Turbo header design

[Jemison Richard]

Fred,

Well, I've got 4 XS1100s and they definitely get a punch from the 180 design
(95hp) stock.  And this was 20 years ago.  The uneven torque helps when the
surface doesn't allow an even transfer of power (like dirt tracks for
instance).  Then the uneven machines have a definite advantage as the lull
between strokes helps the tire 'grab' the track again.  

On the 1100's though you don't notice any uneven firing.  2 cyl up each
power stroke but only one is on the power stroke.  The result is smooth
power pulses.

Like I said, Saturn uses the same basic setup right down to the ignition!
Can you swap them?  Well, not easily due to the fact the Saturn coils are
wired to run to a power control module which talks in turn to the ECM.  On
the Yamaha it is cruder.  But with proper wiring solutions, the coils would
work fine on a Yamaha.  What's more intriging, the fuel injection manifold
sure looks close to fitting the XS!  Nah, thought about it but have decided
on a custom fab unit.

Rick

> -----Original Message-----
> From:	FHPREMACH at aol.com [SMTP:FHPREMACH at aol.com]
> Sent:	Friday, January 08, 1999 8:46 PM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	Re: Turbo header design
> 
> 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