View Single Post
RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,423
Garage
Quote:
Faced with these problems, most engineers turn the dial the other way and make the manifold as short and small as possible, abandoning equal length. In this way the thermal losses and volume are minimized.
That is the easy and cheap way out. It is a matter of returns and effort/time per dollar. The significance of any gain has diminished returns as the effort to get that gain is increased.

There is also the consideration of long tubes vs short tubes when it comes to equal length. Reducing the total header volume while retaining equal length primaries has its merrits in the proper application. This is more commonly seen more in the twin turbo systems than in the single turbo systems, largely due to cost. Optimal header design is application specific. For the stockish 930 masses unequal length short tube 304 headers are the norm. That makes them the best compromise for the dollar that folks are willing to spend, it does not necessarily make them the best design for the application.

In the above Saab example we need to see what the OEM and aftermarket systems look like. The aftermarket system could be a miss-match while the OEM system is designed quite well for that engine.
__________________
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 01-09-2010, 06:46 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)