SatiricalHen Posted March 6, 2019 Share Posted March 6, 2019 So with tax season here I would like to finally give my Comanche a nice exhaust that doesn't leak. I plan to do header and all. I'd like some opinions from ya'll about what route I should take with the truck. The motor is a renix block bored .030" over with a 7120 head, a comp cam 68-115-4, 746 injectors, 99+ intake, and 62mm TB. The truck is a 2wd daily driver with an ax-15, 3.55s and 29ish" tires. I currently have a Thrush Turbo muffler on the truck and it is a little quieter than I would like. I want to hear the vehicle, but I want to be able to do long highway drives without wanting to bash my brains out. So with that background, I would like a new header, new muffler, and what pipe diameter should I go with for the truck? The truck will not have a cat, and the pipe will be fully mandrel bent. So, what pipe diameter, what muffler, and what header? Also, should I have the factory routing duplicated, or exit in a different location? Any and all tips and suggestions welcome. I'm sure there is someone on here that knows a lot more about exhaust flow and mufflers than I. Link to comment Share on other sites More sharing options...
Dzimm Posted March 6, 2019 Share Posted March 6, 2019 The stock 2.25" diameter is just fine for flow on these engines and going larger can actually lose you power. As for exhaust, I settled on Flowmaster Super 44 on my 92, ax15, 2wd street truck as it was one of the most recommended exhausts for the 4.0 and sounds good but is not obnoxious. That said, I haven't installed it yet so I haven't heard it in person but I watched nearly all the YouTube clips of it and it sounds really good. My blue 97+ truck has a Magnaflow exhaust system on it and it sounds good but I know nothing about it as it was already on the truck when I bought it. The aftermarket headers all seem to be about the same and the only complaint I ever see is that some aren't flat and don't seal properly on the head. If you are going to pay higher dollar for one, make sure to read reviews to know it's got a good coating and is properly machined for the head. Oh and don't buy one that has a thicker flange than the intake manifold. I would keep the factory routing as all the mounts are already there. You can put a nice tip on the end to give it a nice look. Link to comment Share on other sites More sharing options...
SatiricalHen Posted March 6, 2019 Author Share Posted March 6, 2019 The stock 2.25" diameter is just fine for flow on these engines and going larger can actually lose you power. As for exhaust, I settled on Flowmaster Super 44 on my 92, ax15, 2wd street truck as it was one of the most recommended exhausts for the 4.0 and sounds good but is not obnoxious. That said, I haven't installed it yet so I haven't heard it in person but I watched nearly all the YouTube clips of it and it sounds really good. My blue 97+ truck has a Magnaflow exhaust system on it and it sounds good but I know nothing about it as it was already on the truck when I bought it. The aftermarket headers all seem to be about the same and the only complaint I ever see is that some aren't flat and don't seal properly on the head. If you are going to pay higher dollar for one, make sure to read reviews to know it's got a good coating and is properly machined for the head. Oh and don't buy one that has a thicker flange than the intake manifold. I would keep the factory routing as all the mounts are already there. You can put a nice tip on the end to give it a nice look. You say that 2.25” is fine for these engines, and that’s what I’ve seen everywhere, but wasn’t sure if the higher flow TB, intake, and head with the slightly larger cam would make a difference. If 2.25” is still fine with that, that’s the route I’ll go. I actually think the exhaust on it now is 2” at the tail pipe because I seem to remember the 2.25” pipe slid right over it when I last had the exhaust repaired. I’ll have to actually measure it and see what the numbers say. I have a 44 on my Cherokee and it’s a little loud for me, but it’s also been beaten, abused and is dumped over the axle which makes a difference in sound. I’ve heard people like the magnaflow stuff on these, but I haven’t looked too much into them yet. I figured pretty much all headers are the same. I don’t see a huge gain coming from a banks, borla, or whatever other expensive brands enough to justify spending 3-4x the amount so I’ll probably end up getting one of the $100ish amazon or eBay specials. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
dasbulliwagen Posted March 6, 2019 Share Posted March 6, 2019 I have a Flowmaster 50 series on mine, but its a 2.5L. If a 44 is too loud for you, this would be the next step. Mine has an almost quiet idle, with a nice growl under load, and NO drone at highway speeds. Not sure how that will translate to a 4.0 but its worth a shot. Also, mine has gotten louder with age. Link to comment Share on other sites More sharing options...
SatiricalHen Posted March 6, 2019 Author Share Posted March 6, 2019 I have a Flowmaster 50 series on mine, but its a 2.5L. If a 44 is too loud for you, this would be the next step. Mine has an almost quiet idle, with a nice growl under load, and NO drone at highway speeds. Not sure how that will translate to a 4.0 but its worth a shot. Also, mine has gotten louder with age. I was looking at the 50, but man that price tag. The 44 is $85 and the 50 is $140 (for the super, not sure what the big difference is between the super and the delta flow, HD, and big block mufflers)Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
dasbulliwagen Posted March 6, 2019 Share Posted March 6, 2019 42 minutes ago, SatiricalHen said: I was looking at the 50, but man that price tag. The 44 is $85 and the 50 is $140 (for the super, not sure what the big difference is between the super and the delta flow, HD, and big block mufflers) Sent from my iPhone using Tapatalk Its probably been 7-8 years since I installed mine. They werent that expensive back then! Link to comment Share on other sites More sharing options...
