Rb26 Aftermarket Exhaust

[Deano 1]

i got Xforce dumps, BeeR fronts, high flow cat, and a kakimoto catback. Steel Wheeled N1's making just over 300awkw.....

[rob82]

An exhaust is only as good as the miniumum flowing section. I still believe that the front half of the exhuast is the most critical tho - esspecially the merge into the Catalytic converter. The air the exits from the turbine housing imparts I would think at least 30percent of its motion onto the walls of the exhuast due to the spiral action of the gases. The problem is when it gets to the catalyst is that the air has to straighten out to pass through it and the majority of the exhuast gases are acculumated at the outer edge of the cat.

A well designed exhuast will not only flow well but will hopefully reduce the exhuast valve temps. I would think that catalyst in an aftermarket exhuast would be moved further down stream to allow for the exhuast gases to straighten - this however for manufactures means that the catalyst will take longer to get up to operating temps - which is highly unwanted. And when it comes to catalyst size bigger is allways better - wait till you see the size of C63 AMG cats, they are about 7" 400cell on each bank.

[BeEnAr]

yeah but when the new season starts it's going to be a little different. Super 2000 rules will come into effect soon which means N/A 2L engines that rev out to near 9000 RPM, thing is that for WRC they are going to be running 1.6L Turbo engines instead, so basically it'l going to be crap! Ford Vs Citroen and engines that are basically the spec of 1987!

[juggernaut1]

Here's another link re exhaust systems.....as they relate to WRX's....... but may have applications to turbo cars in general.

http://www.msengineering.com.au/exhaustsystems.html

...and a couple of interesting quotes from the link on the matter of using bends and smaller tailpipes in the system to help midrange.

Using an S bend leading into the rear muffler via 2 90degs back to back offers the most torque in the mid range, reducing the angles from 2 x 90 degs to 45 degs moves peak torque up through the rpm, using almost straight pipe with angled muffler provides and very linier power band, smooth delivery of power with no "kick" as a result from noticeable losses in torque in the mid range. The S bend has a huge bearing on torque in the mid range, after consulting with Prodrive they verified this for me, a straight pipe might see more top end power, but the loss of low down out weighs the gains.

Also changing the rear tail pipe section from 3" to 2.5" helps torque, using 2.5" rear mufflers greatly help mid range with gains on WRX/STI set ups. Pressure at the turbo is not effected with this and helps to keep gas speed up for better power.

Edited May 1, 2010 by juggernaut1

[xrotor]

i was running a 5 inch no cat straight through ,trust front pipes pushing 400awkw and changed to 3 1/2 nismo cat back and hi-flow cat and this made jack all difference (2kw). The major difference is i dont need to wear ear muffs now .

I think its quality of the system rather than outright size, thats what my missus tells me anyway?