Exhaust Upgrade..What to do with the cat?

[Mark Fry]

I have a '95 Suburban in need of a new exhaust. The cat is aft, just in front of the muffler on the orig install. I'd like to know what others have done with the cat. Would like to get a hi-flow cat, but none of the aftermarket systems seem to readily accomodate this configuration. The only place I have seen offering a hi-flow cat is SS Diesel. If I don't have to get emmisions testing in Virginia, what is the down side of not reinstalling the cat? Also, when upgrading the breathing, most of the systems specify they are for non-MAF equipped vehicles. When did GM begin installing a MAF on these babies?

[GMC Hauler]

I don't know about the MAF sensor, but if you can get away without the cat, then don't run one. There are only positives with not running one..

Less back pressure.

I've heard they clog up on these diesels sometimes.

[Mark Fry]

Hey Hauler, THanks for your reply. Looks like you have accomplished many of the mods that I eventually want to get done. On the air box mods, what did you do? The aFe kit looks great, but the $400 price tag gives me gas so far. What about just putting in a free breathing filter and killing the snorkel. The aFe kit claims a 180 cfm flow, vs. 16o for stock. That does not seem to be as large a difference as I thought it would be. I know I have to do something, but what? Also, have you ever replaced your turbo wastegate control solenoid?
THanks!

[rameye]

I'm running catless...

save that cat in case you get emissions or inspected!

I plant to cut mine in half remove the guts and braise the two shell halves around my exhaust pipe.

we have emi$$ions up here...for diesels too!

ram

[Kennedy]

In my exhaust install overview on my site is a pdf of different cat options.

[GMC Hauler]

Mark,

There is lots of good information for modifying your intake on this website: Kennedy Diesel. (http://www.kennedydiesel.com/) Click on tech tips, then 6.2-6.5 tips. Click on air intake modifications. This will give you all the information you need. Spend some time in the rest of the tech tips, they are usefull.

There is several systems out there that remove the whole intake box and replace it with an elbow, filter, and for some, a heat shield. They are good, but I also don't want to pay that much.

You can go with a factory box for a 1997 or newer. It is a bolt on, and filters better. Those are available at junk yards across America. I have all the factory part numbers if you need them.

I am currently running a gauze type filter (K&N), but want to switch to something else, because of filtration issues. I have been looking at the foam filters, particurally at Unifilter. (http://www.unifilter.com/) They have a nice large universal filter, which in combination with a homemade intake elbow, would yield excellent results, in my opinion. The intake could be plastic, rubber or metal pipe, and shouldn't be to difficult to make. I havent gotten around to fabricating one yet. If you decide to go this route, take pictures and notes. Many will want to know what you did and how you did it. This is the route I will be taking.

As far as the wastegate control solenoid, I have squirted some WD-40 in mine before. It was sticking. I ended up getting rid of the whole system. If you are in need of a wastegate solenoid, I have a new one for sale here. (http://forum.thedieselpage.com/ubb/ultimatebb.php?ubb=get_topic;f=19;t=000365)

If you are thinking of going with a mechanical system, and want to compare the systems, I can provide links with information for that.

If you could, please provide a description of what you are driving in your signature line.

Welcome to The Diesel Page. :D

[Wheat Whacker]

When I upgraded my exhaust to JK's 3.5" system(which is still nothing short of awesome :D :D ) my cat ran away so it did not get reinstalled and my '95 runs and sounds great.

P.S. If anybody finds my cat please give it a good home.

[Dvldog 8793]

Howdy
Welcome to the DP. If you do a search on this forrum you will find loads of info on what to do and what not to do. In my opinion the cat serves no real purpose for a diesel BUT certain folks want to SEE them there. (I don't think there is a sniff test for diesels) If you think that you might be getting a test then you should probably keep something that looks like it might be a cat. My truck is exempt because it is a 1 ton :D Have fun and ask lots of questions there is allot of knowledge here.
L8r
Conley
USMC 87-93

[ak46champ]

I have a 2000 CC 6.5, and bought a unifilter. I have looked at the filter box mods and kits and am wondering if an easy fix for now would be to leave the stock airfilter box cover off for some improved airflow or does it really matter?

[garre1tt]

I recently had a 4

[BrentN]

I am preparing to run with JK's exhaust and set my cat out on the front porch.
For those that arent running a cat...how is the noise? My wife, drives the Sub every day. She actually likes the sound of a diesel...but I dont want to push it and make the thing sound like a garbage truck by getting rid of the cat and its inherrent muffling abilities.

I also dont want something loud or have an obnoxious drone that will drive the family crazy on multiple thousand mile road trips. I cant deal with the little punks that put the loud muffler on their small cars and you have to turn up the stereo on the freeway to not hear them. I definitely dont want to hear my own exhaust when going down the freeway. Any feedback from the group regarding how much louder the system is without the cat.

Thanks

[GMC Hauler]

I don't have the cat, and I have the 4" free flow exhaust with a see through muffler, and the system is quiet with a little bit of rumble. Most of the noise is absorbed by the turbo.

It doesn't annoy my wife, so it must be ok.

[Barry Nave]

When my last truck was a gasser,I just ran stright from cat back with no muffler,Not loud yet a nice rummble. Have any one just ran back from the cat alone on the 6.5? Myself I'm running stright from turbo back. Sound more like the Dodge truck with what some must be running what ever that is? Maybe stright also.
I like the stright system myself :cool:

[G. Gearloose]

I also have a see-through muffler and 'high flow' ;) cat, regret putting on the muffler, its like teets on a bull. Can't hear narly a thing except spool-down whistle and some white noise, and it exits in front of the rear wheel. The GM5 has much more muffling effect than the Banks. The Banks has more braap.

[tom.mcinerney]

I renewed my cat because i had convinced myself the old was clogged [not so, at 175Kmi].
I didn't buy a new assembly from the dealer for $6-1200, however.
There exists a supplier of just the cat itself, which may be welded in place of the old one, after cutting the old out. The price is about $300 delivered.
It would be possible to install two OEM-style cats in parallel ahead of (or in place of) a muffler, allowing a legal/clean, and lower-than-stock restriction exhaust, for well less than the price of a replacement new cat assembly from many dealers. I will post the supplier if anyone is that interested.

[ace58]

I replaced my stock system with JK's 3.5" system and now have a house cat. Emissions are strict here and, if I get an ambitios technician for inspection, I will follow the same plan as rameye.

[dstoops]

I ran a 3" pipe straight back from the convertor for over 100,000 miles.(no muffler) sounded good and ran better than stock.A muffler shop installed it for a reasonable price. When I rebuilt the motor I replaced that rusted system with a complete Pinnacle 4" system with a straight muffler. Sounds great too. I ordered the system for a 1993 model since the convertor was not required on the earlier models. Cant comment on difference in performance since we changed many other things at the same time. ( 18:1, bored .030" over)

[Robthechitkicker]

If you want my two cents on the cat and exhaust, run 3" or 3.5" strait exhaust, and gut the cat if it has the "honeycomb" like material inside. If you're putting an exhaust system, gutting the cat is easily done with an air chisel or hammer and chisel. If you're just going to put a strait pipe in the place of the muffler, you can easily make a long enough chisel out of 1.5"X2"X.25" plate welded on the end of a piece of small pipe, tubing, sucker rod or etc. To clean material out, start the truck from time to time as you break it loose and it will blow right out. I have gutted the cat's on both my 94 and 98, and its much cheaper than buying a high flow cat, at the same time you have a shell still in place if any inspection agencies make a big deal about the cat, and it adds a distinct echo or ring to the ehxaust.