i have been around cars along time and one thing i have heard alot about is poeple saying that u lose compression in your engine by going with the bigger exhaust pipe. but all my life i was lead to belive that the bigger would allow your engine to breath better. what do u guys suggest, i am getting another set of mufflers later this wk for my 97 hx and would like some help decideing on the pipes.

 

too big causes a negative effect because the pulses do not flow correctly...and its just silly

The only reason you would ever need a 3" on a 4 cylinder is if you were turbo and making a lot of power.
2.25 is more than enough for an NA D16 (probably more than enough)

 

you can't loose compression in your motor by getting new exhaust....and 2.25 is more than enough for a stock or slightly modified car, a turbo or built all motor is another story...

Also you can loose exhaust gas velocity which can make less torque than stock

 

<--- slightly moded HX. 2.25 exhaust

 

Id definatly stay with the 2.25 for N/A especially. But would a 2.25 flow good enough on a low boost motor? sorry for posting on a post

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lord Milferdeen &raquo;</TD></TR><TR><TD CLASS="quote">Id definatly stay with the 2.25 for N/A especially. But would a 2.25 flow good enough on a low boost motor? sorry for posting on a post</TD></TR></TABLE>

i would go to 2.50 if your gonna boost. 3 at most if you have a nice setup with a t3/t4

 

you only need up to 2.5 if you are boosting. there is no need for anything bigger than 60mm on a all motor car till you get into really big cams. 2.5 in and up is for boost only as far as im concerned, 3 is only needed if you are going for numbers in excess of 300whp imo.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pythoner &raquo;</TD></TR><TR><TD CLASS="quote">you can't loose compression in your motor by getting new exhaust....and 2.25 is more than enough for a stock or slightly modified car, a turbo or built all motor is another story...

Also you can loose exhaust gas velocity which can make less torque than stock</TD></TR></TABLE>

You are not gonna lose compression with a larger exhaust. Maybe you meant another term.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by excivicboy96 &raquo;</TD></TR><TR><TD CLASS="quote">

You are not gonna lose compression with a larger exhaust. Maybe you meant another term.</TD></TR></TABLE>

back pressure

 

the first 2 replys to the OP was correct, Velocities will be cut drastically, which mean the engine has to work harder to extract, and if the extraction isnt going in a timely fassion, your throttle response will go down to 0.

There is no such thing as back pressure, there is restriction, and velocities. Back pressure is more of a emotional way of describing a "system". However, back pressure better described in a high powered rifle.

THe actually bullet is creating the force, the back pressure is the pressures behind the bullet, being "controlled" by the rear piston. The velocities are high, because the pressure loss is minimal.

think about it this way, the size of the barrel, is built around the size of the bullet. If they had a 7.62 NATO round, but had a .50 barrel, the bullet will just flop around, since pressure loss has occured. (the pressures have excaped past the bullet)

Same thing with the exhaust system, however there is no bullet, only X ammount of gasses your engine puts out per stroke. Too small of pipe = choke, Too large = exhaust gasses F- around like a set of groupies at an EMO concert.

Getting the perfect size and composition of piping is an art, believe it or not, same thing with intakes, but the output is minimal.

So with the whole gun thing, the m60 uses a lower gas chamber, to effective fire more rapidly. As the bullet is pushed from the barrel, the lower gasses are extracted to quickly fire off another round. If you look at the gun, its kinda close to a NA engine (but not really)

back pressure is just a restriction, causing the gases to find another way out = gaskets. You want no back pressure, and high velocities to extract the next stroke. If you could visualise this, you could probably know, that a shorter pipe, with a small diameter would flow more efficiently.

However most engines are designed around the conventional exhaust system. You dont see porsches with 17' exhaust pipes sticking out.