2.25" or 2.5"

[drkpnoy]

Hi, I'm planing on having a muffler shop do a custom exhaust system for my 95 240. I plan on having piping from the cat to the muffler. My friend told me to go with 2.25" piping but I see that plentyof 240SX owners have 2.5" piping. My question is whether to go with the 2.25" or the 2.5" piping. I have no other mods so far but I plan or keeping it "NA." My mods in the future would inlude the typical intake system and headers. What would be best for my situation? What is the advantages and disadvantages of both 2.25" and 2.5" piping. I plan on having the exhaust done in the next 7-10 days.  Any suggestions would be appreatiated.

[DrDubbleB]

I was not in the right frame of mind when I posted this last time, 2.5" would be fine for an NA application and 2.25" might be a little restrictive on a 2.4 litre car. Please refrain from using the FAQ to post questions in the future though. This question could have been asked in the General forum (or tech talk, it's kind of in between the two) the FAQ forum is not meant for questions, only answers.

[BRSTYLE240SX]

not written by me.. i read it in another thread...

"have you ever seen the experiement with the egg and the bottle?
flame goes inside.. stick egg on top and it gets sucked in... all the air is getting used up by the flame creating a vacuum so the pressure outside the bottle is stable but pressure inside is dramatically decreasing cause of the air being used... (THIS IS NEGATIVE PRESSURE INSIDE THE BOTTLE AND STABLE OUTSIDE) so in relation.. the pressure inside the bottle was less then outside...

just like an exhaust.. all the work done inside the engine as it compresses, then combust causing numerous pounds of pressure.. goes out the exhaust manifold... (for a four cylinder you'd see that it has 4 pipes going to one... cc area in the combined part of manifold then individual feeders out of each cyliner)
then the air flow would go down the down pipe connected to the exhaust manifold.. its starting to get cooler which means the air becomes less pressurized... now into the exhaust there is underdraft air coming from underneath the car as you're driving aiding in the cooling of exhuast pipes... this somewhat help as well but point is that the farther away you go from the engine.. the cooler the air/CO2 etc. is.. so pressure becomes less and less...
... even though the pressure becomes less you still applying the same cc as pressure lessens...  so 2 1/2 should be fine if you are stock"

Very good explanation huh?
Later!

[ShiftLock]

Is your car lowered, cuz when i got 2.5" piping on my car, the piping scraped on some speedbumps.  Just another thing to keep in mind if your car is slammed to the ground.