Tom:
Dunno where you got your numbers on the needles. Here are the
numbers in my Zenith Needle Catalog:
Station B1AQ B1AR % Difference
------------------------------------------------
1 0.096 0.095 0.8
2 0.094 0.093 1.9
3 0.092 0.091 1.1
4 0.089 0.089 0.4
5 0.086 0.085 1.2
6 0.083 0.082 3.0
7 0.079 0.078 3.9
8 0.075 0.074 3.3
9 0.070 0.072 -3.3
10 0.066 0.069 -8.6
11 0.062 0.066 -12.9
12 0.056 0.066 -26.1
13 0.056 0.065 -24.7
As you can see, the B1AR is barely richer at the idle/cruise end
(stations 1through 8) and much leaner at the power end (Stations 9 through
13). A larger diameter is leaner, a smaller diameter is richer.
To determine the % change, you must take the jet size (0.100") and
convert that to area. Then take the diameter of the needle, and convert that
to area as well (Pi * r^2), then subtract the area of the needle from the
area of the jet. Then compare the resulting areas to determine the change in
fueling.
As you can see, the low end fueling is almost identical to the B1AQ,
but the high end fueling is much *LEANER*, NOT RICHER as you claim. You
stated originally that the B1AQ let you avoid knocking on the low end and
was good around town, but was too rich on the high end. I stand by my claim
that the B1AR needle solves your problem by leaning out the mixture at the
power/acceleration end of the fueling range, but leaves the idle and cruise
alone.
As for the lumpy idle with the B1AR, that is a result of your cam +
rockers. I think you will find that if you go back to your stock rocker
ratio, the lumpy idle will smooth out just fine. If it doesn't smooth out,
you probably have a vacuum leak somewhere. A 270 degree cam is extremely
sensitive to vacuum leaks, and if you add high ratio rockers to such a cam,
it will push it over the edge into lumpy idle territory. High ratio rockers
are equivalent to adding 10 degrees to your cam, so at 280 degrees you are
into the lumpy idle/poor cold start behavior of autocross cam rather than a
street cam.
Vance
-----Original Message-----
From: Tomislav Marincic [mailto:tomislav.marincic@earthlink.net]
Sent: Wednesday, May 04, 2011 7:01 PM
To: Vance Navarrette
Subject: RE: [6pack] SU needle for TR6 Conversion?
Vance,
<snip>
I made some Excel charts of various needle profiles, and B1AR was one I
looked at, just because it was readily available. For the first 8 of 13
stations, it was almost the same as B1AQ, but then it got much richer.
Since I was having trouble down low, I doubt it would work for me.
<snip>
Cheers, Tom
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