1bad91Z

iTrader: (1)

I just wanted to share some info I found using Datamaster and my LM-1 (wide band o2).

I have tuned my motor (in sig.) to a constant 128 BLM at idle and all part throttle (idle to 3000 rpm's - NOT in PE) is right on the money ( 128 ).

I have also monitored my WBo2 display at these cruise - part throttle rpms.

Talking with several big tuner shops over the last couple of years, they mostly all said with a N/A motor, tune from 14.7 at idle to 12.8 - 13.0 at WOT, and to never run leaner than 13.0 at WOT.

Eventhough my BLM's are right on the money ( 128 ), the wide-band show a VERY lean AFR of 17.5 - 20.1 / 1 !!!!!

It seams that the WBo2 fluctuations between the above A/F ratio's are pretty close to being in sync with the integrator fluctuations showing in datamaster. Also, the INT doesn't even show lean, it's usually fluctuating between 118 and 132.

If I richen the tune up to display a wide-band A/FR of 14.7 at idle, then the exhaust smells VERY rich. The exhaust fumes are ALOT more tolorable when tuning to 128 BLM vs. the recommended 14.7 actual AFR.

If anyone would like to add any input, I would appreciate it!

91L98Z28

Perhaps you could try your WBO2 in a stock vehicle and compare the results? It does seem as if it's reading inaccurately.

3.8TransAM

16-17 - 1 is my AFR at idle with my blm's tuned to 128

Wideband will always read the content of the exhaust, but the exhaust is made up of how much fuel/air gets blown thru due to overlap, duration and all the other fun stuff of any decent camshaft :-)

Also note all the talk of self egr'ing at idle :-)

Lot more than 128 = 14.7 to one

stock ecm 128 does not always = 14.7, compare in your readings to what the commanded air fuel is at a given time as well.

later
Jeremy

91L98Z28

i'm sure all that could contribute. I don't know what cam 1bad91z is running.

I just have a hard time buying into 20:1, or even 18:1 or 16:1 being anywhere near accurate readings, that sucker would be surging like crazy and drivability would probably be crap if those AFR's were real. hence my suggestion to throw the wbo2 on something that is stock just to do a reality check (my wbo2 reads right at 14.7:1 under steady state conditions with good crosscounts).

are we talking a huge cam here, something 250+ at 0.050"? or advertised 310+?

it's an interesting post though. I've often wondered just how accurate any exhaust-content AFR measurement device is, when you start running huge cams and sending raw fuel, partially burnt fuel, blasts of oxygen and who knows what else out the exhaust port...

not to hijack the post, but a more general question would be - what's the relation between cam 'radicalness' to wbo2 accuracy?

11sORbust

One thing is that yor stock o2 is not working correctly. So when you tune the blms to it, things are skewed. Or like 3.8 said, your engine combo is messing with the acuracy of the stock o2. You might just want to pull the stock o2 and recheck the a/f in open loop. If it's still off then tune the car open loop and keep it that way.

On my car the blms are slightly rich but my plugs indicate a very lean condition, as does the wideband. In fact when I pull the wideband out it was white. So the computer thinks I'm rich but really I'm lean. That would be due to the big cam. Open loop works much better...

406TPI

iTrader: (1)

Same here...if I tune to 128/128 at idle my W/B shows 18-19:1 AFR. However, if I go richer than that the exhaust fumes really start to burn my eyes and smell REALLY strong.

3.8TransAM

Its all about the over;ap/duration/LSA that all contribute to a dilution of the exhaust from what one wouod normally expect on a stock or very near to stock vehicle.

