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Boost-a-holic
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Discussion Starter #1
ok this is whats up... my vf data is at 2.22 indicating a stoich mixture i think... but i installed a air fuel guage today and it indicates off the dial lean until i rev and then barely stoich.. and back to off the dial lean... am i lean or what. im running lex and 550s stock pump. also i hooked the af guage to the blue wire at the o2 sensor any help would help..
 

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Aftermarket A/F guages are nothing more then a blinky light that looks neat in the car. They aren't an accurate representation of what your mixture is. Also is it lean at idle? Cause your mixture will be set lean. If I'm mistaken at idle the A/F mixture is around 14.7:1 until you start giving it some gas. It is set that way for bottom end power and fuel economy.
 
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The oxygen sensor doesn't work well at idle. It cools off and doesn't respond, at least in my car. It drops to a low level, hence the indication of lean on your meter, but it's really just not working.

Drive at a steady pace on the road, and the meter should work.
 

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Discussion Starter #4
so i need to look at vf data as more accurate? i can only check that at idle. but it seems to get a little ping under high boost say around 13psi so i thought i was lean. and the af gauge scared the shoot out of me. i got an afpr so should i try to tune a little more fuel pressure?
 
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Unfortunately you cannot use the inexpensive a/f meter for tuning.

It doesn't tell you how rich you are. All it really tells you is if you're around 14.7 ratio, or richer or leaner than that. It doesn't know by how much richer/leaner, since the stock oxygen sensor doesn't have a clue either.

The VF data doesn't tell you much either. It just tells you that the engine thinks it knows what it's doing, but since you're probably not stock, it cannot help you when you're accelerating hard, or at wide open throttle.

You're flying blind unfortunately. But yes, more fuel is usually much safer than too little.
 

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Hello Alan

Normally you only use the Vf signal for setting the base adjustment of your Lexus air screw, here is a small writhe-up of how to adjust by Vf:

When at idle the Vf signal should be around 2.5v (stoichiometric).
Connect Vf and E1to your multi-meter at the diagnostic connector
and reset the Lexus AFM air screw to achieve 2.5v at idle. Vf is the
feedback (ie, short term trim) on how much fuel the TCCS ECU is
adding or subtracting from the Basic Fuel Calculation for the
conditions the various sensors (TPS, AFM, Ambient Air Temp,
Altitude Sensor, Coolant sensor, O2 sensor, others) are reporting.
Take the reading at idle or any other condition less than 70%
throttle. Set the air screw to achieve 2.5v or less - basically, at less
than 2.5v Vf, the TCCS ECU is removing fuel from the Basic Fuel
Calculation to achieve stoichiometric conditions and adding fuel
when the Vf voltage is greater than 2.5v to achieve stiochiometric
conditions. For more info on Vf, do an Archive search.

In order to determine your fuel mixture on the road I would strongly suggest a Wideband O2 sensor, for information take a look at my side regarding fine tune at:

http://www.supra4ever.dk/Fine Tuning.htm

HTH and feel free to ask again

Later
Karsten
www.supra4ever.dk/index.htm
 
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Great site Karsten. It has been added to my favorites. :bigthumb:

It is interesting to see how the a/f gets richer the higher the load on the engine.
http://www.supra4ever.dk/Diverse grafik/AF_2.jpg

I'm guessing this is 4th and 5th gear?

It would be nice to see how it correlates to the AFM output versus RPM and throttle. I believe the ECU calculates the load solely on these inputs?

Keep up the good work.
 

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Hello Shawn

Thanks for the kind words, just trying to share some of my achieved knowledge :)

On my car, with the same set-up on the S-AFC, it will run richer when I'm raising boost. I have played a lot with my fuel pressure in order to counter that specific problem, as I see it the only way is to re-wire the S-AFC in order to control fuel by boost pressure instead of RPM.

The recorded run is made in third and forth gear, doing 6500 rpm i fifth will cost my drivers license if caught :))

As I see it, fuel above 70% opening of TPS(open loop) is only controlled by the pre-programmed maps in the ECU. The Karman Vortex signal will only control FC, correct me if I'm wrong.
When under 70%, it will be controlled as you are mentioning.

Later
Karsten
www.supra4ever.dk/index.htm
 

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when this baby hits 88mph
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agreed. id hate to think (and know they are probably several) that tune using Vf and a blinky a/f gauge.

btw- you in ky? if you are ever in the louisville area lmk. i could help you tune at the local dyno equip'd w/ a wideband.

dave
 

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Discussion Starter #10
well thats why i love supraforums cuz i can stand on the shoulders of all the mad scientists....
unfortunatly thats exactly what im doing, using fuel pressure guage, vf data, af guage and member knowledge. thats all i have right now. Ive done all the upgrades and purchased all the goodies. now i have to tune the darn thing. thats my weak spot.
 
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