Scott 88 GTA

OK, I went out for a ride with my scanner earlier, and noticed that when I floored it that the scanner was still reading Closed Loop, and the O2 was reading Rich the whole time, even though the O2 volts was only .790 Is this normal? I thought the scanner would show Open at WOT. So I looked at my TPS voltage and it was only 4.42 V at WOT, so I adjusted it to be 4.66 V, but it didn't change anything. How can I tell if the ECM is kicking into Open Loop or not?

Also, my O2 voltage never got above .820 mV while I was cruising around. I thought that it was supposed to be around .860 mV. I've increased my fuel pressure a little, but I don't have a gauge so I don't know what it's set at. Also, what is the duty cycle for the stock 22 lb. injectors? At WOT they were running at 12.5 ms, is that too long? Should I increase my fuel pressure even more?

Thanks,
Scott

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Black 88 GTA L98
!Airbox, !IAT, !MAF, !TB, !Plenum, SLP 1 3/4" headers, Dynomax Hi-Flo cat & cat-back, Corvette Servo
14.389 @ 95.2 mph, 2.001 60' {Before headers, new times coming soon)

Pablo

iTrader: (1)

ok while you are driving around your Air fuel ratio is supposed to be 14.7:1 = efficient
when you floor it, your afr wants to be around 12.7:1 = innefficient, but most power

you DONT want your afr to be anywhere around .8 on the 02 sensor when you are cruising around as that is extremely rich for part throttle, its supposed to be in the range of .4

WOT, is when it should be up richer usually above 8 BUT, these sensors are NOT accurate at anything away from 14.7:1 as that is all they were designed to be accurate at. SO, dont use the 02 sensor as your only guide ideally you should experiment at the track and see what yields your best times
Also, when you floor it, your tps should go past 4.5 and you will be in WOT which is power enrichment mode. Most people see their o2 come up into the mid 8 range up to 9 and thats probably where you want to start off as your baseline for finding the 'sweet spot' that your engine wants to run at.
I dont know about how your scan tool reads on your car but the tell tale sign to see if you are at WOT or not is to just look at the blm values, if they just go straight to 128 when you floor it then you are fine.
but remember, you DONT want your car anywhere NEAR 8 at part throttle! way too rich! lots of gas money!
the scanner should have an explanation of BLM and integrator values, read about that as they are important for part throttle tuning

Kevin G

Since your o2 is steady around .800 mv.s you defintely in open loop, for some reason the scanner isnt saying it. I am sure all of the values wil show open loop. I had a Snap On scanner that did it to me..minor glitch I guess.

As Pablo said, o2 sensors arent too accurate, but I have always had very good luck using the voltage to tune with. I always had the best luck tuning WOT around to .820 mvs N/A lean is mean...... .790 is a little on the lean side, so I would bump the fuel presure up a little and check the .mvs again at Wide Open Throttle. Best time to check for WOT is on the top of 2nd gear...(most load) automatic, or top 3rd gear manual

in closed loop under normal driving, you O2 mvs. should jump back and forth constantly... if it holds, then you could have a lazy O2. check the O2 cross counts parameter if your scanner has it.


[This message has been edited by Kevin G (edited September 16, 2000).]

Kevin G

Quote From Blade on another post

Seems like several different scanners have some problems representing closed and open loop status...

Scott 88 GTA

Thanks guys. At part throttle cruising the O2 was jumping back and forth between around .8 and .2 like it is supposed to. I'm just trying to find out how I should set things at WOT to get the most performance.

The scanner is an older OTC model, and displays everything. I'll watch the BLM and Integrator today and see how that goes. Also, what is the O2 Cross anyway? How do I read the values that it displays?

Also, the O2 is brand new - I put a new one in with my headers a few weeks ago.

And does anyone know what the max duty cycle for the stock injectors is?

------------------
Black 88 GTA L98
!Airbox, !IAT, !MAF, !TB, !Plenum, SLP 1 3/4" headers, Dynomax Hi-Flo cat & cat-back, Corvette Servo
14.389 @ 95.2 mph, 2.001 60' {Before headers, new times coming soon)

[This message has been edited by Scott 88 GTA (edited September 16, 2000).]