I have a 05 Z MT with a vortech running 6-7 PSI. When I am just cruising around and let off the throttle when I am NOT in boost there is about a 1-2 second lag from when I let off the throttle and when the RPM's finally drop. This is WITHOUT the clutch pushed in. I have owned corvettes, S2000's, FD RX7, etc and this is the only car I have ever had this issue with. Does anyone have any ideas? This is very annoying... mods are:

Vortech SC
Borla Headers
Bassani Exhaust
5/16 Plenum Spacer
600cc DW Injectors
Berk HFC's
JWT Clutch/Flywheel
UTEC

 

That's a delayed fuel cut that is part of the stock ECU drive by wire system... for the most part it's normal. It's to make the car less 'jerky' when going on and off throttle. To be honest I barely notice it, maybe your throttle body needs recalibrating.

 

I have the utec/turbo. I do not get this when I let off the gas

 

I've seen this with the Vortech...I think it may be due to the bypass valve not getting the air out quickly enough when you get off boost and go into vacumm...maybe you can check or adjust you bpv....

 

I have tried adjusting the bpv from 10 threads showing all the way to 4 threads showing with no difference. It's very noticeable. When I am in boost it doesn't do it, but when I am just cruising still under vacuum it takes almost a full 2 seconds for the rpms to drop after I let off the gas to slow down.

 

Either your throttle body needs to be re-calibrated which is very common, or your fuel cut in the ecu needs to be adjusted. I have done a couple different Vortech cars and not seen this... Common for the drive by wire to be delayed for smoothness. Also are you dedicating a vacumn line or is it t'd multiple times for other things such as boost sensor or FPR?... The DBW can be adjusted also with changes in the factory ECU through uprev in terms of how the stock ecu applies fueling in decel. I did this when I had a Utec on my stock block TT setup and fixed the awful vacumn/ boost jerking.

 

I have my bpv, boost gauge, and utec map sensor all t'd off of the vacuum nipple on the front of the plenum.... Could that cause any problems? To recalibrate my TB all I need to do is disconnect the negative battery terminal for a few hours and then do the relearn procedures right?

 

There isn't any control over decel cut in Uprev as far as my experience goes. Perhaps unless they added it recently in newer ROMs.

Still think it's either something up with the BPV (pushing boost off throttle) or the TB not closing all the way. The stock decel cut settings shouldn't be that intrusive.