Lean Condition, Help me troubleshoot!! - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Gavster · 06-12-2006, 02:31 PM

Hey guys. First off, thanks for taking time to read this, here we go!

K, I went to the dyno the other day and I got a sort of nasty shock. Throughout the whole powerband, my car ran 13.8~14.2ish afrs to red line. Im running a completely stock ECU, Black top S13 SR with 8psi on a GT28R with the usual bolt ons (mani, FMIC, DP, Exhaust, etc). The car runs well, driving it around you'd never know. It pulls hard, and up to this point, Ive been beating on it pretty hard since January, lol and still the motor is holding together. The spark plugs dont look lean, in fact they are a nice mocha color like healthy spark plugs are. I just dont know what gives....maybe it was a fluke on the dyno. Im getting ahold of a wideband this afternoon to hook up and drive around with to make sure its really a problem or not. If it is still running lean...what do i look for? I mean im running a fully stock ECU, teh afr curve was sooo straight the tune held to the targeted afr well, it was just up 2 points to high lol....if the line it made had been ar 11.5:1 id be stoked it was so straight.

Im wanting some pre-emptive fuel insurace though. Im still on a stock fuel pump, and i have a fresh fuel filter in. Should I maybe get a walbro 255 or maybe something like a SARD FPR to bump up the fuel pressure and get some more gas in? I can only afford either the pump or the fpr at this time, so which should I get of the two and if not, what else should I look at?

This is really baffling to me as the car runs like a top....its so strange...if it was really *that* lean I figured I wouldve blown it months ago....HELP!!

Gavster · 06-12-2006, 02:33 PM

Stock fuel sys BTW!

driftfactory · 06-12-2006, 03:12 PM

IT could be the stock fuel pump not pushing out enough fuel. The strange thing is that the plugs look ok. Plugs are a good indicator of whats going on in the motor. I would check it again to make sure the readings were right and drive it pretty tame in the mean time.

reactor · 06-13-2006, 01:25 AM

Your AFR is fine. 14.7 is stoichiometric and anything below that number is rich, anything above that number is lean. For a turbo motor you want to run a little more on the rich side under boost, but just up to the point where the motor doesn't ping. If you aren't pinging then you're fine, but you must keep an eye on whether or not the motor is pinging. Get the fuel pump first because even if you get the FPR you're stock pump isn't going to be able to put out much more pressure, and even if it does put out more pressure, it won't do so for long.

SpeedMonkeyInc · 06-13-2006, 01:35 AM

Its not fine. A turbo car should be 11.5-12:1 or so for safety. Sounds like a universal bump in fuel pressure would really help. Do the fuel pump first.

Gavster · 06-13-2006, 08:55 AM

yeah 14.0 is definately not good at all...like speedmonkey said, id like to see 12.0~11.5:1. Ill go ahead and get me a walbro!

06-12-2006, 02:31 PM	#1
Gavster Zilvia Junkie Join Date: Mar 2005 Location: Charleston, SC Age: 39 Posts: 512 Trader Rating: (4) Feedback Score: 4 reviews	Lean Condition, Help me troubleshoot!! Hey guys. First off, thanks for taking time to read this, here we go! K, I went to the dyno the other day and I got a sort of nasty shock. Throughout the whole powerband, my car ran 13.8~14.2ish afrs to red line. Im running a completely stock ECU, Black top S13 SR with 8psi on a GT28R with the usual bolt ons (mani, FMIC, DP, Exhaust, etc). The car runs well, driving it around you'd never know. It pulls hard, and up to this point, Ive been beating on it pretty hard since January, lol and still the motor is holding together. The spark plugs dont look lean, in fact they are a nice mocha color like healthy spark plugs are. I just dont know what gives....maybe it was a fluke on the dyno. Im getting ahold of a wideband this afternoon to hook up and drive around with to make sure its really a problem or not. If it is still running lean...what do i look for? I mean im running a fully stock ECU, teh afr curve was sooo straight the tune held to the targeted afr well, it was just up 2 points to high lol....if the line it made had been ar 11.5:1 id be stoked it was so straight. Im wanting some pre-emptive fuel insurace though. Im still on a stock fuel pump, and i have a fresh fuel filter in. Should I maybe get a walbro 255 or maybe something like a SARD FPR to bump up the fuel pressure and get some more gas in? I can only afford either the pump or the fpr at this time, so which should I get of the two and if not, what else should I look at? This is really baffling to me as the car runs like a top....its so strange...if it was really that lean I figured I wouldve blown it months ago....HELP!!

06-12-2006, 03:12 PM	#3
driftfactory Zilvia Member Join Date: Jun 2004 Location: LA Posts: 200 Trader Rating: (0) Feedback Score: 0 reviews	IT could be the stock fuel pump not pushing out enough fuel. The strange thing is that the plugs look ok. Plugs are a good indicator of whats going on in the motor. I would check it again to make sure the readings were right and drive it pretty tame in the mean time. __________________ The Performance Super Store. Nardi, Silk Road, Agency Power, KAAZ, Peak Performance, Cusco, and More! www.hachilife.com http://www.myspace.com/driftfactory

06-12-2006, 02:33 PM	#2
Gavster Zilvia Junkie Join Date: Mar 2005 Location: Charleston, SC Age: 39 Posts: 512 Trader Rating: (4) Feedback Score: 4 reviews	Stock fuel sys BTW!

06-13-2006, 01:25 AM	#4
reactor Leaky Injector Join Date: Aug 2005 Location: Washington Posts: 118 Trader Rating: (0) Feedback Score: 0 reviews	Your AFR is fine. 14.7 is stoichiometric and anything below that number is rich, anything above that number is lean. For a turbo motor you want to run a little more on the rich side under boost, but just up to the point where the motor doesn't ping. If you aren't pinging then you're fine, but you must keep an eye on whether or not the motor is pinging. Get the fuel pump first because even if you get the FPR you're stock pump isn't going to be able to put out much more pressure, and even if it does put out more pressure, it won't do so for long.

06-13-2006, 01:35 AM	#5
SpeedMonkeyInc Zilvia FREAK! Join Date: Apr 2003 Location: Oakland Age: 45 Posts: 1,271 Trader Rating: (0) Feedback Score: 0 reviews	Its not fine. A turbo car should be 11.5-12:1 or so for safety. Sounds like a universal bump in fuel pressure would really help. Do the fuel pump first.

06-13-2006, 08:55 AM	#6
Gavster Zilvia Junkie Join Date: Mar 2005 Location: Charleston, SC Age: 39 Posts: 512 Trader Rating: (4) Feedback Score: 4 reviews	yeah 14.0 is definately not good at all...like speedmonkey said, id like to see 12.0~11.5:1. Ill go ahead and get me a walbro!