800mV @ WOT
Thread Starter
Instructor
Joined: Mar 2003
Posts: 239
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From: Toronto Ontario
800mV @ WOT
I'm playing with my fuel pressure and was wondering what is the optimal voltage for performance of a O2 sensor from idle to WOT.I have also noticed the more fuel pressure I give the more bottom end I lose so Ive been setting back my TPS voltage to gain it back is It OK to do this?
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Re: 800mV @ WOT (scorp508)
If you are adding more fuel pressure then you are adding fuel across the board and especially down low. What pressure are you running now? The ECM may not be able to correct enough to get the fuel trims in line at the lower RPMS and TPS points.
It is more advisable to add fuel in the PE tables of your fuel map. But that would take custom tuning of your PROM or PCM which ever you may have. Setting the TPS may or may not make it any better depending on what year your car is the ECM auto zeros in the later model years and anything below .85V is looked at as zero throttle position by the PCM.
[Modified by tjwong, 1:06 AM 9/19/2003]
It is more advisable to add fuel in the PE tables of your fuel map. But that would take custom tuning of your PROM or PCM which ever you may have. Setting the TPS may or may not make it any better depending on what year your car is the ECM auto zeros in the later model years and anything below .85V is looked at as zero throttle position by the PCM.
[Modified by tjwong, 1:06 AM 9/19/2003]
Melting Slicks
Joined: Sep 2000
Posts: 3,099
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From: PITTSBURGH PA
Cruise-In IV Veteran
Cruise-In V Veteran
Re: 800mV @ WOT (tjwong)
i try and shoot for 800 mv in high gear at the drags if you want to slow it down some you could add more fuel to bring the mvs back up and richen up the mixture :cheers:
Melting Slicks
Joined: May 1999
Posts: 2,037
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From: Sarasota FL
Re: 800mV @ WOT (91superram)
The stock O2 is only a above/below 14.7:1 switch. 800mv ONLY tells you rich. Might be 14.0:1, might be 11.0:1. Tuning for a mv range on a narrow O2 is almost useless.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Re: 800mV @ WOT (91superram)
I'm running 48psi with stock 22lb/hr injectors which gives me about 920-940mV going through the traps. On a dyno with a WB O2 sensor the A/F ratio at WOT was about 12.6:1. I don't have a bog problem with my A4 so don't realy care if it's a little rich at WOT on the low end so long as it's close in mid and upper RPMs.
You can use the stock O2 sensor readings as a rough indicator of A/F though indeed the curve is very flat off stoch so accuracy isn't very good. A few weeks ago Scrop posted some data relating his stock O2 sensor readings vs those using a WB O2 sensor and they correlate pretty well with what I've observed.
You can either tune fuel pressure for best trap speed over several runs (here consistency is the issue) or use a dyno with WB O2 sensor for tuning fuel pressure. If you record the readings from your stock O2 sensor you will then have a tuning guide when adding more air flow mods.
You can use the stock O2 sensor readings as a rough indicator of A/F though indeed the curve is very flat off stoch so accuracy isn't very good. A few weeks ago Scrop posted some data relating his stock O2 sensor readings vs those using a WB O2 sensor and they correlate pretty well with what I've observed.
You can either tune fuel pressure for best trap speed over several runs (here consistency is the issue) or use a dyno with WB O2 sensor for tuning fuel pressure. If you record the readings from your stock O2 sensor you will then have a tuning guide when adding more air flow mods.
