Jump to content
SAU Community

Recommended Posts

your probably loosing most of your bottom end power... but ull probably feel an increase top end..

U dont have to change your whole system.

Y dont you change your front pipe to a 2.25inch system.

the rest can stay..

if you restrict the flow in the front pipe, the cat/catback wont really matter as much.

that way you will keep your "cool" sound plus get some performance back.

PS. i have a 3inch xforce system on my gtst 33.. LUV IT

Eug, what do you mean?

Correct me if im wrong Eug,

The term is "volumetric vacume" or "volumetric efficiency"

I.e

If the pipe is too big.. the exhaust just lingers around and doesn't exit the exhaust piping in the most efficient way. Too big of piping can result in worse performance than stock.. as you found out.

If the piping is too small.. the exhaust fumes struggle to fit through the piping and the flow is choked and slowed as there is too much gass exiting the engine and the piping cannot cope.. again.. hindering performance..

With the right size piping.. the exhaust gass will flow evenly.. and create a form of "vacume" where by the gas will almot accelerate in "speed" throughout the length of the exhaust sytem..

Its a simple explination.. but I hope it gets the point accross..

back preassure is when, for eg. you have a turbocharged car without an evacuation system (Blow off valve). So when you take your foot off the accelerator.. the turbo continue to force air into the intake manifold. Because there is no were to go for the air to go.. it will build up.. forcing itself back down the intake, creating back preassure. This preassure will slow the turbine of the turbo down. When you eventually get back on the gas after changing gears.. you will have to wait for the turbo to spool up to its previous point (before the back preassure began to slow the turbine down) to continue making power..

thats the diff..

On the subject of xforce.. I drove my car with only exhaust mani connected.. I think it was quieter than with the xforce cat back I used temporarily.. I was willing to drive my car into a wall just so as to not hear the exhaust after 10 min of driving the thing..

Edited by GTS4WD

that's pretty much it in a nutshell Cris. good man

on what you said with smaller piping, that may cause back pressure also. just by breaking down the word literally should be more than enough explanation.

Eug, what do you mean?

if you have posted in here, there is no need to PM me. i will see your post in due time.

He's said it many times in many threads now :P

good man, into the good books you go :whistling:

HEy guys, (I couldnt wait)

All done, today I went to Liverpool exst 9.30AM hehehe and was there until 1pM, got a custom 2.5 system installed with Hurricane 2.5in muffler(4.5 tip) with silencer, and the rest of pipe is 2.5 mild steel. I drove home without the silencer OMG...........felt like shooting my self, so much noise hehehe :) , but I could feel the pickup speed better than 3in one. now I drive it with silencer, which is good, nice beat........(But not nice as xforce I have to say)

Guys thanks for the explanation of back pressure, I really appreciate it.

Now I have to sell the xforce system soon, so I can pay my cc :D here some picture of my new cat back system........... :banana:

Thanks heaps guys.............

post-33178-1203308365_thumb.jpg

post-33178-1203308504_thumb.jpg

post-33178-1203308567_thumb.jpg

Y dont you change your front pipe to a 2.25inch system.

the rest can stay..

mmmmmmmmm good idea tho, now at least I can advice this one to someone else, cheers

My Varex XForce muffler arrived today, she's beautiful. I took the 2.5" inlet route too, with a 4.5" cannon. Will post some videos once its installed.

wow thats nice, is this the one with controler, that you can change the tone? if so how much was it and where did you buy it?

Cheers

wow thats nice, is this the one with controler, that you can change the tone? if so how much was it and where did you buy it?

Cheers

$350 + $25 delivery from ebay. From this guy; http://myworld.ebay.com.au/x...f

I don't know if you can change the tone so much, just the volume. It's a 4.5" cannon that can be opened fully or completely sealed so that the air has to travel along another path which leads it up and down the muffler several times, dampening it significantly. So you can have it loud enough to hear from 4 blocks away, 2 blocks away, just down the street, or quiet enough to sneak by the police. Well, that's what I'm hoping anyway.

It's a lot better than I thought it would be, wires come with a fuse (on easily replaced) and a cigarette lighter jack. Plan on wiring up a cig lighter port off the battery into my boot this weekend and getting it installed during the week.

Your current muffler is an Xforce one correct? This one will just bolt straight onto your current exhaust system if you're considering it.

$350 + $25 delivery from ebay. From this guy; http://myworld.ebay.com.au/x...f

I don't know if you can change the tone so much, just the volume. It's a 4.5" cannon that can be opened fully or completely sealed so that the air has to travel along another path which leads it up and down the muffler several times, dampening it significantly. So you can have it loud enough to hear from 4 blocks away, 2 blocks away, just down the street, or quiet enough to sneak by the police. Well, that's what I'm hoping anyway.

It's a lot better than I thought it would be, wires come with a fuse (on easily replaced) and a cigarette lighter jack. Plan on wiring up a cig lighter port off the battery into my boot this weekend and getting it installed during the week.

Your current muffler is an Xforce one correct? This one will just bolt straight onto your current exhaust system if you're considering it.

