Re: 5 bangers galore

[Eliot Lim <eliot@u.washington.edu>]

On Thu, 10 Nov 1994, Bruce Bell wrote:

> >from Carl DeSousa
> >I think it was brilliant of Audi to use another cylinder to balance
> >the motor instead of adding a balance shaft. 
 
> Is this true? Don't I remember something from the 70's about the 5 cyl being
> more dificult to balance from a design point of view? You know fireing order
> crank design etc. Remember in a 4cyl. you get two bangs each revolution. A
> 5cyl alternates between 2 and 3 firings each revolution. So just think half
> the time were driving a 4cyl and the other have weve got a 6cyl. 

the 5 banger has its cranks spaced 120 degrees apart and it does fire
evenly.  it is perfectly balanced in terms of the 4 modes of
vibrations that people normally look at.  the inline 4 is not balanced
in the mode of vibration known as the secondary couple.  but as i've
said, the 5 shakes longitudinally and this is absorbed by soft engine
mounts.  


eliot