[Diy_efi] Throttle body size

[Eric Byrd]

Excuse me, Paul,

But in my experience, erroneous sweeping generalizations offered as
advice occur so often, and from such presumably trustworthy and expert
posters as yourself, that only the correction is appropriate.  The
sarcasm, and the rebuke, are not necessary.  The fact that all the
experts put together in one room could not agree on any but the most
simple issues leads us to one conclusion:  this is a forum for
discussion, and discussion occurs, and any "advice" offered should be
accorded only conditional credibility by *any* reader until they can
corroborate it more reliably.  Hence the old cliche, "don't believe
everything you read."  I certainly don't, although I consider this forum
to be wonderfully informative.  I am, however, getting tired of running
into guys without a very healthy perspective, guys who don't yet realize
that hostility or self-righteousness is utterly pointless, worthless,
inappropriate on a forum of this kind.  I wish it could go without saying
that communication, especially written communication, is fraught with
dangers of misunderstanding.  I am tempted to say, "Grow up," but that
would be unnecessarily harsh.  I honestly don't want to insult you.  But
I wish you, and other guys here prone to hostility, would get the point
finally.

On Fri, 13 Dec 2002 09:44:39 EST Tlsalt at aol.com writes:
> Eric Byrd wrote,
> 
> The SDS folks I just got done reading from their site say this about
> throttle bodies:  if the vacuum taken off the MAP sensor is higher 
> at
> full throttle than at idle, your throttle body is too small.
> 
> I found out some more info.  An engine needs 5.7 cc/min of fuel per 
> hp. 
> 
> 
> Hello Eric,
> 
> Read that again......another impossibility.  MAP sensors read 
> manifold 
> pressure, vacuum in an NA engine.  Just what kind of engine could 
> have higher 
> vacuum at WOT than when the same engine is sucking against a closed 
> throttle 
> plate?  No chance. What they mean is if vacuum start climbing after 
> reaching 
> a minimum at WOT under load.
> 
> The amount of fuel an engine needs is not 5.7cc/min per hp.  It 
> varies for 
> every engine and is the BSFC.  How much ?  Engines from the same 
> manufacture 
> can vary by as much as 18% (high comp Heron vs low compression Hemi) 
> and 
> there are no accurate sweeping generalizations about BSFC. In fact, 
> most of 
> these subjects are far more complicated than you suggest.
> 
> I'd speculate that the main reason some Hondas are less detonation 
> prone is 
> not the bore size, it is the design of the combustion chamber at and 
> near 
> TDC. The difference in distance is very small on these little 
> engines. There 
> are plenty of small bore detonation prone designs.  Small bore 
> engines with 
> large, open combustion chambers (like Hemis), that need tall piston 
> domes to 
> have decent compression ratios, are very detonation sensitive. Their 
> 
> combustion chambers at TDC are long thin crescents.  Many Hondas 
> have small, 
> compact combustion chambers, with almost flat top pistons and are 
> much less 
> sensitive.
> 
> I agree, speculation is not a crime, but offering erroneous, 
> sweeping 
> generalizations as "advice" on this list should elicit some 
> response.  What 
> ever happened to Bruce ?   I'm sure he would have something to say 
> about this 
> subject........
> 
> Paul
> 
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> 


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