Should I remove my cat?

[JDiepstra]

I am wondering if removing my cat will help me do anything helpful, such as but not limited to:

1. lower EGT's

2. decrease turbo spool up time

3. give me a deeper exhaust tone

4. increase MPG's (even . 1 mpgs is an increase!)



I've never had to do emissions testing here in Michigan so not worried about that.



Will I get more smoke? I don't mind that.



Also, will the truck be louder? I'm not looking for louder! Thanks guys.

 

[Ducman82]

ill be keeping my eye on this one... ... ... ... ... . id kinda like to know as well.

 

[jelag]

As we get near the new dates for emissions you'll find that your state is going to be changing the rules to conform... They've asked the diesel engine builders to have a common data stream off the data connector under the dash just like cars have... .

I attended a very interesting class on DPF's for class 5-8 trucks a while back and here is some of what I learned... .

Some states now do the test... 1 - make sure all parts are their and function, re: EGR, CAT, DPF... ... 2 - look to see that nothing has been modified or removed... .

But to answer your question... . if you have a marginal CAT in that it has some material plugging it, than..... with lower back pressure you ... .

1 - will get lower EGT's
2 - have faster spool up time...
3 - might get a deeper tone... I don't know this one...
4 - Nope... . mileage is based on physics and math...

Finally, where you have your car tested... . in some states its a private company, or garage or state agency, give them a call and ask them whats coming for Diesels... and than share it here...

I know changes are headed this way in WA...

 

[Mobius1]

When I removed my cat, I did get a deeper tone. It did get louder. Slightly lower egts, slightly faster spool up. Then again, nothing to write home about. about the egt's and spool up but an increase none the less One thing you will notice is your truck will actually smell like a diesel and it will have a more throaty tone.

 

[jtwcummins]

If your truck doesn't have O2 sensors any inspection might just be see if the cat is in place. On my Calif 97 I took the CAT off and ran a speed drill thru it until there was a tunnel, then pounded a 3 1/4 pipe thru it and reinstalled. Would pass visual and if tapped would still sound like a good unit - not hollow.

As much as we hate the idea smog tests are coming for diesels. Pickups from 2007 on are the trucks that are really going to have issues. Getting caught removing devices has a pretty good fine and tampering can get you if it looks like devices have been possibly removed and replaced for the test. Another thing going to happen is you won't be able to register vehicle if emission recalls aren't done.

Big Brother is here and it will only get tighter. I, personally wouldn't remove the CAT, BUT...

 

[BMH95]

I've always heard / read that the real restriction in our trucks is the muffler. Mine fell of, but the cat seems to be holding on tight. Sounds great and was a noticeable difference in EGT, spool up, and fuel mileage.

 

[ToddK]

I would say it is not worth it. If you can do it on the cheap then ok, but you won't get the gains and losses that some say you can. I have an '06 MC CTD G56 and the first exhaust mod I did was an MBRP COOL DUALS cat back. I was having, what I deemed, an egt issue even with the free flowing muffler. So I consulted 2 diesel performance shops and they both told me that I needed to get rid of the cat and go to a 5" turbo back system. The shop I used took out the old, cleaned the cat and put the 5" through it. This was supposed to lower egt's by 150 to 200 degrees. Well, it did not. Same egt's as before. BTW I use my truck as a daily driver and tow a 12k tt toyhauler on weekends usually in the Rocky mtns. Egt's are unchanged, still can hit 1500 no problem. Yes I keep the rpm's up over 2500 to keep airflow.



After all I have done to this truck I have realized that the best egt control is done through the right foot. I have always wanted to blow by all the other trucks towing and be the first over the pass. This costs too much $$ and causes too many issues.



If I could do it over again I would add a 50-70 hp tuner, do a muffler delete and add gauges. That would be the extent of my modding.



The best mod I have done to date is the Pacbrake. Hope this helps. Good luck

 

[hearingyourlies]

Westchester County, NY requires all vehicles with a GVWR over 8500 lbs to go to a truck inspection station now. It cost me 65 bucks. They plug into the computer, stick something in the tail pipe, hook up a decibel meter, and rev the engine for about 15 minutes. Smog patrol dix.

 

[abrankod]

I'm a HD truck inspection station in NYC, and we only do a snap rev smoke opacity test and a visual safety inspection. We've heard nor gotten ANY information regarding any computer hookups or noise mesasurement. The snap test consists simply of 3 snap accellerations in neutral to the rev limiter and hold for 4 seconds.

If you pass, you get a Diesel Safety/Emissions sticker. If your vehicle is over 26000lbs GVWR, you get the second heavy duty safety sticker too.

I dont know what shop you're going to in westchester, but they're doing a lot more than is required by NYS law for truck inspection.

-Dan

 

[Forrest Nearing]

definately remove it, but keep it in the garage. There is no performance/drivability/economy DOWNSIDE to removing it

 

[jltcasper3]

With a full straight pipe is alot louder than stock. My kitty and muffler fell off. As far as performance goes it's really hard to tell, im sure it didn't hurt performance though.

 

[george]

the never did smog checks here either on diesels

the never did smog checks on diesel pick ups here either until they started a few years back, they do a visual for the cat.

 

[Cattletrkr]

I have the same engine as you do (original poster). Keep the kitty. Mine is gone and I wish it was back. For normal everyday empty driving I love it. Sounds like a diesel again. Towing I hate it. I yanked the muffler years before I yanked the cat. didn't do much soundwise. Pulling the cat made it bellar. Nice deep tone and lots of it. I have 4" flo wthru mufflers in place of both the cat and the muffler and it's too loud for towing.

If you don't tow at all, then go for it. You will notice it at freeway speeds. Then it's annoying too.

 

[AH64ID]

I've always heard / read that the real restriction in our trucks is the muffler. Mine fell of, but the cat seems to be holding on tight. Sounds great and was a noticeable difference in EGT, spool up, and fuel mileage.

x2 works well for me... .

 

[nunya]

I was told by a long time exhaust man the cat makes no difference on my 06, replace the factory muffler and good to go. .

 

[Forrest Nearing]

did that long time exhaust man tell you that your engine needs some backpressure too?