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Re: Dual exhaust benefits [Re: Skippy722] #4980919 01/16/19 10:50 AM
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SubieRubyRoo Offline
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Originally Posted by Skippy722
From what I’ve read and heard, H pipe will give it more of an old school muscle car. X-pipes mellow it out the individual pulses, giving it a somewhat higher pitch and blending them together. X pipe also has a better scavenging effect than an h pipe, but both x and h pipes have way better scavenging than true duals.

Engine Masters did a comparison of them on an engine dyno, the x pipe makes more power up top where the H-pipe made more low end torque. Both were better than true dual’s with no crossover at all.

That said, I like the sound of x-pipes better than H pipes. H pipe is louder, definitely at higher rpm as well, than the x pipe. But I like the smoother tone of the x pipe.


The H pipe likely makes a little more torque because it generates the highest backpressure of all three designs, pipe diameters being equal. There are a TON of ways to implement them, and the best place to implement an X or H pipe is usually extremely inconvenient from a packaging standpoint. (It's been a long time so forgive me if I err slightly on details) The correct way to do it would be to start with "true duals" (ie. a straight pipe from each cylinder head, and you mark it with a paint stick, do a full-power run (dyno or street), and then where the paint stick stopped burning on the pipe is where the crossover needs to be placed. Most engines this would typically end up right under the transmission case which is already fairly low to the ground. I can tell you though, I had several 5.0s back in the 90's and early 2000s, and the rage at that time was catless H pipes and Flowmaster mufflers. When I put a Spintech X pipe and Spintech mufflers on my car sometime around '98, it didn't even "sound" like every other Mustang around and drew quite the crowd. The sound is smoother yet "angrier" than an H if that makes sense, and the car most definitely pulls harder on the top end because the X not only merges the pulses more smoothly, but also scavenges the exhaust much better.


De omnibus dubitandum.
Re: Dual exhaust benefits [Re: OilUzer] #4980934 01/16/19 11:08 AM
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anndel Online Content
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Dual exhausts used to mean sound, more horsepower and better gas mileage since less exhaust back pressure to choke the engine. Nowadays gains are small to nothing, only sound, as a certain size exhaust system single or dual with exhaust back pressure are taken into account in the engine design.


1993 Toyota 4x4 p/u, 2.4L 22RE 4 cyl - Amsoil SS 10W-30, Amsoil FIlter
2005 Toyota Avalon XL, 3.5L V6, Amsoil SS 5W-30, Amsoil Filter
2014 Toyota Tacoma 4.0L V6, Amsoil SS 5W-30, Yota OEM Filter
Re: Dual exhaust benefits [Re: anndel] #4980957 01/16/19 11:24 AM
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Don’t forget the 4 barrel carb LoL

Re: Dual exhaust benefits [Re: OilUzer] #4980988 01/16/19 11:45 AM
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I avoid dual exhaust systems, they add weight, more expensive to repair and add little benefit unless you road race.

At normal city speeds, etc, legal, you don't need the 'extra power' which only exists at the top of the RPM band! LOL!!

Re: Dual exhaust benefits [Re: ka9mnx] #4981156 01/16/19 02:10 PM
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Originally Posted by ka9mnx
Torque is not a factor at high RPM. Torque starts out at low RPM and at the cross over between torque and horsepower, torque dies and horsepower takes over (generally at 5,200 RPM). Pipe diameter is a critical factor. Too large and no low-end torque. You need torque to get the vehicle moving. It all depends on what you are doing and what you want to accomplish. A single large exhaust system will produce the most torque. Torque gets you going and horsepower gets you across the finish line. An optimal pipe size for a non highly modified dual exhaust system is 2 1/5 inches. For a single exhaust system it's 3 inches. The gains in horsepower and fuel economy in today's vehicles are very minimal. Years ago that was not the case. So it's about the sound. I run single 3 inch stainless steel exhaust systems on my vehicles (except the Ranger - It's a 2 1/2 inch single). 90 percent of driving is done within the torque range of the engine and that's why I concentrate on torque, not horsepower.



For a specific reciprocal engine power = torque x revolutions per unit of time.
By that definition you need torque to make power at any RPM high or low, therefore it is always factor.

Re: Dual exhaust benefits [Re: OilUzer] #4981194 01/16/19 02:33 PM
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bdcardinal Offline
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I have an x-pipe on the 14 Mustang that came with the catback from Borla, it retains the factory cats because they are not part of the X pipe on that year Mustang. It does have the factory tri-y headers on it still. I did it purely for sound. My 95 that I am slowly rebuilding will have an offroad X but I made the decision to pull it off road permanently and have it be a track rat car.


