O2 Question...

[Andy]

I posted this in the general section but I wasnt sure if this was more for this section.

Does anybody have a really good understanding of O2 sensors and LTFT's on our cars. For the longest time I thought I had a 1 volt o2 sensor and now I am starting to wonder. The V8s have an O2 sensor that reads .89 - .91 as the stoich ratio.
This is fine if you have a 1.5 volt O2. I thought this whole time I was running rich because thats what my gauge said and so does autotap. After some brief discussion with those guys I got to thinking that maybe mine is also a 1.5 volt.

My LTFT is fine and stays pretty close to o%. Actually its like 3%. If I were running rich wouldnt the pcm try to compensate and shift the trim down some?

If anybody knows or has a helms manual please let me know. I have a chiltons and it says that it should be a 1 volt.

[Magnus]

Good Post. [img]smile.gif[/img]

I have a GREAT understanding of our air/fuel system, LTFT's, O2's, MAF readings and pulse widths. [img]smile.gif[/img]

We have the same O2's they do.. Heated Oxygen Sensors where as the 3.4's have non-heated ones.. The wire connections do varry between the years.

Mike Huff recieved a 96 engine with flat style connectors for the O2's where as his 98 has the square style like mine does.

I always thought they were 1 volt. I have never ever seen readings past 1 volt.. I don't know if they are actually 1 or 1.5 volt sensors though.

You should shoot for around .89 o2's at WOT. Our cars run better a little leaner. .850 might even work at the track well, but you would have to do some testing to get some more solid results.. I'll try to do testing next time I go for that.

If you were running Rich, the pcm would shift the LT's down a little. I notice our cars typically see 1.6-3% LT's at WOT.

I see -12% because of my ported TB and have picked up 4 degrees or so of advance because of this.

LT's at WOT are worthless.. I think LT's period are pretty much worthless.. People shoot for 0% LT's at cruise but what for.. So the PCM thinks everything is fine and has to make less corrections. I do not believe this. And.... so what if the PCM has to make corrections, it's a computer, it will calculate FAST.

The problem with LT's come during cold starts. If you have high LT's at cruise and idle, then you will run lean on a cold start (open loop) and if you have very negative #'s you'll run very rich on a cold start.

I run VERY rich on a cold start and tend to run rich at normal idle as well.

If you want to tune the car with a MAF Translator, I recomend you do not touch the base setting.. THe more you adjust the base setting, the more your #'s will vary at WOT. I would tune only for WOT using the WOT settings on the MAF T+.

If you have ANY more questions at all or are confused in any way about this, just say the word and i will try to help clear things up for you. [img]smile.gif[/img]

[Andy]

My average O2 sensor reading was 0.884071429. It was pretty close to that on both sides. I too have the square O2 connectors. My LTFT #s were 1.913986014 and 3.951366815. I got at the highest 1.5 knock and I only got that three times in about 20 minutes of driving and a hand full of WOT runs.

The only thing that bothered me was that all along I thought I had a 1 volt O2 which a reading of .88 would indicate a rich mixture by about .28 volts. However, on a 1.5 volt .88 would be right in the stoich range.

I used a friends MAF translator and tried to adjust the levels but the fuel trims just adjusted it out.

So...

This is what got me thinking. I think we have a 1.5 volt just like the V8s do. Otherwise Some difference would have been made when I changed the levels. In Conclusion if we do have one then I am running just fine.

Reason I am wondering so much about this is because I am looking at NOS as a really close future mod. Tell me did it cause any changes in how the car ran that you had to tune out? A/F? How did you install it(location) and what kit (wet, dry, before maf, after maf, intake)?

Thanks Again

[Magnus]

I ONLY use the WOT settings on the MAFT.. and the PCM can't learn thouse out. Whatever my cruise long trims are... they are.. doesn't mean a thing. Don't get too cought up on finding an ideal long trim at cruise or even at WOT. Just look for your WOT o2 #'s and play with those.

I ran a wet shot. I would look for at least .910 o2's on nitrous. If I was running a dry shot I would probably bump up the WOT settings on the MAF T to richen up the mixture.

My MAF T + causes no changes in the car that I have to tune out.. I simply lean it out a little at WOT and add 2 degrees of advance. Only time the MAF T+ is actually working is full throttle.

I just let my unit hang near the ABS unit under the fuel lines next to the SLP CAI.

[Jason McCallister]

Quick question... I'm assuming .50 volt = 14.7:1, correct? Also, how many parts of air per hundreth volt?

Thanks! I'm trying to further educate myself in the art of O2 tuning! :D

[Andy]

On my gauge which reads 0 - 1 volt, 20 leds that are .05 volts each. 4 leds are for rich .85 - 1.0, 6 leds are for lean 0 - .3, and ten others for midrange .35 - .8

I am currently on the first green light (rich). That is also what the autotap reads. If it is supposed to be that then I am ok. I just wanted to make sure that my o2 were still reading good and accurate readings and if those readings are what everyone else is getting.

