Downleg Annular

[Right hand drive]

Had time today to test out these mini annulars again. I have taken them from the 825 Demon and put them in the 750 Demon with 1.40” venturi and 1.68” throttle. 4 hole Quickfuel blocks.

First up was no change other than boosters from downleg tune of primary MJ 72, sec 80, .033” mab and emulsion .031”, .028”, X, .025”. Downleg @ 60kp/h lambda around .94. With mini’s around .90 lambda. Out on the highway @ 100kp/h (~3250 rpm) leaning out to over 1.0 lambda. Doing the dragy WOT 100 - 120kp/h test was a best of 1.27 sec. All other carbs including this one with downleg have been in the range of 1.20 to 1.23 sec for the same test. Most notable was the lack of acceleration when rolling into the throttle from slower speeds.

Next up was reduce emulsion and mab. Reduced to .028” mab and X .020”, .020”, .020” emulsion. Fixed up the rich low speed and enriched highway speed a little. Rolling into the throttle at lower speeds felt better now. I wanted to see if heading more in that direction made for more improvement so the easy swap was to .025” mab. Knowing this would lean the highway speed I went from 72 MJ to 75 MJ primary. I expected .98 or thereabouts lambda at highway speed but was still above 1.0. WOT managed to get to as low as .87 lambda but it’s taken a large 75 jet with a .025” mab and emulsion with an area smaller than x2 .028” e-jets. Rolling into the throttle from low speeds still good. Couldn’t improve dragy 100 - 120kp/h test.

I’m thinking a couple of things, one - with the emulsion stack and mab used with downleg may have been over atomizing the mix as well as leaning leading to the less than stellar acceleration especially rolling into it at lower speeds. Two - I need to take Marks suggestion and open the discharge holes from .050” to .052” minimum for additional fuel flow. So I’ll remove the inserts again and open up the holes to .052” minimum and reset to .028” mab. I think I’ll move the top e-bleed to the top hole for .020 X .020”, .020”.

I think these mini’s will workout fine, it’s just a matter of finessing them and finding the calibration they like.

[Right hand drive]