real-time A/F analysis of carb hard turn mixture leanness

While I am tweaking the carb jetting, thought I would post this real time Air Fuel mixture plot of a highway on ramp, with a hard turn-in generating mixture leaness corrected by coming on throttle correcting with the accellerator pump.
So, when under corner load, apply throttle for constant power.
Hope this is interesting for some
Back to tweaking...
rt

For those hard core carb guys, jetting was: 135;F24;190;53idle;60accel;36mm with K&N, Durable1 short air horns, stock airbox
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this is all just the basic kit - i really wish i had gotten the rpm plot now;
it's like you can do a real world rolling dyno - if you know that the A/F is right on a real world road pull, you have a max tuned set up

Wonder how much the rpm sensor is now?

 

Does anyone out there have any AF charts or data for just on the real world road driving? I do not really have a benchmark to compare.
Many thanks

 

Transition tuning

I do think that the main jet and a/c are on for hard use above 3500 according to the dyno graph below with A/Fs near 13 for hard pulls - the dip you see early on the dyno is obviously the accell jet firing. The problem is the transition circuit (isn't it always). A transient leaness that occurs with small throttle openings around 3500 (that can be over come by larger movements firing the a-pump) might be addressed by a richer idle/transition jet above the 53's I have now or decrease the venturi slightly to 34mm from 36mm to gain some air velocity. You can watch the intermittant transition leaness from small throttle openings on the LM-1 graph.
The pump shot at 60 even though large, does not cover the transition leaness unless large throttle movements are used. Since it does not cover the transition leaness, you could also make a case that the pump jet could be smaller as it takes the A/F pretty near 10 sometimes on accelleration. As Mitch Alsup notes, the transition is a bit lean in spikes, but catches up suggesting to me a possible velocity problem; low load/rpm (e.g cruise, slow speed) is still rich. It is here I am tempted to swap the F24 ets for the F36 ets. The two emulsion tubes are shown side by side.

So, in summary I am thinking of:
1. increase the idle/transition jets from 53 to 57 to cover the transition leaness
2. Go back to 34mm venturis to increase the velocity
3. Decrease the pump size from 60 to 40 to not drown the mixture on heavy throttle
4.Go to F36 et tubes, but would need to watch the new top end A/F

All advice welcome everyone
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I spoke with Gron today at Pierce; He agreed mostly with theory that there is a hole between transition and main jet coming in. When told what I was running, he stated that my main circuit was not coming in soon enough leaving a hole. When told of my venturi and main jet size, he said that could be part of the problem, as a 36 mm venturi needed about a 145 main jet to start flowing soon enough. What he suggested was to go to a 145 main to see if that brought the main circuit in sooner, and consider going back down to a 34mm venturi to increase the air velocity if the hole was still there. He relayed an almost exactly similar experience on a hot cammed 356, where you went up on the main jet, then backed off on the idle/transition.
Will try it tomorrow, but may cheat and drop a 210 a/c on top to adjust the top end. It sure seems that a 145 with an F24 is pretty darn lot of gas!

more soon
rt

 

Son of a gun - it worked!!!!!
Gron at Pierce Manifolds was right.

Went up to a 145 main (F24;210;53) and you could feel the main circuit come in earlier, filling the previous lean spot!! Clinically, the flat spot is about 80% gone - if you try hard you can induce it sometimes a little, if you are looking for it, but the anoying recurrent flat spot at 3500 - 3800 rpm 5th gear cruise is GONE. I almost don't believe it. I am now tempted to ever back off on the idle/transition from 53 to 50 to lean out the low end cruise richness of the mid/low 12s. the other temptation is to go back to a 34mm venturi which would lower the transition to the main circuit a couple of hundred rpm, but the current improvement is amazing. While slow throttle opening before poked a hole to 17, now it just hits 15 and the main kicks in, you really do not feel it.
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