any unburnt fuel.
--A free RPM drop releases unburnt fuel into the exhaust (hence the pops) which is bad for co2 emissions.
--What he said. It is emissions related to help burn left over fuel before it enters the catalytic converter.
--Rev-hang is when the rpm tends to hold steady without decelerating. As mentioned, it is to keep the catalyst lit for emissions.
When people say they reduce the rev-hang, they generally made adjustments at high RPM/WOT and kept the OEM parameters intact during normal cruising conditions.
--If they "did it right" the new APR tune should also have eliminated the rev hang... The rev hang is most noticeable at low RPM city driving, anyway.
--Stock rev hang should annoy just about everybody.
--This has been discussed quite a bit in the past. Yes it is emissions related. I hated the rev-hang when I got my R. I ended up with a UM Stage 1 flash that has pretty much eliminated it. I am not sure other tuners will represent that they can eliminate it but UM advertises it. Now it's much more fun when blipping on downshifts.