Best A/F ratio for HP & reliability with 87 Octane
 

'Whipple Charged' said that stock NA motors, cast iron heads, with 91 octane fuel should run around 12.5:1 for peak HP and reliability.

What would be the recommended A/F ratio for peak HP and reliability with 87 octane for the same stock NA motor, cast iron heads ~9.1:1 compression ratio and 28 degrees max advance?

Re: Best A/F ratio for HP & reliability with 87 Octane
 

RAGE
I had this conversation with a friend last night that runs the fastest v6 buick turbo dragster in the country Barry was telling me they are running 11:5.1 and they found it makes more power then the leaner ratios now on the 556 I just finished that I also posted on the af ratio was real close to that and that was also the best power the plug is not going to be the nicest color you've ever seen but it will be the best power Good luck Laz Mesa

Re: Best A/F ratio for HP & reliability with 87 Octane
 

MESABALANCING,

Thanks for the information.

The dragster is running on 87 octane?

Re: Best A/F ratio for HP & reliability with 87 Octane
 

no not 87 but we run the minimum oct we can for the power were making like the 556 I just finished with 89 oct the buick runs 112 oct with 8.1 comp with 45 lbs of boost .

Re: Best A/F ratio for HP & reliability with 87 Octane
 

Very interesting to see the fatter AF ratios making more peak HP. Does the motor rate as fast with the fatter ratio? It seems alot of drag race guys are running super lean to get the best ET. Is it possible the leaner mixture is making less peak HP but the motor rates faster thus better ET's in these cases?

Re: Best A/F ratio for HP & reliability with 87 Octane
 

Acceleration(WOT) Enrichment is needed to compensate for increase in air velocity in the intake manifold. Fuel is heavier than air and does not accelerate as quickly. The mixture will become lean under normal fuel control (14.7:1 A/F).

At Full Load/Full Throttle extra fuel is needed for two reasons,To develop maximum power. Normally reached at a value of λ=0.9 (12:1 A/F) and to reduce combustion and exhaust gas temperature

Re: Best A/F ratio for HP & reliability with 87 Octane
 

Does the difference between 91 octane and 87 octane gas have anything to do with the optimum A/F ratio for an engine?

Re: Best A/F ratio for HP & reliability with 87 Octane
 

There is not a one size fits all Optimal A/F ratio for every engine. Each engine design is going to be different, and require a different amount. Also the fuel you run will require a different A/F ratio even if they are both 87 octane, they may have different additives in the fuel to get there, which will require different tuning.

Re: Best A/F ratio for HP & reliability with 87 Octane
 

Thanks Mike&Paula,

Then λ=0.9 (12:1 A/F) @WOT would be a good starting point for me after improving the air flow in my stock 496HO and adjust from there based upon on the water results?

Re: Best A/F ratio for HP & reliability with 87 Octane
 

If your looking to Increase power you need to be doing this on a dyno. In the boat I think this will be harder to do. I guess if you watch for RPM increase I guess that would mean a gain in your power output. I would also monitor you’re plugs for aluminum on the outer ring where the threads end and on the center electrode area, this would be a telltail sigh of detonation..