Ignition advance, was Re: alternative engines, WARPED

[Don.F.Broadus at ucm.com]

The problem with going to manifold vac on some HEI's is that the vac can has
as much as 25 degrees (crank) advance built in.
with  say 12 degrees initial you have 37 degrees at idle, then when you
start to get into it the cent. advance starts and the knocken
commences. If you go manifold vac change the can to one with 10 degrees
(crank). Now you have 22 degrees (crank) changing to lighters springs will
bring the cent curve in quicker also. 
                                                                     Don   

> -----Original Message-----
> From:	bearbvd at sni.net [SMTP:bearbvd at sni.net]
> Sent:	Wednesday, May 19, 1999 8:07 AM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	Re: Ignition advance, was Re: alternative engines, WARPED
> 
> >At 12:47 PM 5/18/99 -0400, you wrote:
> >>Just use manifold vacuum.  Carb vacuum is ported so there is no vacuum
> at
> >>idle.  This can help or hurt the idle quality.  Try it and see.
> >>
> >>Gary Derian <gderian at oh.verio.com>
> >>
> >	
> >
> >	You sure about that?  I have always understood that a vac advance
> can
> >reads ported vacuum in order to affect a curve that begins as the
> throttle
> >is opened and increases as more throttle is applied, up to the point at
> >which all vacuum (manifold and therefore ported as well) fades under
> heavy
> >throttle openings, at which point the advance will decline again and the
> >engine will see only mechanical advance.  This is apparently to provide
> >extra advance for economy at part throttle.  Anybody who can further
> >illustrate this concept, please do because if I am wrong here I'm going
> to
> >have some serious rethinking to do!
> 
> Sorry Aaron--
> 
> Ported vacuum was first used to provide LESS advance at idle so as to
> decrease idle emissions! (But to still keep more like the ideal advance at
> cruise.)
> 
> Regards, Greg
> >
> >
> >	Aaron Willis
> >	ICQ #27386985
> >	AOL IM: hemiyota
> >	http://surf.to/garage-te51 Garage TE51 International
>