Fuel Ratio question - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

240sxworkinprogress · 02-18-2007, 05:06 PM

A few days ago I went to the dyno and got some good numbers. The question is that when I was at 13psi the air to fuel ratio was on the lean side. I was running about 13.3 between 3000 and 4500rpm and then dropped to a safe fuel ratio of about 11.5. The red line on the graph in 12.1 it not labeled. What is the normal fuel curve for a S14 black top? The only thing that is done to it is fmic, full exhaust and a manual boost controller. After dyno it just got me nervous about how lean it was running. What would cause it to run so lean? Also would a safc2 fix the problem?
http://i173.photobucket.com/albums/w...g?t=1171842605

GSXRJJordan · 02-18-2007, 05:44 PM

That's kind of lean for full throttle, but it's not "lean" stoicheometrically (sp?). If it richens up later, you know it's not your injectors running out or your fuel pressure being too low...

The red line is a guide, meaning at full throttle you'd like to be about 12:1 or 11.5:1 on a safe tune, but as I understand it it's pretty common for stock ECUs to run a little less fuel there, and I wouldn't worry too much as long as it richens up as you get closer to redline.

An air/fuel controller would allow you to make adjustments, yes, but unless you're going for more mods I wouldn't worry too much about it.

eastcoastS14 · 02-18-2007, 05:57 PM

^^ +1 i was really worried about my AFR when i first got my car up and running...take a look at this... my car was idling around 16 can be fixed by getting an good tune i have a enthalpy rom tune ecu

6.o rich burn limit (warm engine)
9.0 Black smoke bellow power
11.5 Approximate rich best torque at WOT
12.2 Safe best power at WOT <---- this is what you want
13.3 approximate lean best torque
14.6 Stoichiometric AFR (chemically Ideal) <--- this is what you want for Low throttle setting [cruise]
15.5 lean cruise
16.5 usual best economy
18.0 carburated burn limit
22+ ecc/EFI lean burn limit.

^^ hope that helps some how

240sxworkinprogress · 02-18-2007, 10:54 PM

Yea I wasn't sure if this fuel curve was normal or not. I think I'll try getting a afc and get the ratio to about 11.5-12.1 so I can play it safe. I don't want to take any chance with the motor.

bardabe · 02-18-2007, 11:43 PM

yep that graph eastcoastS14 posted is exactly the one I wrote not too long ago. search nextime pal. but yea you are safe.

eastcoastS14 · 02-19-2007, 01:56 AM

^^^ hahah yeah i def stole ur graph lol it was very helpful posi rep for u because i didnt do it before

240sxworkinprogress · 02-19-2007, 02:21 AM

Hey EastcoastS14 could you send me a link of you graph you posted. I tryed Searching by the looking at the one you posted but I can't seem to find the graph. Also Thanks for the help!!!!!!

eastcoastS14 · 02-19-2007, 03:01 AM

^^ lol sorry the table i posted is what i meant by graph

6.o rich burn limit (warm engine)
9.0 Black smoke bellow power
11.5 Approximate rich best torque at WOT
12.2 Safe best power at WOT <---- this is what you want
13.3 approximate lean best torque
14.6 Stoichiometric AFR (chemically Ideal) <--- this is what you want for Low throttle setting [cruise]
15.5 lean cruise
16.5 usual best economy
18.0 carburated burn limit
22+ ecc/EFI lean burn limit.

^^ this is what i was talkin about...theres no actual visual graph or anythin if thats what u mean...lol sorry

and yeah np so easy to freak out over AFR issues hopefully everythin turns out ok

02-18-2007, 05:06 PM	#1
240sxworkinprogress Leaky Injector Join Date: Feb 2006 Location: Crestwood Posts: 118 Trader Rating: (1) Feedback Score: 1 reviews	Fuel Ratio question A few days ago I went to the dyno and got some good numbers. The question is that when I was at 13psi the air to fuel ratio was on the lean side. I was running about 13.3 between 3000 and 4500rpm and then dropped to a safe fuel ratio of about 11.5. The red line on the graph in 12.1 it not labeled. What is the normal fuel curve for a S14 black top? The only thing that is done to it is fmic, full exhaust and a manual boost controller. After dyno it just got me nervous about how lean it was running. What would cause it to run so lean? Also would a safc2 fix the problem? http://i173.photobucket.com/albums/w...g?t=1171842605

