Cat back exhaust question

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Ruttinbuck

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My 2017 2500 SLT is basically a stock setup 6.4l 3.73 GEARS 33" tires 2" level kit.
I live in the British Columbia interior,tow a 7000# travel trailer and its 8% grades to go anywhere from my city. I'm going to put in a cat back system to try and get more performance and with that gas mileage as the truck goes 4hrs max between fuel stops. I've narrowed it down to Borla 140801bc or MBRP S5149304.
The mbrp is a 4" kit borla is 3.5".
Is the extra .5" pipe size really noticeable in any gains from the cat back system?
Thx for any input RB
 

HEMIMANN

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You'd get a lot more bang for the buck with a tuner. You pay a lot of money for a cat back without much torque gain. I decided against exhaust work, as most gain comes from long tube header scavenging - not cat back restriction. Data loggers (Engine Masters) show app. +10% torque gain with long tube headers, but these are very expensive and difficult to install.

The tow mode on my tuner really opens up the fueling - I don't know how they can claim it is 50 state EPA legal. It is very noticably better towing for me. I just towed several trailer loads @ 7,000 pounds of dirt last weekend with it.
 

HEMIMANN

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Tuner are you talking about the pulsar?
Or another option?

You choose whatever you want. I had my reasons for chosing Pulsar in-line add-on PCM. Mostly legality reasons due to our state laws.
 

MADDOG

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My 2014 got a resonator delete & a Magnaflow muffler upgrade. Not much improvement in performance but it sounded good.

I purchased a Diablosport programmer and got a custom tune done. Now that REALLY woke the truck up. The throttle response improved, mid-range power improved and I got a little bit of a low end torque bump as well.
 

Nick@GotExhaust

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That .5" wont matter, especially with the stock manifolds, cats, and y pipe all before it. You will not get a performance difference going from 3.5" to 4".

We offer both of those brands plus many more. We have the 2 options you listed IN stock. Message me for a quote
 

62Blazer

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A catback exhaust is primarily for sound and vehicles designed in the last 20 years. The OE exhausts are not restrictive and why they have huge mufflers. That is what is required to keep the sound levels down but not restrict exhaust flow. Yes, these aftermarket exhaust companies may advertise power and mileage increases on paper but in reality you would have a hard time knowing there was any increase without looking at dyno numbers. I worked in the automotive engineering world for many years and can tell you that car companies spend a LOT of time and money designing efficient exhaust systems. People consider the power and fuel economy of a vehicle when they buy it, and the government regulates emissions and fuel economy. Based on that auto companies have a lot of incentive to get efficient and non-restrictive exhaust systems.
 

Gr8bawana

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A catback exhaust is primarily for sound and vehicles designed in the last 20 years. The OE exhausts are not restrictive and why they have huge mufflers. That is what is required to keep the sound levels down but not restrict exhaust flow. Yes, these aftermarket exhaust companies may advertise power and mileage increases on paper but in reality you would have a hard time knowing there was any increase without looking at dyno numbers. I worked in the automotive engineering world for many years and can tell you that car companies spend a LOT of time and money designing efficient exhaust systems. People consider the power and fuel economy of a vehicle when they buy it, and the government regulates emissions and fuel economy. Based on that auto companies have a lot of incentive to get efficient and non-restrictive exhaust systems.
Let's not cloud the issue with facts.
You're absolutely correct about OEM exhaust systems being very efficient.
They have to be so they can get every last bit of MPG from the vehicle.
 

Tray Burge

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My 2017 2500 SLT is basically a stock setup 6.4l 3.73 GEARS 33" tires 2" level kit.
I live in the British Columbia interior,tow a 7000# travel trailer and its 8% grades to go anywhere from my city. I'm going to put in a cat back system to try and get more performance and with that gas mileage as the truck goes 4hrs max between fuel stops. I've narrowed it down to Borla 140801bc or MBRP S5149304.
The mbrp is a 4" kit borla is 3.5".
Is the extra .5" pipe size really noticeable in any gains from the cat back system?
Thx for any input RB
You'll get zero gains from just the cat-back, just a better sound fwiw.
 

rosco11

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My 2017 2500 SLT is basically a stock setup 6.4l 3.73 GEARS 33" tires 2" level kit.
I live in the British Columbia interior,tow a 7000# travel trailer and its 8% grades to go anywhere from my city. I'm going to put in a cat back system to try and get more performance and with that gas mileage as the truck goes 4hrs max between fuel stops. I've narrowed it down to Borla 140801bc or MBRP S5149304.
The mbrp is a 4" kit borla is 3.5".
Is the extra .5" pipe size really noticeable in any gains from the cat back system?
Thx for any input RB
A cat back exhaust is going to make your truck sound cool. But it is not going to increase your performance or get you better gas millage much if any at all. The restriction starts at the cats, not behind them. Car manufacturers left very little hp on the table to be found with bolt-ons. Same with cold air intakes. The only place you will see a gain with one is on a dyno with a fan blowing into the engine bay. The moment you put it on the street, that cool looking chrome thingy goes from a cold air intake to a hot air intake. It pulls air from the engine compartment where the factory system pulls it from the fender well.............If you want to be like the cool kids, go for it. If you want more performance, pony up the money for a supercharger. If you want better gas millage, sell the 6.4 and buy the Cummins. Performance and millage are two ends of a tug of war rope. You cant get more of one without sacrificing the other.
 

