Bill,
I have copied the following from a web article by Tomislav Marincic at
the following link:
http://www.mit.edu/people/zimerman/Documents/tr6/advretard.html
He is referring to an early model in this example, with both vacuum
advance AND retard canisters:
"You just started your fully warmed up engine, which is idling smoothly
at 850 RPM.
Static Advance: 12 BTDC. The Triumph mechanic set this by rotating the
distributor and clamping it. It won't change in operation.
Mechanical Advance: Zero. Mechanical advance is a function of engine
speed
only, and your distributor is "curved" for zero advance at this
engine speed.
Vacuum Advance: Zero. Although the manifold vacuum is very high, the
vacuum
advance unit doesn't sense it. The vacuum pickup, on top of the
carb, is masked
by the throttle butterfly.
Vacuum Retard: 16 degrees. Manifold vacuum is high, and the vacuum
"signal"
runs from the bottom of the carb, where no "masking" is occurring,
to the vacuum
retard capsule, which is providing its max retard value of 16.
TOTAL ADVANCE = 12 deg BTDC + 0 + 0 - 16 deg = 4 deg ATDC
And behold: this is why you set static timing to 12 BTDC with the engine
off, but when
you idle the engine with a timing light hooked up you see 4 ATDC."
I hope this helps you understand the static/dynamic relationship.
Personally, I set my engines at 10* static, then tune for best
performance by the trial and error method, trying to achieve maximum
performance once the engine fires and I can get a good idle.
Hope this info helps,
Jim Davis
William Elliott wrote:
>
> But the workshop manual says to disconnect the retard when setting
> timing, so that should take it out of the picture in the static vs.
> dynamic setting. Or am I missing something here?
>
> Bill Elliott
>
> Jim Davis wrote:
> >
> > William,
> > It's because the '71 and newer TR6s have a vacuum retard and mechanical
> > advance. The retard operates at high vacuum, at idle and deceleration.
> > Jim Davis
> > Fortson, GA
> > CF38690UO
> > CF37325U
> >
> > William Elliott wrote:
> > >
> > > Sorry for the stupid question, but a new TR6 owner asked me and I
> > > realized I didn't have an answer...
> > >
> > > In virtually every other car on the road, static and dynamic timing
> > > specs are the same (or at least very close). On the TR6, they are VERY
> > > different...even though the static procedure appears to be conentional.
> > >
> > > Why the difference?
> > >
> > > Related question: where are you guys running timing? Standard dynamic
> > > specs? My car is a dead stock '71, my friend's car is a late '74 with
> > > most smog gear removed.
> > >
> > > Thanks!
> > >
> > > Bill Elliott
> > > Lake Barrington, IL
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