What should AF ratios be on a traditional SB? The presets on my sniper seem very rich. Rich like Bill Gates before his divorce. It's target while warm up is 12.5 and once it hits 160 degrees it is up to 13.5.
The smell is overpowering in my garage with doors open on both ends and the lbs per hour fuel use is 6.8.
I have played around with the AF ratio and pushed it up to 13 for warm up and 14.3 once it hits 160 and my smell-o-meter says it is much better. I have left the WOT at 12.5 and cruise at 14.5.
Just curious if anyone has played around with AF ratios on a dyno that simulates driving?
78buckshot is correct for the sweet spot once warmed up anad with no or light load. I would leave WOT at 12.5 at least until you have some time to evaluate how it performs in the real world.
14.7:1 is stochiometric, which means that the amount of air and fuel match and you get complete/clean burns.
I will run my truck 5% lean (15.4:1) when cruising at light throttle. It has slightly higher NOx and lower power, but saves 5% fuel. You will be generating more heat running lean, but as long as you have sufficient capacity in your cooling stack it saves money.
You can get more power by running rich. That is the idea behind "rolling coal" and power enrich on throttle snap. Depending on who you ask, the peak power is around 13:1. I would recommend waiting to adjust that until you have it on the road and can experiment with it.
I put a couple of thousand miles on a 4 gas exhaust analyzer adapted to run on a 12 volt inverter, on a road trip to and from a GM technical school up in yankee land from Tennessee. That's probably better than a dyno simulation. Two of us took turns driving while the other guy watched the readout on the analyzer. Light throttle with high intake manifold vacuum cruise produced A/F ratios in the high 14's- - - -pretty close to stoichiometric- - - - -which, BTW, means the exhaust emissions are only CO2 and water vapor- - - - -little to no carbon monoxide or oxides of nitrogen. Opening the throttle for hill climbing or passing richened up the ratio to 12.5:1 or so.
The test was run on an AMC Ambassador station wagon without a catalytic converter, with a dyno tuned, blueprinted and balanced 343 cubic inch V8 and a Comp Cams 260-H hydraulic RV cam, 9.5:1 compression, and slightly ported cylinder heads, running a Carter AFB 4 barrel and a Motorola electronic ignition system, on 87 octane unleaded regular gas, back in the early 1990s. The transmission was a Torqueflite 727 direct drive, and a 3.43 rear axle. Interstate cruise speed was in the mid-70 MPH range. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Ratios leaner than 14.7 burn holes in pistons and roast exhaust valves. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Modern engines run at 14.7 almost always, and they can hold it to within about 2% even on the most aggressive throttle movements and within about 0.03% on average. But that ratio is for emissions, and it really only gives the lowest emissions because it is balancing the chemistry (reduction of NOx, oxidation of CO and HC) happening in the catalyst. Timing also is tuned and not limited to vacuum advance, exhaust gas and valve and piston temperatures are measured during calibration and timing is set so everything stays below the burn-up temperatures, usually for lowest fuel consumption while avoiding knock. I had a 305 Chevy Caprice that would run at around 18:1 on the highway, but it also added around 5 or 6 degrees of timing when it switched to this “lean on cruise” mode. I got just under 30 US mpg with it.
1959 Canadian GMC grain hauling dump truck with 235
