tuning with afr meter

[danta]

what is the ideal a/f ratio at w.o.t. for a carb engine
421 sbc shift at 7800 strip only .
thank you

[Warp Speed]

what is the ideal a/f ratio at w.o.t. for a carb engine
421 sbc shift at 7800 strip only .
thank you

What fuel?

[Firedome8]

The one with the best results

[Warp Speed]

The one with the best results

Ya, that will get him close

[danta]

100 octane (c12 and 94 unleaded mix to obtain 100 oct)

[rfoll]

The one with the best results

Every fuel/engine combo is going to be different. I read somewhere that people were making more power with ratios in the 13 range, but in my car wouldn't go down the track well. It might have dynoed better, but it wasn't happy in the car at all

[ustahava67]

Your gauge , your fuel, your car, .... With my car when I first started tuning Folks said best power will be at 12.5-12.7... As I tuned I found that best E.T./MPH was about 13.4-13.7.... Sensor went bad, replaced sensor New best #'s 13.2-13.5... Same engine , same fuel, same car new sensor.

[Warp Speed]

About 9-10% rich from the stoic of the fuel is a good starting point.
It has been this way in our deal, over the past 20 years, through 3 different fuels, 3 different engine designs and 2 different delivery methods.

Your mileage may vary, but if your timing and sensors/logging system are correct, this is where you will end up +/- a couple tenths of a ratio.

[ClassicComp]

Tune by the mph, af is just a reference

[F-BIRD'88]

The afr gauge is best used as primarily a warning tool that you might be getting to far lean.
Tune from (plenty) rich towards lean(er) jetting in search of power (MPH) while also looking at all 8 spark plugs
keeping a eye on the 2 leanest hottest appearing cylinders. appearance and ground strap

It is a tuning tool to be used with other , not a absolute. As said in these posts.

[perfconn]

How close to being right will the BSFC be on a dyno if the Dyno has no AFR readout?

[FC-Pilot]

An O2 sensor has no control over BSFC. That has to do with the fuel flow and the amount of power the load cell is reading. A dyno can calculate a/f ratio based of air consumption and fuel consumption, so that is other way to help get yourself lost. I tune for best power, and let the dyno tell me what the BSFC is and the O2 sensor to tell me what to look for in the future. I have seen that some manifolds, carbs and engine combos may be much less efficient than others so what makes best power on one can be way different than the next. One BBC I ran with an old factory intake and the owners carb made its best power at 12.4 on the O2 readout. I would never have believed it if I did not test it myself. The inductions and heads just wanted fuel pouring down the engine. The very next SBC wanted 13.2. Just give it what it wants.

Paul

[MadBill]

Yes, equating B.S.F.C. with AFR is a common mistake. Mixture strength is only one of a dozen or more factors contributing to the number and it reveals nothing about the cause of higher than expected consumption.

[racear2865]

I have a problem doing much with B.S.F.C. To me, it is an indicator of efficiency of an engine. Ive had engines make same HP but totally different BSFC. And yes I have gone back into engines to try to improve the BSFC.
reed

[danta]

Timing and jetting for max mph is already done. I installed an afr meter to check my engine comportement .