Cheap Speed - Cat Pipe Mod

[chuckspeed]

Late model cars are set up to pass LEV emissions tests; to do this, some manufacturers have gone to a precat/cat setup. This is essentailly two catalytic converters in series - one for the first five minutes of operation, and one for normal running.

You can eliminate the cold start cat without ill effect to the emission control system, save for slightly dirty starts. The benefit is an additional 5-7 HP over a multpile cat setup.

To do this, you gotta take off the cat pipe. Once off, the cat housings are opened up using a die grinder (dremel) and the bricks are removed. Then - weld up the cat housings.

The cat pipe 'looks' stock, passes emissions, is a bit louder (this I like) and makes more HP - all for a few hours of elbow grease.

Cheap speed.

[ta12sec]

its alot easier then cuting and welding.
Straighten out about 3 couat hangers and and but a small hoose clamp on the end. stick the other end into a electric or air drill and fire it up and feed it though the pipe and into the cat just like you snaking a sewer pipe, it will break up all the bricks and then you just pour them out. Alot easier then cutting and welding and also undectiable to the eye when your done,.

[chuckspeed]

Originally Posted by ta12sec

its alot easier then cuting and welding.
Straighten out about 3 couat hangers and and but a small hoose clamp on the end. stick the other end into a electric or air drill and fire it up and feed it though the pipe and into the cat just like you snaking a sewer pipe, it will break up all the bricks and then you just pour them out. Alot easier then cutting and welding and also undectiable to the eye when your done,.

That's a good suggestion, but it only works well when it's a straight shot into the cat and the cat is older and more brittle. New cats are rock hard; I tried breaking mine apart and could not using that method. Mustangs also have an elbow on one side and an S curve on the other; real hard to get into the cat thataway.

FWIW, what you described was the way we'd blow out the innards on SHelby Charger cats. Took all of 15 minutes; quick and dirty.

[ta12sec]

works great on ls1s which is far from a straigt pipe the coat hangers will follow the contours, (i actually use some brazing rod but know others who have had good luck with coat hanger)
Works well even on low milage and new cars.

[WishIHadACamaro]

wow thats really another great idea!!!

this website is really helping me out!

keep on posting good cheap mod ideas

[chuckspeed]

Originally Posted by ta12sec

works great on ls1s which is far from a straigt pipe the coat hangers will follow the contours, (i actually use some brazing rod but know others who have had good luck with coat hanger)
Works well even on low milage and new cars.

I tried brazing rod on the Max the Mach; the precats were the hardest I'd ever encountered. Also - I was worried about crap from the precats getting into the main cats, plugging them up, overheating them, and then they'd break down. So - I gave in midway, unzipped the housings with a diecutter, and lifted them out whole (well, mostly whole on one side).

[ta12sec]

dont just do the pre cats
gut all the cats

[chuckspeed]

Originally Posted by ta12sec

dont just do the pre cats
gut all the cats

I disagree with that.

Two reasons:

1. That test was done on a mod motor Mustang; while pulling the precats dropped the ET about a tenth, going 'all the way' actually increased the ET back to a fully catted state. Reason is, modern motors have low-tension rings that 'inflate' based on some backpressure; dropping the backpressure to zero results in a loss of ring seal - and HP.

2. See #1 above. The side effect can be some serious oil consumption. I'm running the equivalent of a straight pipe and a cat on my wife (AKA the Peebmonster)'s car, and just dropping the exhaust pressure drop increased oil consumption. Granted, it's not bad (1500 miles/quart) but before the mod, it didn't burn a drop. Got a header for it (yeah, it's a 4 cyl - gotta keep the wife's shiny side up) and have held off based on oil consumption increase; figure the increased scavenging of the header will increase consumption. Will prolly try the header in the spring anyway - just for the heckuvit. I like getting small N/A motors to run like turbos - it's a gas.

[WishIHadACamaro]

I cut off a muffler on a neon the other day. It was raining, 7 oclock at night, really dark and i had a sawz-all with a shitty blade on it.

The end result. Another neon that sounds like, well personally i dont like ricer exhaust, so it sounds like shit (or a neon without a muffler).

We sliced it off right before the elbow in the pipe as the pipe goes into the muffler. So its pointing straight out the back but probably 14" from actually going past the rear bumper cover. So we did two things, made it sound noisy and obnoxious, and also all the exhaust gas can dump under the body to probably enter the passenger compartment and kill us all if we spend more than five hours in the car.

The Complications:
We sliced it off with only a few problems, we first wanted to unbolt the clamp and pull it off, we lacked sufficient lighting and tools to get the clamp off, so after some banging we decided it was getting cut off, much more interesting anyways, then we would have a straight shot to clamp a glasspack on later (or probably flex pipe and a tip). but it was dark and i couldnt see where the hangers were in relation to where i was cutting and i positioned myself rather in a not good spot and dropped a toasty muffler on my face. Thank god for safety glasses, no injury, just a little bit of a black eye.

So moral of the story. Dont cut off muffler on neons. And safety first, realize what your doing before you do it, and never in the dark with power tools.

[chuckspeed]

Originally Posted by WishIHadACamaro

I cut off a muffler on a neon the other day. It was raining, 7 oclock at night, really dark and i had a sawz-all with a shitty blade on it.

The end result. Another neon that sounds like, well personally i dont like ricer exhaust, so it sounds like shit (or a neon without a muffler).

We sliced it off right before the elbow in the pipe as the pipe goes into the muffler. So its pointing straight out the back but probably 14" from actually going past the rear bumper cover. So we did two things, made it sound noisy and obnoxious, and also all the exhaust gas can dump under the body to probably enter the passenger compartment and kill us all if we spend more than five hours in the car.

The Complications:
We sliced it off with only a few problems, we first wanted to unbolt the clamp and pull it off, we lacked sufficient lighting and tools to get the clamp off, so after some banging we decided it was getting cut off, much more interesting anyways, then we would have a straight shot to clamp a glasspack on later (or probably flex pipe and a tip). but it was dark and i couldnt see where the hangers were in relation to where i was cutting and i positioned myself rather in a not good spot and dropped a toasty muffler on my face. Thank god for safety glasses, no injury, just a little bit of a black eye.

So moral of the story. Dont cut off muffler on neons. And safety first, realize what your doing before you do it, and never in the dark with power tools.

I've done a neon before...

It takes a straight 2-1/4" glasspack, a 3' length of steel rod, 2 - 4" hose clamps, a 2-1/4" elbow, two muff clamps, and the fart tip of your choice. Clamp the bar on the 'pack using the hose clamps, and slide the bar into the rubber hangars. This locates the muff.

Clamp the muff to the pipe, and clamp the elbow to the muff. This gets the exhaust out back where it belongs - then you can hang whatever tip you want on the assembly.

Neons are a tad raspy with this setup; the tone can be mellowed by adding a second glasspack as a resonator in the straight pipe under the interior compartment. That's the setup that's running on the Peebmonster's car - a PT Cruiser. It's not raspy at all.