Tunnel ram try out
I'll throw a lot of info here so I'll try to break it up:
A. @yellow rose was banned from FABO, apparently permanently.
While I'll try to answer you, be aware that I'm not even looking in much, never mind signing in. Too much politics and BS. However when I do check in, Racers forum is one of the ones I do check.
B. I beleive YR was suggesting TS restrictors because of the proform bodies. Just a guess here. Check out hte links in post 15 that discuss when and why TS slot restrictions are needed in some situations.
C. Hopefully helpful responses to your observations posted above.
I have a similar 440 with an oxygen sensor and am fat under cruise.
It's typical for many hot rods and race engines the AFR to be richer than stoich under low throttle cruising.
That alone should not be a concern.
I believe the transfer slot is dumping in excess fuel. I tried closing my primary butterflies and cracking the secondaries, no change as when I'm just tipped in cruising down the street it's at 12.5.
12.5 just above idle and at very low speeds (like 25-30 mph) may be a little richer than it needs, especially fully warmed up.
I'd experiment with idle air bleed and idle air bleed- idle feed restriction first.
With two carbs, there's double the fuel supplied for a given manifold vacuum.
Similar problem exists with single 4 corner idle carb on an engine with relatively strong vacuum at idle.
A little throttle goes to 14.5 then leaner until I open the power valve.
This is exactly what it should do. The AFR should get leaner with more throttle (for more power) until at least half power and sometimes not until close to 90% power is needed.
Let me repost this here so you can see. Where the AFR line goes richer again approaching maximum power is where something like a power valve opens.
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"The [relationship] is rich idle, lean cruise, leaner (leanest, actually) part-throttle acceleration and rich WOT. The leanest is at mid-load, half-throttle or" somewhat more. Cruising, especially at lower speeds, requires little throttle and puts relatively little load on the engine. Half throttle or mid-load would be going up hills or part throttle acceleration. "The thing to understand is most engines respond to being leaner...at part-throttle..."
In summary "at moderate to mid load, engines will run lean and like it, and burn much less gas while doing so. They must be rich at idle and very low load, lean in the middle, and rich at WOT." The load where richer is needed varies with engine, gearing and vehicle. It may be 60-70% as shown here, or as high as 90%. Load relates to manifold vacuum, and therefore vacuum is used to signal when enrichment is needed.
F is Fuel/Air ratio for gasoline. Invert the numbers to convert to Air/Fuel ratio.
0.08 = 12.5 AFR
0.667 = 14.7 AFR
0.06 = 16.6 AFR
Constant power is any steady throttle condition.
Steady 15% might be something like driving 40 mph on a flat.
Steady 25% might be cruising 60 mph on flat or steady 40 mph up a long grade.
Steady 100 % might be something like towing or dragging max load up up a really steep long grade, foot to the floor, without losing or gaining speed.
The acceleration loop shows that maximum acceleration (full throttle) has about the the same fuel-air needs as constant 100 % power.
"This ... graph is from Walter B. Larew, Carburetors and Carburetion. At the time he wrote his book on carburetors he was a retired Brigadier General who taught Military Science at Cornell, among his other accomplishments. He published this carb book in 1967. He didn't specify an engine type for this graph but his information is in the context of engines in general. His sources were most likely military aviation research. The math in his book is from NACA TR-49 and similar publications.
This graph is representative of a richer part-throttle that may be necessary to tolerate with an engine that has radical valve timing and perhaps not so good A/F distribution at part-throttle."
quotes and graph from Tuner on Innovate Motorsports Forum and full text now reposted at RFS
----------------------------------------------------------------------------------------------------------
My suggestion is to tune for performance.
Use the WBO2 to observe what, if any, effect changes on carb setting have on particular conditions.
Whether your particlar engine will 30 mph cruise at 13.4 or 12.9 AFR or somehting else you'll have to establish by experimentation.
Idle and off-idle (low throttle). Best performance is defined by pulling strong (least drop in rpm when going into gear) and no hesitation when slowly opening throttles above idle. Do the best you can with throttle positions, IAB and IFR before starting to restrict the transfer slots. Remember the t-slot is a variable airbleed as well as a restriction. It is also located downstream from both the IFR and IAB. Trying to restrict fuel at this point is not the same as controling it when its just liquid fuel from bowl.
Wide Open throttle. Strongest pull in high gear (3rd or 4th), MPH in the quarter or hp on a dyno. Jets and PVCR together. You can trim the shape with the MAB if you see it drifting rich or lean as it goes through the rpms.
Crusing at interstate speed. Go as lean withthe main jets as it will tolerate without surging, then a jet richer. It will be on primaries only. Exacty what mph before its mostly on the primaries I don't know with the tunnel ram. Gearing offf course makes a differnece too. But somewhere above 55 mph the wind resistance and friction is high enough generally the throttles have to be opened enough thee main circuits are taking over from the low speed circuits.
Once you get those conditions worked out, then come back to the trickier conditions if needed. Trickier to work out is anything that is changing rapidly (like pump shot) or using several circuits (like overlap betwqeen low speed circuit and main circuit).
Sometimes you have to jump tuning order, but that's the concept.
