Quote:
Originally Posted by cdigerlando
I looked at the setup http://www.full-race.com/catalog_ima...fold-5_jpg.jpg
I don't really see how this would layout would translate to a 6 cylinder twin scroll compressor housing application, but it would seem to me the best and easiest way to mimic this on a 6 cylinder would be to use the stock manifolds and run two equal length headers to the turbo. Would probably require a special fitting to properly plumb the two pipes into each scroll of the turbo to keep the lines separate. |
That picture was just to show how the pulses are kept separated as long as possible before going through a collector. Doesn't matter if it's a Subaru flat 4 turbo, or a Porsche flat 12 turbo. The benefit of a divided housing is to keep the exhaust pulses isolated from one another as long as possible before the turbine. This delivers more energy to the turbine for faster spoolup. The EG33 stock manifolds will not work well for this as they mash the exhaust pulses together too soon to be effective in any sense in a twin scroll housing. Plumbing the exhaust from the OEM manifolds into a divided housing would just be a restriction and more than likely reduce power on the top end. You need to separate the pulses longer to make the system effective and use all the benefits of a divided setup. That's the reason why the FR twin scroll setup in the picture you linked to pulls each pair of runners from opposite sides of the head as the firing order of an EJ25 is 1 3 2 4....again keeping the pulses separated as long as possible(cylinders are grouped as 1+2 and 3+4).
Another thing to remember with a twin scroll manifold design is the primary diameter is normally smaller than that of a standard housing setup as you're looking for exhaust velocity and low expansion until the exhaust reaches the turbine. Using a typical primary size of a standard setup and you'd lose that velocity, gaining nothing in the end. If you're going for all out power a divide housing is not in your best interest. If response is your game, so is twin scroll.
You most definitely can use the OEM manifolds for a standard turbine housing though and I'd go that way as it's cheap and easy and the reversion in those manifolds has been "tuned" by subaru's R&D. No need to mess with that too much. Just match an appropriate A/R and turbine to your needs and you're set.