Lean Or Rich?

[Hites]

do our sc400s usually run richer or leaner than the stoichiometric 14.7:1 air/fuel ratio?

[AWJ]

What year? Emission controls have the most impact on this. The ecu will regulate a/f ratio based on oxygen sensor signal, throttle position, air flow through the intake, intake temperature, and probably a couple other things. I would expect to see a post 1996 model year car to pull back on fuel much more than earlier models. I could be wrong though. Just guessing.

I would be surprised if any car ran leaner than stoich. Of course the leaner the mix, the closer to detonation we get. That is bad. It is the goal of modern emissions systems to run as lean as possible though for environmental reasons. I'd expect that at idle, a/f would typically hover around stoich possibly lean or real lean. Conversly, at wide open throttle, the car is going to be richer. Exactly what the ratio will be ultimately falls down to the specific vehicle in question because every car is different. Only way to know for sure and accurately, as far as I know, is to hook up to a wide band of some sort either on a chassis dynamometer or with an aftermarket plug in sensor and display.

For reference - many turbo charged cars, especially the more aggressively tuned ones - tend to shoot for ratios at 11 to 12:1, sometimes even 10. At wide open throttle that is. the trees and the green party.

[bean_8044]

Ive been checkin out some different peoples fuel settings for the S-AFC and alot of the soarers run way rich on high throttle. Alot of people have the fuel set at 10-18% below the stock ecu, but thats on the earlier turbo models...

[Hites]

i was thinkin about looking for a wideband o2 sensor (the sc400 doesnt come stock with a wideband, right?), af gauge, and an apexi safc to squeeze a scant few extra hp out and also improve gas mileage. but after buying all that, ill probably be in the hole over $300 which would defeat the whole purpose of pinching pennies (isnt this like the same problem with hybrid vehicles currently? they cost too much to justify their efficient gas mileage?). guess ill get that eram thingamabob to overcompensate for the richness at wot.

[bean_8044]

Well, im sure the hybrids may cost alot at first, but it seems like you save money in the long run, especially with the tax credit. If i could squeeze an extra 50-75km from my tank then that stuff would pay for itself....well, maybe in a year or so.

[Lex Luthor]

Hites, a wideband is an A/F meter, you wouldn't need to buy it twice. You could save yourself some cash by just buying the AFC and having a competent shop tune it with a WB, then don't touch the settings yourself.

[SPORTcoupe300]

So for a car that's stock so far but will be getting intake and exhaust, which piggyback is the best?

Actually, to rephrase the question: Which one is the best bang for the buck?

[AWJ]

If you're just doing I/H/E I'd say the afc is fine. Cool little unit. Had one in the '93.

[SPORTcoupe300]

Well apexi has the older AFC, the newer SAFC and the brand new SAFC-II.

If they all do the same thing, I'd go with the older one just cuz it'd be easier to mount discretely.

[AWJ]

Sorry. S-afc is what I had. Gave a cool display. Lots of different options too. I hear the second gen has some more options though.

[Hites]

there are absolutely ZERO shops that could tune my car. the apexi safc is probably the best bang/buck piggyback, and i personally think the most user friendly.

[SPORTcoupe300]

So you've wired yours to an SC?

If yes, how did you choose which of the knock sensors to use?