420A Tuning

1fastRS · 06-26-2005, 05:04 PM

I've searched for answers to this before, and asked a few people, and I've yet to get any where, so I'm hoping someone can help. I just put in my wideband, so I've been playing with my S-AFCII, and leaning the fuel out a little to gain a little power. I know guys are making up to 10whp on relatively stock motors ( 420A ), and I'm just curious as to what there settings are. I know every car is different, but it seems like I have mine leaned out a lot, but Its still running rich above 4200rpm, at full throttle. My wideband is hooked up right, as far as I can tell, but I'm a little skeptical to keep turning the fuel down just in case. I was running as low as 11:1 a/f ratio, and I've only gotten it to mid to upper 12's. So would like to get someone elses advice, who's done this before. Is there some pointers, that I'm missing? Also, how accurate is the knock reading on the new S-AFC's?

420aVOS · 06-27-2005, 07:25 AM

leaning out for horsepower is a touchy thing at best, at higher rpms your engine is alot hotter so it is using a richer condition to cool things down a bit (before anyone says anything i know it is doing alot more than that), the more you lean it out the high chance for preignition, so be very carefull, and run 92 or higher gas. sorry i cant give you any numbers

1fastRS · 06-27-2005, 10:56 PM

I always use 93 octane, sometimes 94, so that's not a problem. I'm just trying to lean it out to 14.7:1, which is the best a/f for the car, in n/a form. So wouldn't that apply to higher rpms as well? Besides, I'm only running like mid to high 12's right now, thats up from low 11's, for the stock trim. So I haven't changed it much yet.

GVR4592 · 06-28-2005, 12:38 AM

Higher rpm's doesnt neccesarily mean you need more fuel. 14.7:1 is NOT the a/f ratio you should be shooting for at wot. That is the chemically perfect a/f ratio for combustion but it's far from perfect inside your engine. I'm assuming you are n/a so you should be shooting for somewhere in the 12.5:1 to 13:1 range at the torque peak and 13:1 to 13.5:1 at all other rpms when you are at wot. More fuel is required in torque peak not at higher rpms. You can lean it out after the torque peak and it will give you more power. 14.7:1 is fine for cruising but not for wot situations. The knock readout on the safc is not accurate at all. You really should be tuning on the dyno because you probably aren't going to notice an increase from a/f tuning by just driving around. I've seen gains as much as 75 whp on f/i cars just from a/f tuning but not on a n/a car.

1fastRS · 06-28-2005, 07:11 PM

Well I guess that works out for me then, becuase I'm already close to that range. I'm not going for numbers, so a dyno is not of a huge concern to me. Although, I have actually felt a difference, especially in third gear, which really sucks in my car. So whats the best way to read knock then? Is there a estimate you could get from the S-AFC, how far off is it?