Bad Kitty???

[SilverSage]

I have posted before about really poor mpg on my 05 auto 3. 73 diff, I am easy on the go pedal and keep same-as-stock tires fully inflated. I get 10 MPG in town on winter blend and almost 12 in summer. Unloaded on the highway at 60-65 I get 13-14 MPG and 10-12 with a 4000# travel trailer. I have a straight through muffler and opened up the air box with a cool air intake and better air filter. Those mods did not help or hurt MPG but she spools better and cools EGT faster. I uploaded a Smarty Jr and there is a slight improvement in town (I haven’t been on the highway because of the lousy weather). The Smarty Jr makes a big puff of black smoke if I gun it on takeoff but no noticeable smoke on a normal takeoff.

A sales person for a dealership in town told me that he had seen several CATs clog and ruin MPG. I have never heard this from a dealer before. I asked if the CAT could be replaced under warranty and he said no way. I have excellent power and make close to 30 #s of boost (max) drivability is excellent. EGT hits 1300 on hard pulls in the mountians with 4K trailer at about 60-65 MPH so I back off. Should I expect any improvement with a high flow CAT. Any idea what a new CAT would cost and where to get one. I do not want to eliminate or gut the cat. My OH computer is always about 3 MPG higher than actual, which makes me think the computer is part of the problem. Also I have read several posts about bad injectors. I have had it several dealers in town and they all al say the computer and injectors are fine. Any ideas on the CAT?

 

[cerberusiam]

The CAT on these trucks is not the same as the gassers and is really more of a particulate trap than anything else. They don't plug easily and unless you are running some really high EGT's for a long period of time they don't seem to give much problem. They can melt and cause a restriction but that is usually heavily fueled trucks that are constantly hitting 1500+ degress. A stock fueled truck does not seem capable of generating the heat needed to really hurt one.



This year has been the worst for mileage I have seen on mine also, even running stock tunes and the supposed mileage Smarty tune. Its getting 10-12 pulling anywhere from 3k to 7k. I have even seen 9 mpg but that was temps in the 20's and a stiff head wind. With 100k I am starting to suspect a combination of fuel and injector wear that is causing it. When I do get a chance to run in warm weather and take it easy it will still make 18-19 mpg. I am thinking weather is contributing a lot more than I have seen previously.



I am thinking F1 is gonna get an injector rebuild and see if that is a potential problem area.