YACT - What is the purpose of dual exhaust?

[Eli]

Originally posted by: funboy42

How will going larger hurt unless your engine is a 2 stroke engine which is maily found in off road dirt bikes where back pressure is needed to have it run better?

Backpressure is not the term you are looking for.

As was said, when the exhaust valve opens(or port, in the case of a 2-cyl), exhaust gas velocity is high. It rushes through the header, creating negative pressure behind the positive pressure pulse. This helps pull all exhaust gasses out of the cylinder.

In a 2-cycle engine, the same principle applies. Except with a 2-cycle engine, the expansion chamber will be designed so that it reflects the pulse back towards the engine at just the right time. Some of the new fuel/air charge will be pulled into the exhaust header, and the return positive pressure pulse will actually shove it back into the cylinder through the exhaust port, effectivly filling the combustion chamber a little beyond normal capacity. Sort've like an acoustically driven supercharger.

Animated GIF

 

[otispunkmeyer]

let the engine breathe abit more

more ways to get out, = less back pressure = more efficiency and power

 

[DivideBYZero]

Originally posted by: Eli

Originally posted by: funboy42

How will going larger hurt unless your engine is a 2 stroke engine which is maily found in off road dirt bikes where back pressure is needed to have it run better?

Backpressure is not the term you are looking for.

As was said, when the exhaust valve opens(or port, in the case of a 2-cyl), exhaust gas velocity is high. It rushes through the header, creating negative pressure behind the positive pressure pulse. This helps pull all exhaust gasses out of the cylinder.

In a 2-cycle engine, the same principle applies. Except with a 2-cycle engine, the expansion chamber will be designed so that it reflects the pulse back towards the engine at just the right time. Some of the new fuel/air charge will be pulled into the exhaust header, and the return positive pressure pulse will actually shove it back into the cylinder through the exhaust port, effectivly filling the combustion chamber a little beyond normal capacity. Sort've like an acoustically driven supercharger.

Animated GIF

Sweet link, Eli!

 

[NutBucket]

Originally posted by: DivideBYZero

Originally posted by: Vic

Originally posted by: DivideBYZero

Originally posted by: Vic

Originally posted by: DivideBYZero

Originally posted by: Vic

Originally posted by: DivideBYZero
You know up until the 06 model(and certain JDM's) the Impreza WRX has very bad pulse interference. That's what gives it character, but the eaqual length headers are more effecient. Ergo, I conter that a twin pipe setup on a boosted scooby would in fact be an OK solution.

But as we have ELH's it doesn't matter.

Meh. I love my unequal-length headers. I'll sacrifice a couple hp so my Scooby doesn't sound like a Honda.

Agreed. That's why I looked at an '06 the other day and walked away.

My MY00 GF sounds awesome with the prodrive centre and a 3" bore rear section, expading to a ricey 4" tip. Nice bassy flat four throb, and over 4K it is very loud.

I love tunnels. 😛

I run an Invidia downpipe and mid with the Prodrive oval-tip axle-back on my 03 WRX. It's a beautiful thing. 🙂

Full decat? I only have the downpipe cat for emissions purposes and it still cracks out ~250hp (215hp is the MFG quoted figure for these models).

Yep. Plus VF39, STi TMIC, stage 4 ECU reflash and some other goodies. I haven't had a dyno tune (although my ECU map was done by a highly reputable tuning shop and based off many comparable builds), but I'm told it should be in the 350 bhp range (270 whp). It screams.

I would not be surprised if you are running those numbers. I'm just on the humble TD04, but it's only puffing the stock 12lb right now. I keep toying with the idea of a remap for an easy 270+...

You gotta get a tune man! Worth every penny! My gf and I just have generic upgraded maps for our cars and it makes a huge difference. She's running a Helix catted downpipe with a Espelir cat-back....claimed 280/285 crank hp/tq on the 2.0 w/ the stock snail.

 

[Syrch]

so whats the point of the (forgivemy spelling or lack of the name) cadillitic converter? Why is it illegal to just have your pipes go straight back?

 

[NutBucket]

Originally posted by: Syrch
so whats the point of the (forgivemy spelling or lack of the name) cadillitic converter? Why is it illegal to just have your pipes go straight back?

http://auto.howstuffworks.com/catalytic-converter.htm

Helps with emissions.

 

[Eli]

Originally posted by: Syrch
so whats the point of the (forgivemy spelling or lack of the name) cadillitic converter? Why is it illegal to just have your pipes go straight back?

Emissions.

It catalyzes unburnt fuel.

 

[ijester]

Originally posted by: funboy42

Originally posted by: CraigRT

Originally posted by: pray4mojo
I've always wondered why my 4cyl Mazda6 has 2 exhaust tips...

so many 4 cyl cars have dual exhaust stock.. my old neon R/T had dual exhaust stock...

You never had DUAL exhaust. A inline 4 cyl cannot have true dual. At best you can only have one pipe coming from the engine into the exhaust muffler that has 2 output pipes making it "look" as though it is dual.
Just because you have 2 pipes coming out the rear of the car doesnt always mean you have 2 seperate pipes from your motor. Most cars mainly v6 and in line 4 and 6's do this unless you go have it done and then your just an idiot. If you dual your v6 your an idiot because most beope do the v8's for sound and performance. The v6 dual sounds like crap and can never get the low tone you will hear from a american v8.

Now dont think that all v8's with two pipes especially if stock is a true dual too. There are plent makers that do the 2 into 1 and then back into two out the exhaust pipe (Stock Cameros, Trans ams, Firebirds, and some mustangs are some that come to mind.

Now for the real reason. You dont put after market true duals on your car to look pretty. You do it for performance gains and the fact it sounds cool. The less restriction or back pressure allows the engine to breath better. The faster you can get air in and out of an engine the more performance gain you will acchieve. Also going with bigger piped if you can fit it under your car the better flow and air in and out you will get giving you more HP.

Most will do the bigger pipes especcially if they modded the engine more with liek a turbo, supercharger, nitro, etc. But for the most of us it is about sound and style nothing more unless you have deep pockets to do more to your engine to warrant going with better cats and bigger pipes.

For me if I can get away with it is to ditch the cats and the mufflers all together and run a straight pipe from the engine all the way to the rear. The eliminates all back pressure and opens the exhaust as free as it can be. Down side it is against the law to remove the cat and muffler in most states. Plus side is if you live in one that doesnt care it is the best solution and it also the loudest and will set off every car alarm you drive by.

What a moronic post. Have you ever heard a Buick Grand National? Or driven anything with a powerful V6? My last project car was a 68 mustang with a supercharged buick v6. It certainly needed the dual exhaust, and sounded awesome. 410 HP from 231 cubic inches.

And noise regulations would get you a ticket in 4 seconds anywhere I have ever lived if you run without mufflers. Talk about annoying. Almost as bad as the ricer coffee can muffler tips.

 

[Compton]

Originally posted by: GuitarDaddy

Originally posted by: Howard
Oy... please don't bring up backpressure or we are going to have a real mess on our hands. 🙁

Yeah where's Ryan and Adam? The can probably explain the backpressure?🙂

LMFAO