Question about turbo exhaust restriction ?

[sidewaymambo]

People prefer go 3.5" system for their turbo, because give the gas better flow, however does less restriction really help? if so, regardless legal issue, remove the mufler at the end will this help?

[GTS-t VSPEC]

The best setup for a turbo car is for virtually no restriction. The exhaust wheel will spin more freely the less exhaust backpressure there is. A 3.5" system sounds good, and removal of centre mufflers and cat will also work well, the less restriction the better.

See'ya:burnout:

[JH32]

Paul, what size dump pipe would be the best for an RB20 turbo?

I mean, I've heard of people talking about 5" dump pipes! Is this feasible/practicle?

[sidewaymambo]

so, does it mean the turbo will benifit most if I don't have anything behind the cat? thanks..

[GTS-t VSPEC]

JiMiH,

With a factory turbo on a samll capacity engine then there is almost no benefit to going too big, I'd say that a 4" dump is more than enough.

sidewaymambo,

The best in terms of power is a dump with nothing after it, but this is too loud and the cops will pull you over straight away. A large dump with separate wastegate pipe followed by no cat or cetre muffler and with a muffler at the very end is the best street setup. Be warned however that this is still very loud and no cat is illegal.

See'ya:burnout:

[red17]

I can testify to my brothers 180SX which runs an apexi N1, fat dump pipe and no cat. Goes like s.hit of a shiny shovel, but the drawbacks are A: no cat's are highly illegal and B: the noise shakes your car port apart when you come home and leave the turbo timer on.

GTSt V-Spec: you know anyone in perth who does good dump pipes?

[GTS-t VSPEC]

There are plenty of people who can do a good exhaust dump but I tend to use Genie exhausts in Myaree, they are very good as the do all of the Xspeed work and are now very good at doing custom work for Jap cars.

See'ya:burnout:

[benm]

I have an R33 with stock turbo + Nismo 3" Cat-back exhaust.

Can someone -please- give me an exact URL of exactly what front section of my exhaust i need to replace the standard section ?

I have absolutely no idea what i need, where to get it done and how much it'll cost but i -do- want to get it done very soon.

[Duncan]

C'mon guys.

Running without a cat is a $10,000 fine.

Is it worth that for a few kw?

You'd be much better of running nitrous on the street and paying the smaller fines

[GTS-t VSPEC]

benm,

If you go to any exhaust place and ask for a custom turbo dump pipe with separate internal wastegate pipe to connect to your 3" system then they should have no problems. Expect to pay anywhere from $250-$350 for a custom job, you can always buy a Jap dump but they are usually more expensive.

See'ya:burnout:

[G0DF4Th3R]

GTS-t VSPEC,

i have a 3 inch catback exhaust. so should i do just the dump or the whole front pipe and how much difference would the two make? is doing the dump enough? must i have a high flow cat? thanks.

[GTS-t VSPEC]

GODF4Th3R,

Doing everything it alway the best, the dump is very important, but if your strangling it with the front pipe and cat then it's not going to do too much. The exhaust will only flow as well as the most restrictive bit.

Hi-flow cat's are the go, will add a little bit extra power at standard boost, but will make more difference as you increase the power.

See'ya:burnout:

[Kichigai]

Also, correct me if I am wrong, but doesn't the turbo heat up quicker if there is more restriction behind it? i.e. standard front and dump pipe

Better flows means the turbo can work more efficiently.

[GTS-t VSPEC]

Your dead right, heat is our enemy. By increasing the airflow then the heat is removed via the exhasut system, with a restriction in the exhasut then it causes excessive heating of the turbo exhaust housing and this leads to the car pinging as it pre-heats the air.

See'ya:burnout:

[G0DF4Th3R]

thanks man...btw how much do u reckon it would cost for a dump + front pipe + high flow cat? just a ballpark figure

[Kichigai]

I got XSpeed to get me the whole lot (dump, front pipe and 3" hi flo) They get theirs done at Genie Myaree as GTSt VSpec mentioned earlier. It cost me just under $800.

Apparently, it used to be cheaper as they used different cat(ceramic?), but they tended to break apart. Mine was one of the newer designs. It cost a little more, but I haven't had any problems so far.

[Ronin 09]

Another question; isn't is true that the further from the turbo the restriction (eg the rear silencer) the less effect on back pressure and HP? So if you do the dump and front pipe in a decent size (say 4") then run a high flow cat and legal 3" cat back it should be better than running say a stock dump and front pipe with a 3.5" cat back?

[GTS-t VSPEC]

G0DF4Th3R,

Kichigai is right, you can get a complete system from Genie pretty cheap these days, but if you want a name brand muffler like APexi/Trust etc then they cost about $500 by themselves.

Ronin 09,

Yes your right, what happens is that a wave of backpressure, like sound waves, oscillates between the ends of the exhaust system, the further the restrtictions are away the less effect this has on the backpressure and ultimately HP, also the reason tuned length exhaust manifold are better.

See'ya:burnout:

[benm]

Oh man i wish i could find a workshop that actually knew what they were on about.

Midas had no idea and told me to come back next tuesday when their "exhaust specialist" would be in and Muffler man just told me to go and see a turbo shop.

ARGH maybe i should just walk in somewhere with a $50 note glued to my head so that they realise im serious.

[Ronin 09]

Benm, search the threads for 'exhaust' and see if there are any recommended in Perth. I would get a custom dump and front pipe made for your car instead of getting the Nismo one, as it will be heaps cheaper and do as good a job. Because your Nismo cat back is already pretty quiet, the addition of the dump and front pipe shouldn't add too much dB.

Or you could get a premade dump and front pipe from somewhere like Japanese Motorsport, they have stainless dump pipes for 350 and stainless front pipes for 350. Just make sure they will bolt up to the cat converter in the factory position (assuming you have the stock cat)

-cheers m