whats a good air/fuel ratio (aggressive) for a NA car ?

[2002BLGT]

getting a wideband to hook up on my 93 LX , I wanna tweak the fuel pressure regulator to get a better air/fuel ratio at WOT ....I am really rich right now ..... what is a good number to shoot for ??

 

[jrichker]

As long as you aren't trying to cool the engine with excess fuel, I'd use 13.5:1 for lean best power.

 

[cleanLX]

13.5-13.7

 

[2002BLGT]

hypercrapic pistons should I go with 13.3 or so to be safe ????

 

[Grn92LX]

12.9-13.2 up top and a little leaner in the mid range for n/a.

 

[90Notch]

All depends on the combo.

 

[2002BLGT]

stock bottom end 94K miles , B303 cam , GT40 y303 heads , typhoon intake , 70mm EGR and TB , 24 lbs injectors , granatelli MAF calibrated for 24s ,255lph pump , adj FPR , stock shortys , gutted stock hpipe , flowmaster catback , 410s on the way ......308s in it now .......thats the combo if anybody else wishes to give advice

 

[gt90stang]

Mine is tweeked to run 13.0-13.5, it will be +/-0.25 AFR unless you do an insane amount of tuning.

Good Luck, Don

 

[90mustangGT]

Isn't 14.7 suposed to be optimum???

 

[gt90stang]

90mustangGT,

Stoich or 14.7:1 is best for emissions. For power NA 13-13.5:1 is best, for power adders 12:1 is usually recommended.

2002BLGT,

Just re-read your post. Adjusting your FPR will not change your AFR, the computer will re-learn and adjust the AFR to the tables in the PCM. Adjusting the FPR will only make the injectors look larger with higher pressure or smaller with lower pressure. The PCM can adjust about +/-20% and will throw codes if it can't contol the AFR properly. You will need a Tweecer, or similiar chip to mess with the AFR. I adjusted mine using the Base OL fuel table in the PCM.

Don

 

[Michael Yount]

It's a bit more complex than referencing a particular number for 'best power' or 'best emissions'. But the guys have zeroed in on the range for you. If you can keep it in the 13.0-13.5 range, slightly richer than stoichiometric (14.7), you'll make the most power. That will result in slightly cooler combustion temps, which will reduce nitrous oxides emissions; however, both CO and unburned HC will be higher than they would be if the mixture were leaner. HC and CO drop significantly as the mixture gets leaner, but temps increase too, which increases NOx. That's the dance that emission control engineers have to do - you go in one direction and it hurts in some areas/helps in others; go in the other direction and the opposite occurs.