When i went to Sexson Muffler to have my glasspack put on my zx2, they said it already had 2" piping all the way back and they would not need to increase the size... I've been told that they should've put 2.25" piping on... is that true/necessary?

You have 1 7/8ths piping. It's not a bad size, but it doesn't let that motor breathe as it should.

What's holding you back mostly though, is the stock log-style manifold. upgrade to a 4-1 (use 2.5" catback) or 4-2-1 header (use 2.25" catback), and the respective catback sizes for some great performance.

Oh... :oops: I honestly didn't know, just going off what he told me. But i'll keep that in mind. (about the catback and piping)

You're fine. :)

I wish we had 2" piping, that would have made a lot more sense. It's a pain in the ass to try and get any sort of fittings made for our stock exhaust, because of its weird size.

My guess was that the mechanic just eyeballed it. 1/8" is only about | | difference, easy to miss over a large pipe. ;) Plus, 2" is a lot more common.

Don't be so afraid to be wrong on things. If you notice, I didn't yell at you or call you an idiot. You're not going to see that kinda stuff here. We all understand that you didn't burst forth from the womb knowing everything possible about the Zetec/ZX2, and since you're willing to learn, we're willing to teach. :)

That's what I like about this site as opposed to others, people don't realize that they were once noobs too. Everyone on here seems down to earth. I like that.

2 1/4 n/a, 2 1/2 forced induction, wether it be Nitrous or boost

for exhaust piping? i assume thats to better the flow of heat from the engine?

Eh. 2.5" piping can be done on our motors N/A if you're going top-end and plan on having some sort of head-work done, or matched intake / header.

There is no rhyme or reason, for instance, for a 1.6L B16 Honda motor to have >= 2.5" piping on a stock rev limiter without headwork. Our motors breathe a fair bit more (almost half a liter -- basically a piston's worth), and with a little work can rev as high as those Honda motors can. Our extra displacement requires larger piping ... but only in the upper revs.

Loss of flow velocity will kill the low end, as will the 4-1 design.

Heat losses / gains (from wrapping, for instance) are fairly constant between designs.

I wouldn't run 2.5 on a n/a engine, to me I dont see a point of it, only achievement you'll get by running that .25 larger is noise

2.25" = 3.97 sq. inches of cross-section
2.5" = 4.9 sq inches cross-section.

That's a 20% gain in cross-sectional area. Perhaps CJW can chime in and enlighten us just how much can be gained from that ...

2.5 will make it deeper not louder. With a turbo it will be a lot deeper regardless as turbos are basically built in resonators. 2.25 is fine.

Truthfully 2.25 and 2.5 will both work just as good on a mtx. It wont shift power enough for you to notice. On a turbo on low boost 2.5 is perfect. On extremely high boost on this car 3" is ideal.

Overall if you have nothing else done Id say 2.25(and an intake doesnt count)

As for flow the best thing Ive found is to start at a big collector and slowly work back to a smaller size. Like for example on turbos it has been proven to be a good thing for 3.25" dump and down to 3" cat to 2.75" catback to 2.5" muffler. All not right after. Spaced evenly but you get the point. Exhaust gases are most expanded at their hottest and dont need much room once it gets cooled further back. And you actually benefit from the sloap style design. Those numbers are not for a zx2. they were off an STI if you must know.

If going with dual mufflers I would suggest going 2.25 so you dont lose too much backpressure.

But hell even a 2" mandrel exhaust is better than the 1 7/8 that is on it.

Also the straightest route you can take back is better for flow. Like on cars where the muffler is cocked sideways. it isnt like that for looks(well it may be to that person but truthfully it helps flow.)

i dunno if I helped at all or I just confused people but eh whatever. let me know if you want me to explain anything further

Bah

You're fired.

:lol:

Fine, I'll do the rate-flow calculations.

... soon as I learn them.

For the flow calculations you need to know a lot of variables like:
How much is being moved from each cylinder at X rpms
What the current flow and sizes of runners, pipes, etc
What the volume of said pipe is
How many bends the pipe has in it
How big said bends are


And quite frankly its not that important for me to sit for hours to figure out. lol cuz that’s pretty much what itd take

the difference between .25 isn't that important for us, we're a 4 cylinder. We're not flowing air like a v8 or a larger engine. The difference between 2.25 and 2.5 with same mods is going to be what -2/+2 hp/tq

Well, CJW, we move 1L of air (0.9985L) per revolution, not counting extra gasses generated by the combustion. At 5000 RPM, We're moving 5000L per minute.

Now, assuming 1 liter = 0.0353146667 feet^3 as a conversion factor, that's a modest 176 CFM. Increasing the tubing diameter by .25", as found earlier, allows for 20% more air at the same pressure. 211 CFM with as much backpressure as 176. Lets look at the speed of the air ...

To measure the speed of the air, we have to see how much we're moving along a 1" area. 176 cubic feet divided by a 3.9"^2 is a column of air over a mile long. To evacuate the 1.23 mile long column in one minute, means the exhaust flow has to be traveling just about 75 miles per hour. To evacuate the same 176 cubic feet through a 4.9" area means the air has to move just under 60mph, a substantial difference.

Once I find out the stock injector cycle at 5000 RPM's, I can actually factor in the gasoline, and figure out how many extra liters of gas it makes, and redo the calculations. These numbers are gonna be at 5000 RPM, open throttle, and no spark.

Hmmm... You have a lot of down time at work don't you?? :lol:

What he said / / /

very nice Insta.

And yes he has much downtime cuz he is breaking servers. :P j/k bro :lol:

LOL! :lol:

"Holy Hell I broke it all"
^that was funny shit^

like I said, do all the math you want...it .25 doesn't matter that much on our 4 cylinder. Example, who runs who here...hmmm?

I run everything here. Didnt you know that? You are in the shadows. Being all sneaky and such. Doing your dirty in the corner and then coming out all quiet and such.

Dont mind me Im a little tipsy. w00t w00t :twisted:

Oh, I dunno ... Mr. I-took-everything-out-of-my-engine-bay

Maybe I'm so slow because I only have 2.25" exhaust? ;)

but thought my 1 7/8's STOCK exhaust was holding me back...