Turbo header design

FHPREMACH at aol.com FHPREMACH at aol.com
Sat Jan 9 01:47:10 GMT 1999


In a message dated 1/8/99 9:47:24 AM Pacific Standard Time, JemisonR at tce.com
writes:

<< I don't know the in's and out's of this 180 degree situation but as a frame
 of reference, the Saturns use a 180 degree crank, 2 coils, fire 2 injectors
 at a time, etc.  Runs dead smooth.  
 
 Rick >>
Yes, it is true that four cylinder motors use flat cranks, BMW twins run them
and a host of other uses. They equal power pulses. Triumph Twins used a a
single throw crank and suffered from lots of interesting balance problems when
they were raced, some experiemtation was done with opposing throws, but it
went to a 90/270 firing order. Actually better on slick tracks or with tire
restrictions, but sounds strange and a lot of trouble to do. I raced one of
the few ones locally that didn't try to shake apart. Ran about 78% total
weight for balance. Full weight flywheel helped. Flat cranks on V8's are
another matter, they treat the motor as two nested straight 4's. As a note
Chris Craft in England was making a V8 from two Yamaha 1100's on a 90 degree
crank case. Used Carrilo rods and custom crank. Never heard a price. Used all
stock parts from the base gasket up and made great power.
A note about uneven firing and such. Harley and Ducati have had advantages
over other bikes at times in racing. Harley's uneven power pulses allowed the
tires to plant better betwen pulses. Ducati twins were better off the corners
than the fours for the same relative reason. Some of the Japanese racing two
stroke fours were set up to pair the power strokes for the same reason. more
of a tractor torque instead of a jet. Didn't affect dyno HP, just
tractability.
Fred



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