Im sure Bruce or Rbob will chime in hear and give their take son this as well. I know Rbob and Traxion have had the eye watering rich idle issues and tuned to 16 or so to 1 on the
wideband and it worked fine for them as well.
later
Jeremy

11sORbust

I don't care about the smell. No cat has alot to do with it also. My beef is that closed loop is not catching my lean condition. I would rather have stinky exhaust than run my car soo lean the wideband is white when I pull it. For my setup the only way is to go open loop. Or change the o2 constants, which I have tried. The constants are more work than just switching to open loop. Call me lazy

jjvette

I have noticed the same. When I tune my BLMs to 128 my wide band shows 17:1 afr. I didn't believe it at first but the high engine temps, hot header smell, melted wires etc finally all added up. What really made me look into it was when I cracked my plastic power brake booster! I replaced it and noticed it would get hot at idle. Infact so hot that you could only put your hand on it for 3 seconds! I now run in open loop thanks to this Forum. The AFR is much better cycling aroung 14.0 - 14.5!

John

1981TTA

:hail:

Excellent post! It seems (to me) that in other posts there has been a lot of NB O2 "bashing" going on. While some of it is well deserved given the experiences of others, it seems like a *lot* more of it is based on a poor understanding of how they operate and the calibration required to make them work. Given enough time and people moving in a direction, it suddenly becomes fashionable to jump on the WB bandwagon. Again, not that it's wrong to go in that direction, it's just that it should be done with some knowledge of what's going on..... Consider what we'll do if/when our WB sensors have to be replaced. Our open loop 14.7 might suddenly shift. And, it seemed to happen right after I replaced the Bosch/NTK/etc sensor...... Hmmmm..... Now what to do......? (We probably know what we'd do. Hopefully, you get my point.)

11sORbust, I don't think you're being lazy trying open loop. If nobody ever tried anything different, we wouldn't learn anything! For what it's worth, it's good to know you're making your decision with facts in hand. That's where the opportunity to learn resides. If someone hadn't bucked the early 80's approach of removing all the "computer stuff" to slap on a carb, we wouldn't be here now!

Off my soapbox (for now)...

11sORbust

FYI, I'm not the first to ditch my stock o2. But I have spent many hours learing how things work....

jjvette

I'm just glad that I hooked up the wide band and figured out the engine was excessively lean. Maybe the o2 parameters work fine for an unheated stock O2 sensor that is 6" from the exhaust valve but in my case after modifying the engine from intake to exhaust they definately don't do it now! I trust the wide band sensor accuracy way more than any factory one. I will gladly run open loop if it means not melting a piston. If I can figure out the o2 parameters in the ecm to recalibrate for the heated o2 sensor I will do so but not before tuning it in open loop first.


I agree with 11sOrbust on this one. I have played with the O2 parameters for hours upon hours and couldn't get anywhere.
Open loop made the AFR changes instantly!!!!!!!!

Thanks again!
John

Grumpy

Please define, bashing.

Jumping on the WB bandwagon is fashionable?. Please explain that one to me.

Might do better with some actual facts. ie what's going to *replace* a WB, etc..

406TPI

iTrader: (1)

1981TTA...Face it factory narrow bands have much to be desired! They cannot be trusted...it's not "jumping on the wideband bandwagon" it's the fact that it nice to know what's actually going on in your motor. Believe me, I resisted the W/B thing for a long time....now I know better!

If I known then what I know now, I wouldn'd have spent another dime on modifications until I bought a W/B sensor.

1981TTA

Without some constraints on what's going on in the engine, this is the type of comment that I was referring to previously. (Grumpy, this is what I called "bashing". I admit it was a poor choice of terminology.) If you mean they can't be trusted to tell you 20:1 or 12:1 on any given engine, I'd agree. (This is where the WB shines brightly.) If you mean they can't be trusted to tell you ~14.7:1 on a "stock" engine/configuration, I disagree. For modified engines with more radical cam profiles, I wonder if either of the sensors can really be trusted.....? Is the difference we see simply due to filters and signal conditioning being done inside the WB box? I don't know. But, given the number of people who are talking about differences between NB vs. WB readings, it makes me wonder.....

