[Diy_efi] Throttle body size

[arnie]

Bruce relinquished his membership some time ago.  Bruce had a way about him,
but ya have to hand it to him, he is very knowledgeable and showed it on
this list.  Heaven only knows how he would have responded to some of Eric's
posts.  :)

> but offering erroneous, sweeping generalizations as "advice" on this
> list should elicit some response.

Oh, it has.  :)

GAS


----- Original Message -----
From: <Tlsalt at aol.com>
To: <diy_efi at diy-efi.org>
Sent: Friday, December 13, 2002 8:44 AM
Subject: Re: [Diy_efi] Throttle body size


> 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



_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi