View Single Post
Old 06-19-2012, 06:18 PM   #15
Senior Member
Jason@Nameless's Avatar
Join Date: Jun 2012
Drives: '88 BMW 535is Turbo
Location: La Center, WA
Posts: 287
Thanks: 119
Thanked 822 Times in 156 Posts
Mentioned: 52 Post(s)
Tagged: 0 Thread(s)
Originally Posted by icemang17 View Post
sweet header!!!!

I also think a torque increasing header is a great idea....the high flow exhaust and intake will increase top end power.....the ideal powerband for racing (track) is 4500-7000 or so....unless you need 2nd gear, then it would be 7400 (redline)...
Intuitively I think that a good design (ie equal length and routing) would offset the possible small losses in a smaller stepped design. So far it is the direction I'm leaning. Either a 1.5-1.625 or a triple step 1.5-1.625-1.375. Biasing peak HP at 6000rpm our software said 1.375-1.500-1.625!!! 7500 it indicated 1.500-1.625. But we're doing a few major assumptions on camshaft profile as well as lift, which no-one has at this point. I got the valve sizes, I talked to the guys at Brian Crower to discuss what their thoughts were given their experience with naturally aspirated Subarus and we made the best guess for the information we had on hand. I've searched every FSM and had our contacts at 2-3 major dealerships help in that search and found nothing.

We also used the other data available: What the factory used. While I doubt a lot of the factory's reasoning for a lot of their design concepts, header diameter doesn't have any 'reason' to change the bias for economy or engine behavior for the most part. Now, why they ran an unequal length design (32% variance between Y lengths) from the factory when they could have accomplished exactly what we did is beyond me...but then again, Subaru sends the US insanely unequal length headers for the STi and the JDM model gets EL header w/ Twin Scroll turbo.

Jason Griffith
Engineering Director
Nameless Performance, Inc.
Jason@Nameless is offline   Reply With Quote