Ok so I've grown up in a state where we have yet to have emissions tests, and I've never heard anything good about a catalytic converter. But I've had 2 different people tell me lately that deleting the cats on gas or diesel engines will hurt gas mileage and performance. What are the true facts about his? I've got a friend wanting to know if he should pull his off of his 06 6.0 or leave it.

 

I have mine deleted. It will help mpg's on diesels because of less resistance/ back pressure. Gas engine exhaust requires alot more back pressure. So i dont know about gas. I have seen a slight difference. Plus i have a straight pipe. I now get a highway average of 18.5 mpg's. I personally think anybody who says it doesnt help or will hinder the performance of a diesel by deleting the CAT doesnt mnow what their talking about. But i know alot of people who dont like them without the CAT cause of the noise.

 

Well the friend of mine that's wanting to know is already getting a highway average of 21mpg, and he even has the latest flash that supposedly kills fuel mileage. But supposedly we're supposed to be starting visual testing next year, so we're wanting to do it so that we can have a piece that bolts up just like the cat does so that if he has to start testing, he can just bolt his cat back up for the test.

 

That is unheard of. How did you or him ever get that figure?

 

ya 21mpg?????? and if he wanted, he could gut the cat and put the pipe back so its really just a straight pipe that looks like a cat.

 

Deleting a cat on a diesel will improve mileage and performance. Deleting a cat on a gas vehicle will give some better performance, but will kill the mileage. Either engine will sound a lot louder with no cat.

 

That's what he is saying...he drives it 2 hours on the interstate every weekend and clocks it. I'm not there with him but I mean he knows his math pretty well so I doubt he's doing some dummy calculations.
We thought about that, but if they start doing actual tests after doing the visual tests then he'll have to get a new cat...

 

Get a delete pipe, and keep the cat comfy in the garage. 3 bolts and a jerk, no problem.

 

So if he's at 21 mpg now, he can delete the cat and get 25? Personally, if I was getting that kind of mileage I would not touch it. Unbelievable unless that part of the interstate is downhill.

 

I had bad turbo lag with the stock exhaust. Would step on the GO pedal and sometimes it was dead. Took out the cat and installed an MBRP delete pipe. Lost 50% of the turbo lag. Then put on the 4" MBRP T-back exhaust and disconnected the EGR valve and lost all turbo lag. Now I have a very old version of ECM software but with the MBRP, EGR cooler plugged and valve unplugged and the SCT tunes, I have never had another turbo lag issue.

I got 21 MPG with my X going from MD to AL running 70 to 80 MPH about 3 years ago with 4 adults, 2 kids, the back loaded and a trailer hitch carryall. At that time I had the Edge Juice tuner set on level 3. Now I get 18 MPG going from MD to MI with the SCT and the street tune.

I need to clean my MAF sensor and get ED @ FICM Repair to upgrade my FICM before it goes tango uniform. I'll probably see an improvement in MPG and performance.

DSMMH

 

The real reason to delete the cat is... to lower your egt's! Then there is the sound factor, its a great sound without!

 

He said he resets his dash gauge right before he leaves and that's what it tells him. He said the first 10 or so times me hade the drive he did the calculations himself at the pump and it was within .5 of what his dash gauge says. He said his gauge has always been accurate, whether it's highway, city, or pulling his trailer. But he said he gets 21 highway, about 16 around town, and 12-13 pulling his 5,000lb trailer. And that's stock untuned. He just got a tuner and tunes yesterday but haven't been able to run them because the stupid plastic CAC pipe blew on his way to meet me with them.

 

I never see mileage like that when running winter fuels. In the summer, I get upper teens at best.

 

If your going to keep your stock exhaust...you can substitute a "factory delete" pipe from a '98 to '02 7.3L powered truck that was equpped with the slushbox. That's what I did with my truck. And my mileage improved about a mile to the gallon. I've still got the factory cat sitting on the shelf just in case the day comes and the tree huggers get their wish.....50 state emissions testing.

 

If he blew his plastic hose, have him get the alinum replacement from tousley ford