high-flow, quiet mufflers...suggestions?

[JeepcoMJ]

so my '99 cherokee is running real nice...other than the crappy exhaust.

 

the motor is set up for performance. I have a borla header and downpipe on it, among other things.

 

basically, I need a fairly open and flowing muffler for this thing. I don't want it too loud, and I can't afford a cat-back system. I'd put my flowmaster 40 on it, but I just don't want it that loud. this is a daily driver, so i'd like it to be something that won't give me a headache.

 

 

any suggestions? I was thinking dynomax...thrush welded series are too similar to the flowmaster in sound, and obviously cherry bombs aren't going to cut it.

[jeepsouth]

Do you have to pass a smog inspection? If not i had a cherrybomb inplace of my cat. ,and a flowmaster right after. It was too quiet for me so i removed the cherrybomb ,and put in straight pipe. Now it sounds right! Anyways just a suggestion. :cheers:

[JeepcoMJ]

Do you have to pass a smog inspection? If not i had a cherrybomb inplace of my cat. ,and a flowmaster right after. It was too quiet for me so i removed the cherrybomb ,and put in straight pipe. Now it sounds right! Anyways just a suggestion. :cheers:

 

 

both of those are too loud. combined won't help me.

 

as stated, I have a flowmaster...and i'm not putting it on because it is too loud for a DD.

 

 

but no, all I have is emissions...no smog. have to have a catalytic converter on anything '96 and newer, and they just plug in a scanner, if it doesn't have any check codes, it's good to go.

[jeepsouth]

I have actually tried them together ,and they are quiet. Two mufflers inline think about it. :yes:

[JeepcoMJ]

I have actually tried them together ,and they are quiet. Two mufflers inline think about it. :yes:

 

 

gotta have room for that...i don't.

 

thanks for your input. i'm looking for a single muffler that allows higher flow and goes in like it's stock.

[Donkey]

i just got the dynomax muffler on my dodge v8 and it is nice and quiet and according to the box it flows more air then most mufflers. Who knows how true the box is they could be making that stuff up but it is quiet and has some valve on it to control the droning noise you hear when at idle and at highspeeds. don't know how it sounds on a 6cyl but on my v8 its great.

[dasbulliwagen]

I put a flowmaster 50 series on my 2.5 with a gutted cat, and it is quiet but has a little growl when under load. if you still have a stock cat with its guts it might even be a little mellower. I would think you would have similar results with a 4.0.

[philbert001]

On my ZJ, For several years, I was running 2 1/2 inch all the way back to a 2 1/2 inch supertrap. It had a nice rumble to it, but since it was even further back than a stocker, it was very quiet. Even with all the discs in it! That, and the tuneability of the supertrap is real nice, especially if you have access to a diagnostic scanner that'll read out weather she's lean or rich, or if you have a power programmer.

[kyleag89]

X2 on the Dynomax. I have one on my 93XJ 4.0 and its as quiet as stock but flows a lot better.

[btm24]

Ive heard both flowmaster 40 and supper 44, and the supper 44 is much quieter. I know thats what I put on my truck and i love it. Not very loud but still sounds very nice. Should be fine for you old ears :cheers: Oh and that is with a working cat.

 

Brandon

[Eagle]

How do you drive and what's the gearing?

 

Basically, unless you're doing drag racing or road racing, I think a stock replacement is all you need. Buy it once from Auto Zone and it's guaranteed for life.

 

The thing with wanting a high flow is ... do you need it? The 4.0L engine is redlined at 5,000 RPM, and you probably can't get much beyond that even if you tried because the valve trail will float and act like a rev limiter. But a daily driver is probably going to spend the majority of it's life under 3,000 RPM, and probably under 2,500 RPM. You just don't NEED the extra capacity of a high flow muffler to do that.

[dakal]

if you still want one, look up burns mufflers on line.

[kro10000]

Ive heard both flowmaster 40 and supper 44, and the supper 44 is much quieter. I know thats what I put on my truck and i love it. Not very loud but still sounds very nice. Should be fine for you old ears :cheers: Oh and that is with a working cat.

 

Brandon

The super 44 is the louder muffler, my brother has one on his tj with 2.25 exhaust and is louder than mj mj with a 40 series and 2.5 inch.

 

For a quiet good flowing exhaust I'd run a dynomax ultraflow. They are as pricey as a 40 series, but my buddy has one on his xj and it is very quiet. A little louder than stock, but not by much.

[JeepcoMJ]

How do you drive and what's the gearing?

 

Basically, unless you're doing drag racing or road racing, I think a stock replacement is all you need. Buy it once from Auto Zone and it's guaranteed for life.

 

The thing with wanting a high flow is ... do you need it? The 4.0L engine is redlined at 5,000 RPM, and you probably can't get much beyond that even if you tried because the valve trail will float and act like a rev limiter. But a daily driver is probably going to spend the majority of it's life under 3,000 RPM, and probably under 2,500 RPM. You just don't NEED the extra capacity of a high flow muffler to do that.

 

 

Thanks for your input, Eagle...as well as the rest of you guys.

 

I will be abusing this jeep. nicely abusing it, if that's possible.

