Engine Design Philosophy

[robert weinberg]

timing belts are usually used in high-revving DOHC engines like the 3B and AAN. chains are heavier and have more rotating mass. the 525 I6 engine is not a super high revver compared to the 3B. stock is 7,400 rpms until fuel cutoff i believe and the little bastard will spin 8500 without much drama. thought it's sorta pointless with the stock intake manifold (it won't make much power up there).

BTW, just took the 200q20v to get smogged. passed with flying colors in cali. man, i should really drive the car more, but i just don't feel like sitting in the pouring rain, in the dark, in traffic on my daily 60 mile commute. let the old girl enjoy her weekends instead ;-)

one things for sure, it sure is a hell of a lot faster than a 2008 Jetta SE (my 200 is chipped, of course ;-)

see ya,
Robby



________________________________
From: Matt Suffern <msuffern at gmail.com>
To: Tony Hoffman <auditony at gmail.com>
Cc: 200q20V mailing list <200q20v at audifans.com>
Sent: Monday, November 14, 2011 4:55 PM
Subject: Re: Engine Design Philosophy

Tony,

Thanks for the input.  I didn't even think about the weight issue, but
I suppose you want to have as little weight as possible on the nose of
the engine when the whole engine is hanging out in front of the axle
line as is.  Good point.

-Matt

On Mon, Nov 14, 2011 at 5:27 PM, Tony Hoffman <auditony at gmail.com> wrote:
> Obviously there are a lot of design parameters that go into these sort of
> decisions, but here are some to ponder:
>
> You hit on one, less maintenance,
> Smaller, as in shorter. This is probablyl a bit key part of the BMW design,
> as the inline 6 is already a lot longer than most other engine designs
> Noise
> Weight
>
> BTW, Audi put a timing chain design on their V8 to fit it in the B6/7
> chassis for the S4. This was because it would not fit with the belt design.
>
> Tony
> (who prefers belts, but understands they have to be changed)
>
> On Mon, Nov 14, 2011 at 2:38 PM, Matt Suffern <msuffern at gmail.com> wrote:
>>
>> No point.  I just found it interesting that to perform essentially the
>> same job, Audi chose a seemingly-flimsy rubber belt whereas BMW opted
>> for a beefy double-row (duplex) chain, and was pondering the engine
>> design philosophies that might have prompted the automakers to go
>> their respective routes (especially since BMW's M50 is the successor
>> to their M20, which DOES use a timing belt).
>>
>> I suppose I was going for an open-ended technical discussion more than
>> anything else.
>>
>> -Matt
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