Eagle Posted March 6, 2019 Share Posted March 6, 2019 The only aftermarket exhaust I have ever heard that sounded good behind an in-line 6-cylinder engine is a Banks. The problem is, Banks is hyper-focused on maximizing flow, so they use a 2-1/2" system and that reduces low-end torque in favor of more flow in an RPM range that 99.9% of Jeeps will never, EVER see. I'm happy with the OEM exhaust but, if I were to go looking for aftermarket, I think I'd start (and end) with Gibson. https://gibsonperformance.com/p-27232-jeep-exhaust-systems.html Link to comment Share on other sites More sharing options...
SatiricalHen Posted March 6, 2019 Author Share Posted March 6, 2019 The only aftermarket exhaust I have ever heard that sounded good behind an in-line 6-cylinder engine is a Banks. The problem is, Banks is hyper-focused on maximizing flow, so they use a 2-1/2" system and that reduces low-end torque in favor of more flow in an RPM range that 99.9% of Jeeps will never, EVER see. I'm happy with the OEM exhaust but, if I were to go looking for aftermarket, I think I'd start (and end) with Gibson. https://gibsonperformance.com/p-27232-jeep-exhaust-systems.html My jeep fits in that .01% you describe, but from what I saw there weren’t any kits for a Comanche, and I’m going to have the tube bent by the muffler guy I’ve always used. My Comanche sounds MUCH different than the stock 4.0 in my Cherokee. I’ve driven both with the exhaust cut before the cat. The Cherokee I crushed the cat offroad and cut it off to get back the power to drive it home and to the exhaust shop, and the Comanche when I swapped in the HO front pipe. The cam makes a big difference in sound. Also, “sounding good” is all relative. I’m sure those guys who drive around with fart cans think they sound good... Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Eagle Posted March 6, 2019 Share Posted March 6, 2019 1 hour ago, SatiricalHen said: My jeep fits in that .01% you describe, but from what I saw there weren’t any kits for a Comanche, and I’m going to have the tube bent by the muffler guy I’ve always used. Really? How much time do you spend at 6,000+ RPM? Link to comment Share on other sites More sharing options...
SatiricalHen Posted March 6, 2019 Author Share Posted March 6, 2019 Really? How much time do you spend at 6,000+ RPM? It’s been up to or past redline quite a bit. It pulls past 3k more than it does in the lower rpm range. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Eagle Posted March 6, 2019 Share Posted March 6, 2019 1 hour ago, SatiricalHen said: It’s been up to or past redline quite a bit. It pulls past 3k more than it does in the lower rpm range. Sent from my iPhone using Tapatalk Your priorities seem to be different from mine. I prefer to tune for the RPM range where my engines "live" most of the time, which is typically at my normal highway cruising RPM. That gives the best fuel economy, and that's where I'm most interested in maximizing performance. Link to comment Share on other sites More sharing options...
JMO413 Posted March 7, 2019 Share Posted March 7, 2019 My XJ has a Magna Flow on it and I like it allot. It was a cat back system from Mopar back in the day. I wish they made a system for the MJ. It was expensive but it was stainless and it's still on 15ish years later. I am in the same boat as you though mine needs replaced from the manifold back if not the manifold also. Let us know what you decide and how it sounds and performs. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 7, 2019 Share Posted March 7, 2019 I've going to disagree with the loss of back-pressure equals loss of bottom-end idea. This is essentially an open exhaust...........no losses.........AFE header. Link to comment Share on other sites More sharing options...
Eagle Posted March 7, 2019 Share Posted March 7, 2019 1 hour ago, Jeep Driver said: I've going to disagree with the loss of back-pressure equals loss of bottom-end idea. I've seen it in action. When the original exhaust in my '88 Cherokee 4.0L went bad, my brother was managing a Speedy Muffler shop. For my birthday he brought it into his shop and installed a 2-1/2" turbo muffler and a 2-1/2" custom-bent exhaust pipe. It sounded ... bleh. It was louder than factory and had an annoying harmonic at highway speed, but aside from that it still sounded like a very old Maine lobster boat. As for performance, I could instantly feel the loss of power in my operating range (which doesn't exceed 2,500 RPM). It's a five speed, so differences are easy to detect by the seat-of-the-pants dyno. And the gas mileage dropped by anywhere from 2 to 4 MPG, depending on whether a tank was mostly highway or mostly local roads. I'm 75 years old and I've been driving since I was 12 (legally since I was 16). This was the only time in my entire life when I couldn't wait for an exhaust system to rust out so I would have a reason to replace it. When the time finally came, I went with an AutoZone OEM replacement, 2-1/4" tailpipe and a Walker OEM replacement muffler. One of the better choices I've made in life. Link to comment Share on other sites More sharing options...
Limeyjeeper Posted March 7, 2019 Share Posted March 7, 2019 Try the Dynomax super turbo muffler with a stock Walker system. Quiet in the cab but sounds awesome. It is the best compromise I have found to date.Sent from my SM-G955U using Tapatalk Link to comment Share on other sites More sharing options...
SatiricalHen Posted March 8, 2019 Author Share Posted March 8, 2019 My exhaust pipe seems to be factory judging by looks, but everyone seems to say that 2.25” exhaust is standard and the ID of my tail pipe was 1.8” and the OD was 2” Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Limeyjeeper Posted March 10, 2019 Share Posted March 10, 2019 The stock system should be 2.25" from the downpipe to the muffler at the very least. The walker I have is 2.25 to the tailpipe. Maybe somebody narrowed the tailpipe. Link to comment Share on other sites More sharing options...
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