 

the motor is bored .030 over with a comp. torquer type cam shaft, high flow oil pump, 2001 intake, borla header and cross-tube, 62mm TB, srt4 injectors. I NEED a higher flowing exhaust...the stock one is robbing it of power and affecting my mileage negatively.

 

I've gotten as high as 24mpg with this motor in my mj running 35" tires on 4.10 gears.

 

this xj is stock height with 3.07 gears and 235's.

 

 

it looks like dynomax is going to be my choice. flowmaster series are just too loud. i know from personal experience, also cherry bombs. if I wanted one of those, I would not have said that they are not what i'm looking for.

 

thanks,

 

Pat

[Eagle]

235s and 3.07 gears does not make for a combination that calls for a high flow exhaust.

 

Back when my '88 XJ was fairly new, the first time the exhaust went my brother was managing a Speedy muffler shop. He talked me into letting him install a Speedy (Walker, I think) 2-1/2" cat back system with a 2-1/2" turbo muffler. I will admit it sounded great. Not much louder than the OEM exhaust, but a bit deeper and throatier.

 

Problem was, I hated it from the day it was installed. It's the only time in my life that I counted the days until an exhaust system rusted out so I could justify replacing it. I LOST toque -- I could feel it didn't have as much power when accelerating, and (more important to me) I also lost about 2 MPG in fuel economy. When that system finally needed to be replaced, I went to Auto Zone for a stock 2-1/4" exhaust and an OEM-type 2-1/4" muffler. The torque was back, the gas mileage came back to where it had been pre-turbo, and life was (generally) good.

 

With 235 tires running through 3.07 gearing, your 70 MPH highway cruise will be just over 1900 RPM. Skip 5th gear and run in 4th and it's still only 2580 RPM. I don't think the high flow is going to do for you what you think it is, or what you want.

 

If you MUST go high flow, I'd suggest Gibson. Their exhausrs are tuned for torque-type cams and power bands. And they sound GREAT behind the Jeep 4.0 engine -- the only performance aftermarket exhaust that (IMHO) doesn't sound like crap.

[JeepcoMJ]

235s and 3.07 gears does not make for a combination that calls for a high flow exhaust.

 

Back when my '88 XJ was fairly new, the first time the exhaust went my brother was managing a Speedy muffler shop. He talked me into letting him install a Speedy (Walker, I think) 2-1/2" cat back system with a 2-1/2" turbo muffler. I will admit it sounded great. Not much louder than the OEM exhaust, but a bit deeper and throatier.

 

Problem was, I hated it from the day it was installed. It's the only time in my life that I counted the days until an exhaust system rusted out so I could justify replacing it. I LOST toque -- I could feel it didn't have as much power when accelerating, and (more important to me) I also lost about 2 MPG in fuel economy. When that system finally needed to be replaced, I went to Auto Zone for a stock 2-1/4" exhaust and an OEM-type 2-1/4" muffler. The torque was back, the gas mileage came back to where it had been pre-turbo, and life was (generally) good.

 

With 235 tires running through 3.07 gearing, your 70 MPH highway cruise will be just over 1900 RPM. Skip 5th gear and run in 4th and it's still only 2580 RPM. I don't think the high flow is going to do for you what you think it is, or what you want.

 

If you MUST go high flow, I'd suggest Gibson. Their exhausrs are tuned for torque-type cams and power bands. And they sound GREAT behind the Jeep 4.0 engine -- the only performance aftermarket exhaust that (IMHO) doesn't sound like crap.

 

you missed the part where the motor has a higher flowing intake and fuel system, as well as a cam shaft which brings where the hp and torque curve meet to a lower rpm. 70mph is more like 1700 rpm with it right now. the restrictive exhaust is taking away from this motor. i can feel the difference between no muffler and a muffler, and i've driven 12k miles on this motor with a flowmaster...i know what the response should be, and it's just not there.

 

thanks. i'll look at gibson.

[Eagle]

you missed the part where the motor has a higher flowing intake and fuel system, as well as a cam shaft which brings where the hp and torque curve meet to a lower rpm. 70mph is more like 1700 rpm with it right now. the restrictive exhaust is taking away from this motor. i can feel the difference between no muffler and a muffler, and i've driven 12k miles on this motor with a flowmaster...i know what the response should be, and it's just not there.

 

thanks. i'll look at gibson.

No, Pat, I did not miss the part about the intake and the cam. I also did not miss where you said it will be primarily a daily driver.

 

Lowering the torque curve does not result in a need for a high flow exhaust system ... and especially not for an engine that's not being run most of the time up at or near the red line. FWIW, the choice of cam has no effect on the engine speed/road speed relationship -- that's a mechanical ration that is entirely determined by tire diameter, axle ratio, and transmission ratio. If you are running 235/75-15 tires through 3.07 gears, then I respectfully submit that if your tach is telling you 1700 RPM at 70 MPH, your tachometer is wrong. Those numbers I toss out are all calculated based on actual tire manufacturers' data, in most cases actual revolutions-per-mile ... which is the only accurate way to calculate the engine speed from the road speed. A different tire model or make may vary by a few RPMs, but not by 200.

