Here is a Summit Racing tutorial on choosing tube diameter.
http://www.youtube.com/watch?v=c7PfOXP2Vf0
http://www.youtube.com/watch?v=c7PfOXP2Vf0
Stahl Headers
- Thread starter m5bb
- Start date
Bob,
that was a helpful piece of information - when you apply the formulas on summit video - here's what comes up for maximum torque RPM based on a given primary tube diameter. Remember, this is peak torque RPM, HP moves beyond that.
1 3/8" 1 1/2" 1 5/8"
2.8L 3933 4779 5667
3.0L 3671 4460 5290
3.5L 3147 3823 4533
To further what that says, if you want a flatter torque curve (more low end) approaching the peak torque RPM ... use a longer primary tube. if you go with a shorter primary tube, then you will extend the flatter torque curve to the higher RPM side of the curve (with less low end torque).
that was a helpful piece of information - when you apply the formulas on summit video - here's what comes up for maximum torque RPM based on a given primary tube diameter. Remember, this is peak torque RPM, HP moves beyond that.
1 3/8" 1 1/2" 1 5/8"
2.8L 3933 4779 5667
3.0L 3671 4460 5290
3.5L 3147 3823 4533
To further what that says, if you want a flatter torque curve (more low end) approaching the peak torque RPM ... use a longer primary tube. if you go with a shorter primary tube, then you will extend the flatter torque curve to the higher RPM side of the curve (with less low end torque).
Mike Goble
Well-Known Member
Which brings up the age-old question - how long is long? Which length header will accentuate the curve at the torque peak? What size collector should you use? How far behind the primary collector should you join the secondary pipes? When you compare V8 headers to M30 headers there is a difference in the timing of the scavenging pulses. In a V8 the pulses are not evenly spaced in the collector, 270°, 180°, 90° and 180°. You can get true 180° headers by crossing two primary tubes from side to side. In an M30 they appear every 240° evenly spaced.
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long basically goes down to where the exhaust turns parallel to the road. that's the way the e30 m3 headers worked - even the gruppe A race headers, so did all of the motorsport designs.
the medium length header is about half to 3/4 down ... and the shorties are less than half the distance down - they're just a wad of spaghetti at the top - a little deeper than a stock manifold.
actual length - no clue.
the medium length header is about half to 3/4 down ... and the shorties are less than half the distance down - they're just a wad of spaghetti at the top - a little deeper than a stock manifold.
actual length - no clue.