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Snow4Lif3 12-12-2011 07:56 PM

Taylor shorties/Gibson catback observations and Need advice
First, my observations was made after the installation of a Gibson catback and the shorty wires and compared with before the
Also, IM using the superchips programmer with the 91 performance tune. I've not played with the Superchips trans apps settings
and I used the SC recommended.

Yesterday, I did a 200 miles highway trip and I set the cruise control at 65 MPH. The first thing I observed is that the MDS
was On at least 80% of the time (before, for the same trip, it was ON 5-10 % or less). The evic also showed 11.4 L/100Km (MPG
?) and before the installation, it was 14-15 L/100 km. Soon after, I noticed that my I was on the 4th gear (2000 RPM at 65
MPH). I used the gas pedal to go on the 5th gear. On the 5th gear, the rpm dropped and the MDS light was rarely ON and my MPG
began to increase (on the evic).
I decided to make the trip on the 4th gear...
Well, its probably a stupid question but is it better running at 65 MPH on the 4th gear and saving gas or on the 5th with a
lower RPM ??
Also... do you think that its related to the Gibson Catback/taylor shorties wires ??

if its not related, I can say that after the installation of the Gibson catback, my jeep feel more strong on acceleration.
Perhaps, the taylor sorties made the greatest difference. I was not expecting anything before installing the sorties but my
jeep run way better and feel more powerfull... I would liked to have data to confirm this.

On another note, here are my Gibson catback sound observations :
The sound is very nice, not too loud but loud enough, from engine start to 40 mph, especially during accelerations ! The
problem begin after. At a cruising speed of 50-55 mph the sound is loud but endurable, except when accelerating, its a little
bit too loud. At a cruising speed of 60 mph or more, the sound is tolerable on the 4th gear but unbearable on the 5th gear....I
not tested it over 70 mph.
When I say unbearable, I mean that the two ears stops after 5 minutes. I don't know what people mean when they say "drone" so I
can't say its "drone". I'll try to retighten the exhaust to see if it change anything. Its not a vibration sound, its a
resonation sound.
I love the sound of the exhaust be I'll have to do something for the highway... any advice ?

jeepgcoman 12-12-2011 11:37 PM

Re: Taylor shorties/Gibson catback observations and Need advice
Well, welcome to the world of crappy RFE transmission shift schedules and 5.7 exhaust tuning. I will give you my experiences and observations, FWIW, in hopes that it may help you a little.

First, if you have over ~50-60K on your 05, the stock (over the top of the engine) wires were probably on their way out, and the Taylor Shorties made an improvement. Did you also change the spark plugs? If so, what did you put in?

Second, the stock 545RFE shift schedule has the 4-5 upshift (light throttle) occurring at ~61 mph. The unmodified SC 91 tune will move it up a couple miles per hour. I have found that the best speed for the light throttle upshift is at about 64-65 mph.

Your fuel economy will be better when in the MDS mode, so leaving it in 4th, with MDS on, is better than in 5th and MDS off. The problem with being in 5th is the vehicle is too heavy (over 5000 lbs. w/you and full tank of fuel) and lousy aerodynamics (~.41 drag coefficient) make it like pushing a box down the highway. Also, at 1700-1800 RPM, you're farther out of the torque range of the motor than you are at 2000-2100 RPM. Speed up and the wind drag increases drastically and the mileage starts to tank.

I normally drive mine at 63-67 mph, and manually upshift/downshift depending on the terrain I am in......which is mostly hilly and mountainous. I'll select the gear that holds the MDS on the most. I leave it in "Drive" most of the time. I'll "goose" it to get it into 5th when I can keep the MDS on. When not, I'll backshift to 4th and then back to "Drive" and the MDS will come on.....even up some pretty good hills the way mine is modded. If I am in mostly mountainous, or longer climbs, I'll turn on the "Tow/Haul" mode. Back on level ground I shut it off. Bottom line, is the transmission, the converter clutch and the MDS are all frequently cycling, depending on the highway conditions.

On the exhaust, you've probably already found that you get a nifty drone when it is in the MDS mode. It took me three tries to get mine right. No matter what you end up with, you'll probably need to have a good resonator to augment the muffler you're using. I have a 12 in. glasspack, a Magnaflow 14589 muffler, and an Xlerator, XS1229 muffler in the resonator position. This gives a great sound at cruise, a throaty roar at WOT and almost no note change from 8 cylinder mode to MDS mode.

Hope this helps you a little.

Snow4Lif3 12-20-2011 07:16 PM

Re: Taylor shorties/Gibson catback observations and Need advice
Thank you very much for answer.

My jeep have 90k, so like you said, my wires was probably not very good.
I changed my spark plugs last year with the Champion copper ones.

I did some MPG (on evic) tests. I was driving on a flat road, little front wind. I did my tests at 65 MPH with the cruise control. The MDS was not often ON because of the winds (and maybe the 5F temperature). I reseted the evic before each tests and drived for 5 minutes on the same road/direction.

Sorry but the results are in L/100KM (lower number = better mpg)

On the 4th gear no MDS > 14,3 L/100KM
On the 5th gear no MDS > 13,4 L/100KM
On the 4th gear MDS ON > 12,5 L/100KM or less

I'll do other short trip tests with refilling between.

The MDS will not go ON when manually on the 4th gear.. is it normal ?

Also, I observed that for the same speed/gear, RPM vary a little... is it because I have a problem in the tranny, transfercase ?

About the muffler, I will probably end up like you... with some modifications. I'll bring my jeep to a exhaust shop to see what they can do. Again, thank for your advice.

05wkguy 12-20-2011 07:33 PM

Re: Taylor shorties/Gibson catback observations and Need advice
For my "non-metric" friends:

L/100 km-------MPG

Snow4Lif3 12-20-2011 08:19 PM

Re: Taylor shorties/Gibson catback observations and Need advice
Thanks for the conversions !!

dssilvestri 12-20-2011 09:21 PM

Re: Taylor shorties/Gibson catback observations and Need advice
is this the gibson catback with the resonator ? or without ?

jeepgcoman 12-20-2011 09:25 PM

Re: Taylor shorties/Gibson catback observations and Need advice
Looks like your fuel economy is not that bad. For the MDS to work, the selector must be in the "D" position. It will not work in any other position or when in the "Tow/Haul" mode. The RPM will vary (usually 75-125 RPM) when it goes in and out of converter lock and MDS. More transitions means more RPM shifts. If you're in a windy area (like me), at altitude (like me), or in a hilly mountainous area (like me), you'll see a lot of this.

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