Engine Design Philosophy

[Matt Suffern]

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
>>>>>
>>>>>
>>>
>>>
>
>