I'll throw a lot of info here so I'll try to break it up:
A. @yellow rose was banned from FABO, apparently permanently.
While I'll try to answer you, be aware that I'm not even looking in much, never mind signing in. Too much politics and BS. However when I do check in, Racers forum is one of the ones I do check.
B. I beleive YR was suggesting TS restrictors because of the proform bodies. Just a guess here. Check out hte links in post 15 that discuss when and why TS slot restrictions are needed in some situations.
C. Hopefully helpful responses to your observations posted above.
I have a similar 440 with an oxygen sensor and am fat under cruise.
It's typical for many hot rods and race engines the AFR to be richer than stoich under low throttle cruising.
That alone should not be a concern.
I believe the transfer slot is dumping in excess fuel. I tried closing my primary butterflies and cracking the secondaries, no change as when I'm just tipped in cruising down the street it's at 12.5.
12.5 just above idle and at very low speeds (like 25-30 mph) may be a little richer than it needs, especially fully warmed up.
I'd experiment with idle air bleed and idle air bleed- idle feed restriction first.
With two carbs, there's double the fuel supplied for a given manifold vacuum.
Similar problem exists with single 4 corner idle carb on an engine with relatively strong vacuum at idle.
A little throttle goes to 14.5 then leaner until I open the power valve.
This is exactly what it should do. The AFR should get leaner with more throttle (for more power) until at least half power and sometimes not until close to 90% power is needed.
Let me repost this here so you can see. Where the AFR line goes richer again approaching maximum power is where something like a power valve opens.
---------------------------------------------------------------------------------------------------------------------------------
"The [relationship] is rich idle, lean cruise, leaner (leanest, actually) part-throttle acceleration and rich WOT. The leanest is at mid-load, half-throttle or" somewhat more. Cruising, especially at lower speeds, requires little throttle and puts relatively little load on the engine. Half throttle or mid-load would be going up hills or part throttle acceleration. "The thing to understand is most engines respond to being leaner...at part-throttle..."
In summary "at moderate to mid load, engines will run lean and like it, and burn much less gas while doing so. They must be rich at idle and very low load, lean in the middle, and rich at WOT." The load where richer is needed varies with engine, gearing and vehicle. It may be 60-70% as shown here, or as high as 90%. Load relates to manifold vacuum, and therefore vacuum is used to signal when enrichment is needed.
F is Fuel/Air ratio for gasoline. Invert the numbers to convert to Air/Fuel ratio.
0.08 = 12.5 AFR
0.667 = 14.7 AFR
0.06 = 16.6 AFR
Constant power is any steady throttle condition.
Steady 15% might be something like driving 40 mph on a flat.
Steady 25% might be cruising 60 mph on flat or steady 40 mph up a long grade.
Steady 100 % might be something like towing or dragging max load up up a really steep long grade, foot to the floor, without losing or gaining speed.
The acceleration loop shows that maximum acceleration (full throttle) has about the the same fuel-air needs as constant 100 % power.
"This ... graph is from Walter B. Larew, Carburetors and Carburetion. At the time he wrote his book on carburetors he was a retired Brigadier General who taught Military Science at Cornell, among his other accomplishments. He published this carb book in 1967. He didn't specify an engine type for this graph but his information is in the context of engines in general. His sources were most likely military aviation research. The math in his book is from NACA TR-49 and similar publications.
This graph is representative of a richer part-throttle that may be necessary to tolerate with an engine that has radical valve timing and perhaps not so good A/F distribution at part-throttle."
quotes and graph from Tuner on Innovate Motorsports Forum and full text now reposted at RFS
----------------------------------------------------------------------------------------------------------
My suggestion is to tune for performance.
Use the WBO2 to observe what, if any, effect changes on carb setting have on particular conditions.
Whether your particlar engine will 30 mph cruise at 13.4 or 12.9 AFR or somehting else you'll have to establish by experimentation.
Idle and off-idle (low throttle). Best performance is defined by pulling strong (least drop in rpm when going into gear) and no hesitation when slowly opening throttles above idle. Do the best you can with throttle positions, IAB and IFR before starting to restrict the transfer slots. Remember the t-slot is a variable airbleed as well as a restriction. It is also located downstream from both the IFR and IAB. Trying to restrict fuel at this point is not the same as controling it when its just liquid fuel from bowl.
Wide Open throttle. Strongest pull in high gear (3rd or 4th), MPH in the quarter or hp on a dyno. Jets and PVCR together. You can trim the shape with the MAB if you see it drifting rich or lean as it goes through the rpms.
Crusing at interstate speed. Go as lean withthe main jets as it will tolerate without surging, then a jet richer. It will be on primaries only. Exacty what mph before its mostly on the primaries I don't know with the tunnel ram. Gearing offf course makes a differnece too. But somewhere above 55 mph the wind resistance and friction is high enough generally the throttles have to be opened enough thee main circuits are taking over from the low speed circuits.
Once you get those conditions worked out, then come back to the trickier conditions if needed. Trickier to work out is anything that is changing rapidly (like pump shot) or using several circuits (like overlap betwqeen low speed circuit and main circuit).
Sometimes you have to jump tuning order, but that's the concept.
