Craig Moates

Folks,

I don't want to flirt with danger at the combustion zone, but I'm trying to take some fuel out. I'm going gradually, but wanted some rule-of-thumb guidelines if someone is so kind. For instance:

- What are some lower limits of O2 sensor / fuel mixture I should target? 15.5 at 400mV?
- With respect to the lean boundary, what are the values at idle/cruise compared to WOT? What's the danger threshold of mixture at WOT?

I know I shouldn't trust the O2 sensor implicitly, and ought to go WB instead. Maybe soon, but in the meantime...

Also, I'm looking to speed the warm-up time /w/ headers. What part is a good swap-in for our O2 sensors for a heated deal? Is a pig-tail available for the car-side connector?

I'm sure this stuff is in the archives, I'm being lazy and bumping up to the top since it might be relevant for some others also.

While I'm at it, one more question: For Jet-Hot coatings on headers/etc, has anyone had to get some warranty coverage for the stuff bubbling off & peeling away? Just wondering, lord knows if I still have the receipt on that one, been a couple years.

Thanks,
Craig

86TpiTransAm

The Heated O2 from the ZR1 Corvette is a 4 wire heated O2 sensor that will work. I don't know how you would hook it up though, you'd have ask someone about that.

If you can find a 3 wire heated O2 its easy to hook up, one wire hooks to the signal wire, one wire hooks to the power wire and the other one you have to make a wire to hook switched power to for the heating source. Something like that. I know it's in the archives somewhere.

Jza

Their (Jet-Hot) warranty won't cover the coating bubbling off do to bad tuning (running lean, bad timing). I'm about 90% sure I remember reading that on their warranty card. I can verify 100% when I get home.

I'd like to know about the car-side pigtail as well.

grumpygreaseape

i have the answers for you guys tommorow. i have boxes of both male and female 3 way weatherpak connectors, the shells, and then i put in the wire and pins with a delco electrical kit-but if you have a pep boys or similar they have the same wire ends and silicone seals that go on the wire too. the connectors are a standard ign product. afs-74 i think is the # for the delco 3 wire i use -but nah-wait till tommorow too on that # dont want to supply any bum steers. i will post when some monday morning goes by and i get a chance.

Grumpy

No,
no, no, no, no, no,

The ecm toggles the AFR over the 14.7 setting so that the average is 14.7. Period.

If you have a commanded 15.5 then it will spend about 10% of the time on the lean side, to get the average of 15.5 rather then 14.7.

There are no accurate guide lines for a switching type O2 sensor for AFR ofther then the GM cross from rich to lean at about .45v.

Some kinda line up, but that's a big assumption to risk an engine on. Read thru the Gnttype archives, and see how many guys consider .82v as being safe, and then read about how many are blowing headgaskets. .83v in may car was 12.5:1, which is way too lean for running as much boost as I do.

formula5

Just don't tell jet hot nothing about modifying your car."If" they ask jst tell them its on your street car.The warranty will cover defects like you have discribed.The factory o2 sensor is a bit confusing,at first.Really it is just a swiching sensor.I think the mv readout is just for highway mode or stable egt situations.
But can't really be converted to a/f ratios.With a switching sensor there is no a/f conversion.It's like is my air diverter valve on or not?I would imagine GM used a wide band O2 and a dyno to calibrate.Probaly a million other things like sims to tune with also.Then slapped in the swiching O2 for ecm refrence.The w/b is the only solution.You can get close by feel,MPG,G-tech and such.Or the faster the leds cycle on my 0-1 a/f guage the closer to 14.7.But the w/b is the only way to know the a/f limits,and when to push em.I'm going to make the w/b interface soon.I have to have a w/b.If you don't have one then your flying blind.Craig,you need to poke around the carb board.Vac advance dist and carb info is a great place to find out about a/f and timing.Then apply that as a starting point for cruise & wot a/f ratios and timing.You'll find that efi will use abit less timing and can get away with a bit leaner a/f ratios.

