Hi Terry, Its good to hear from you. So to reiterate, the performance gains from 3600+ are due to more constant timing from lack of the vacuum advance mechanism, at the expense of driveability down low?
Andrew > If you condense all of the replies on this subject then the details on why a > solid breaker plate was used with the competition L engines with Mukini or > Weber carbies (as in those without inbuilt vac unit metering) become more > evident. > > Basically, a standard dizzy is fitted with a vac unit and in order for it to > do its job the breaker plates are in two pieces one of which is attached > directly to the vac unit, and also they usually have dual return springs > fitted to the solid plate. This standard vac advance/retard system allowed > dwell variance which relates directly to points gap variance and this is a > bad thing especially in a competition engine. Dwell variance is also caused > by a worn dizzy, as in loabs and shaft bearings etc. Dwell is the number of > degrees that the distributor shaft rotates with the points closed (and > therefore charging the primary coil) and when the points open the coil > fires. Points gap is directly related to engine timing ie if an engine is > timed with the correct points gap and then the gap is made smaller, the > timing will be less and the dwell will be higher and the opposite also > applies - Ppl who use a dwell meter (recommended) instead of feeler gauges > to set the points gap will have seen this. The correct dwell angle is far > more advantageous than the correct points gap, and setting the points gap > get more inaccurate if the points are used. > > As Errol alluded to the timing spikes at certain rpms (usually high rpm) was > why the solid or welded breaker plate was use in racing with carbies that > didn't come equiped with a vac unit metering device, the downside is the > engine can be a bit cranky on cruise below 2500 - 3000 but the performance > gains are really noticeable from 3600 - 4000+ rpm to as high as your game to > go which is were most L series engines are running most of the time. > > regards > Terry > > > Topic: Dizzy > ======= > Date: Sat, 17 Apr 2004 08:07:14 +1000 > From: "Errol Smith" <[EMAIL PROTECTED]> > ---------------------------------------- > The main reason for welding or replacing the breaker plate with a solid item > is to help stop timing scatter. With the standard diaphragm plate the timing > can move 4-6 degrees at high engine speeds. Disadvantage of making the > breaker plate solid is the lack of cruise advance from vacuum. > > > Cheers > Feral Errol > Get Serious! http://www.datrats.com.au/ > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of James Fitness > Sent: Friday, April 16, 2004 11:13 PM > To: [EMAIL PROTECTED] > Subject: Re: Dizzy > > My old turbo 240z had the plates welded up... > static timing - best thing for a Big boost carby turbo... > (probably good with fuel only efi too?) > > > > mark krawczuk wrote: > > >dont they either stretch the adv springs or elongate the adv spring holes > >in the plate? > >i think they usually recurve the dizzy according to what engine setup u > >have?? > > > >mark k > > > > > >----- Original Message ----- > >From: "maldat" <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]> > >Sent: Friday, April 16, 2004 4:03 PM > >Subject: Re: Dizzy > > > > > > > > > >>You dont have or need Vac advance for twin side drafts , hence remove it > >>from the dizzy graph it and weld it up. > >> > >>The timming does not change , I think they call it dwell angle? with > >>high/low Rpm. > >> > >>Malcolm > >>----- Original Message ----- > >>From: "Jeff Oldham" <[EMAIL PROTECTED]> > >>To: <[EMAIL PROTECTED]> > >>Sent: Friday, April 16, 2004 5:09 PM > >>Subject: RE: Dizzy > >> > >> > >> > >> > >>>and to add my 2 cents worth WHY is it welded up.....what performance > >>> > >>> > >gains > > > > > >>? > >> > >> > >>>ta Jeff > >>> > > _________________________________________________________________ > Personalise your phone with chart ringtones and polyphonics. Go to > http://ringtones.com.au/ninemsn/control?page=/ninemsn/main.jsp > > > > --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/[EMAIL PROTECTED]/ ---------------------------------------------------------------------
