on 5/1/06 4:07 PM, Simon Matthews at simon.d.matthews@gmail.com wrote:
> On 5/1/06, Max Heim <max_heim@sbcglobal.net> wrote:
>> My point about flat fours is that they require twice as many head gaskets,
>> cams, rocker shafts, and intake and exhaust manifolds, as an inline four of
>> the same configuration (OHV, DOHC, etc). When you are talking about 8 or 12
>> cylinders that would otherwise be in a V, there is no difference, but in a
>> small engine like a four that is a lot of complexity (and cost) to add with
>> no corresponding improvement in operational efficiency.
>
> Flat-4s give you better dynamic balance. Modern in-line 4s have extra
> moving parts just to improve dynamic balance (balance shafts) -- so
> there is added complexity in the inline-4.
No balance shafts in our MG motors, though...
>
> As I mentioned, the Alfa Flat-4 engine had zero rocker shafts and only
> 2 camshafts.
Right -- but if it were an inline 4, it would only have needed 1 camshaft.
An inline 4 with 2 camshafts would be DOHC, generally considered more
operationally efficient.
My point is that in a small displacement motor (as all recent fours would
be), the main tradeoff is output/liter vs. cost/complexity. Compared to the
inline four, the flat four adds cost/complexity without improving output. In
a larger displacement engine, one might accept this compromise in the
interest of smoothness, say, but it really seems to me to be a bad choice in
the case of Subaru. The Subarus I have driven have been remarkable for
engine harshness, not smoothness, and I scarcely need mention the VW
aircooled four. This may not have been the case with the examples you
mentioned.
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires
|