Chap

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I bought a Gibson single pipe, Black Elite catback for my 2019 PW, it sounds really nice. Not super loud, but has that nice, throaty rumble. I had a 2014 Ram 1500 Rocky Ridge, a few years back, with a Flowmaster Outlaw catback, that thing was loud as hell. My neighbors hated me. Haha,
 

62Blazer

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Don't mistake "loud" or "louder" for better flowing or less restrictive either. The other thing to consider is if you want the added noise and drone when pulling a trailer for long distances. Generally pulling a load means the engine is working harder and you tend to have more exhaust noise. Not saying there are exhaust systems that don't sound good or are too bad, but from my experience a loud exhaust system can get pretty annoying after about 3-4 hours on the freeway when hauling a heavy trailer.
On my last truck (Chevy 2500HD 6.0L gas) I had 4 different exhaust setups just trying to get a good compromise between sound and not getting annoyed when towing on long trips. On my current Ram 2500 6.4L I did try a Flowmaster cat-back that was tagged as moderate sound level on the outside and more mild interior (picked it up really cheap) but went back to stock after a couple months because of the drone. Thinking of making a custom setup where I can fairly easily swap between the stock muffler and something like a Magnaflow.
 

2003F350

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A cat back exhaust is going to make your truck sound cool. But it is not going to increase your performance or get you better gas millage much if any at all. The restriction starts at the cats, not behind them. Car manufacturers left very little hp on the table to be found with bolt-ons. Same with cold air intakes. The only place you will see a gain with one is on a dyno with a fan blowing into the engine bay. The moment you put it on the street, that cool looking chrome thingy goes from a cold air intake to a hot air intake. It pulls air from the engine compartment where the factory system pulls it from the fender well.............If you want to be like the cool kids, go for it. If you want more performance, pony up the money for a supercharger. If you want better gas millage, sell the 6.4 and buy the Cummins. Performance and millage are two ends of a tug of war rope. You cant get more of one without sacrificing the other.
There are cold air intake systems out there that DO give some gains, but not much without supporting mods - same with exhausts. For instance, I had a '99 GMC Jimmy that I deleted the cat, put an exhaust on, and put a K&N cold-air intake on and it did gain some pep, but the intake wasn't just a tube with a filter - it also had basically a canister that let the filter continue to pull air from the fender, and was sealed around the edges and tube (including a seal that fit against the hood).

You've also got to consider that not everyone's definition of 'bolt-on' matches. I consider bolt-ons to be anything that doesn't crack open the engine seals - which means headers, throttle bodies, and the like are all bolt-on. Some people also consider high-lift rocker arms (on OHC motors) to be bolt-on.

That said, you're correct with modern engines - manufacturers are leaving very little on the table anymore without opening up the engine.
 

Trophywa

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Prior to any “performance upgrades “ I put on 25,000 miles bone stock, avg everyday mileage was 12.9 mpg. Here’s what I did, put in the K&N replacement drop in air filter, solo muffler delete. That’s it, now same commute to work same same same everything, my mileage is now 13.3. It sounds awesome (wife not so much) I shouldn’t have to buy an air filter ever, the delete pipe is stainless, should never have to worry about corrosion there, and the stock muffler is on the shelf just in case. Oh crap I forgot I cut the resonator off as soon as I got home from the dealer when I bought the truck 27 miles home. It’s your money have fun with it.
 
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Ruttinbuck

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Thx for the comments gents.
Pulsar is inbound towing Thursday over a route taken regularly so I'll see what difference the pulsar makes.RB
 
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Ruttinbuck

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Pulsar arrived,installed.
200 miles driven in econo mode,milage went from 12.8mpg to 15.3mpg imperial gallons. Time will tell but any increase in mileage is what I was after. RB
 

Gr8bawana

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A 2.5mpg increase? With just a cat-back pipe?
 

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Ruttinbuck

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2.5 mpg with a pulsar and a k&n air filter no cat back yet.
Just home from a 274 mile highway run I burnt 20 imperial gallons avg 62 mph.
That's 13.6 mpg on a road with many 6-8% grades. It's early but looks promising. RB
A 2.5mpg increase? With just a cat-back pipe?
 
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