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Discussion Starter #1
Hi:

I just bought a 1998 Wrangler Sport last week. So far I really enjoyed it, although I do wish the gas mileage is better (13.6 mpg on first tank). It also has this rattling noise in the exhaust system, which I hope is related. Anyway, I asked my mechanics to look into this, and also perform a major tune up.

I wonder if anyone has experience with the Flowmaster 60 Delta Flow 3 chamber muffler (Model 952462 or 952062)? I want something with deep rumbling sound, but not too loud, since I live in a apartment complex. So I ruled out Flowmaster 40 and 50. Plus according to the Flowmaster website, 60 Delta Flow is the only muffler that fit 1998 Wrangler.

Also, will this muffler really improve gas mileage, as claimed on the Flowmaster website?

Thanks in advance.
 

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nah i doubt it will really have a noticeable increase in gas mileage. i couldn't tell you how the 60 sounds as most jeepers don't go with a 60 so i have never heard it but i have a 40 and it sounds great...the 50 is a little quieter and isn't too loud. the 40 only drones around 40 and 50 mph and you can definitely hear it when it cranks up yet its not that loud when your pullin up. my dad was drivin and i couldn't even hear it till he got to the driveway.

if you wanna go with the 60 it should sound pretty good and decently quiet. it will probably sound more like a borla or a magnaflow since they are quieter but that is a complete guess. only soundclips i've heard were of the 40 and 50 and i heard a magnaflow yesterday in person and it was quiet but had a nice rumble and sounded real good...and the 60 won't be the only one that will fit yours as i have a 40 on mine
 

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I don't have much input on the exhaust but I think you might have a few more issue's since your MPG is so low. I have a stock 03 with the 4.0 and I get around 20MPG. I hope your major tune-up will help. You might also want to consider changing your fuel filter.
 

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yeah 13 is very bad on the MPG. I just bought my 98 in July and the worst ive gotten is like 16 and thats when im heavy footing around town. I have a flowmaster 40 and I love the sound. Ive never heard the 60 but if its quiet like the borla and magnaflow, that would be a little to quiet for me.
 

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On the mileage- 13.6 is pretty low, but with the lift and big tires on mine, even with the re-gearing, I only get 14.5-15 on average and that's highway. If my tires have low pressure in them from being offroad, the mileage goes down even further. So, routine maintenance and checking your tire pressures can improve your mileage, if only slightly.
 

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Forgot about that. I bought my jeep and it had 30psi and my gas mileage was sucking bad. I aired them back to 50psi and my gas mileage shot back up.
 

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Holy cow 50 psi? I don't think I've ever had more than 35 in mine and that was when they were brand new. Went right home and let 10 lbs. out. :D

Doesn't Flowmaster have a new Off Road Muffler out now? It's fully welded with diamond plate so that it's tougher and can take a hit if it needs to. I think I saw that it was around 90 bucks.
 

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I agree with 1blkjp, 50PSI! that's too much man, I never run over 30psi in mine. Never exceed the rated pressure for your tires, check the sidewall, it will tell you what max pressure is. Not only can it cause your tires to wear extremely fast, it can cause a catastrophic failure (Read: blowout).
 

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i've heard that more psi will actually help them to last LONGER. my probably soon-to-be brother-in-law :)D) is goin to clemson and he said his professor pumped his tires up with a lot of air so they would last longer and that he got 80K or 100K out of the tires! even so i still wouldn't pump em' up that much
 

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I'm running 31x10.50x15's on 15x8 wheels on my 94. Every time I have the thing serviced, they keep pumping them up to 42-44 psi. (Sidewall rating is 50 psi if I remember correctly)

At this pressure the professor is correct. Center of the tire is bowed out just a little more as the sides can only go so far. Results in the edges not actually running on the pavement. My mileage goes up. However, I don't care for the feel of the ride. So I air them down to 35 and still get reasonable mileage but a better ride.
 

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Discussion Starter #12
Thanks

Hi guys:

Turns out the rattling is the cat converter falling apart. So the shop installed a Magnaflow cat for me.

The shop does not carry Flowmaster 60 (although they do carry Flowmaster 40). But they do carry Magnaflow muffler. So that is what I ended up.

With the new exhaust system and a major tune up, the Jeep runs nice and sounds even nicer. But it is too early to tell the gas mileage.

I am thinking of ordering oxygen sensors online and have the shop install them for me. The Jeep has 104K miles and is still running on the original sensors. Maybe that will help w/ gas mileage too.

Thanks again.
 

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ironmonk said:
I am thinking of ordering oxygen sensors online and have the shop install them for me. The Jeep has 104K miles and is still running on the original sensors. Maybe that will help w/ gas mileage too.
O2 sensors are so ridiculously easy to install that i wouldn't pay to have someone else do it. save the money and buy your jeep another gift!!!
 

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Discussion Starter #14
Just finish a tank of gas since the major tune-up and installing Magnaflow catalyst converter and muffler. Now gas mileage is about 15.3 mpg. Much better than the original 13.6 mpg.

My jeep is running a 30" tires. Based on my searching on the web, the factory tire for 1998 Wangler Sport is P225/75R15, which is 28" diameter. Assuming the previous owner did not change the odometer gearing, then my gas mileage should really be 16.4 mpg. Am I correct?

Hopefully with new O2 sensors, it will be even better.
 
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