mpeugeot

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So I installed the Flowmaster Axle Back Exhaust... My first impression was that it was way too loud at cold start... But then I realized I had forgotten to close the tailgate. LOL. That plus I was in between two walls and it was resonating off the concrete.

So I closed the tailgate, backed out from between the two houses and things were much more mellow. Now my big concerns were how loud was it really going to be and could I tolerate it on a 5-6 hour road trip at speeds from 65-85+ MPH (back to that in a moment) so I could put an additional fuel cell where the muffler used to reside.

Driving it around town, off and light throttle, it's anywhere from unobtrusive to throaty but certainly livable. Give it some throttle and it starts to sing, loudly, but it doesn't sound like a fart cannon or anything remotely import like - just louder and throatier. At all speeds, shifts were much more noticeable since you can hear the obvious change in the engine note (I drive in Sport Mode most of the time and it was interesting to see how long the Bronco really held the shifts), before the exhaust, I had to pay attention to notice the shifts... And purely by feeling, it remains smooth, but the engine tones give it away. All in all, it gets a passing grade from me around ton.

So it was off on my highway adventure from San Angelo to Corpus Christi - which normally involves a fuel stop around 1/2 way during the 365 mile trip due to the craptastic fuel economy my Bronco historically managed (usually about 16-17 MPG highway with the 33.5" Milestar Patagonia M/T's and stock exhaust). Switching back to the OBX stock tires had me at nearly 19-20 MPG, definitely not enough to make 365 miles without refueling.

The noise, while cruising from 65-85+ MPH was noticeable, but not excessively droning, it wasn't any more noticeable than the tire or wind noise - but it was there. It was never unpleasant or annoying and I drove the trip straight through... That's right, I drove it straight through WITHOUT needing to stop for fuel in a 2 door Bronco with a 16 Gallon Tank and room to spare. I maintained an average speed just north of 70 MPH despite a horrific accident and traffic jam in San Antonio which didn't help my average speed or fuel economy. I arrived with nearly 20 miles of range left and averaged just a shade over 23 miles per gallon with an average speed of 70MPH.

What that means for me is no longer really needing to add the fuel cell. There was some low end grunt and spool that clearly improved as well, but for $140, this exhaust delivered and then some. A 15% increase in mileage was not something that I was expecting from an axle back pipe.

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Roll Sound

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So I installed the Flowmaster Axle Back Exhaust... My first impression was that it was way too loud at cold start... But then I realized I had forgotten to close the tailgate. LOL. That plus I was in between two walls and it was resonating off the concrete.

So I closed the tailgate, backed out from between the two houses and things were much more mellow. Now my big concerns were how loud was it really going to be and could I tolerate it on a 5-6 hour road trip at speeds from 65-85+ MPH (back to that in a moment) so I could put an additional fuel cell where the muffler used to reside.

Driving it around town, off and light throttle, it's anywhere from unobtrusive to throaty but certainly livable. Give it some throttle and it starts to sing, loudly, but it doesn't sound like a fart cannon or anything remotely import like - just louder and throatier. At all speeds, shifts were much more noticeable since you can hear the obvious change in the engine note (I drive in Sport Mode most of the time and it was interesting to see how long the Bronco really held the shifts), before the exhaust, I had to pay attention to notice the shifts... And purely by feeling, it remains smooth, but the engine tones give it away. All in all, it gets a passing grade from me around ton.

So it was off on my highway adventure from San Angelo to Corpus Christi - which normally involves a fuel stop around 1/2 way during the 365 mile trip due to the craptastic fuel economy my Bronco historically managed (usually about 16-17 MPG highway with the 33.5" Milestar Patagonia M/T's and stock exhaust). Switching back to the OBX stock tires had me at nearly 19-20 MPG, definitely not enough to make 365 miles without refueling.

