I own a 1999 Ford F-150 ext. cab 2wd with 5.4. I already have a magnaflow si/do exhaust. I want to remove the two rear cat. converters, and just replace with a pipe. My question is will i mess anything up or run into any problems as long as i do not mess with the O2 sensors. I think i will leave the two front converters/resinators alone. By removing the rear converters, will i have an increase in power or gas mileage, will my exhaust get any louder? (many have told me yes to all) Please give me all the advice possible.

 

The rear ones are the actual converters. The fronts are more like preheaters to help the cats light off faster and be more efficient.
It will be louder, may increase some higher rpm hp, but will lose some low endtorque from the lack of backpressure. Check engine light will stay lit unless you get special dummy sensors that fool the computer into thinking that the cats are working. I have seen them for Mustangs.

 

You can order some MIL Eliminators, two of them, and plug them into the last two O2 Sensors so that it tells the computer that your truck is running fine. If your cutting of the two rear cats you might as well cut off the other two, it would'nt hurt. I cut my cats off a few months ago and it sounds like a monster, it's VERY loud; especially with my side exit 40 Series Flowmaster. You will gain some MPG on long highway runs but there won't be much of a difference on the streets besides the looks people give you when scare the hell out of them with your exhaust. Heh Heh. The only drawback is the loss of low RPM torque but it makes up for it when you get to about 4000 RPMs.

Chris

 

You need to make sure that your truck will pass inspection before you cut off the cats. This is illegal in Texas.

 

Where did you get those "MIL Eliminators" and how much are they. How do they connect to the O2 sensors. I have the rear CAT's on mine off also.

 

Check a Mustang magazine. They are always in there for when you put off-road exhaust on a 96-up Stang.
If you do any towing or haul a decient amount of weight, I would leave them on. The loss in torque will be bad for lugging more weight.


Jimmy

 

mil elimnators are a way to do it, but the right way would be to shut the light off in the eec itself.

JH

 

I bought a pair from Dallas Mustang because they make them themselves and they sell them cheaper. Just go to DallasMustang.com and order a pair for the OBD II System.
The way you install them is fairly simple. All you need to do is crawl under your truck find the last two O2 sensor,(the ones located after the cats), disconnect the wiring, (be sure to leave your old O2 sensors in place, they don't need to be removed or anything), then plug the MIL Eliminator to the O2 sensor and the wiring to the other side of the Eliminator. When you finish that just tuck them away with the supplied ties.
I believe the price is between $25-$35.
By the way if you live in Texas you CAN get away with removing the cats. On all OBD II vehicles inspectors only connect their inspection computer to the vehicle's On Board computer. If you have these MIL Eliminators plugged in, the On Board computer in your truck would report that the emmissions are fine, therefore legally passing your vehicle's emmissions test. The only way you would be screwed is if your inspector happens to use the "sniffer" or that stick they put in your tailpipe, then you might have a problem. But I think they only use the sniffer on older OBD I vehicles. I passed with flying colors. Heh Heh

Chris