Are two tailpipes better than one?


#1

My question involves something about which I can’t make heads or tails (so the speak), namely: tailpipes.
I’ve observed that in almost all cars, the number of pipes increases along with their horsepower. For example, an entry-level Honda Accord has a single tailpipe, whereas the Sport and V-6 models have two – one on either side.
The Nissan Altima is the most common exception to this. Even the entry-level model has two tailpipes, one on either side. I have trouble believing this has any performance-enhancing value because if it does, why haven’t more car companies followed suit? My suspicion is that it’s a marketing device to enhance the Altima’s appearance and increase sales.
What’s the actual answer as to why has the two pipes?


#2

Mostly for looks on any plain Jane sedan. But once hp really climbs, say 300 hp and up, there can be a real advantage. But if there’s only one cat, they could just go with a large diameter single exhaust.


#3

Some dual tail pipes look good and if you look close a single exhaust runs most of the length of the car and then splits. For larger engines, especially high performance, a dedicated exhaust from the engine to the tail pipe helps the engine breath better. This must be designed in. I cannot just add a dual exhaust to a car designed with a single and expect any improvement. I may end up making things worse.


#4

There’s a direct relationship b/t engine HP and the size of the exhaust pipe system. Bigger engines might have two tailpipes rather than one larger tailpipe b/c the space available to run the pipes under the car dictates that. Also there’s some “mine is better than yours” gimmicks in the car design business, and sometimes what appears to be two tailpipes is really just one, that’s split into two just before it emerges at the rear of the car. And the size of the tailpipe you see at the rear of the car often is bigger than the size under the car you can’t see, so the oversized tailpipes or duals may have no function, just for looks, bragging rights.

Reminds me of when desktop computers often had a big red LED display on them of how fast the computer was working … lol …


#5

Most of what you see are fake dual exhaust. You have to crawl under to take a look but they’ll have a single exhaust pipe until the back and then it will split off into two tail pipes for looks. Highway patrol cars and performance cars will have two exhaust pipes running all the way from the engine back which helps performance.


#6

You’ve done this?


#7

2005 Mustangs with V8’s came with dual oulet exhaust and V6’s had one. Along the product line, the V6 cars got dual exhaust outlets even though horsepower only changed a bit. Ford did this because customers wanted their cars to LOOK like V8’s even though they weren’t. They did get 2 mufflers, though.


#8

Image is one of the most important features in selling cars and most other products as well.


#9

Some of them don’t even bother to have two real tailpipes, much less two full exhaust pipes.

Look close and you’ll notice they’re not even connected to anything:


#10

Those chrome vents in the bumper covers are everywhere now. Saw one that looked like twin pipes on each side, with a single exhaust hiding behind each.


#11

In fairness, the V6 only went to dual exhaust when the 3.7L became the standard engine, It had more than 100 HP over the outgoing single exhaust 4.0L


#12

I had real dual exhausts in my Passat V6, but never noticed them, they were both hidden.

Downside: twice as many cat converters, mufflers, pipes, etc. I did have to replace the cats, but the mufflers were still good at 120k when I traded it in.


#13

At least you had a ‘real’ dual exhaust. Most with dual pipes split after the cat, and are mostly just for looks.


#14

Back in 1955 when Chevrolet introduced its V-8 engine, one option was the “power pack” which included dual exhausts and a 4 barrel carburetor. Ford and Plymouth offered a similar option for their V-8 engines. Less fortunate owners would put a Y-pipe from the back of the muffler to the rear of the car to look like the car was equipped with dual exhausts. Of course, dual exhaust kits were sold as after market accessories. For V-8 engines, converting to dual exhausts wasn’t a problem. On inline engines, the exhaust manifold had to be replaced with a split manifold. The Y-pipe was a cheap way out if one just wanted the appearance.


#15

Dual exhaust power ratings were much more noticeable back in the old days. I’ve got some old manuals and with all things being equal as far as the engine; the dual exhaust engines put out about 15 to 20 more HP compared to the singles.

My Lincoln has dual exhaust tips but the system is a single exhaust spllit after the muffler. The LSCs had a true dual exhaust system on them.


#16

Only one cylinder is exhausting at a time so a single exhaust is more of a steady flow instead of pulses of high flow followed periods of zero flow.
Realizing this obvious fact is the reason four cylinder motorcycles with four mufflers have gone out of vogue. A single muffler slightly larger than one of the four mufflers used in the older designs actually flowed more exhaust with an exhaust system about 1/4 the weight of the old four pipe exhaust systems.


#17

Are you shocked that a car guy would look under his car?


#18

He uses the bus a lot and I wouldn’t advise checking under the bus for tail pipes.


#19

I’m surprised that he looks under other people’s cars.


#20

Back to the original question. On non-turbo/super charged engines yes, a properly engineered duel exhaust system can add power. Duel exhaust allows better scavenging of exhaust gases. But in most cases the primary reason is for appearance and sound.