exhust ??

[dazzler]

soundz good mate whats the manta exhust and mufflers or?? cause i dont want mufflers i jus want 1 hotdog muffler...and yea a quote fitted would be great cheers

 

[The Hornet]

Not_An_Abba_Fan is the guru.

Anything higher than 2.5" you will just be losing power and will be a droning pain in the ass! 3"+ Should only be for forced induction cars really (power wise) OR High Output V8's. Pretty sure on N/A cars back pressure is quite important (well finding the fine line)

P.S only speaking from experience, could be wrong

No, i belive you are right. Backpressure is good for N/A, maximum flow is good for forced induction. here is a good read (it was in an article on turbocharge cars but has some info on N/A);

Normally aspirated cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.

Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side.”

"As for the geometry of the exhaust at the turbine discharge, the most optimal configuration would be a gradual increase in diameter from the turbine's exducer to the desired exhaust diameter-- via a straight conical diffuser of 7-12° included angle (to minimize flow separation and skin friction losses) mounted right at the turbine discharge. Many turbochargers found in diesels have this diffuser section cast right into the turbine housing. A hyperbolic increase in diameter (like a trumpet snorkus) is theoretically ideal but I've never seen one in use (and doubt it would be measurably superior to a straight diffuser). The wastegate flow would be via a completely divorced (separated from the main turbine discharge flow) dumptube. Due the realities of packaging, cost, and emissions compliance this config is rarely possible on street cars. You will, however, see this type of layout on dedicated race vehicles.

To the OP - I'd be inclined to go with what the above guys say re brand. I never have owned one so can't be of any assistance, i just prefer the sound of sureflow from what i have heard

 

[Not_An_Abba_Fan]

You just contradicted yourself with your quote.

Back pressure is bad under any circumstances. That article is misleading when it is comparing velocity to back pressure. Back pressure can NEVER increase exhaust velocity. In terms of increasing velocity, the key is pipe diameter and heat. As the exhaust gets further away from the engine, it cools down requiring less room to keep the desired velocity. In no way is this similar to back pressure.

If you look at factory Japanese exhausts, they are insulated. Not to protect anything, but to keep the exhaust as hot as possible to induce flow. Another reason why they fail, steel does not like heat, but thats another kettle of fish.

The best exhaust is actually none. The only reason it is there is to keep the combustion noise to a minimum and to get the gases away from the cabin of the car. The most practical exhaust is in the design seen on early Holdens and GM cars, where the engine pipes are larger than the tail pipes.

The price for extractors, twin high flow cats and a twin 2 1/2" system fitted on the VT 5.0L will be $1800.

 

[capitalgainz]

well the crazy cat with what appears to be a m-16, has the name exhaust guru, maybe listen to him, i always thought some back pressure was good in n/a you dont want it in a turbo turbo+backpreasure*extra boost/BOOM!!!=
IF IT WERE ME i would just buy one with out cats unless they bark like the 304 manuals with out cats
its always up to personal preference, some like it loud some tinny some want more power, what do you want? then find the product that suits your needs

 

[The Hornet]

You just contradicted yourself with your quote.

Back pressure is bad under any circumstances. That article is misleading when it is comparing velocity to back pressure. Back pressure can NEVER increase exhaust velocity. In terms of increasing velocity, the key is pipe diameter and heat. As the exhaust gets further away from the engine, it cools down requiring less room to keep the desired velocity. In no way is this similar to back pressure.

If you look at factory Japanese exhausts, they are insulated. Not to protect anything, but to keep the exhaust as hot as possible to induce flow. Another reason why they fail, steel does not like heat, but thats another kettle of fish.

The best exhaust is actually none. The only reason it is there is to keep the combustion noise to a minimum and to get the gases away from the cabin of the car. The most practical exhaust is in the design seen on early Holdens and GM cars, where the engine pipes are larger than the tail pipes.

The price for extractors, twin high flow cats and a twin 2 1/2" system fitted on the VT 5.0L will be $1800.

My bad, i meant to quote the first line