I want to do NOS but I want to make sure that everything else is operating perfectly first though. So with the addition of NOS I shouldnt have any problems magnus? Since I dont have any now.

Andy

[Magnus]

Yes your O2's are good and your readings are also very good. Your running in the sweet spot.

You shouldn't have any problems with the addition of N20. Many people just slap it on their cars and go... I recomend getting the car to run a little richer for safetey reasons. On juice, I would shoot for no less than a .900 o2 and try to average around .920 for safety reasons.

Better to run rich then to run lean on nitrous.

If your running a dry kit, I recomend buying a MAF Translator or a MAF Translator Plus and increasing the WOT fuel by +2 or +4 %.

Note: The only difference between the MAF T and the MAF T + is the + version also can manipulate timing (Which might be benaficial to retard the timing).

If your running a wet shot, you should be ok with your air/fuel ratios but you still need to double check with a scan tool.

- Keith

[RedbirdV6]

Ok, I have a question that I have yet to get a straight answer to. I removed my cat and am getting a bad o2 reading(SES light) is this effecting performance, fuel mix, air mix, etc..... I just got my o2 sims in the mail yesterday, will this cure the problem and can I expect a performance gain from it. I only ordedered, to go pre cat. Should I have oredered 2? Thanks :D

[Magnus]

The only o2's that affect performance are the ones in the primaries.. O2 B1S1 and B2S1. The o2's before and after the cat are for emissions purposes. The one before the cat (toward the front of the car) doesn't really do much and the newer cars don't have them. The one after the cat checks how well the cat is functioning.

If any O2 fails it will throw an SES light.

Adding an O2 simm AFTER the cat will correct the "insuffecient catalyst" codes. It will not give you any more performance because those o2's are not used to calculate fuel trim cells.

Put the o2 simm AFTER the cat and you should be ok. Leave the pre cat o2 still in the exhaust and you won't have to buy another o2 simm.

I have a simm on my post cat o2 and the pre cat o2 still in the exhaust.

- Keith

[Andy]

I used a friends maft, where would I get a maft+? how much? Is there a special model for our cars or are they universal?

Thanks again for the replies! :)

[Magnus]

ramchargers.com

They only make one model of the MAF T and one model of the MAF T+.. they just update the versions.. My MAF T+ version is 5.2.

They are pretty much universal. I used the MAF T and that worked and then ordered a MAF T+ and it works as well. [img]smile.gif[/img]

MAF T+ is around $270 or so. Kinda heft price but it can do what the pricey DIS-4 can do in terms of timing retard and also can do what the pricy Jet PCM modeul can do in terms of timing advance.. and also allows you to change the air/fuel ratios .. [img]smile.gif[/img]

[Jason McCallister]

Thanks for the response, Andy.

Here's a O2 gauge that appears to display the actual voltage of the O2! I think "on the fly" tuning would be much easier with this gauge. It's on my "next mod" list! :D

http://www.nordskogperformance.com/m9200.html

EDIT: Summit carries these gauges in stock. Just add NRD- in front of the manufacturer part #. Ex: NRD-M9200 That goes will all of Nordskog gauges.

The B2200 gauge would be excellent for those running N2O. It has a programmable output for "lean" condition warning.

[ January 08, 2002: Message edited by: Jason McCallister ]</p>

[slacker69]

I got a ?? for yall. I when and had my comp tested cause of SES lights and it fas and still is cause or the right O2 running high and triggering SES every like 100 miles after I reset it. So how can I fix or do I need to get a new O2 sensor . I have 3 inch cat 2.5" i-pipe and rksport headers. I also have a O2 sim could that have gone bad so now it triggers an SES light. Thanks for all your help

[94-3.4]

http://www.apexi-usa.com/electronics_timer.asp

This looks like a pretty cool gismo and also reads a/f and o2 readings. What do you guys think?

Also, i have 2 O2 sensors, one on each primary, how would i hook this meter up to it? Thanks

[Andy]

I chose to use the gauge from autometer and tap into the line from the O2 sensor just before the cat. I read through a long reasoning why you should put it there instead of anywhere else.

"basically by putting it on one of the primaries you are effectivly only reading one side. By using the sensor just before the cat you get an overall picture of the levels from both sides. Obviously you wouldn't want to use the one after the cat since it is mainly for emissions reasons."

As for the Apexi ... I dont know. It looks abit to much. I wanted something a little more standard. But to each his own. I am sure it will work fine and my only suggestion would be to hook that bad boy up to the O2 just before the cat.

Andy