grumpygreaseape

hey, afs-74 in ac delco it is-there is something left functioning upstairs after all. the connector in standard ign. are a cg43 3 way male and a cg42 3 way female i get them in that #and they are shipped ten each in a box. they probably are available separate though thru pep boy or a vendor who sells standard .hope it helps seeya frank

grumpygreaseape

o2 sensor is NOT a switching sensor in our cars. its accuracy is questionable above or below 14.7 to 1 and thats the a/f ratio that will always tickle its fancy, it is just the way that they work. they meaning zirconium based o2 sensors. now most jap junk uses a titania based o2 and they operate closer to an on off switch as they vary resistance in relation to ex.gas content but still it is not completely on /off- the jap ecms generally interpret the fluctuations as on/ off but they react to the changes at a pre determined resistance threshold above and below it is either on or off. think of the o2 sensor in our cars as a small battery that will create voltage when fed-charged-with a LACK of o2 in the exhaust stream causing the ambient o2 within the sensor to transfer out and charge the sensor and creating the millivolts seen when testing. it certainly is not an cut and dried thing-thats why wide band o2 sensors are needed cuz they are accurate across the wide a/f ratio band . later hope i didnt step on toes

Craig Moates

Thank you Sir, may I have another?

OK, so ignore the O2 readings in the differential sense (pretty much known, been told time & again), but 'trust' that they will get you stoichiometric when you ask for it in the time-averaging cross-counts sense. So if I have the fuel request at 14.7 for part-throttle and the temp & all at the sensor is good, and all my BLMs come in around 128, then to the next question:

For a MAF system part-throttling at 14.7 with 128 BLMs, can you go then, with reasonable accuracy, and request enrichment to 12.8 via fuel table %'s at WOT and expect to be right in the neighborhood? Depends on setup I'm sure, but...gotta look at combustion efficiency as a function of the various factors like cylinder pressure, temperature, etc.

By the way, I need to get a DIY WB put together. Spent some quality time with the car this weekend, and it's been neglected something fierce. I'll read up unless someone wants to just put the info for it in my hand. Any problem leaving one installed permanently and just switching between it & the stock? Better to leave it running all the time? Prone to fouling? Take it out when not used?

Thanks again Bruce for keeping us in check!

-Craig

formula5

Thanks for correcting me.I should have said think of it like a switch.I have seen data that confirms egt is a signifigant factor in mv output so yes its junk.

grumpygreaseape

you know,thats a good question, if i am understanding it properly. a determination of a certain repeatable and reliable accuracy concerning o2 sensor output above and below its cross would be considered a sucessful end result of what you are trying to ascertain here. actually being concerned mainly with being rich enough, more concerned w/ accuracy above the cross, correct so far? as long as it shows lean is that enough to know to add fuel till it shows fat and work from there or is accurate readings below required? oh, they are here, you wanted to go towards lean for hwy.drive economy. am i reasonably close to understanding the theory here? kind of a correction factor to use in the determination for the fueling requirements of a particular combo. or am i all off the mark? completely?

grumpygreaseape

egt=exhaust gas temp?

Grumpy

Yes it is.
Look at the slew rate of it's response.
As it crosses 14.7 it's almost vertical, so it switches above and below 14.7 at .44v (some vaiances).

If it was not a switching type the output would be more linear. Switching can mean states, not purely on and off.

grumpygreaseape

ok-you mean the transition from rich to lean or lean to rich. yes that is understood, it is a state switch. what got me to post was an analogy to how a solenoid on an air mgmt.valve functions on (completely) or off (completely) unless i misunderstood the words. yes, for tuning purposes the o2 sensor can only really accurately show, what, 3 states-lean, rich, and stoich 14.7? it was placed in the system to fine tune fuel delivery enough by having the ecm dance around its output above and below the cross point after the combustion takes place anyhow. so your correct. for what the computer uses it for is only to recognize those 3 exhaust gas conditions and constantly correct, but it is still not just a switch, how its output is used to deduce fuel delivery it might as well be a switch. it does vary its output over time, no? im open to any enlightenment offered

