I was wondering for those with widebands in your N/A cars, what are you seeing for a/f numbers at wot. I just got my car put back together, and i'm using some clightly larger injectors and i'm going to turn down the fuel pressure some on the afpr to get it about right, but I don't know what right is. I didn't have the wideband in before the new fuel setup.
Looking for actual numbers. Also, what do you see on cruise control on a flat road at about 65 mph? 14.7:1 ? higher? lower?
When I was NA at idle I was right at 14.6 on the Highway sort of half throttle it jumped between low 14s high 15s, at full thottle quickly jumped into 13s as it ran higher in the rpms high 12s then at redline touches the 11s
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
If you're tuning I believe you would want to reach 12.6-13.1 @ WOT for max power and safety, although I'm not 100% and would love to hear from someone who actually knows this for sure.
15.3 @ 89.97mph, 14's on the way?
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Well, the reason i ask is becaose i now have 19 lds/hr injectors in my 95 sunfire, which stock had the 17lbs/hr, and the only thing i have to tune fuel is a fpr. Now i believe stock psi on fuel pressure is 45. What should the pressure be set at for these new injectors. Is it impossible to tune this with only the aerometer adustable fuel pressure regulator. Maybe this is my reason to get the emanage. since i'm going turbo in the future anyways.
On an NA car, you would want low 14's to be on the safe side. 14.7 is great if you can attain that and hold it without going leaner though. That's where you'll find the most power (at least in most cases).
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on my most recent dyno run with my ecotec with cams and TB i was at 15:1 - 15.2:1 and was only getting 118 whp but at the end of my run my a/f went to 13:1 and the hp jumped to 150 so id say no richer then 13:1 but nothing leaner then 14.6:1
04 sunfire auto, mid 15's n/a, and still going
Hmm, ok, I'm definately richer then that. I sometimes hit the 12's. I would be satisfed with it except that when i'm at 0 throttle, and the engine is coming down from high rpm, i hear what i believe is a backfire. and the wideband goes from the 19.9 lean to around 15 or 16. Right when there is the backfire. Is this maybe another issue, maybe i should try the mr. pute resistor trick on the car.
Anyone know at what pressure the 2200 injectors are rated at for their 19 lbs/hr. Then i can see at what pressure they will act like 17lbs/hr like my ecu is expecting.
my best advice would be about 14.2 or 14.3 with your setup
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Spotabee Racing wrote:my best advice would be about 14.2 or 14.3 with your setup
That seems awfully lean for WOT, even on an NA car. Do you know this, or is it a guess? I'd hate to see someone burn down their motor because they listened to bad advice on the internet! I've always been told to aim for 12.8-13.1 on an NA car, richer on a boosted car, but there's misinformation all over the place.
15.3 @ 89.97mph, 14's on the way?
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'01 SFGT springs $50CAN
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the stoichiometric window (14.5-15 : 1) is purely for emmission and nothing else, if you want fuel economy you can go 18:1 for cruising (a lot of cars even go higher) but it will increase NOx, if you want power you go rich but the cutoff is around 12.5 : 1 and you will have excessive CO and HC.
the 14.7 simply allows the cat to do a better job with lower emissions and decent fuel economy.
excess pressure on a stock computer won't do too much, as the PCM will shorten the duty cycle / pulse width. however the stock computer will also go rich on WOT. O2 sensors usually read around 800mv on WOT, it is designed into the system which is pretty much why the venom and similiar "magic boxes" seem to work, because it reads WOT and goes full rich reguardless of throttle position.
on a boosted car it isn't so much the ratio but the pressure - because there is pressurized air it is more resistance for the fuel to enter the combustion chamber. but on a N/A car pressure doesn't matter as much as duty cucle.
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