I'm learning the ins and outs of tuning a weber carb. Still. I have a wide-band A/F meter, and I'm trying to figure out exactly what ratio I should be looking for for lean-best idle. I figure tuning for 17.0+ will be the most economical, but that tends to be a little rough Idle. Is there a 'perfect' ratio I'm looking for? I assume it's supposed to be on the lean side, right?

I thought that stoichiometric at 14.7:1 would give you a complete burn without lean miss.

Yes, but if you set idle to 14.7 then you go pig-rich when you cruise.

Your setting up a Weber, right? It's been 10 years since I touched a carburetor, but why would setting the idle mixture correctly make it "go pig rich at cruise"? Can't you just play with jet sizes and or metering rods to properly set the fuel mixture at cruise speeds also?

So you're saying it's possible to tune the carb so all throttle positions yield at or near 14.7?

Possible but not desireable.

 

Idle is going to depend on the engine. Most will not idle well that lean. It's lean *best* idle for a reason. You want a smooth idle but as lean as you can get and still have it smooth.

Edited February 19, 201214 yr by GeneralDisorder

Possible but not desireable.

 

Idle is going to depend on the engine. Most will not idle well that lean. It's lean *best* idle for a reason. You want a smooth idle but as lean as you can get and still have it smooth. Sometimes that mean stoich - sometimes richer. Usually not leaner though.

 

WOT is going to be somewhere around 13 or 13.5 for best power and to keep EGT's reasonable.

 

Part throttle cruise should be as lean as you can get without a lean surge.

 

GD