Anyone have any idea what was done to my truck so that it will only run on 92 octane or higher ? 96 Ram 2500 with the 360. There is an after market sticker on the gauge cluster as well as the gas tank door that say "Minimum 92 Octane required" When I first got the truck I tried regular old regular and the truck backfired constantly and pinged like mad. On 92 it runs fantastic.

How would I be able to tell whats been done ?


Also where is the ECM located in these trucks ? Is there more then one ?


Thanks, you guys are a godsend to those of us who require your wisdom.

 

You may have the Mopar Performance PCM computer which requires 92 octane,
but that sticker sounds like the one Jet Performance includes with their product.

The Jet chip has a reputation for dying suddenly.

The MP PCM computer on a 1995 Magnum 5.9V8 definitely has more torque in the 1500-3500 rpm range. The 'Magnum Engines' book by Larry Shepard claims it gains about 20 ft-lbs of torque in that range, but has only a mild gain from 3500-4500 rpm.

I ran the 1995 MP PCM for several thousand miles, liked the performance but found a slight MPG loss.

See old post below:
----
This past Friday afternoon I had some free time and finally got around to
doing a highway test run of a 1994-1995 Mopar Performance PCM (part number
P5249546) to my factory 1995 5.9V8 PCM (Chrysler P/N 56028325)

This was over the same 218 mile round trip from Clayton NC to Wilmington NC on
I-40 that I have done past reports on. Speed was a steady 70 mph on cruise
control and the AC was on with the temp control set to the 11 o'clock
position. Engine speed was 1750 rpm and the countryside is mostly flat with
some rolling hills. There was a 5-10 mph crosswind and temps were 80-75
degrees on the first run and 75-70 degrees on the second.

I used Hess 93 octane gasoline on both trips.
{Longtime readers will remember that I previously used Exxon 87. I am still
going to the same Wilco gas station, but its owners recently switched from
Exxon to Hess.}

On the first trip with the factory PCM and the gas pump gallons,
I got 19.85 MPG.
As a second opinion, the Oztrip aftermarket trip computer I have installed
said I got 19.60 MPG.
Midway through the first round trip at the turn-around point the Oztrip was
reading 19.04 MPG.

With the Mopar Performance PCM installed, I drove around with the new PCM
computer for 30 miles in different types of driving before starting the second
round trip test run to allow the PCM's internal 'Adaptive Fuel Factor' and
"Added Adaptive Fuel Factor" registers to "learn" new calibration points. It
is my understanding that these AFF and AAF factors in the PCM software can
adjust themselves in about 10 miles of driving.

On the second 218 mile round trip with the MP PCM,
the gas pump gallons said I got 19.12 MPG.
The Oztrip computer said 19.41 MPG.
At the mid point of this second round trip the Oztrip was reading 19.19 mpg.

I was surprised by the result,
but both the gas pump calculation and Oztrip both indicated that the Mopar
Perforrmance PCM with its more advanced timing gave worse MPG. I do remember
reading several posts in the past where Ram truck owners reported better MPG.

I don't have a ready explanation for these results, but I do note that the
first trip where I was using 93 octane and the standard factory PCM gave me
the best result I have gotten on this particular test run. (19.85 MPG and
Oztrip 19.60)

Always in the past I have used 87 octane gasoline. For example, on 5-10-01 in
similar weather and temperatures I did this trip testing new Autolite 3923
sparkplugs and got 19.19 MPG from the gas pump and 19.15 MPG from the Oztrip.
It may be that Hess 93 octane gives slightly better MPG than Exxon 87.

I can tell that the Mopar Performance PCM does increase the ignition timing,
because even with the Hess 93 octane I get some pinging starting around 2800
rpm. At full throttle, with the standard PCM and 87 octane I get pinging
starting at around 3800 rpm. {with 93 octane using the standard PCM the 5.9V8
does not ping at any rpm or load)