I'm by no means an expert on O2 sensors. But, in your case, I'd have to ask the question *why* the NB O2 is so far off. I understand you're basing your results on the WB O2 in addition to exhaust temperature. And, you can probably tell it's richer when the WB is reading 14.0:1. But, is the WB telling you the truth...? Is the AFR *really* what the sensor reports? Could there be something with the way the engine is set up (cam specs, intake/exhaust system, ???) that is causing one (or both??) sensors to deviate? Maybe not. But, I think the question should be on anyone's mind that sees such large deviations between the two.

As per the above, I was trying to point out that instead of determining the details of what the NB sensors are telling us (and why), we're (at times somewhat blindly) plugging in a new sensor, liking the readings and saying the original sensor is faulty. I can understand this. I just paid $250 for my WB and I'd be very disappointed if it's not "accurate". But, I really have no way of knowing whether or not it is without a 3rd measurement in the event my NB disagrees. And, I'd be very hesitant to fork out another $250 just to verify which is right. So, I'm highly tempted to conclude my $250 sensor is "good" and my factory sensor is "bad". And, besides, everyone "knows" WBs are good and NBs are bad, right???

When I mentioned "replacing", I meant replacing the WB sensor itself. Just like when we "replace" the NB sensors when they "go bad". I wasn't trying to predict the future of AFR measurement. I was trying to point out there is very likely going to be variances between WB sensors similar (but not necessarily identical) to NB sensors. I wonder if some of the applications where the sensors are so far off isn't being caused, in part, by the WB O2 sensor being biased one way or the other...?

And finally,..... I wasn't trying to "bash" anyone's efforts or motives for using the WB or running in open loop. I think the WB sensors are a wonderful thing. Hopefully, everyone's engine is much happier with the resulting tune. It's just that I worry when people report *HUGE* differences in readings between the two sensors and leave things at "the WB is telling me the truth while the NB is not". Not that this isn't the case. But, I think understanding why the differences are there can be just as important as getting the AFR right. Because, what happens when/if the particular WB sensor/system isn't as accurate as we think it is?

Grumpy

1) NBs are considered switching sensors. They are designed to sense rich or lean of stoich.. I believe a patent search would prove my point, if you want verification. Most any GM training manual will also call them that, at least circa early 90's.

2) There's enough data on line about them to be well versed, in them.

3) Does one need to understand electron flow when turning on an electric light?. For the designers of the group fine, and working summary knowledge of them is all the average tuner needs to know.

4) What ever.

5) A search at DIY-EFI will shed more light on what NBs actually sense. Try O2, EPA, and CARB for search perimeters.

JPrevost

Oh, and to add insult to injury; Narrow band sensors are slow in comparison to NTK wide band sensors with good hardware. A narrow band can't see exhaust pulses on a v8 idling... the wide band can, it's just that much better. Some hardware or software filtering gets you a good AFR value.
I wish I could understand the problems you guys are having with the lean idle. I've never seen this but then again I've never tuned a really large cam in a SBC. Also, don't go by anything other than the engine. If it likes the lean idle and you're not getting ugly plugs or a lean backfire when snapping the throttle open then leave it. I bet the sensor is getting some fresh air either from the cam or an exhaust leak.

SBNova

JPrevost- I agree. I am very new to this tuning thing, and I am two days experienced with my new WB, but my carb'd 71 Nova pegs the scale >20;1 at idle. Raise the throttle just a bit, hold it steady, and it goes to 13-14;1.

Are you guys with lean idle readings sensing at the tip of the tailpipe or somewhere in the middle? Mine is in an adapter at the tip. As soon as I get a chance I will add a bung midline and compare. Right now I feel my reading is diluted by my cams lope (242@.050 on 110lsa) pulling in fresh air to the sensor.

406TPI

iTrader: (1)

SBNova-I have my sensor in a bung about 7 inches away from my collector flange....I switched from one side to the other just to varify that I was getting consistant readings on both banks.

I found the answer to my problem on the lean idle......my Bosch N/B was almost shot..... it wasn't keeping up with the motor.....I swapped it out with another I had lying around after I became suspect that it might be bad.

