My Exhaust Muffler Theory, Just thought I might share... 56K BEWARE. Options

[ExSane]

Ok, here is my theory on exhaust mufflers. Basically this... faster exhaust goes out the faster air comes in. Lesser back pressure, the better the exhaust flow. The better the faster the exhaust flow, the better the gains. Here are the designs I used to conclude this theory.



HKS, Apexi N1 type mufflers - Becuz of the design and the edge of the canister is kinda sharp tipped, there maybe a little back pressure on the air flow. HKS Hi-Power has rather a large canister (larger than N1) and can cause a 'slight' back pressure depending on the output of fuel pulses coming from the engine. The stronger and faster the pulses, the less to worry about it. That's probably why most of these mufflers are used for Turbo's. Besides that, people just go for looks with these.

Otto Racing, Blitz type mufflers - The canister designs on these type of mufflers are curved into the tip pipe causing straight through exhaust flow. I don't even think there is any back pressure on this type of muffler design. Everything is pretty much straight through design. I think this is probably the best choice for N/A engines.

Greddy SP, Magnaflow type mufflers - This type of design is known to increase horsepower without ruining the stock look. The only difference between this muffler and the stock one is the piping size. The inlet/outlet diameters are bigger causing a little bit more flow. As you can see up in that picture, there are a lot of back pressure and restrictions made to air flow. This could also be the reason why this muffler isn't that loud and is slightly louder than stock.

Greddy EVO, OBX (EVO wannabe) type mufflers - Now this is an interesting design. From the looks of it, this muffler is design to have no back pressure. But considering the fact that it isn't straight through design, there might be a very slight back pressure on the exhaust flow. I haven't seen anyone with this muffler on at the races but I bet you this muffler will probably be a good add to performance as well as different.

Stock type mufflers - As you can see pictures, the piping for this type of muffler is rather small and they restrict fuel pulses in your exhaust. Back pressure is pretty heavy with this muffler and is probably why you feel so much gain when you take this thing out. As I said about my theory, "faster exhaust goes out the faster air comes in". Basically your engine breathes faster and farts faster. Your heart will beat faster. And then your legs will run faster. LoL. Metaphorically speaking...

Straight Piping type mufflers - Ahhh one of my most interesting ones. This is design is just pretty much straight through design without canister filteration which means no back pressure what so ever. Probably one of the best for choices for 6 cylinders and over. Thus reason being GT mustangs become so freakin quick with this mod. A 2002 Honda Civic EX VTEC coupe burned me and a V6 Firebird (I think stock) out of the streets with his straight pipe. And to think I kept up with that Firebird. The civic sounded like a damn muscle car. Probably one of my most interesting races I've experienced at the street race meets.

So, what you guys think???

This post has been edited by ExSane: Aug 10, 2006 - 12:33 AM

[puretone]

expanding gasses (like in a chamber of the exhaust canister...) lose pressure and more importantly heat.

the expanding/cooling gasses thus also drop the back pressure....just like the case with a log-manifold and real built long-runners manifold that has a dedicated runner per cylinder.....

the spent gasses coming out of the chambers (that are still expanding as they enter the exhaust manifold...) and expanding into the manifold as they keep burning also create some vacuum (behind their expansion...) as they move thru, which is also a good thing for NA motors...

turbo motors just need as little restriction as possible, because of the low compression and that its up to the turbo to "feed" the motor the air it needs, so if you make it hard for the turbo to spool up by adding lots of back pressure it will slow the turbo from spooling......the same still-expanding gasses that leave the engine and head into the manifold are also the same still-expanding gasses that help spin up the turbo better.

now it all depends on the engine's volume of course, so say a 1,5 liter engine with a good back pressure exhaust thats built for a 4liter engine would have no effect because the entire volume of the 4liter exhaust is way more volume than a 1.5 liter engine can ever fill up efficiently to build its back pressure correctly....