Engine Design Philosophy

[Mike Sylvester]

Also to keep the total engine height down.
A large cam belt gear on the intake cam would add additional height to
the engine.

Mike

www.urq20v.com

> -------- Original Message --------
> Subject: Re: Engine Design Philosophy
> From: Bernie Benz <b.benz at charter.net>
> Date: Tue, November 15, 2011 1:20 pm
> To: Matt Suffern <msuffern at gmail.com>
> Cc: 200q20V mailing list <200q20v at audifans.com>
> 
> 
> Combustion chamber design likely a factor.
> 
> On Nov 15, 2011, at 10:13 AM, Matt Suffern wrote:
> 
> > 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
> >>>>>>>>
> >>>>>>>>
> >>>>>>
> >>>>>>
> >>>>
> >>>>
> >>
> >>
> 
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