02-18-2007, 05:44 PM	#2
GSXRJJordan Post Whore! Join Date: May 2006 Location: << 626 >> Posts: 9,135 Trader Rating: (19) Rides Gallery: GSXRJJordan Feedback Score: 19 reviews	That's kind of lean for full throttle, but it's not "lean" stoicheometrically (sp?). If it richens up later, you know it's not your injectors running out or your fuel pressure being too low... The red line is a guide, meaning at full throttle you'd like to be about 12:1 or 11.5:1 on a safe tune, but as I understand it it's pretty common for stock ECUs to run a little less fuel there, and I wouldn't worry too much as long as it richens up as you get closer to redline. An air/fuel controller would allow you to make adjustments, yes, but unless you're going for more mods I wouldn't worry too much about it. __________________ Jordan Innovations has a new web site! www.JordanInnovations.com -- All your favorite FD Pro Drifters love it, trust me -- www.JordanInnovations.com

02-18-2007, 11:43 PM	#5
bardabe Post Whore! Join Date: Aug 2005 Location: SoCal Age: 31 Posts: 4,716 Trader Rating: (10) Rides Gallery: bardabe Feedback Score: 10 reviews	yep that graph eastcoastS14 posted is exactly the one I wrote not too long ago. search nextime pal. but yea you are safe. __________________ Review Thread

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02-18-2007, 05:57 PM	#3
eastcoastS14 Post Whore! Join Date: Oct 2006 Location: the land of snow potholes and no tracks Posts: 3,984 Trader Rating: (1) Feedback Score: 1 reviews	^^ +1 i was really worried about my AFR when i first got my car up and running...take a look at this... my car was idling around 16 can be fixed by getting an good tune i have a enthalpy rom tune ecu 6.o rich burn limit (warm engine) 9.0 Black smoke bellow power 11.5 Approximate rich best torque at WOT 12.2 Safe best power at WOT <---- this is what you want 13.3 approximate lean best torque 14.6 Stoichiometric AFR (chemically Ideal) <--- this is what you want for Low throttle setting [cruise] 15.5 lean cruise 16.5 usual best economy 18.0 carburated burn limit 22+ ecc/EFI lean burn limit. ^^ hope that helps some how

02-18-2007, 10:54 PM	#4
240sxworkinprogress Leaky Injector Join Date: Feb 2006 Location: Crestwood Posts: 118 Trader Rating: (1) Feedback Score: 1 reviews	Yea I wasn't sure if this fuel curve was normal or not. I think I'll try getting a afc and get the ratio to about 11.5-12.1 so I can play it safe. I don't want to take any chance with the motor.

02-19-2007, 01:56 AM	#6
eastcoastS14 Post Whore! Join Date: Oct 2006 Location: the land of snow potholes and no tracks Posts: 3,984 Trader Rating: (1) Feedback Score: 1 reviews	^^^ hahah yeah i def stole ur graph lol it was very helpful posi rep for u because i didnt do it before

02-19-2007, 02:21 AM	#7
240sxworkinprogress Leaky Injector Join Date: Feb 2006 Location: Crestwood Posts: 118 Trader Rating: (1) Feedback Score: 1 reviews	Hey EastcoastS14 could you send me a link of you graph you posted. I tryed Searching by the looking at the one you posted but I can't seem to find the graph. Also Thanks for the help!!!!!!

02-19-2007, 03:01 AM	#8
eastcoastS14 Post Whore! Join Date: Oct 2006 Location: the land of snow potholes and no tracks Posts: 3,984 Trader Rating: (1) Feedback Score: 1 reviews	^^ lol sorry the table i posted is what i meant by graph 6.o rich burn limit (warm engine) 9.0 Black smoke bellow power 11.5 Approximate rich best torque at WOT 12.2 Safe best power at WOT <---- this is what you want 13.3 approximate lean best torque 14.6 Stoichiometric AFR (chemically Ideal) <--- this is what you want for Low throttle setting [cruise] 15.5 lean cruise 16.5 usual best economy 18.0 carburated burn limit 22+ ecc/EFI lean burn limit. ^^ this is what i was talkin about...theres no actual visual graph or anythin if thats what u mean...lol sorry and yeah np so easy to freak out over AFR issues hopefully everythin turns out ok