serious exhaust question

[meggala]

ok my sr is going to to the cefiro.
ftting the t518z turbo cooler etc.
any way I'm sick of really loud exhausts and my cefiro has a 21/2 inch system on it atm with the rb 20 I know this isnt ideal but I have a 31/2 inch system in the garage but it is 105 -110 db loud so not really good for every day. I realise the smaller exhaust will hamper power but will it be ok for every day duties I'll fit the big loud one when I go to the drags or go drifting.
boost will be limited to around 1 bar for every day driving with the small exhaust
I can cop the power losss but will it flow ok.
long resonator and a muffler on the back.
power goals 200-220 rwkw more later with more boost.
meggala

[Jim]

get a 3" Super Turbo or similar straight through muffler, and put it near the middle of the car, and a multi pass 3" near the rear of the car.

the compromise is that at the back of the car the exhaust gas is getting denser as it cools, so is restrictive to pass it thru a multi pass muffler, but it's volume and velocity is slightly reduced so it doesnt need to pass thru a massive pipe, but at the front of the car where the gas is the thinnest and will pass through a muffler easier it is very hot and will burn the guts out of it. somewhere near the middle of the car is the best compromise for the first muffler.

if it's manderel bent pipe you shouldn't notice much significant power loss.

[GTSBoy]

Or, look into a boost triggered exhaust cut out like they reviewed on Satan_net....I mean Autospeed.

cheers

[Datto-Zed]

Sorry bout my little hijack.

Just wondering, how much of an effect does the exhaust diameter have on the volume? I would have thought the main factor in the exhaust volume will be the muffler types and setup, as a pose to diameter.

The thing is you hear people saying stuff along the lines of "blah blah if i get this eleventy billion inch exhaust then it will be too loud blah blah" all the time.

[GTSBoy]

Bigger diameter exhausts are louder and take more effort to shut up. A given muffler usually generates muffling based on some pressure drop, and the bigger it is the slower the gas flow and so the lower the pressure drop, and hence reduced muffler effectiveness. The bigger pipe makes for different and louder resonances, therefore requiring better muffling. Putting small mufflers into big pipe systems seems like a waste of big pipe. Catch 22.

cheers

[jampac]

On my late 200sx I had a 3" exhaust from turbo back, that was straight through designed mufflers(basically steel tube with heaps of holes in it wrapped in steel wool). Used two very large muffler cans and a 3" cat, and exhaust noise was measured at 86db using the NSW noise testing regs. The piping thickness was very thick (exhaust weighed heaps) mild steel. I'd say at a guess, 4-5mm. The brand was fujitsubo, and it was an old school exhaust, like from 1994, got up to 190rwkw with that exhaust, but still standard turbo. No droning, very nice in cabin.

[meggala]

and thats where the other problem lies in the material beign used as I have a stainlees exhaust I would like to use as a base.
thanks jampac that give me something to go by. I'll be running makeing more than 190 rwkw s o ti will be interesting.

on the topic of exhaust. we picked up a rent a car today as the cefiro is in being done and the missus complained when driving the pulsar that she scouldnt hear it.
dont you love that from a woman.

meggala

[VHDREAMS]

just a quick question/suggestion (although fairly out there)..

would it keep the same exhaust flow properties or even better if you split the exhaust in two, close to the engine and then ran a very large balance pipe towards the rear?

my basis for this is the larger balance pipe you go the less noise the car seems to make...and you would get to keep the same diameter pipes and use fast flowing mufflers... although the cost of twin custom pipes and mufflers may be a lil expensive,


Cory

[GTSBoy]

The only bad thing about twin exhaust systems is the increased frictional losses in the gases, courtesy of two pipes of the same cross sectional area as one bigger pipe having more circumfrential length for the same area.

Short version.....1 big pipe less restrictive than 2 smaller but equivalent area pipes.

cheers

[VHDREAMS]

ahhh, thanks GTSBoy, today I have learnt something!

Cory

[thehelix112]

As you said previosuly GTSBoy, bigger pipes make for different and louder resonances. Thus two smaller pipes, while more restrictive are also more likely to be quieter than the equivalent big single.
Regards,

Dave

[meggala]

and gtsboy like always is a great source of information.
twin system hadn though of that
cheers