What's the diameter on your exhaust pipe? If you're 2.5" or greater, I
would suspect the high flow volume is killing your exhaust gas velocity and
hurting your low-end torque. For the 5.2L, 2.5" - 3" exhaust pipe is great
if you're into racing, running quarters, etc., but for everyday driving, I
would prefer 2.25" max. to keep my low-end torque and mileage.
-----Original Message-----
From: James Thomas <callisto@flash.net>
To: dakota-truck@buffnet.net <dakota-truck@buffnet.net>
Date: Saturday, February 20, 1999 9:31 PM
Subject: DML: Mileage Drop
>Have done the following to a 1994 Std Cab 4X4, 5.2L, auto, 3.55 gears.
>Started with a Transgo shift kit then added Magnecor wires, brass cap
>and rotor, Champion truck plugs, MPI Super Street throttle body, K&N
>FIPK, Mopar Performance SBEC, Dynomax cat-back, hi-flo catalytic and new
>O2 sensor. All upgrades done within the last month or so. Everything up
>to the exhaust work gained very significant torque and throttle response
>and 3-5mpg city/highway. The gas mileage increase with the performance
>gains was just what I wanted. When the exhaust work was done I lost the
>mpg gains and then some. I went from getting 16.5 combined city/highway
>down to as low as 14.2. On strictly highway mileage I went from 20.1
>(best) to 15mpg at best now. I gained some nice breathability with the
>exhaust albeit at a high expense of economy. Has anyone else ever run
>into similar mpg problems with a combination like mine? Am wanting to
>add an MSD soon but would like to get mpg problems identified first.
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