Closed Throttle Problems with T-Trim.

I have been running S-Trim with a Bosch BOV without any problems for a long time.
I just installed a T-Trim to replace the S-Trim with the same relief
valve and piping. I am running a draw thru MAF with 60 lb injectors and was making 15-17 lbs boost.

Installed new T-Trim......
When closing throttle after light cruise the AFR gradually goes from normal to 10.5 and stays there until throttle is increased or vehicle speed is
reduced to engine idle speed.

Datalogging the event shows high MAF (50-100KGM) and loads when the throttle is closed. Previous data logs of the S-Trim has no such conditions.

My theory is the T-Trim is moving more air than the Bosch valve and piping
can dump back into the input tract.
For a test I removed the Bosch BOV and replaced with a plain piece of piping
with the same result .

I would replace the BOV system now inplace
If I was sure this was the problem.

Comments please.

i don't think that is your problem. the "t" will move more air,. but at the level you are describing( low speed ) i doubt it would have that effect. i have run a "T" and had no issues with my bosch bypass.

Can I ask if you have a AFR meter in the car with your T-Trim?
The reason I ask is it is a very small problem, If the meter wasn't there
you might not pick it up. I know it is there not only because of the meter
but am able to datalog over and over.


I am thinking ,as you pointed out, it might not be the BOV. Only thing I was thinking was a mechanical problem with the install. had to modify
90 degree elbow into the blower and still had to fight with it to get it on.
Maybe something unseated. The car runs great otherwise
Closed Loop good adaptive fuel insignificent.Other than do some backtracking
not sure where to go from here.

yes i did. always showed lean upon decell.

Again thanks for the comeback...

Well its pretty cold out here in NJ right now but I am going to go over all the
inlet and outlet piping as soon as possible. Maybe something has come loose.

This is a Lincoln Mark VII install so things are pretty tight under the
discharge and inlet tubes.

Well finally got to the bottom of problem. Changed to mini blow off valve
still had problem. Turns out I had a bad ISC (Idle control valve) which
coincidentally failed when I did the blower install.
Not really sorry about dumping the Bosch valve as the T-trim makes
more boost than the S-trim and probably a better environment for the blower.

Thanks for the help.