 

Nonetheless ... Gibson's Jeep exhausts are tuned for hauling and they are reputed to really work. I never tried one but I dated a gal who had a Gibson system in her TJ. If I were ever to go for an aftermarket system, that's what I'd get.

[kro10000]

you missed the part where the motor has a higher flowing intake and fuel system, as well as a cam shaft which brings where the hp and torque curve meet to a lower rpm. 70mph is more like 1700 rpm with it right now. the restrictive exhaust is taking away from this motor. i can feel the difference between no muffler and a muffler, and i've driven 12k miles on this motor with a flowmaster...i know what the response should be, and it's just not there.

 

thanks. i'll look at gibson.

No, Pat, I did not miss the part about the intake and the cam. I also did not miss where you said it will be primarily a daily driver.

 

Lowering the torque curve does not result in a need for a high flow exhaust system ... and especially not for an engine that's not being run most of the time up at or near the red line. FWIW, the choice of cam has no effect on the engine speed/road speed relationship -- that's a mechanical ration that is entirely determined by tire diameter, axle ratio, and transmission ratio. If you are running 235/75-15 tires through 3.07 gears, then I respectfully submit that if your tach is telling you 1700 RPM at 70 MPH, your tachometer is wrong. Those numbers I toss out are all calculated based on actual tire manufacturers' data, in most cases actual revolutions-per-mile ... which is the only accurate way to calculate the engine speed from the road speed. A different tire model or make may vary by a few RPMs, but not by 200.

 

Nonetheless ... Gibson's Jeep exhausts are tuned for hauling and they are reputed to really work. I never tried one but I dated a gal who had a Gibson system in her TJ. If I were ever to go for an aftermarket system, that's what I'd get.

 

Never been a big fan of Gibson, a little too much $$$ for what you get, nice stuff though. However, I am going to have to disagree with you strongly on reducing backpressure/lowering torque. Unless you are going wild with your exhaust you are still going to have adequate backpressure for proper exhaust scavenging. It is true that oftentimes you will raise the torque peak up higher in the RPM band, but the torque will still be there where the original peak was. At most you might lose 5ft/pounds in any part of the band, but the change is almost always worth it.

 

That whole large exhaust/no torque deal is way exaggerated, I switched from a cat+turbo muffler, to no cat, 40 series with a 2.5in pipe and turndown and might've picked up a little bit of power on the top end, but any changes in power weren't very noticeable.

[HOrnbrod]

Threads like this are opinionated, theory, and useless BS unless you confirm and prove before and after data results on the dyno for your performance mods. Y'all know that.

[89eliminator]

i would go with a flowmaster 40

[JeepcoMJ]

If I wanted a flow master it would be done already...but thanks for the input. I'm probably gonna toss mine on and see how it sounds tonight

 

 

Eagle, higher air and fuel intake make it necessary to go higher flow exhaust. That is all that needs to be said on the subject.

[Eagle]

Eagle, higher air and fuel intake make it necessary to go higher flow exhaust. That is all that needs to be said on the subject.

Not at 1700 (or 1900) RPM.

 

An internal combustion engine is, fundamentally, an air pump. Flow mods don't make any significant difference in the lower part of the RPM band. You benefit from flow improvements at high RPM, where the stock system can't flow enough to produce the power needed. For a race engine it's important. For a daily driver, it's not important.

 

At 1900 RPM, a 4.0L engine is moving an absolute maximum of 133 CFM through the engine ... and that's assuming 100 percent volumetric exchange on every cylinder, which an internal combustion engine never achieves. The real key is ... what's your shift point? 3600 RPM? So you need to flow 266 CFM if you're shifting at 3600 RPM -- which is probably high if you're running an RV (torque) cam.

[Motion Offroad]

We run the Dynomax Cat-Back system with a Catco cat. on Rebecca's XJ. It sounds very good in my opinion. She didn't want something loud and she's really happy with the way it sounds. Sounds good at idle and has a nice growl to it under load (not droning). You can buy the Dynomax Super-Turbo muffler itself.

 

[streetjeep2.5]

I have been on the trifive website (55-57 chevies) to get good 327 rebuild info. Recent discussion there really recommended Dynomax over flowmasters. Flow as well but far less resonation that ends up in the cab. I have flowmaster but will go with dynomax

[HOrnbrod]

I've screwed around with my exhaust system many times and it took awhile to get it right. The stroker has a Mike Leach header and I tried both the "quiet" Flowmaster (series 44?) and a Dynomax. While the Dynomax was marginally better than the Flowmaster, both had unbearable resonance and droning that drove me crazy. My friend runs a muffler shop and he thought the droning was mostly caused by the combination of the header and the single 2-1/4" exhaust pipe. We ended up using a Walker SoundFX muffler with a single 2.5" inlet and dual 2.5" outlets and running separate 2.5" exhaust pipes out the back. We also replaced the HI-FLO cat with a Cherry Bomb. This did the trick; absolutely no droning and just a slight notch above stock in sound level for normal driving. However, when you get on it at WOT, it barks pretty good, but not obnoxiously loud. The system also made decent gains on the dyno across the entire RPM range.