2014 Ford Mustang GT Track Pack
1995 Ford Mustang GT

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Opinions expressed are my own.
Re: Dual exhaust benefits [Re: WyrTwister] #4981197 01/16/19 02:35 PM
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Most exhausts now are a lower grade of stainless steel. They last the normal life of the vehicle. Some lower grade cars use aluminum killed steel, it is usually good for 5 to 10 years most places. The good ole days they used mild steel with no coating, or galvanized, which will burn off after a while, sometime OE lasted just 2 years.

The best sounding IMHO old time exhausts used chambered mufflers. There used to be a big chambered side pipe that was the best of all, burns on your leg getting in and out of the car were a learning experience. Thrush was the cheapest and were quite loud, Best et. Constant announcing your presence to the local law enforcement is not my thing. Chevy had a 36” (I think) 3 chamber muffler that was quite expensive but great sound, quieter than thrush that advertised your presence everywhere . Never owned one to run on the strip. Glass packs were a little quieter but the heavily louvered cores were somewhat restrictive higher ET. When fresh had a nice deep tone. Still announced your actions to the law. On those days, a huge caddy muffler with 2 ½ inlet and outlet for the old 500 CI V8 had the same or slightly better ET than most glass packs, and was quiet enough not to attract law enforcement attention. Had a nice lower sound, on the caddies they had resonators to get rid of the last little bit of noise. They were expensive, oddly the caddie dealer was the cheapest place to buy them. They were huge though. The famous turbo muffler was much smaller, and moderately louder, unless you liked stealth mode they were a good option. Again convincing people that even though they were quieter, the Caddie muffler had less restriction and a lower et was impossible.

Re: Dual exhaust benefits [Re: OilUzer] #4981198 01/16/19 02:35 PM
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duals can be a benefit when you cant get a big enough single system to support your power level. todays cars + trucks are surely choked to meet EPA rules, with cats + resonators as well as mufflers + undersized pipes. exhaust is surely a science + what works + what fits can be different. the most gains are on turbocharged engines + today they are many + the downpipe just off the turbo is most important. on my 1.8T 2001 jetta i could see on the boost gauge i installed about 3 lbs more + quicker boost everything else stock after upsizing from an sickly 1 5/8 twisted system to a 2.5" still catted + no check lites + on really powerful engines gains can be even better as they need more breathing in + out. prolly for about 10 yrs all OE exhausts are 400 grades of stainless, they corrode + look ugly but don't rot thru + some like my 2001 jetta used non-magnetic 300 grades of stainless that only discolors + outlasts your car. there are surely benefits but noise levels will increase + depending on your state regulations modifications may not pass inspections. even catted pipes that are bigger + higher flow can trip a check lite. as i often reference check the gains on goapr a top line audi, vw, etc tuner, not cheap but good stuff that works!!

Last edited by benjy; 01/16/19 02:41 PM.
Re: Dual exhaust benefits [Re: OilUzer] #4981229 01/16/19 03:05 PM
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I think my understanding with true dual exhaust(not the faux-duals used by Subaru and Honda) is that the X/H-pipe is there to "tune" the exhaust for efficient scavenging, with the X-pipe providing a little less backpressure for more top-end and the way the exhaust manifolds are made affect how the system is "tuned".

My parent's Lexus LS430 has a true system - if it wasn't for the center pipe assembly that branches into a Y-pipe into a cat and then back out to separate resonators and mufflers. The car does have a slight rumble to it if you listen very, very very closely. Probably the same deal on the Tundra, the Lexus system was designed not to disturb the peace. Toyota V8s do sound good with an exhaust on them. Almost like a Ford Mod motor.

Re: Dual exhaust benefits [Re: OilUzer] #4981246 01/16/19 03:19 PM
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Given a choice I’ll take dual drive shafts any day

Re: Dual exhaust benefits [Re: 4WD] #4981329 01/16/19 04:17 PM
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Malo83 Offline
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I'll stick with single drive shafts wink2

Re: Dual exhaust benefits [Re: Malo83] #4981339 01/16/19 04:28 PM
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But you have two now … a driver side and a passenger side … 🤔
(On the car, not the pickup) …

Re: Dual exhaust benefits [Re: WyrTwister] #4981407 01/16/19 05:44 PM
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Originally Posted by WyrTwister
But back in the day , they tended to rust out twice as fast , especially when short tripped . Did not get hot enough to evaporate the water / moisture form the inside of the system .



