69' Dune Buggy 1600cc wrote:
>
> In the bigger bore and stroke engines such as 2000+, 2100+, etc. what
> type of distributor advance is needed(type 1 engines)?
> The 009 seems to be the "fix-all" however the original 1600's had so
> many variation of the timing curve that it only makes sense that larger
> size engines would have their own unigue timing requirements.
>
> Basically, starting with a new built stroker engine how would you tweak
> in the advance on a mechanical only distributor.
>
> Scott



Run the engine on a dyno. Start with an out-of-the box distributor (ANY
Distributor, 009 will do too).
Hook up a mixture gauge.
Hook up a head temp sensor & gauge (Or two)
Hook up and calibrate a knock sensor. (!!!!!)

Now plot the power curve in a matrix, and add another curve that shows
the advance at the same rpms you plotted power output at.

Now start giving the engine more advance at each measured rpm point, to
see how much advance it can take before pinging. This gives you your
critical curve. You can do this simply by turning the distributor and
not tweak it yet. Then do the run again to find the best power output,
not the biggest advance. You could also do this at the same time when
looking for biggest safe advance actually. (To save your engine one
stressful dyno run). Just twist the distributor so that you get the most
power at each measured rpm, making sure it's just below knocking/pinging
point. You get your "desired" curve as a result. This is when you define
your safety margin too. (Can you guarantee you will always get the same
grade fuel at the LEAST? How about altitude? Heat?).

Once you've completed the run, you will have the optimal ignition
advance curve mapped out for the engine, but still no changes are made
to the distributor. Time to TWEAK.

Tweaking:

Basically you have three things to adjust. Advance rate, maximum advance
and advance points at different rpms.. you can get progressive advance
by adding an extra spring (like the stock SVDA has). If you were
adventurous enough, you could get several progression stages my changing
the mechanical parts of the centrifugal advance mechanism... Oh but now
I'm getting carried away.
Let's assume you didn't want to go in too deep. Just play with the
spring pre-tension, and stiffness. You can experiment with different
springs. If you don't want to add an extra spring that would kick in
later, (like the stock SVDA), you could maybe find a progressive spring
to replace the original with. or hey, make your own...
When you're done with the spring, Then play with the travel stop tabs to
get the total amount of advance you need.
You will soon learn that the advance curve of the 009 cannot easily be
altered to match the "optimal" curve you mapped on the dyno when you
twisted the distributor body at each rpm point to achieve "cheated"
optimum. The curve may fall short somewhere, while it might give too
much advance (pinging) at another part of the rpm range. You need to
find an acceptable compromise, a curve that never crosses the critical
(pinging) limit, but follows the maximum power line as close as
possible. When all this is said and done, no more power can be extracted
from the engine, if you did all the tricks you could to the distributor.

To save the engine from repeated dyno runs, you can just plot the engine
power and optimum advance on one chart, (along with the critical curve),
then take the distributor out and tweak it on a distributor bench
instead. Those have an electric motor that drives the distributor, and
imitates the engine. You can run the distributor on the dizzy bench all
day long, and not risk your engine. Just plotting the curve on the
chart, trying to match the curve you plotted on the engine dyno when you
started.


Naturally, all of this would be only half of the work if you didn't
bother to fine tune the carburator (or injection) too, to gain more
power. That's where the "normal" engine dyno tuning comes in. It's a
whole lot more work but I'd rather not go there in this article.



OR YOU COULD ALWAYS JUST BUY A 009 DISTRIBUTOR AND BOLT IT ON, SET IT AT
34 DEG MAXIMUM AND LEAVE IT AT THAT.

-That's what 99.99% of 009 buyers do, anyway. LOL (It would work...
reasonably well)


It's late and I'm tired, if I made any mistakes there, I hope someone
else would point them out.

Jan