$ee lt1 tuning cruise and idle

[zoomo]

God ive edited this so many times. so i was thinking, i guess what yall are saying is if its switching back and forth somewhere around 500 at cruise then it should be close to stoich. That does make sense. But mines all over the place at cruise, the 02s on this system switch so fast its crazy even at 25% speed its hard to say where it hangs at longer but it could drop down to 200 or get up to 800. so with those readings its a guess where the air fuel ratio is really.




I'll be the first to say this stuff is way over my head. And I deal with diagnosing cars every day. Its always over my head and always a learning experience

It would be good if someone with a stock know good car and an AIr fuel gauge had done some testing

Also how can it just be calibration of my wideband when it reacts directly to closed loop?

Maybe i just have an exhaust leak or a lean condition im missing.

[steveo]

But mines all over the place at cruise, the 02s on this system switch so fast its crazy even at 25% speed its hard to say where it hangs at longer

your ALDL sampling rate is so low that you're not even seeing the actual switching rate. you'd need a 'scope to do that. however if you took a running average of the o2 voltage on your system you'd achieve an average value of 420mv or whatever you have programmed as a target voltage.

It would be good if someone with a stock know good car and an AIr fuel gauge had done some testing

if you have a properly calibrated wideband, it'll flutter back and forth at lower airflows, moreso in closed loop when the o2 sensor is causing modulation of the AFR. but, like your narrowband, if you take an average of a bunch of those values, it'll show near stoich when in closed loop.

[lionelhutz]

OK, I'll try to break down what is happening a bit.

The O2 sensors are called narrowband sensors. They only switch back and forth between a high voltage (>500mV) and a low voltage (<500mV) when the AFR is oscillating around stoichiometric or the perfect AFR. Being a narrowband, this switching happens very quickly with a very small change in the AFR. The O2 sensor voltage would never drop to 500mV or lower if the AFR was 17:1.

How or why do they switch? The PCM monitors the O2 sensors. When the PCM sees a voltage >500mV it will reduce the fuel until the O2 sensor voltage is <500mV. Then, it adds fuel again until the O2 voltage is >500mV. It keeps repeating this action as long as it's running in closed loop. The PCM also stores the amount of correction in the BLM table as a number offset from 128.

I'm not using any AFR value like 14.7 because the actual ratio varies depending on the fuel. For example, E10 might put you around 14.2:1. Hence, saying stoichiometric or lambda=1. Lambda of 1 is the perfect AFR. Lambda = 0.9 would be 10% rich. If you search for lambda here you should be able to find a really good post that explains this in more detail. FYI, lambda=0.9 is typically a good AFR for power enrichment.

Now, most times the wideband sensor is programmed so that lambda=1 is displayed as 14.7:1. So, technically the sensor is OK as long as you understand that 14.7 is just the "ideal AFR" but might not be the actual AFR.

What I meant about tuning the MAF is that you don't just pick the AFR at WOT you want and then just adjust the MAF table to achieve it. You have to setup the PCM to get the AFR you want and then adjust the MAF until the real AFR and what the PCM thinks should be the AFR match. So, did you calculate what the PCM was using for AFR and then tune the MAF to match or did you just tune the MAF to get the AFR you wanted?

I'm not sure what kind of poke you were expecting to take.

Obviously the LS1 engines being released after '96 and using OBDII and having coil-near-plug ignition could not use an OBDI platform that also doesn't support coil-near-plug. At the moment, I own a LT1 and a couple of LS1's and am quite aware of the differences and how both are programmed.

The LS1 from the factory doesn't have any kind of lean cruise in it. People might do programming to get a lean cruise, but they didn't come with a lean cruise from the factory.

[zoomo]

Hmmm so that all makes sense. I think tonight I should take an average over one of my cruise 02 number logs and see what I come up with and how it compares to what the wideband says.

Thanks for broadening my horizon guys
Edit
Skemthing else I would like yo understand.

The more I read about narrowband 02s the more i read about how they are unnacurate but a stoich reading is around 450. Edit: still doing a lot of searching on this, seems on ltx they have attempted to make a map of narrowband mv- wideband Afr and feel good that 14.7 is around 450 or so. Of course there is still on going debate of accuracy of narrowband especially when rich.

So in hindsight I still wonder what a factory known good lt1 would show on a wideband at cruise.

And I'll still see what my cruise 02s average out yo tonight.

