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Originally posted by 25GTT

Heya Wassabi,

If you already have a cat back exhaust then Brett at PSI can prob help!

I got my full exhaust system (Dump Down pipe and hi flow cat) done with him added 20HP at the wheels, I have the dyno sheets to show this! i was VERY happy with his work and didn't charge too much at all! then i had SAFC and boost wound up a bit  and it was another 20HP extra 40HP in 1 day made for quite an excitring drive home...need i say more:uh-huh:  

From my experience giv Brett at PSI a call..... some people have had probs but i don't want to start arguments but from the people that i have recommended to him such as IMACUL8 they are more than happy with him!

Hey man thanks for your help but i am kind of put off PSI after hearing horror stories from adam and from ND4SPD... i think i might go cypher

Originally posted by rev210

If the factory computer has anything to do with it, I'd say it retarded the timing on you.

Turbo's do not like backpressure at all! Get rid of back pressure on the turbo and power is there for the taking.

Retarding timing because of why exactly?

Please explain

If you're real picky about the quality, I thoroughly recommend Geoff at Exhaust Dynamics.

The following is a shot of my old S15 with a turbo back 3" s/s system.

http://www.exhaustdynamics.com.au/silvia.html

Whilst you pay for the quality - you won't be dissapointed.

Jeff Ash @ c-red is able to fit you up with a system thats almost identical to a Apexi N1 cat back system for around $1100. Its 3.25" from the cat back with no resonator to a large barrel style muffler to a 5" tip, sits at a nice angle its thin wall polished steel and looks the goods. I gained 15kw @ wheels on the dyno at SST from the exhaust and has a good throaty sound as well. All I need is a decent pipe off the turbo back and removal of the cat and It'd be even louder and blow flames. Jap exhausts and parts in general will also be a better alternative to australian made products, they will flow and work 100% better. The drawback, costs more.

Rob

Get a jap exhaust fit it, test it for noise output and power output, put an australian system on and it wont be as good. The in-cabin drone of the exhaust will always be lower on the japanese unit than a simular australian made one. Same thing goes for intercoolers, I compared a trust unit and a ARE core and just by visually looking at the core you can see how much better constructed japanese parts are. I cant wait to see a 9second GTR made souly from australian parts.

Rob

You may have more than 1 muffler in your system for example mine came across with no cat but with 2 small mufflers (resonators) and 1 large back muffler all straight thru Trust gear

Thats what is going to determine your loudness more than anything as they arent real mufflers if u can see thru them :-))

Jap or Australian the physics of exhaust design still remain. If you know the theory and can weld better than a monkey you can expect to produce a decent exhaust.

The japs go for larger pre-silencers on most of their exhausts thats why they don't drone as much, its quite simple and a good idea.

The less restrictive zorts are often louder as par for the course.

Here are a few ideas for high flow.

1) turbos don't like backpressure.

2) Make the exhaust length as short as possible (ie: fewer less angular bends decrease the total length).

3) Straight through mufflers flow the best , you just have to seek out the best brand for noise and flow.

4) muffler and cat placement effect the thermal dynamic aspect of flow but also noise. The exhaust is hottest up the front and gets colder as it goes back, it loses speed and energy as it does this.Pipe diameter as you go back should decrease slightly to accomodate, not increase as many people do. The exeption is the tail pipe if it is 'megaphoned' this produces an attractive pressure drop for exhaust to run to.

5)Trapping the heat energy in the pipe will increase the speed of the gas molecules making more power, do what you can to this effect. Coating the muffler bodies in HPC or more practical is wrapping the dump pipe in thermal wrap.

On the idea of the infallable jap exhaust - they are useless at doing NA rotory exhausts, possibly the hardest to design. If you know a place that does a good job of this type of exhaust then go running to them if you want the "best quality" in design they must know their stuff.

thats bullshit about jap exhausts being better, but if you want to spend twice as much on one, well im not going to stop you

they may be VERY SLIGHTLY better constructed, but as rev said, if you can weld better than a monkey and make it out of 3" mandrel bent pipe then youre going to produce an exhaust of reasonable quality. i dont think weve done enough laps around nurburgring to start counting 1-2kw gains from using an overpriced japanese unit as opposed to a locally made exhaust.

:cool: Yeah, what they said :P

Originally posted by rob77

Same thing goes for intercoolers, I compared a trust unit and a ARE core and just by visually looking at the core you can see how much better constructed japanese parts are.

Sure you weren't comapring apples with oranges? If the ARE was tube & fin while the Trust was bar & plate, of course the trust is going to look like it flows a lot more air, its a by product of the core's design. AFAIK, ARE use top quality cores.

Most of you probably know this, but heres an insight on why the Japanese sell everything (from exhausts to underwear) in kit form: Laour. Its just too bloody expensive to pay someone the labour to build custom parts, works out cheaper for them to mass produce.

Asking us to build a 9sec GTR without Japanese parts is a bit silly. Why not ask the Japs to build a 9sec LS1 without Aus or US parts? I'd like to see a PowerFC for that one! :P Note: the GTR probably could be built, but why reinvent the wheel for things like tubular exhaust manifolds.)

I'll stick with my jap stuff, I know it works, its tried and tested. The trust unit is a tube and fin and yes I was comparing a tube and fine ARE unit to the trust unit. And you're right, why re-invent the wheel? Jap's have done the research and created what works best and it bolts practically straight on and in. My exhaust took less than 10 minutes to fit and the intercooler wont take much longer than a day after cutting and trimming the front bar to suit.

Rob

so i got my exhaust fitted today, decided to go for 3" after hearing a line with 3.5 (too loud, dont like police attention) and anyway dosent sound heaps different to my previous 3" cat back BUT now it seems its making more boost higher up in the rev range and knocking!!@&@!* does this sound right?

i think i might just turn down the boost till i take it to cypher next week :cool:

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