Turbo header design

[Gary Derian]

Ultimately, it is best to merge all the exhaust tubes into a single muffler
(even if two pipes lead into it and out of it) to  raise the frequency of
the sound (the same effect as a balance tube).  The high frequency sounds
smoother and also is easier to silence, meaning less backpressure for a
given noise level.  I think it is typical for Hi-Po foreign V-8's to have
two into one cast iron manifolds with two downpipes that in turn merge into
a single cat for each side.  Alternately, having four smaller cats, one at
the first merge, gets the cats closer to the engine.  Today's cars have
their exhaust systems designed first for quick cat lightoff, then for
performance or cost.

A standard crank V-8 has a rotating couple (front pushes up while the rear
pushes down) of constant magnitude that is in the same direction as the
crank rotation.  This is easily counteracted by weights at the front and
rear of the crank.  Ever notice that the crank weights on the ends are not
opposite the journals?  The offset angle is 18 degrees.  These weights
cancel the rotating couple imbalance.

A flat crank is like 2 4cyls and each bank, as Greg indicated, has a
vertical shake at twice engine speed.  Placing two banks at 90 deg, each
with a vertical shake, results in a rotating force, but not a couple,  at
twice the engine rpm.

Obviously, every manufacturer but Ferrari, whose largest V-8 is 3.5 liters,
has chosen the 90 deg crank route for their V-8's.  It is my opinion that
the tri-Y setup on a 90 deg crank V-8 gives up very little if any to a true
180 deg exhaust for street engines.

Gary Derian <gderian at cybergate.net>
>
>>A reasonably close approximation to true 180 deg. headers can be made with
>>the old tri-Y approach.  As Aaron wrote, true 180 would require merging
>1-6,
>>8-5, 4-7, 3-2 which is difficult to make.  Merging 1-5, 3-7, 4-6, 2-8
>>enables cylinder pairs to share an exhaust pipe without interfering and is
>>relatively easy to build.  This is common in high output European and
>>Japanese V-8 engines.
>
>Do they have 4 exhausts exit the car? Or are there collectors further
>downstream to make it duals or a single?