Leaded gas had scavengers so the lead wouldn't stay in the combustion chamber, but it wound up in the exhaust pipe where it corroded the heck out of things.

Today's faux-duels have packaging advantages and allow adequate flow with less noise or more flow at the same noise. You can do more with more cubic inches of baffles and things.

Re: Dual exhaust benefits [Re: OilUzer] #4981772 01/16/19 11:02 PM
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Let's get one misconception out of the way. Back pressure does not help an exhaust do anything at all. Zero, zip, zilch.

When testing an exhaust for blockage, anything greater than 1.25 PSI at idle is a fail, and anything greater than 3 psi at 2000 rpm is a fail. Mind you, this is on a factory OEM exhaust with cats, mufflers, and all. A catless exhaust will generate almost 0 psi unless fitted with a grandpa-car "can't hear it running at all" muffler.

There is no specific minimum for back pressure. If an exhaust were to have 0 psi at both speeds it would be considered a pass with flying colors.

Pipes that are too big, or exhausts that are made wrong cost low end power due to a lack of or incorrect exhaust velocity or scavenging.

The back pressure theory has been tested in a million different ways and is a solid failure every time.

The gains of an OEM dual exhaust system over a single is simple. Take an OEM muffler. Designed to flow as much as it can while maintaining a certain sound level. Let's just use some arbitrary numbers here and say that "OEM Muffler X" flows 400cfm and emits 69 decibels. "OEM Muffler Y" flows 500 cfm and emits 75 decibels. Let's say the target noise level is 70 decibels. What's an engineer to do? Just split the exhaust, put two of the "X" mufflers in, and now you still have 69 decibels (or maybe less) and 800 cfm flow.

Of course, sometimes the OEM will decide that their "aggressive" dual exhaust should also sound different, and will be louder despite being a dual. Complete style issue there.

But anyone in the know is aware of the fact that a single exhaust with a big single muffler makes the most power. This is mostly due to the Dynamics of combining dual banks without splitting the exhaust again. Let's call this "OEM muffler Z". Why use two "X" mufflers rather than a single "Z"? Packaging and styling.


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Re: Dual exhaust benefits [Re: DoubleWasp] #4981813 01/16/19 11:44 PM
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Skippy722 Online Happy
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Originally Posted by DoubleWasp
Let's get one misconception out of the way. Back pressure does not help an exhaust do anything at all. Zero, zip, zilch.

When testing an exhaust for blockage, anything greater than 1.25 PSI at idle is a fail, and anything greater than 3 psi at 2000 rpm is a fail. Mind you, this is on a factory OEM exhaust with cats, mufflers, and all. A catless exhaust will generate almost 0 psi unless fitted with a grandpa-car "can't hear it running at all" muffler.

There is no specific minimum for back pressure. If an exhaust were to have 0 psi at both speeds it would be considered a pass with flying colors.

Pipes that are too big, or exhausts that are made wrong cost low end power due to a lack of or incorrect exhaust velocity or scavenging.

The back pressure theory has been tested in a million different ways and is a solid failure every time.

The gains of an OEM dual exhaust system over a single is simple. Take an OEM muffler. Designed to flow as much as it can while maintaining a certain sound level. Let's just use some arbitrary numbers here and say that "OEM Muffler X" flows 400cfm and emits 69 decibels. "OEM Muffler Y" flows 500 cfm and emits 75 decibels. Let's say the target noise level is 70 decibels. What's an engineer to do? Just split the exhaust, put two of the "X" mufflers in, and now you still have 69 decibels (or maybe less) and 800 cfm flow.

Of course, sometimes the OEM will decide that their "aggressive" dual exhaust should also sound different, and will be louder despite being a dual. Complete style issue there.

But anyone in the know is aware of the fact that a single exhaust with a big single muffler makes the most power. This is mostly due to the Dynamics of combining dual banks without splitting the exhaust again. Let's call this "OEM muffler Z". Why use two "X" mufflers rather than a single "Z"? Packaging and styling.


Thank you! I was waiting for someone to post this!

Also, in regards to different mufflers, here’s some OEM ones from a Charger. One is an R/T or v6, the other from an SRT. SRT is a lot more open and free flowing while being louder.

89986B19-E0EB-493C-BED4-393EEA3E0009.jpeg1A0C589F-46AC-4F57-9AC8-A2CAA2FE8F8F.jpeg

2019 Ram 1500 Classic
2018 Dodge Grand Caravan GT

Slight Mopar obsession
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