I guess that's another vote for "jumping on the W/B bandwagon" I would have screwed around with programming for days if I hadn't had the W/B to see just how wacky the N/B had become...instead it took me a couple hours of looking at scans and some head scratching to realize what was happening. As far as I'm concerned, it paid for itself already!

11sORbust

The wideband is acurate. There is things that will throw off the meter though. I had false lean conditions before with the wideband. But I knew it was plug misfires. If you know what you are doing it's easy to tell when the WB is off. 98% of the time, the WB works great.

My lean condition is because I tried to tune idle with the help of closed loop/blms. I have realized that it's not the best way though. Thats because my blms register slightly rich at idle and low speeds while the WB showed a lean condition. Now one could pick blindly to trust the BLM or WB. Like I said, I pulled out the WB and the tip was white, that indicates lean. So I know the WB is right and BLM is clueless. The reason BLM's are off is because of my cam. It takes a little exhaust and regurgitates(sp?) it back into the engine. It's like an endless cycle. That's also why the exhaust stinks, because it has been recycled through the engine. IMO,Locking the blms or going open loop is the only way to really tune your VE.

FYI, I always install the WB in the exhaust somewhat close to the engine. Never on the end of the exhaust. Seems that it would not be as acurate at the tail pipe....

1bad91Z

iTrader: (1)

Good discussion gentlemen!

FYI, my hyd. roller cam specs with 1.5 rockers are:

.503 / .510
224 / 230 @.050
276 / 281 advertised
112 LSA
108 ICA

When tuning VE to a 128 BLM, the exhaust smells like a brand new car (not rich, not lean), just right.

When tuning to 14.7 on the WB at idle and part throttle, it gets quite stinky.

However, at WOT (3,000 - 6,000 rpm's), I'm still on the rich side (11.8 : 1).

SO, I have a proposed solution for myself that I would like opinions on.....

I'm going to tune (idle - 1,000 rpm's) to a 128 BLM with a NEW Denso heated narrow band o2 (excellent sensor, by the way!!).

Anything after that with part throttle cruise, I'll tune VE to 14.7 - 13.5 (from 1,000 rpm's - 3,000 rpm's). Then after than, I'll most likey be in PE (which I will tune to 13.0)....... all via WB readings.

That should take care of my stinky idle and part thottle lean conditions while still retaining closed loop gas milage and functionality.

If that doesn't work well, I'm jumping on the open loop only tuning bandwagon!

Thoughts?

11sORbust

Just keep in mind what I said. The blms was rich and WB showed lean. I did lean out idle to get rid of the exhaust smell. To be honest it never totally goes away though. Then, blms are rich so the ecm pulls fuel, even though I'm actually lean. Stupid computer is messing with MY calibration! That's why I said F-it and plan to stay OL. Food for thought!

By no means am I suggesting for everyone to go open loop, full time....

11sORbust

Another thing I like about open loop. In closed loop, the ecm is trying to maintain 14.7, even while you are applying throttle(untill you hit PE). OL will change a/f ratio AS you dig into the pedal.Think about it.....

Grumpy

Bottom line is, Tune to make the engine happy.
The engine has no idea if it's in closed loop, open loop, or hula hoop. Also don't care if it's at an inidicated 14.7 or 13.2, or San Diego Zoo.

While it's nice to have a full and comprehensive over view of the whole system, in practice the oems use teams of specialists to get their desired results. And even reading thur all the patents of things even remotely related to EFI, will just give you what they want to share with the public.

Grim Reaper

Yup, observed the very same thing too. The O2 sensor was replaced - no change. Thought Highway Mode might be getting invoked...made all the values in the Highway Mode tables force the AF to 14.7 in case it accidentally was invoking...no difference either.

The motor doesn't have an EGR either. It would be interesting to see if this exists even on a bone stock engine when you put a WB on.

