AFM measurement/backpressure

[Bernd Felsche]

Mike writes:

>At 07:58 AM 10/3/2000 -0700,  bearbvd at cmn.net (Greg Hermann) wrote:
>>>A little EGR and you need to retard a little more over some threshold
>>>and oyu need to advance again. I remember something in SAE about this
>>>but it was almost 20 years ago and my memory is dynamic ;)

>>What you are really saying here is that IF you have poor fuel atomization,
>>a little bit of EGR helps it, and thus speeds up the burn, but after the
>>atomization is helped, then the true nature of EGR--slowing down the
>>burn--comes into effect.

>no i didn't mention fuel atomisaton at all, yours your inference, which
>may very well be valid - I just don't know, though there is some logic
>to it. I guess with TBI its less of an issue, unless the EGR is plumbed in
>"way' upstream from the manifold and near the TBI unit - perhaps ?

>I'm not acquainted with separate EGR at all, just have vague recollections
>of a couple of articles and that particular one said something about the
>non-linear relationship. I suppose if we want reasonable power then minimal
>EGR would be the order of the day - but if you want good power why introduce
>an inert gas - better to work on cooling inlet charge, increasing octane etc.

"Knock Suppression in a Turbocharged SI Engine Using Cooled EGR" 
has some interesting things to say about that.  SAE paper 932476

I'll post a summary this weekend after I've absorbed it properly.
The impatient can download the document from the www.sae.org site.
(Costs US$10.) There's an SAE book SP-1393 "SI Engines: Combustion
and Emission Formation" which includes that paper as well as two
dozen others, half of which are relevant to either knock or EGR.

A followup paper, SAE 1999-01-3505 "Replacing Fuel Enrichment in a
Turbo Charge SI Engine: Lean Burn or Cooled EGR" exists, but I
haven't yet downloaded it. It's contained in "Combustion and
Emission Formation in SI Engines" (SP-1485) which contains several
other papers which may be of interest so I might just order that
book instead.

See http://www.sae.org/products/topics/GV_SI_P.htm for a summary of
papers, etc.

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
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