Cosmo,
You are right about the turning orientation. I just think of this as a nut
which raises or lowers the jet. Move the nut upward and it leans out. Move
the nut down and it gets richer. Very intuitive.
I am not sure how far you can go to adjust your running mixture by adjusting
the jet. If you make any meaningful change, then you will have a TERRIBLE
idle. The mixture changes proportionally much more at idle than off idle. You
need 9 or more flats of change to make a meaningful change in the running
mixture. It takes 2 or 3 flats of adjustment of make a meaningful change at
idle.
You would need a different needle profile.
However I also question the idea that you are running rich at all!
At least here in PA, we have 10% ethanol in the gas. It takes double the
amount of ethanol than gas for the same amount of air. Therefore with the same
metering of fuel (gallons per hour), the engine will be running LEAN. But you
will have no change in the MPG!
I did some in-depth testing of my bone-stock TR4A engine and I found that even
when I set the idle somewhat rich, the cruising mixture was on the borderline
of too lean. The power mixture was leaner than that: practically at mixfire
lean.
I made some custom needles by trial and error and checked the mixture (using a
wideband oxygen sensor and datalogger) as I made the adjustments. I got it to
run at about 15.5:1 at cruise (a nice efficient mixture, but not peak power).
I also achieved a nice power mixture of about 12.5:1.
As it turns out, the needle profile I make was virtually an exact match for the
RL needles. I got some of these from Joe Curto, and they are great.
I also got a Pertronix Ignitor, 1970 MGB dizzy cap with push-in terminals, some
nice push-in type ignition wires, and the Pertronic flamethrower coil. It runs
REALLY well. The cap and wires + coil made the biggest change (and my original
cap, wires, and coil were virtually NEW)!
-Tony
>Date: Mon, 30 Apr 2007 07:38:25 -0700 (PDT)
>From: Cosmo Kramer <tr4a2712@yahoo.com>
>Subject: [TR] Adj. SU's leaner
>
>Hi List!
> On my TR4A Su SH6 carbs, I'd like to lean them out more than what they are.
M>ainly to give me a little better gas mileage!
> As I understand it: Looking from the top down [from the Damper Cap down to
>the
>ground], one should turn the Mixture Adjusting Nut (Fig # 101 in the Moss/USA
>catalog) RIGHT [clockwise] for RICH.
>
> 1- Therefore turning this nut LEFT [counter clockwise] should LEAN the carb
>out?
>
> 2- Is this Info. correct?
>
> 3- Am I looking at the carb in the wrong direction to interrupt the info.
>incorrectly?
>
> 4- Is there anything else I should be doing to 'Just lean out the carb' more?
>
> Of course, one would turn each Mixture Adjusting Nut EQUALLY on BOTH carbs
>so
>as NOT to change the synchro of the carbs. TIA,
>
>
>- -Cosmo Kramer
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