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Top 2GNT Technical Turbo/Nitrous Tech topic #66797
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Subject: "more air flow=richer a/f ratio??" Previous topic | Next topic
ModeratormicyekMar-10-04 11:59 AM
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#66797, "more air flow=richer a/f ratio??"


          

ok...here's the deal. I'm running 310cc/m injectors, the 2nd biggest sfmu disk and about 7psi of boost. Before, at static pressure in open loop I would run rich...like .96X V at the front O2 sensor....but at full boost it would lean out to about .90X. But I left it this way because it would only cause a CEL for being to rich at static some times and at full boost I didn't get any knock and my EGT's would only climb to 1550 on really long highway pulls. But today I finally decided to tune the car right and rig up a bleed valve set up, and switch to the biggest SFMU disk. And I also picked up a new "better" air filter. My old one came with a CAI I bought on ebay (I know ) Anyway the new one is like twice the size of my old one. It's a S&B but I got it at a performance shop and the dude that sold it to me said it's the one he runs on his 1G AWD plus it was like 10 bucks cheaper then the APC and Ractive filters they had. So I buy the thing right and throw it on out in the parking lot, all the time I'm think I'm really gonna have to watch my gauges when I get on it, because I probably get more air flow and lean out even more under boost. But just the opposite happened...at full boost my O2 voltage reading was .94X So what gives? I couldn't get an EGT reading because I couldn't get a long enough pull. I also wanted to get some fuel trim readings but I couldn't get my pocket logger to connect for some stupid reason. SO more research is necessary...but could anyone enlighten me as to why I got the results I did? And as it stands now I can lower my static fuel pressure a bit and get more out of my car with out switching my fuel system around.

TIA!

getty up

-kent-




'98 Talon...gone, but not forgotten

  

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TeamXtremeRSMar-10-04 02:41 PM
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#66803, "RE: more air flow=richer a/f ratio??"
In response to Reply # 0


          

I think in a way you may have answered your own questions..sort of haha..You need to get your datalogger connected, and get a long pull on the highway at WOT at your full boost(7 psi?). You are right on for 1550 max EGT on a long pull, in 4th at WOT... .96 should be around where you want to be for 7 psi. That really is not rich. .90 is way too lean, and .94 would be a very minimum to run. I know i get almost 1 volt at wot in lower gears at 13 psi. Some would say that mega rich, but its not. The higer the boost, the more fuel you need, and once you start going over 10+ psi, you need to peg your o2 volts. But at 7 psi, you get a bit more room to run a little less fuel. If you got a CEL for too rich, that means that you pegged your STFT and LTFT at -25%, which means you have too high of idle fuel pressure. I run around 21-22 psi at idle, and its great, fuel trims look very good. I run the largest disk in the SFMU also, with about 1-2 turns open on the bleed valve, but thats for 13psi. YOu will prob need between 80-90 psi of fuel at 7 psi boost on the 310's. Oh, and that air filter you put on, prob is not really doing much of anything over your older one, unless it was super restrictive for some reason..It won't really make that big of difference, at least not enough to change your A/F ratio.


13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)

My webpage: http://eclipsed4evr.home.comcast.net
-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)

  

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DSMRoadsterMar-10-04 03:25 PM
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#66809, "RE: more air flow=richer a/f ratio??"
In response to Reply # 1




          

almost 1.v at 13psi? Damn I'm about .90-.92 at 13psi wot. And it pulls like a motherfucker on the highway.

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"Tell them of us and say,
For their tomorrow,
We gave our today."
-- The Kohima Epitaph

  

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TeamXtremeRSMar-10-04 04:21 PM
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#66815, "RE: more air flow=richer a/f ratio??"
In response to Reply # 2
Mar-10-04 04:24 PM by XtremeRS

          

Originally posted by DSMRoadster
almost 1.v at 13psi? Damn I'm about .90-.92 at 13psi wot. And it pulls like a motherfucker on the highway.


See the thing is, is that the stock o2 sensor sucks..really Its in no way accurate outside of the Stoich operating range(14.7:1) Thats why I really try to tell people to not tune to o2 volts that much. Just use it for a basic reference. I remember when Matt_95tgs was on the dyno, and at around 16-17 psi, the datalogger showed .99-1.0 volts, and the true A/F ratio was around 11.7:1 or so..Thats where you need to be when running hihger boost. .90 sounds way to lean for 13 psi. What are your EGT's? I always eyeball my EGT gauge on a hard pull, esp in 4th gear wide open on the highway. Remember, the lower the gear you are in, the less load on the motor, which results in lower EGT's. Thats why i always tune to WOT 4th gear long pull. Not too often I get to go WOT in 5th gear..


13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)

My webpage: http://eclipsed4evr.home.comcast.net
-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)

  

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ModeratormicyekMar-11-04 12:34 AM
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#66834, "RE: more air flow=richer a/f ratio??"
In response to Reply # 3


          

interesting...I always thought .92 was the target range. And that was what was considered a "safe" conservative number. But like you say the O2 voltage should just be a base line...I pay more attention to the EGT's more than anything. Thanx for the insight Matt.

getty up

-kent-




'98 Talon...gone, but not forgotten

  

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