Andrew,
That's been very much my experience with weber fed engines - "A" series actually were much crankier than the L series especially at altitude. City fuel consumption is probably down 10% but in Canberra not real bad as our arterial roads are like a freeway in Melbourne - cruising consumption is good if you keep below 4000 rpm and in 5th thats around 130kph in my 1600. I paid closer attention to the way it behaves on the way in this morning, ambient temp was 5 degrees, L1889 SSS engine has a 66 degree cam with CR of 10.7:1. It is cranky below 2 grand, will pull well above 2 but really starts to smooth out around 3 grand, and there is a distinctive change in the induction note around 3500 and then at 4000 its just a banchy whaling noise. "I love the sound of webers sucking in lots of Optimax in the morning" My dizzy is a real Nismo factory one with a single breaker plate that was made by Mitsubishi (most stock stuff is Hitachi), came with my engine! from Japan and it has done a squillion miles and the dizzy still has bugga all dwell variance, also doesn't chew points like a stock dizzy.
It's a very worth while mod.
regards
Terry
>
>Date: Tue, 20 Apr 2004 21:02:42 +1000 >From: "Andrew Greenbury" <[EMAIL PROTECTED]> >---------------------------------------- >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: DizzyGet Extra Storage in 10MB, 25MB, 50MB and 100MB options now! Upgrade here!
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