Dual exhaust benefits

[OilUzer]

What are the impacts of dual exhaust beside nicer sound?
I'm talking about true dual exhaust (not the ones that split at the end)

My Tundra came with factory dual exhaust (has no X or H pipe) and I happened to do some research for fun ... and read that you lose some low end torque and gain some high end torque ... The loss/gain were very minimal and I'm not concerned about it. I think the car has near 400 lb.ft torque and hp ... However torque loss at low rpm was a surprise! Also What I read may not be correct either ...

What is the typical impact on torque, engine heat, exhaust system temperature, mpg, etc.

Not really concerned about any of the above but like to know technically what are the pros and cons of having a dual exhaust besides the sound!

 

[Silk]

I don't know about more cylinders, but on my twin cyl motorcycle, I use a 2 into 1, and two seperate pipes. I did a dyno run with both systems, and the 2 into 1 makes more top end, the twin pipes more mid range. You could spend all day on the dyno and get diferent results, but with just a quick swap with no other changes that is what you get. And on a motorcycle you notice these small changes.

 

[CharBaby]

In today's vehicles(compared to the 60s-80s), I think that the gains are so small that, you may only hear the difference and not feel the difference.

In the case of a torque monster, you may want more high(er) end power so, the dual exhaust may help. As they say, TORQUE is what we drive and HORSEPOWER is what we buy. One needs to find their own perfect balance.

 

[Skippy722]

I know on some FCA vehicles, like the Durango, the normal output is 290hp for the v6, dual exhaust gets you 295. Not sure if the cars are like that, I know the standard 300 gets 292hp while the sportier ones get 300 but I'm not sure if that's just tuning or what.

I assume you mean an actual dual exhaust that may or may not have a crossover somewhere in the system. Some, like the Ram trucks, use a 2-1-2 type system, and most 4 cylinders have a single pipe feeding a muffler/resonator that then splits into 2 tail pipes.

 

[OilUzer]

I have 2 totally separate exhaust pipes coming from different parts of engine. It's a v8 i guess each side has its own pipe. I don't have a X or H ...

I know some guys add aftermarket H or X and some say you gain back the low end torque and it also gets rid of the drone sound at certain rpm but the side effect is quieter exhaust (noise) than the oem dual ...

 

[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.

As far as impact on EGT's, engine temp, mpg... nothing noticeable or noteworthy.

 

[CharBaby]

Even though this is not exactly what the OP is referring too, I'll throw this out anyway. Similar to what Skippy722 is saying with the FCA vehicles.

When I was buying Honda Accords(4 cyl), the upper trim levels(or SPORT model) above the standard LX trimline, made only about 4-5 extra hp with their specific exhaust. And I've seen as little as 3 hp in some cars with an upgraded exhaust or 2 mufflers instead of 1 muffler. BIG DEAL!

 

[OilUzer]

I guess I just don't understand the mechanics of it.
With 2 exhaust you would think gases should flow easier and be more efficient but I've read that's not the case and in a single exhaust system or with a dual with X or H, one side helps the other side flow better ... idk

@Skippy722 is that what you refer to as scavenging ...

Also dual exhausts must have 2 cat converters. That would seem like extra overhead! But the cat temperature must be lower than single cat. Not sure if that's the case or if has any significance !

 

[Donald]

The original dual exhaust was for V8 engines with one exhaust for each set of 4 cylinders. Then "cherry bomb" mufflers (I think thats what I remember).

 

[WyrTwister]

Originally Posted by OilUzer
What are the impacts of dual exhaust beside nicer sound?
I'm talking about true dual exhaust (not the ones that split at the end)

My Tundra came with factory dual exhaust (has no X or H pipe) and I happened to do some research for fun ... and read that you lose some low end torque and gain some high end torque ... The loss/gain were very minimal and I'm not concerned about it. I think the car has near 400 lb.ft torque and hp ... However torque loss at low rpm was a surprise! Also What I read may not be correct either ...

What is the typical impact on torque, engine heat, exhaust system temperature, mpg, etc.

Not really concerned about any of the above but like to know technically what are the pros and cons of having a dual exhaust besides the sound!


Do not know about now , exhaust systems seem to last longer . 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 .

Oh , did I mention , tickets for loud exhaust ?

 

[Kira]

My exhaust system knowledge came from several trusted places.

1) Exhaust systems provide calculated back pressure. This effects an engine's breathing. One has to assume the engineers who designed your engine knew what they were doing.
That came from a guy in high school

2) Having true duals (on a V8) means nothing unless you have the cam to go with it. I took that to mean an engine's performance came from the fuel delivery/spark and that the exhaust pipes simply carry the hot gas rearward.
Source: Near life-long friend

3) Dual exhausts tend not to reach full hot temperatures in "normal" passenger cars and are to be avoided. An unacceptably high percentage of steam is allowed to condense during a day's driving.
Source: #2's father in law.

 

[meep]

with today's well-designed systems, there's really not much difference besides look. And a dual system, with the tailpipes outside and to the rear of today's well-insulated cab, I can't see how you'd benefit from the good old true duals sound. Something else to consider - my 06 tundra had a rather unusual exhaust design in the headers - in that - they looked a lot like true 4-1 short tube headers on each side, beneath all of the heat shielding. Every other factory V8 I've seen used a manifold - I'd never seen oem headers. Things brings to a point - if yours has headers, which would imply some level of tuning, then altering what's behind them might take you backwards.

I discovered it had this factory setup because the exhaust was pretty loud under load while towing, and I didn't like it. Headers usually do add noise along with the additional power. I wasn't excited to learn all this, as really I felt like it needed more torque down low, which would have been more of a long-runner header than short.

And then all that to say - if you tow with your truck, any exh that adds noise is not a good thing, and exhausts that dump to the side are helpful in keeping things behind the vehicle cleaner.

-m

 

[ARCOgraphite]

I cant believe The Tundra doesn't have an H pipe or and X pipe. I've NEVER seen a factory dual exhaust in the past 15 years that didnt have a crossover. Then again its a Toyota .... Are you sure?

Thinking further, Maybe its for Bank 1 and 2 LAMBDA
control and emissions purposes.

Firing order make s a difference. I hear GM uses FORD firing order on V8. I havent checked this out of if it internet lore since I no longer do HEAVY wrenching on engines daily.

No more 1-843-6572. : (

 

[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.

 

[ka9mnx]

Originally Posted by WyrTwister

Do not know about now , exhaust systems seem to last longer . 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 .

Exhaust systems today are stainless steel. Back in the day they were cold rolled mild steel.

 

[SubieRubyRoo]

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.

 

[anndel]

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.

 

[4WD]

Don't forget the 4 barrel carb LoL

 

[i_hate_autofraud]

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!!

 

[NGRhodes]

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.