New Exhaust

[mdb4879]

so i just put a CA18DET in a 1987 Nissan Pulsar, and the exhaust is kinda loud (about a 4 inch long pipe after the down pipe. So i would like to get and exhaust made for it. if the boost gauge is at all accurate then it's running 10psi of boost. ultimately (like in the next year or two) I want to get around 230-250hp (at the crank), but what is best for how the car will drive now supercedes any plans for the future. i want it pretty quiet, but maybe open up a bit once it hits boost. maybe about as loud as an 8th gen civic si or a 350z, or a little quieter (it's been a while since i've been in either of these cars with a stock exhaust, so i can't really remember just how loud or quiet it is). I was thinking like a 2.5 inch full exhaust from the stock down pipe, no cat, with a 2.5 inch OEM style muffler. would the muffler flow enough for those goals and my current set up? and if so, would that actually be too big and should i go for like 2.25 inch?

I guess i figure 2.25 inch is big enough, but my biggest concern is would that type of muffler flow well enough for this? if there's no practical way to make it quiet then that's fine, I can live with a louder exhaust if it'll flow that much better, but i would prefer to be reasonably quiet. i want it to be loud enough for me to be able to hear how fast the motor's turning and how its running, but not to draw any more attention than any other modern sports car

sorry if i sound like i'm blabbing on. it's really late. and thanks in advance

[mdb4879]

another thing i got to thinking about today is will an exhaust help steady my power curve? right now the car has a straight vacuum line going to the wastegate actuator, so it should be running like 7 or 8 psi, right? well my gauge is reading 10 then dropping to 7 between like 6k and 6500 rpm. at first i thought either the gauge was messed or something was wrong with the actuator. i had always heard that turbo cars should have a bit of back pressure in the exhaust, but i never knew why.

well today i think i figured it out. since there isn't any back pressure to slow the turbine some, then if the wastegate is small enough then even with it wide open it won't let enough exhaust bypass the turbine to keep the compressor from producing any more than 7 psi. so the minimum right now is 10 psi until the exhaust pressure is low enough to allow it to drop to 7 psi and the wastegate can actually have control over it. either that or until the motor chokes out the turbo.

so my question is would actually having a properly sized exhaust help to control and steady the amount of boost pressure along the power curve? especially to keep it from dropping off in the top end? i know if this is true then for the moment i would lose power because boost would drop to 7 psi, but if i got a boost controller and set it at ten psi would i get more power because the wastegate wouldn't open until that pressure. (if the turbo is choking out then of course that wouldn't be the case, but if the wastegate can't let enough excess pressure bypass the turbine at low engine speed as stated before then i should have less of a power drop off in the top end, right)?

i think i may as well go ahead and get a cat. i realized that as float said in his upgrade list a high flow cat is only like $85 and as he said, "the air you pollute today is simply being borrowed from tomorrow's children." plus it'll help quiet it down without adding much restriction