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Differential ratio fun

Got the information pack for the new 5 series the other day (you can
request it from BMWs WWW page), most revealing.

I'd known for a while that there is only a 10-15% difference in output
beween the new 2.5 and 2.8 engines so why is there such a difference
in acceleration. Now I know, the final drive ratio on the 523 is
taller than the 528, something like 3.15 vs 2.93 (from memory).

Strikes me that putting the differential from the 2.8 into the lowly
2.3 would close the difference between the two cars in performance
terms quite considerably. This is doubtless a marketing ploy by BMW.

Of course the same is true of the 325iS vs 318iS. For driving <90mph
(the only kind I really do) it seems a shame to compromise accelaration 
by giving the 325i a taller final drive ratio. Anyone care to comment
on my (probably wrong) supositions?

I'm not impressed by the addition of a glass sunroof option, doesn't
seem right somehow. Was surprised to see it cost >300 GPB more than a
plain steel sunroof!
- --
"It is better to remain silent and be thought a fool than to open your
mouth in a meeting with the users and prove it." (Ancient programming proverb)

NB: As I am a gibberring idiot any views expressed here are NOT the views
of Stolt Comex Seaway Ltd. john@domain.elided, Aberdeen, Bonny Scotland