Larry,
I tried it once on a supercharged AH Sprite. With the damper cap
removed, I put a flag on the piston. With the hood removed you could
watch the flag position while driving. It is best to have an observer
along, hard to watch the road & the flag at the same time. Finally gave
it up & installed a Holley carb. I would think that doing it on a dyno
would be ideal. Wish that I had had a dyno when I was trying to set up
the original carb.
Your idea of measuring vacuum in the piston dome sounds possible.
Otherwise it is really a guessing game to know what part of the needle
you are operating on.
I don't know what the vacuum is in the dome, pretty low I would guess,
maybe zero to six inches.
Dave Russell
Larry Colen wrote:
> The application is my MGB with an HP supercharger.
>
> I'm simultaneously trying to get things dialed in and learn about what
> is happening with the motor, fuel/air ratios, power etc. I was able to
> sort of measure piston rise on the dyno, but that doesn't work the
> best under dynamic situations. I can't really have someone running
> along next to the car with a mirror and a ruler measuring piston rise
> as I drive down the road.
>
> The carb is an HIF-44. I've noticed that the damper cap does not have
> a vent in it like my old HS-2s and HS-4s did. I was considering
> getting another damper cap and attaching some sort of vacuum sensor to
> the damper cap and at least under steady state conditions that should
> correlate to piston rise.
>
> Is this likely to work? Has anyone already tried it? What is the
> "vacuum", or pressure differential actually in the dome?
>
> In almost unrelated news, I had an absolute blast at Drivers School
> last weekend as a student rather than a driver. I had all sorts of
> people complimenting me on the MG, and reminiscing about their own. I
> repeatadly and mercilessly blew the doors off a G Prod (though he was
> running DOT legal tires as I was) Datsun Fairlady 1600 Roadster.
>
> A longer story of the weekend will follow.
>
>
> Larry
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