3.8TransAM

whaa???????? Glen lives? how are u sir? long time no see :-)

Lots of people have found out the 128=14.7 does not = what the wideband is telling u neccesarily

11sORbust

Not sure about stock. I have a bone stock tpi car but it's running mafless(if you have read). So I cant really check that. I do think it could be a universal thing though, ever notice how everybody needs to richen up the first few maf table entries for idle?

3.8TransAM

Tween TTA and Formie, I dont know when i can but if I get a chance Iw ill put a bung in the GTA(stock cpet for catback and 24#) and see what happens.

Can go pure stock chip with only the IC changed. Just not sure when I will have a chance too
later
Jeremy

TRAXION

I had my O2 constants cranked way down in order to lean out the idle. The wideband was showing 17:1. The car ran beautifully ... no surging, etc. This was with a 230+ duration cam on a low LSA.

Tim

1bad91Z

iTrader: (1)

Oh, no doubt, that when I tune to a 128 BLM (17.2 - 18.8 WB AFR on my car at idle), the car idles and smells better. Under part throttle (mild acceleration) the car still drives and cruises great either way (128 BLM = lean on WB, also if re-tuned to ~14.** WB AFR).

I think the bottom line might be that as long you dont go leaner than 13.0 WB AFR at WOT from ~3,000 - 6,000 rpm's (PE), that hopefully you'll still be on the safe side.

I'm still pretty nervous about the 20:1 WB AFR at part throttle arround 2,000 - 2,500. I'll be adding some VE in that area to bring that down (which will bring me down to the 110-115 BLM area.

Hmmm....???

va454ss

iTrader: (1)

I never understood how air is drawn into the exhaust with a leak.

Any leaks I've experienced were exhaust gasses being pushed out.

I guess its possible with an efficient exhaust system with low back pressure and good scavenging.

JPrevost

Under WOT most likely yes, but there are other times like cruising and lifting that could suck in some air. You'll notice that exhaust leaks tend to go "away" under some driving conditions and are loud (gas being expelled) in others.
Also a good exhaust system should be able to pull a slight vacuum, just check out long tube headers on cars with PCV systems tapped into the collectors, it works.

11sORbust

I have ran my car at the track with a 13.9 a/f ratio. Didn't knock and ran great. I do agree though 13.0 is safe, in general on a n/a car.....

1bad91Z

iTrader: (1)

Eventhough my WB is showing lean at part throttle cruise, at WOT, I'm at 11.8 (at the leanest) arround 4,000 - 6,000. I have a highly massaged timing table in my .bin that seams to make the car run very well. Making a full pass through the 1st - 4th gears, I occasionally get 1.5 degrees knock retard (which isn't bad at all, IMO) and that's only at random.

When I leaned the car out from 10.6 :1 to 11.8 :1, it made a huge difference in upper RPM power. At 11.8, my plugs have very little brown on them. I'm hoping to gain some more power by leaning it out to 13.0. Once I get to 13.0, if I get any knock retard, I'll lower timing accordingly.

I'll let you guys know if I get any knock retard and also what the plugs look like when I get to that point. I'm just waiting for some time off work on a dry weekend to give me some time to work on a little more tweaking.

devilfish

So what does all this mean? Tune with the WB, locking the ecm in open loop? Gee all this make my head hurts, I thougt I started understand this, now this. I whas just about to start tune WOT using my new WB. thinking I whas OK on part throttel as my BLMs are dead on 128. Time to start all over again...
gee..

conv90

I'm with you, I'm confused...
-Beppe-

Z69

O2 bias voltage.

See above for idle tuning in CL.

Basically, the farther your engine is from stock, the better chance that a wb will indicate different from the NB. Especially in CL.

As long as it runs fine and doesn't show any other indications of being rich/lean, then you should be ok.

devilfish

so this "phenomenon" "only" apply when tuning idle?`Or is it true when you tune part time throttel as well? Non pe tuning?

devilfish

adambros

iTrader: (2)

im experiencing the same behavior. BLM's tell me its rich 115-118, and the WB says lean at idle 15-17:1.