formula5

Do a search on O2 sensors

formula5

Read the previous post again too.Egt is exhaust gas temp.Once you hit wot the egt skews the mv reading.Lke I said it's a switching device.The mv I can only imagine woud be for stable egt situations for increased mpg.I'm sure grumpy knows way more than me about the fuction of the mv readout for the factory O2 sensor.I just used the diverter valve as an example. I do have an a/f ratio guage on my apillar.It's hooked up to the factory O2 sensor.Yes it is helpful tuning my ecm.It will show if I'm way too rich or lean idle,part and wot.Once I'm done tuning and modding and retuning the a/f guage will double as a diagnostic aid.I could be used for things like clogged filter or weak fp.

grumpygreaseape

why do you think the exhaust temp is so high? is the temperature you are talking about, the one that is skewing the output, too high? thats called lean. what type of o2 sensor are we talkin here? heres a screenshot showing the varying voltage above and below the switch point as the fuel delivery follows behind enrichening and leaning the mixture over and over. o2 millivolts are used to determine twc efficiency in obd 2 and also to monitor pre programmed fuel delivery parameters. using millivolts-either hi or lo the pcm monitors the average trend of what the exhaust gas is like-128 being the number in our camaros and in obd2 it is expressed in trim percentages 0% ideal plus or minus 10% acceptable blm and integrator are now called long term trim and short term trim. there are tables to convert trims to counts 154=+20% 102=-20% so the varying voltage supplied by the sensor is a key input for most all self tests the pcm performs. cannister purge, o2 storage capacity of cats, fuel use, degradation of tune up items-its a long list

formula5

Listen ,don't get lost in the details.I will use a glen type analogy.The factory O2 sensor is like rough sandpaper ,a w/b sensor is smooth sandpaper.So you can shape your calibration w/ the factory O2.But you'll need a w/b to finish the tune.Thats under normal conditions though.At wot the oem sensor just flags rich.So in your software the line on the graph will not toggle.Watch that graph at wot ,it's just going to be pegged at the top.Last time I checked my egt rises @wot vs cruise.The mv output can vary no only by egt.But many other factors skews the oem sensor.It just can't be used if your wanting to tune for wot.Unless your wanting to tune for 14.4 afr

grumpygreaseape

the accuracy of the o2 sensor at stoich was one of the 1st thoughts i put to keyboard once i posted the part #'s for the o2 sensor. ok the 2nd thing i typed. grumpy chose not to include it in his quote of me. and concerning accurate smooth sandpaper-i asked what the intent of the original question was-it sounded like senor moates was looking for a way to determine a lean condition accurately and reliably always and the i thought that he was looking to the o2 sensor to do a thing that it really wasnt designed to do -jeeeesh, its been real



:rockon: gotta get the f outa here

grumpygreaseape

one more thing, stop hiding behind, i mean quoting, glens and grumpys what are the facts as you know em'

formula5

Get a life

formula5

Learn how to burn a prom before you talk sh*t on me.I have experience burning and the respect of this board.If you can't add anything usefull or learn with your mouth shut, then you don't belong here.

grumpygreaseape

argueing on a keyboard is about as productive as me trying to "learn" something from the likes of you. yo superman-the day i start driving around with one of those pitiful led gauges and relying on it for diagnosing a bad filter or pump-im closin my shop. oh yeah i aint never burnt one of them newfangled cheeeups yet neethur. you see go into any smog /diagnostic/electrical shop or pull the shirtsleeve of any L1 ase guy, any smog tech, anyone who has been in the trade a few days and tell em all you know about how it is and how it works-besides, learn, aint you the one asking for part #'s on connectors and sensor #'s? add something? go read my posts on the less uptight forums and i think you will find what my motivation is here. ive posted a on a few other forums but i gotta say its been the most pleasurable dealing here. bah

TRAXION

Craig - if you want me to reopen this let me know. But, I'm closing it for now due to the most recent posts to this thread.

Tim