The noise, while cruising from 65-85+ MPH was noticeable, but not excessively droning, it wasn't any more noticeable than the tire or wind noise - but it was there. It was never unpleasant or annoying and I drove the trip straight through... That's right, I drove it straight through WITHOUT needing to stop for fuel in a 2 door Bronco with a 16 Gallon Tank and room to spare. I maintained an average speed just north of 70 MPH despite a horrific accident and traffic jam in San Antonio which didn't help my average speed or fuel economy. I arrived with nearly 20 miles of range left and averaged just a shade over 23 miles per gallon with an average speed of 70MPH.

What that means for me is no longer really needing to add the fuel cell. There was some low end grunt and spool that clearly improved as well, but for $140, this exhaust delivered and then some. A 15% increase in mileage was not something that I was expecting from an axle back pipe.

IMG_20220413_151749.jpg
Hmm, now I'm really curious about the mileage gains from this.
 

mpeugeot

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Hmm, now I'm really curious about the mileage gains from this.
I wouldn't have believed it without seeing it. Your mileage may vary... However, I was shocked. I would have called bullshit on just an axle back pipe having that much of an effect.
 

Roll Sound

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I wouldn't have believed it without seeing it. Your mileage may vary... However, I was shocked. I would have called bullshit on just an axle back pipe having that much of an effect.
Funny, I was sort of calling BS on the HP gains too. Now I can't wait to put it in tomorrow!
 

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FstFrd00

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those bolts on the rear bumper, muffler bracket. I couldn't break them loose. I used an impact, regular ratchet, wrench w/ cheater; and those two wouldn't budge.
 
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those bolts on the rear bumper, muffler bracket. I couldn't break them loose. I used an impact, regular ratchet, wrench w/ cheater; and those two wouldn't budge.
Should just be the clamp you have to loosen. The exhaust then slides out of the hangers. I used WD40 to help.
 

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those bolts on the rear bumper, muffler bracket. I couldn't break them loose. I used an impact, regular ratchet, wrench w/ cheater; and those two wouldn't budge.
I think they're spot welded if we're talking about the passenger side ones. I had a couple wtf why won't this go moments and took a closet look. To me it looked tacked into place. Get a exhaust hanger tool for $15-20 and pop the hanger off and leave the bracket in place.

I just did a 12 hour off/on road ride with the 2.3l. It's not super loud (stereo on vol 9 can hear music clearly) but it does drone with windows up and decreases with windows down. It does sound nice on cold start and off idle.
 

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mpeugeot

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I think they're spot welded if we're talking about the passenger side ones. I had a couple wtf why won't this go moments and took a closet look. To me it looked tacked into place. Get a exhaust hanger tool for $15-20 and pop the hanger off and leave the bracket in place.
I didn't look closely, but I hit it with an impact wrench that normally has no problem taking these off... They didn't budge, I will look again to see if mine are welded. I do have a new plasma cutter to try out... :D I did what you did, I popped the hanger off and left the bracket in place.

I just did a 12 hour off/on road ride with the 2.3l. It's not super loud (stereo on vol 9 can hear music clearly) but it does drone with windows up and decreases with windows down. It does sound nice on cold start and off idle.
At what speed do you get drone? I do get some drone with the 2.7 at around 60 MPH, but I rarely am under 70 MPH on the freeway, so it's a non-issue for me.
 

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mpeugeot

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Super interesting and I've been looking at the Flowmasters for quite a while. Don't quite want the sound of the Outlaw though, and I'm leaning towards the FlowFX Axle-Back Dual. Not quite as loud as the Outlaw and I like the (faux) dual exhaust look.

https://www.holley.com/products/exhaust/exhaust_systems/flowmaster/flowfx/parts/718123

Can I expect a gas mileage increase on this one @Holley Performance Co. ? 🤔
I don't think that they ever suggested that mileage would increase, that's just something I observed and didn't expect.
 

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Installed mine last weekend, it is loud when you take off WOT, the cold start sounds good in the garage, not too bad cruising around easy on the throttle but if you want to sneak away quickly (that isn't happening) I decided to leave the stock brackets on for now in case I decide to switch back, I really think an electric exhaust cut-out like I had on my past Corvettes and Camaro would be nice but for the price you either like it or not.
I am going on a road trip soon and I will find out whether my wife and/or I Decide to like it or not.
 
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