What's the best exhaust / exhaust system?

[DylanFRS]

"Best" option is to just take off your exhaust, because:

• Lightest option
• Most free-flowing option
• More "Sounds like race car" option
• Definitely the cheapest option

So there you go, that is hands down the "best" option.

[N1rve]

Originally Posted by DylanFRS

"Best" option is to just take off your exhaust, because:

• Lightest option
• Most free-flowing option
• More "Sounds like race car" option
• Definitely the cheapest option

So there you go, that is hands down the "best" option.

You actually need some back pressure or else you lose horse power.

[AtlasMick]

Originally Posted by N1rve

You actually need some back pressure or else you lose horse power.

^most often this is a misconception. The most useful thing your exhaust does is draw heat away from the engine.

[N1rve]

Originally Posted by AtlasMick

^most often this is a misconception. The most useful thing your exhaust does is draw heat away from the engine.

Not only heat but the combustion by-products. Without this negative pressure, the byproducts would get sucked back into your engine.

[DylanFRS]

Originally Posted by N1rve

You actually need some back pressure or else you lose horse power.

So let me ask you something, will you gain more horsepower by adding another 7 feet of exhaust piping behind your current muffler?

Just wondering how far that logic extends.

[Cycotech]

Originally Posted by DylanFRS

"Best" option is to just take off your exhaust, because:

• Lightest option
• Most free-flowing option
• More "Sounds like race car" option
• Definitely the cheapest option

So there you go, that is hands down the "best" option.

I wouldn't do it because a friend of mine did it and melted his rear bumper.

[luuser75]

This is like going to a group of girls and asking them what's the best heels out there. Never going to get a unanimous answer in my opinion lol. Just get what suits your individual taste the best...

[N1rve]

Originally Posted by DylanFRS

So let me ask you something, will you gain more horsepower by adding another 7 feet of exhaust piping behind your current muffler?

Just wondering how far that logic extends.

You'll gain weight, which will decrease the performance of the vehicle. No extra horse power will be gained.

Your exhaust pumps out gases in pulses.

The pulse is usually as shown below:

Engine [low pressure area] [high pressure area] ==> [low pressure area] [high pressure area] =======> (Exit).

In this pulse, this helps PULL exhaust gas out because during the exhaust stroke, the engine pushes out the exhaust gases from a high pressure area to a low pressure area.

So with too big of a piping or lack of an exhaust system, the velocity of this pressure will be lower, so with a more narrow exhaust, this increases the velocity of this pulling.

BUT!

If you have too narrow of a piping, the engine will have to work against itself to push the gases out.

So it's really finding that middle ground or "balance".

[DylanFRS]

Originally Posted by N1rve

You'll gain weight, which will decrease the performance of the vehicle. No extra horse power will be gained.

Your exhaust pumps out gases in pulses.

The pulse is usually as shown below:

Engine [low pressure area] [high pressure area] ==> [low pressure area] [high pressure area] =======> (Exit).

In this pulse, this helps PULL exhaust gas out because during the exhaust stroke, the engine pushes out the exhaust gases from a high pressure area to a low pressure area.

So with too big of a piping or lack of an exhaust system, the velocity of this pressure will be lower, so with a more narrow exhaust, this increases the velocity of this pulling.

BUT!

If you have too narrow of a piping, the engine will have to work against itself to push the gases out.

So it's really finding that middle ground or "balance".

While I have heard this theory many a times, i have yet to see a solid amount of evidence to back it up. Although I am far from an expert on engines and exhaust flow, I am an aerospace engineer that does hydraulic design for a living. And while I do understand how people with some basic knowledge in aerodynamics could concoct a theory like yours, that doesn't make it correct. Yes, squeezing moving air into a smaller cross-section does increase velocity. Yes, accelerating air does reduce its relative pressure. But putting those two things together is a far cry from what goes into a car exhaust system.

Now, if we want to talk about exhaust scavenging in the head or even pre-cat, then I can definitely see a lot of that stuff coming into effect. Post cat? Definitely not.

So, given your scenario, at what point can you cut off the exhaust and not lose horsepower? Was the car/exhaust length set up to be the optimized length? Could you cut half of it off with no loss? 3/4?

I am an engineer, I work on theories backed up with fact.

[N1rve]

Originally Posted by DylanFRS

While I have heard this theory many a times, i have yet to see a solid amount of evidence to back it up. Although I am far from an expert on engines and exhaust flow, I am an aerospace engineer that does hydraulic design for a living. And while I do understand how people with some basic knowledge in aerodynamics could concoct a theory like yours, that doesn't make it correct. Yes, squeezing moving air into a smaller cross-section does increase velocity. Yes, accelerating air does reduce its relative pressure. But putting those two things together is a far cry from what goes into a car exhaust system.

Now, if we want to talk about exhaust scavenging in the head or even pre-cat, then I can definitely see a lot of that stuff coming into effect. Post cat? Definitely not.

So, given your scenario, at what point can you cut off the exhaust and not lose horsepower? Was the car/exhaust length set up to be the optimized length? Could you cut half of it off with no loss? 3/4?

I am an engineer, I work on theories backed up with fact.

My guess would be before the cat because everything after is for noise and guiding the exhaust gases away.

[AtlasMick]

Originally Posted by N1rve

You'll gain weight, which will decrease the performance of the vehicle. No extra horse power will be gained.

Your exhaust pumps out gases in pulses.

The pulse is usually as shown below:

Engine [low pressure area] [high pressure area] ==> [low pressure area] [high pressure area] =======> (Exit).

In this pulse, this helps PULL exhaust gas out because during the exhaust stroke, the engine pushes out the exhaust gases from a high pressure area to a low pressure area.

So with too big of a piping or lack of an exhaust system, the velocity of this pressure will be lower, so with a more narrow exhaust, this increases the velocity of this pulling.

BUT!

If you have too narrow of a piping, the engine will have to work against itself to push the gases out.

So it's really finding that middle ground or "balance".

I believe this logic works for motors with no valve's like 2 strokes, and it certainly works on my 73 Harley, because those valves never actually fully seat. However, "Backpressure" implies that there is pressure, forcing "back" on the engine that is needed, but if you aren't trying to keep the gases in the chamber for combustion (ie. no vavle two stroke motors) this means the piston only works harder to push the gases out when the valve does open to the exhaust side. A sealed combustion chamber with valves negate the need for backpressure. Exhausts are still entirely needed however, because you want to funnel all of those hot gases away from the engine, and you were correct in also pointing out the corrosive by products also need to be funneled away.

By the same logic of "backpressure" you would need to keep the same pressure against the engine as stock for performance, why do you get big horsepower bumps when you get a freer flowing cat and muffler?

[AtlasMick]

Quick google search, I found a blog with most of the principles I've been taught over the years from a few guys at my local motorcycle shop. I run a straight pipe on my bike and I constantly get lay people telling me I'm doing it wrong. LOL. It is a good read. It should entertain.

[TRD_86]

Originally Posted by Fortis

You want quiet: Greddy SP or TRD
Moderate: Perrin Resonated, Invidia Q300, Tanabe Medallion, ARK Grip, Nameless 2.5 x 5 inch
More aggressive: Invidia N1 or Greddy Evo 3

Hope this helps.

^ Can't go wrong w/ this list. For the twin, N1 & Evo3 got the best design look and sound great.

[Captain Snooze]

Originally Posted by N1rve

Without this negative pressure,

Negative pressure? Do you mean pressure differential?

Originally Posted by N1rve

this helps PULL exhaust gas out

Do you mean flow into a low pressure volume?