Turbo header design

[Jon Fedock]

Thanks for the information. I have visions of header tubes criscrossing
under everything I own now :).

Jon

-----Original Message-----
From: Greg Hermann <bearbvd at sni.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, January 08, 1999 12:35 AM
Subject: Re: Turbo header design


>>
>>    Care to elaborate on this a little? Are we talking about crank
vibration
>>(hamonic balancer/flywheel) or something else over my head? Also, a Chevy
>>V-8 fires every 90 degrees of crank rotation. How does a flat crank V-8
>>fire? Every 180 degrees would make sense, but then it would take 4 turns
of
>>the crank to hit all 8?! I am so confused......
>
>Secondary vibration, due to the fact that piston accelerations are
>different at the top and bottom of the stroke due to con rod angularity. A
>four cylinder has an up and down shafing force at twice crank speed (which
>is sometimes countered fairly well with two "balance shafts" counter
>rotating at twice crank speed.) A flat crank V-8 is like two fours.  Too
>late at night to try to describe the shaking which results. A 90 degree
>crank V-8 is not in perfect primary and secondary balance, as Gary claimed,
>but it is close. An in line 6 has inherently PERFECT primary and secondary
>balance. Only reason for crank sounterweights inna 6 is to reduce bending
>stress in the crank and block.
>
>Tertiary balance is another matter--it has to do with connecting rod mass
>distribution, and is generally accepted as being not too significant.
>Efforts to obtain/improve it explain the long tangs sometimes seen
>projecting above the small end on a connecting rod, and also the rather
>large pads often seen on the bottom of the big and cap of rods.
>
>Why the Super speedway headers sound so neat (as also did Ford Mark IV's
>and Ford's four -cam Indy V-8's) is cause the individual exhaust pulses
>into each of their two collectors are EVENLY SPACED (180 crank degrees
>apart) , from whence the name. You cannot get that on a V-8 with a 90
>degree crank without crossing tubes from side to side (bank to bank) to the
>collectors. You do get it with a four into one header on each bank (without
>crossovers) on a V-8 with a flat crank.
>
>Regards, Greg
>
>
>