more exhaust sorry :)

[richardpalinkas]

hey people, was doing my research and worked out the area of each exhaust pipe. now ive heard that a twin 2.25 into a 3 is the best. im just curious as to the mathematical reasoning is? wouldnt it be better to just go a single 3 inch to keep it consistent?

2.25" dual exhaust = 7.95 inches square
3" single = 7.07 inches square
2.5" dual exhaust = 9.82 inches square

if anyone can clear it up that would be appreciated.

[impulsesv6]

from the magnaflow website
PIPE DIAMETER AND PERFORMANCE
Use the guide below when calculating pipe size for custom exhaust work. Keep in mind that the goal is to improve exhaust flow. In most cases, just changing the restrictive OEM muffler and replacing it with the same size straight-through, Wide Open Performance MagnaFlow muffler will do this job.

To reduce additional backpressure, the OEM exhaust tubing can be replaced with madrel-bent tubing of the same size or one size up from the OEM. As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4- to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.



Bigger is not always better.


Muffler Inlet / Outlet Size
Engine Size.........Horsepower.........Single Exhaust.........Dual Exhaust
150-200 CID........100 to 150.............2" to 2-1/4"...................2"
200-250 CID........100 to 200..........2-1/4" to 2-1/2".........2" to 2-1/4"
250-300 CID........150 to 250.............2-1/2" to 3"............2" to 2-1/2"
300-350 CID........200 to 350.............2-1/2" to 3".........2-1/4" to 2-1/2"
350-400 CID........250 to 550................3" to 4"...............2-1/2" to 3"
Use as a general guide for engine size and performance.

[richardpalinkas]

what the CID of the alloytec, sorry if thats a stupid Q?

[Dz811]

about 220-225 CI

[richardpalinkas]

about 220-225 CI

cool thanks for that

[Not_An_Abba_Fan]

hey people, was doing my research and worked out the area of each exhaust pipe. now ive heard that a twin 2.25 into a 3 is the best. im just curious as to the mathematical reasoning is? wouldnt it be better to just go a single 3 inch to keep it consistent?

2.25" dual exhaust = 7.95 inches square
3" single = 7.07 inches square
2.5" dual exhaust = 9.82 inches square

if anyone can clear it up that would be appreciated.

As the exhaust gas moves away from the engine it cools down and takes up less space. If you kept the pipe size constant through the whole system, the gas would slow down as well and each pulse would bank up against the pulse in front of it, this creates unwanted back pressure. To keep the exhaust velocity up, you reduce pipe diameter as you get further away from the engine.

Twin 2 1/4" at the start gets the gases flowing nice and fast, as they exit the mufflers they are cool enough to warrant reducing pipe diameter. You could reduce it down to twin 2" after the mufflers but it wouldn't be the most effective.

Going to a single 3" serves two purposes. One, it reduces overall diameter, and two, it combines the exhaust pulses from each bank effectively doubling your scavenging effect. As a pulse enters the 3", it will create a low pressure point in the collector where the other side comes into it. This will "suck" the pulse from that side along with it. The reduced diameter from twin 2 1/4" to the single 3" keeps the velocity up and helps draw the exhaust pulses along behind it.

[zig_zig69]

hey Not_an_abba_fan im really keen on this exhaust set up you have been talking about i tried sending you a pm but it said something about you having to much mail im not sure if im doing something wrong if you could shoot me a pm that would be great im from melbourne and just wondering how much it would be sent including postage i have a vz berlina 175 by the way

[Not_An_Abba_Fan]

PM sent....