Wow thats cool, I had xforce 3" system which i replaced with 2.5" hurricane system...........Pls post some pics of your system once you install it, I certainly condier getting one of those :thumbsup:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • My goals for it atm are to get it registered, respray and some mild power gains eventually... I picked up the car from an elderly gentleman near the border of NSW and VIC, its honestly a bit rough and looks like its been driven on a farm (because there was so much dirt underneath). Last week I dropped the subframe and emptied the old fuel out + added a new fuel pump (think the old one went bad from old fuel). Now I'm onto fixing a coolant leak at the rear of the engine + adding a new radiator as the old one is corroded. After that i have a new bumper, coils (as the old were leaking) and lots more
    • Welcome buddy! Plenty on here and YouTube. What are your plans for it? Good luck with the Rwc and Rego bud!
    • Love this so much! Please post a photo when you have a bike on the trailer.  I was a little bit worried about having a tow bar on the Skyline, but having it hidden behind the number plate is genius
    • Came here to say, put all the wiring from the new motor and gearbox in that you can, then throw the stock ECUs in the bin, and get an aftermarket ECU. Should be pretty easy if you can use a multimeter and read a wiring diagram to then use a PNP aftermarket ECU to suit the motors wiring loom, and make the minimal changes you will to get it to work in with the body loom (If any). This will mean you can very easily circumvent/bypass the Park/Neutral start disable switch, and get everything running really easy!
    • If the roof is dual skinned the whole way, IE, there's a "top" metal piece, and a "bottom" metal piece, to slow it down as much as you practically can, you should be able to get an attachment for a spray can/your spray gun, where it is a long, thin flexible hose, and when you're "spraying" it is spraying it in every direction possible. The I'd get that, and feed it through the roof as much and as far as you can. It's basically like fish oiling the car, but you're soaking it in rust converter. Then do the fix like Murray has described having cleaned up the existing metal as much as you humanly can. I'd also throw as much rust converter on that exposed metal before putting the fibreglass/metal filler over everything.   As for welding a replacement in. I've owned my own MIG welder for about 10 years. I've also worked in an industry doing MIG welding for a job for about 3 months dead straight, and we were doing 11.5 hour work days 5 days a week, plus a Saturday 6 hour day. (I then moved over to running the massive CNC plasma as I could understand the technology, and work with the main guy out there). I also f**k around with my welders a bit at home. So what I'm saying here is, I've probably got more hours on a MIG gun than you'll manage to get under your sleeve doing home sorts of jobs over the next 5 years. I also have an ACDC TIG that I got myself a year or two back. I've got a short amount of experience on the TIG only. My home MIG is also presently setup for doing thin sheet metal. Unless I didn't care about how that roof looked, and I just wanted a functional metal roof, and it being out of alignment, warped, and bowed, I would NOT attempt a roof replacement UNLESS I could do it as a whole panel like Murray described where the spot welds were.  Welding has this REALLY annoying thing, where if you want something to be perfectly square, unless you can clamp that thing to damn perfection (Welding fixture table), it is NOT going to be square, so you start to learn, the type of metal you're working with, how thick it is etc, and weld in VERY specific ways, and by knowing how YOU are as a welder, so that as the welds cool, the metal work pulls itself into place. If you want to see some cool tricky shit done, Bennets Customs is an Aussie guy, and he mentions a guy a lot call "Kyle", who is from "Make It Kustom". Watch some of their welding videos, especially on sheet metal. You can use the welder to shrink the steel in, and you can also use the welder to stretch the panel out. When you have the skill level that I have, you can shrink the metal in and out... But never on purpose like those two guys do. You just manage to f**k it all up. Then I smack it around with a hammer till it sits lower than I will want it too, then I shove filler on top and then pray to deitys that I can sand it into some form of sane shape that doesn't look like a dog has taken a shit, after eating a tonne of pumice stone... I'm all for DIY, and for learning, and please, feel free to give it a go, but be aware, you need to live with the consequences of how time consuming it is to do, AND that it's going to look no where near as good as what you can make it look with just some filler now. Oh AND, even once you replace it, it's like to still rust away again eventually, because you'll have missed putting primer and paint on some part of the newly welded in sheet metal, or against part of the existing metal you couldn't get to...   Oh, and to weld all that in, you will need to pull the window out, and strip at least the roof and A Pillars of interior trim and wiring. You'll then need things like the big fire proof/weld spatter proof mats to lay down, OR you'll end up needing to strip the ENTIRE interior to avoid sending it all up in a ball of flames. If you want to see how annoying sheet metal is to weld, head to bunnings, buy there 600x600 1.6mm mild steel (Not GAL!) sheet, and cut a few pieces, and try and weld them together. Then understand, 1.6mm sheet is nearly 50 to 100% THICKER than the cars sheet metal.   The photos I posted before, I'm replacing with 1.2mm thick mild sheet, and it's very easy to blow through both the original steel (Especially if I hit an area that should have probably been cut out a bit more) or straight through the new sheet metal. And I'm doing the floor, which can be hidden easily, and doesn't matter how pretty I make it, as long as it's damn strong! I'm also doing it in a 4WD, that has seen many off road trails, and doesn't need to look that pretty ever
×
×
  • Create New...