Engine Design Philosophy

[Matt Suffern]

That's fair.  I am cosmetically-biased.  :)

Interesting observation about the included valve angle—I didn't think
of that.  Any reason why Audi didn't widen the angle so they could fit
a pair of cam gears up top?  Didn't want a heavier, bigger head?
Wanted to use existing timing belt hardware on the block?  All of the
above?

-Matt



On Tue, Nov 15, 2011 at 12:24 PM, Bernie Benz <b.benz at charter.net> wrote:
> Your terms “flimsy” and “beefy” show a cosmetic bias on your part, not a
> design preference, IMO. The only reason for the chain between cams is that
> the two valve banks are to close together to use a single belt or chain for
> both cams. If the included valve angle between the two rows were 90 degrees
> a single belt or chain could drive both in a much more flexible, modifiable
> drive.
>
> Bernie
>
> On Nov 14, 2011, at 12:38 PM, Matt Suffern 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
>>
>>
>>
>> On Mon, Nov 14, 2011 at 3:32 PM, Bernie Benz <b.benz at charter.net> wrote:
>>>
>>> Thought you were trying to compare chains to belts.
>>> If the chains are of the same basic design excepting for width (single
>>> vs.
>>> double) the drive from the crank requires twice the torque (chain
>>> tension)
>>> as does that of a single cam. Is this your Q? And if so, what‘s your
>>> point?
>>>
>>> Bernie
>>>
>>> On Nov 14, 2011, at 11:44 AM, Matt Suffern wrote:
>>>
>>>> The context of the original e-mail:  Single- vs. double-row chain.
>>>>
>>>> -Matt
>>>>
>>>>
>>>> On Mon, Nov 14, 2011 at 2:37 PM, Bernie Benz <b.benz at charter.net> wrote:
>>>>>
>>>>> Row what?
>>>>>
>>>>> On Nov 14, 2011, at 10:48 AM, Matt Suffern wrote:
>>>>>
>>>>>> That would be single- vs. double-row.
>>>>>>
>>>>>> -Matt
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Nov 14, 2011 at 1:47 PM, Bernie Benz <b.benz at charter.net>
>>>>>> wrote:
>>>>>>>
>>>>>>> Please explain your meanings of simplex vs. duplex in this respect.
>>>>>>>
>>>>>>> Bernie
>>>>>>> On Nov 14, 2011, at 8:21 AM, Matt Suffern wrote:
>>>>>>>
>>>>>>>> Someone explain this to me.  Looking through the parts catalog I
>>>>>>>> study
>>>>>>>> the valvetrain diagram for the 3B.  I notice Audi has retained a
>>>>>>>> timing belt design with a simplex chain to link the exhaust camshaft
>>>>>>>> with the intake.  My BMW 525's M50, by contrast, has a duplex timing
>>>>>>>> CHAIN with, again, a simplex chain linking camshafts.
>>>>>>>>
>>>>>>>> Both engines can last upwards of 300K miles.  So why the overkill on
>>>>>>>> BMW's part?  Four more valves to operate (1 more cylinder)?  Or did
>>>>>>>> they just assume people aren't going to do regular maintenance like
>>>>>>>> timing belt changes?  It just seems like an awful lot of added
>>>>>>>> complexity and valvetrain inertia to avoid a procedure most people
>>>>>>>> assume is going to have to be done anyway.
>>>>>>>>
>>>>>>>> Curious.
>>>>>>>>
>>>>>>>>
>>>>>>>> Matt
>>>>>>>> Winston-Salem, NC
>>>>>>>> www.spannerhead.com
>>>>>>>> _______________________________________________
>>>>>>>> 200q20v mailing list
>>>>>>>> http://www.audifans.com/mailman/listinfo/200q20v
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>
>>>
>
>