Right....I'm finally gonna put up my hifo cat up...(yes...tufftr, i had it for a year..haha lazy bugger me:D )....anyway I know that the stock pipe on the TS v6 is 2.25". Question is should i borther upping to size to 2.5"? my cat is 2.5 but i asked and was told that its not a problem to fit it up to 2.25" pipe......most likely welding it up.

Any benefits from 2.25" --> 2.5" pipe? Would the sound be louder? (i hope not, current hifo muffer is loud enough)

Performance from just the pipe size major or not?

Any comment is greatly appreciated!!! :bowrofl:

I have read a book called "Maximum boost" a few times over now and one of the best sections is the ehxuast section. It has a simple table outlining the size of pipes and what sort of HP they can flow before they start to make a measurable decrease in power.

2.5" with 1 muffler, propper headers and a resonator or two is still capable of flowing 420hp.
2.25 with 1 muffler, propper headers and a resonator or two is still capable of flowing 380hp.

The only thing that could matter is the stock design of the pipes and if they are press bent. Change in diameter of the piping does cause the majority of the restriction, so mandrell will always be the best bet.

That said, I would upgrade your muffler to a sports unit, but make sure it has baffels and sections. I would then get them to cut out your mid muffler (if you have one) and replace it with just straight pipe.

That way you get a nice note, but its not overbearing, and if its a little too loud you can fit a sports resonator later down the track.

Unless you can get a cheap mandrell system and make it 2.5", I cant see the point in putting a dodgy exhaust shop press bent system on. Their machines generally dont try maintain exhaust pipe diameter at all and they never use spring like they should :doubt:

420hp for 2.5" exhaust eh? Interesting.

I think the answer to your question is, how much money do you wanna spend? And how much do you care? I realise I've just answered a question with 2 more questions, but just think about those for a bit. A full 2.5" exhaust system will probably cost you anywhere from $500-$800, and the gains probably won't be a lot unless you have a host of other mods done to your car. It'll certainly feel punchier, drive better and have a nicer note to it, but peak power will probably only gain 5-7kW. If you're gonna put a 2.5" high flow cat on there, and you have the money, definately go with a full 2.5" system. Otherwise, leave it go for a while and if you're not happy, then upgrade.

I think 6 of the possible 7kw gain is muffler and resonator replacement Disiple, saying that the extra .25" of piping does SFA.

It will make it louder for no peak gain, but that is also what some people like. Its the same with pod filters.

I think 6 of the possible 7kw gain is muffler and resonator replacement Disiple, saying that the extra .25" of piping does SFA.

It will make it louder for no peak gain, but that is also what some people like. Its the same with pod filters.

Thanks all for the comments......I already have a hifo sports muffer up and even bought the mendel bents themselves(anyone wants to buy?:D )....think what i would do is most likely just put up the cat convertor and maybe do something about the 'hotdog' behind the muffer.

If i was to take away the resonator behind the muffer and put in just a straight pipe, it would just turn out tobe louder right? I seriously dun want the exhuast tobe any louder? any benefits changing the resonator to a new 'hifi' one?

Hey i thought the standard pipe on the TS v6 was 1.75.. not 2.25! i just moved up from standard to 2.5.. and its much larger piping...
but 2.5 mandrel won't do much difference unless you rev out to 4500-5000rpm every shift..

Don't they always say bigger is better? :bowrofl:
TS V6 i reckon you could get away with the 2.5". Any bigger = loss of backpressure. I reckon the note would sound deeper on the 2.5 too. But i could be wrong.

Backpressure is a myth. The reason why people with massive exhausts feel drops in power is due to the loss in flow velocity. An ideal exhaust would have high velocity gasses and 0 gauge pressure.

Also if you were going to get a new exhaust made up, I'd probably recommend getting a press bent one over a mandrel bent. Mainly because most exhaust places buy in mandrel bends and then weld them onto straight piping, this leads to welding dags on the inside of the pipe. On a press bent exhaust there will be a slight decrease in the pipe diameter, but this generally isn't as big an obstruction to flow as the welding dags are in the mandrel bent.

backpressure is no myth, talk to any drag car builder about how crucial it is to have the headers the right size, they actually have cones inside the headers that reduce diameter to help suck the exhaust out.
On a 2-stroke engine the expansion chamber in the exhaust and the muffler actually create backpressure which is the only way the exhaust port will work properly.

As far as welding dags go, if the welder knows what he is doing there will be very minimal dags on the inside. As they can set the welder to just the right amps. When you weld it uses a shielding gas on the immediate area of the weld. However the inside of the pipe is not shielded therefore if the weld penetrates the steel oxidises immediately and becomes very brittle.. These dags will blow out with minimal effort once the exhaust is fitted.
Most systems are mild steel and usually Mig Welded. However on a Stainless system (like the one im making for my rx7 atm) it is more common practice to Tig Weld, and if u really wanted to you could Purge Weld it. Purging involves filling the inside of the pipe with its own supply of shielding gas which stops the weld oxidising and the weld on the inside actually looks the same as the weld on the outside.

Also im not sure about 3rd gens, but the 2nd gen exhaust runs over the rear suspension arms which involves alot of tight bends, so a pressbent system can be quite restrictive.

What those drag racers are actually doing is using the venturi effect (http://en.wikipedia.org/wiki/Venturi) to enable exhaust scavenging. The venturi effect is a case of Bernoulli's principle, which states that for a rise in pressure there is a drop in velocity, and vice versa. So just after the neck of the cone there would be a region of low pressure, increasing the velocity of the exhaust gasses. The kinetic energy of these gases makes them continue into the subsequent higher pressure area, creating a vacuum behind them.

In a normal car though the extractors are designed to do this by utilising exhaust pulses. Therefore the 'tuned' section of the exhaust is the critical part. After that the lower the backpressure, and the higher the velocity the better. Although due to the changes in mass flow rate as rpm rises the exhaust can only have a maximum efficiency at a certain rpm. Just like pretty much every other component in an internal combustion engine.

Is the TS v6 stock pipe 2.25" or 1.75" across the pipe is only about 4.5cm or do you measure around the pipe?

Is the TS v6 stock pipe 2.25" or 1.75" across the pipe is only about 4.5cm or do you measure around the pipe?
Well 4.5cm isn't even 2 inches. It's about 1.75".