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Straight Exhaust (No Muffler) ?

S

saint_raider

NAXJA Forum User
Location
Albuquerque NM
I've heard of many people who remove their muffler and run a straight pipe from the catalytic converter back. I was thinking about doing this but I do not know how loud this would be. I like to hunt in my vehicle and I don't want my Cherokee to scare away every living animal in the forest. I have an '89 4.0L everything stock. Does anyone have a sound file or know where I can find one online just to get some idea of what it might sound like? Thanks for any help.
 
i have just the cat on my MJ. I also have a few bends and then the exhaust pointing at the ground in front of the rear axle. I like the sound, but it is kinda loud. Phil Weeks said the other day on the Rubicon that he liked the sound...

I don't have a sound file, and even with that, it doesn't really tell you how loud it is without something as a reference point.

if you can weld your own, just do it and if you don't like it you're only out a few minutes of time. if you're thinking of having a shop do it ask how much extra it would cost to add a muffler later if you don't like it.
 
Im runnin with out a muffler on my 90 4.0 it comes strait out the back via a short megs tip. its not to bad unless your behind me then its loud.
 
One thing to concider, most forestry service land require a spark arrester to be in place. The catalyst is not concidered a spark arrester, even though it may stop any sparks or flames from the engine, the cat comonly burns at 600*F, and if a piece of 600* catalyst material were to break loose while on the trail and land on dry grass, you can guess what would happen.

NAXJA does not specifically designate that a muffler must be in place, but, they do stipulate that each vehicle must meet the vehicle requirements of the lands being used.

Would kinda suck to show up for a NAXJA event and not be let on the trail because you don't have a muffler. Even worse, no body notices and you go on the trail and drop a piece of cat, it smolders for two hours, and when no body is around, burst into flames and burns down the Rubicon Trail. You think the issues with the lakes are bad. Not saying it will happen, but I'd hate to be in your shoes if it did.

Find a nice small muffler that is not a cherry bomb, or any straight through design and use that.
 
You have a very good point Willis, I don't want to be burning down any forests. I guess I'll look into a nice moderately quiet high flow muffler. Does anyone have any suggestions on where I might find one online? What about a direct fit high flow cat? Thanks for all of the useful info.
 
Willis said:
Find a nice small muffler that is not a cherry bomb, or any straight through design and use that.
Click to expand...

whats wrong with the straight through, less restriction is good
 
Ramsey said:
whats wrong with the straight through, less restriction is good
Click to expand...

no.

less restriction sucks.

I've experiemented with quite a few exhaust configurations on the 4.0, and I've found the engine runs the best with a cat and a muffler.
 
oh, guess i need to get a muffler. so your saying a cherry bomb wont help, probably the cheapest thing
 
Here in Newfoundland we don't have any emmisions laws, so what I did was cut the cat out and ran a straight pipe in to a Cherry Bomb muffler. It sounds like the world in going to end! Pretty much everybody whos heard it likes the sound! Seems like I picked up a bit more top end power as well.
 
Ramsey said:
whats wrong with the straight through, less restriction is good
Click to expand...

Straight through isn't a spark arrester. Also, the 4.0 seems to like a bit of restriction. It keeps the scavenging effect of the exhaust and keeps the velocity up. These help with torque. If you go wide open straight through exhaust, you might gain upper end, but torque will suffer. I don't know about you, but I like torque. Even going with a Flowmaster and 2.5" tail pipe, some have noted a loss of torque.

Our cats are already of the hi-flow design. The term hi-flow was in comparisson between the restrictive pellet style cats of yesterday, and the efficient honey comb design of today. Aftermarket cats are pretty much the same size. You buy one for a Ford 460, or buy one for a 1 liter Geo, the catalyst surface area is the same or very similar. The difference is the size of the pipe going in. If a 460 can breathe throught it just fine, our little 4L will have no problem. IMO, don't waste your money on a "hi-flow" cat.

Steve
 
yeah it does get loud without a muffler, i might have to pick up one of those 14 dollar jobs.
 
I know you made your descision, but you lose a ton of low end without a CAT and a muffler. I know, I had a hallowed out CAT and my muffler fell off at the beginning of the trail head. Needles to say, it sucked and it was LOUD!.

I went with a new CAT and the Dyno MAX for Summit. It works great and sounds good. I also had to get my junk smogged, without the CAT it would have not passed.
 
MAGNAFLOW. it keeps the right backpressure to operate properly, sounds good, and is legal. Unlike Flowmaster, it has a straight through design which allows for better airflow and keeping 2.25 helps with backpressure.

Straight pipes equals bad, sounds like crap too, at least on a straight six
 
just punch out the biscuits out of the cat and no chance of crap coming out of it :smoker:
 
i had the muffler cut off of mine with a straight pipe installed once. had a headache before i got home. needless to say i had a cheep'o muffler put back on it till i decide what i was going to do [with the exaust] it. and now less than a year the cheep'o is shot,and its driving me nuts, not loud just sounds like crap. anyway our 4.0's run hot and they will burn out a cheep muffler pretty quick. just something to think about.
 
my buddy lost his muffler on the trail and hasnt replaced it since. it is so damn loud but sounds real good. people come up and ask what hes running under the hood all the time. i dont recommand that route though.
i run just a glasspack and its loud. not ridiciously loud, but ,oud enough where you know im comming. I stay away from the rev though, high mileage engine= backfire!
 
Beezil said:
no.

less restriction sucks.

I've experiemented with quite a few exhaust configurations on the 4.0, and I've found the engine runs the best with a cat and a muffler.
Click to expand...

It works just fine with just a cat!

You just need to shove it right up to the catalytic converter and it creates the right amount of back preasure.

You just need to keep finding cats that fit!

:D

hinkley
 
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