From the responses on this thread i'm assuming its ok to tune idle via BLM readings, and anything else via WB data.

devilfish

Dont forget you have to tune crusing speeds with BLMS as well if you dont lock the ECM in open loop. OR you have to change the commanded A/F in the code. Otherwise the ECM will try to "correct" all of your changes. If you dont do one of these 2 things you can only tune WOT with a WB. Im I correct??

adambros

iTrader: (2)

thanks for pointing that out. . . im still pretty new at all this.

1bad91Z

iTrader: (1)

MY advice is to only tune idle to 128 BLM.

I would tune part throttle cruise to an acceptable WB AFR for that particular RPM.

Always tune WOT with a WB.

Just my $.02

Been raining off and on here. Cant take the car out to tune further as of yet. Oh well, maybe this weekend.

JPrevost

That's impossible unless you go open loop all the time or lock the BLMs and INT after you tuned 128 idle.

Give the engine what it wants, if taking a bunch of fuel out stalls the motor then give it more fuel , it's just that simple! ..... j/k

devilfish

"That's impossible unless you go open loop all the time or lock the BLMs and INT after you tuned 128 idle"

My point exactly..

devilfish

.. oops

1bad91Z

iTrader: (1)

Well, I dont know that I fully buy into JPrevost's theory.

A motor can run dangerously lean with-out stalling (even at part throttle cruise speeds).

If you tune closed loop idle (650-1,000 rpm area's of VE ) to 128 BLM, you are probably on the lean side (mine is at least), but it's OK because you're sitting at a low rpm and 128 BLM at idle seems to be a stable idle with-out the eye watering gas smell.

However, at 128 BLM (closed loop) at 2,500 rpm, my WB shows a very lean A/F ratio of 19:1 !! This area of VE at this RPM range vs. the Kpa needs some fuel added in these areas (eventhough my BLM shows 126 - 128 on the scanner).

It's just a little too lean for my taste at part throttle cruising speeds.

Once you make the changes in those areas of VE, the WBo2 shows a more acceptable A/F ratio of ~low 15:1's - high 14:1's.

Then lean out or richen PE to get as close to 12.8 - 13.0:1 on the WB as you can.

How is the above impossible without locking BLM's etc... ???

Not arguing, just a little confused.

RBob

iTrader: (1)

There are several factors that come into play when dealing with idle and closed loop. Off idle there is at least one less factor along with one additional factor.

The most important factor is the O2 window terms. Typically there are three terms: upper O2, lower O2 and Mean Rich/Lean O2.

These three terms define the range of AFR found at any point in time of closed loop operation.

Additionally, while at idle, the O2 error term is reduced in magnitude. This allows a greater varience in AFR while at idle.

One thing to understand about the O2 'window', is that the O2 reading not being held inside of the window. It only needs to enter the window. So a BLM term the comes up will provide a different AFR from a BLM term that comes down.

IE: A BLM of 124 will provide a different AFR then a BLM of 132. This is even more true at idle with stock calibration.

Maybe I should change the topic to 101 reasons to hate closed loop

RBob.

JPrevost

Yes, that would be nice.
One thing that is apparently clear is that the BLM will adjust the AFR to switch within the o2 windows. I found that the prop duration tables can move the AFR a LOT more when in closed loop. Right now I have it running more rich than lean, you can see it in the sensor datalog, it runs VERY smooth. I got my best gas milage this way too .
Basically if your BLMs are 128 or 138, both are getting the o2 sensor to pass rich/lean windows which does mean it should be averaging closely to 14.7 , not perfect but it should be swinging around this AFR.

devilfish

still dont get it, perhaps im just having trouble understad what you saying ( english not my main langue ).

Rbob: I tought that a BLM of 124 vs a BLM of 132 would both be close to 14.7:1 AFR in closed loop, cause its within range of what the stock O2 censor could compensate for? Is that not ture?

Or is "just" that you got lean or rich "spots" in the VE that the NB o2 dont have time to compensate for?