Thanks for the thoughts and help guys

[lionelhutz]

Yes, I used 500mV but the real "center" point tends to be around 450mV.

Either way, here is a graph of the O2 voltage vs AFR. This curve should help you understand how your AFR is not averaging a lambda of 1.16 (or "17:1") if your O2 voltage is constantly swinging between 200mV and 800mV.

Attachment 8414

Now, the tuning software has made the O2 threshold values available so you could set the voltage that the PCM tries to switch around. You could make the voltage way higher and the vehicle would run lean. There is a problem with this though, the O2 sensor is not meant to measure anything but the stoichiometric fuel ratio (operated on the vertical part of the curve).

[zoomo]

Well good update, tonight i re-did my exhaust where my wideband was located because it was slightly smaller than the rest, and i welded it with a gasless so it was horrible.

long story short, at cruise i now get a reading of about 15, much steadier than before, and at idle it hangs around 15 -16 as well. so that makes me feel a lot better, and kind of makes everything make more sense.

now heres a log i took earlier this week, i think everything is looking pretty well, but if anyone has time to look let me know if you see anything i should work on.

Also what other ways would yall suggest i try tuning the wot?
When i adjusted it with the two tables, pe vs rpm, and pe vs temp to get the ratio i wanted i ended up with the car running rich if i were to enter pe at like 3 quarter throttle.

[lionelhutz]

Set the tables so that you know what the PE AFR should be and then tune the MAF until you get that PE AFR.

Or, program it so that PE is not entered and tune it in closed loop. Be careful you don't lug the engine too much if you do this.

[steveo]

with a wideband, i had the best luck setting the entire open loop table to 13.5:1 or something around there, disabling both closed loop and PE entirely, and just do a couple runs. that's really safe (unless it's way off to start with), and usually enough to get the entire MAF table nailed quickly. the more data the better, i wrote my own analyzer for it.

[zoomo]

Steveo, do you use this method purely to tune wot or is this something for cruise as well?

I have already changed my maf about 10% lower from about 25 airflow to 50 (approximately) to get my blms good, if you watched my cruise log they seem good enough to me about 127-129 .

As of now the wot is adjusted 5%lower than normal on the pe vs wot table and 7% leaner in the maf table from about 100-300.

This has all given me pretty numbers on my wideband and cruising blms but I would like to work on making it better By tuning the wot and maf the way you guys suggest

[steveo]

you'd use that method to adjust base airflow, whether MAF or VE.

[zoomo]

So after I do this its still acceptable to change it a little if neccissary to get blms correct?

But also once I've done what you suggest, should I purely adjust pe air fuel ratio by the two tables it offers?

Sorry it takes me a bit for things to start making sense buta little at a time I'm understanding this tuning I believe.

Is there anything terribly bad with what I've dome as of now programming the wot air fuel ratio?
I will be correcting it but I'm going on a long trip tomorrow and just trying to make sure I don't need to spend tonight tuning ha.

[brian617]

The AFR values in PE tables are only accurate if your VE table is accurate (speed density) and your MAF scaled properly (airflow). the AFR numbers are a reflection of your base fueling. You can cheat by changing the AFR numbers, but your actual and commanded AFRs will never match.

[zoomo]

So foes that mean its kinda OK I just took a weird way of getting there ? Ha I guess it also means it will make the rest of the rune hard to get dialed in because other things are adjusted incorrectly.

I suppose I need to tune on the ve tables, now that I kind of have an idea how. As of now the only thing I did was adjust the entire high table more rich by a percentage because it was pretty lean with the maf unplugged but now its pretty close to right. But I need to actually tune it.


I'm just learning all this tuning stuff slowly and trying to have a full understanding of exactly what I'm doing. I plan on driving this car for a while everyday so I will always be trying to make it better and make it last.

Thanks for the advice guys

[steveo]

So foes that mean its kinda OK I just took a weird way of getting there ?

exactly. it's "kinda ok". although you may have tuned for the cases of 'cruising' and 'flooring it', there are going to be other situations that are less than ideal.

you'll find it usually runs best in subtle ways when your base airflow and fuel calculations are pretty accurate; because there are calculations based on those airflow and fueling numbers that you can't just manipulate to band-aid poor base calculations (especially in masks like EE which aren't all mapped out yet).

now, that said, i've found i get the most consistent and smoothest driveability when i aim for something like 'as close as you can get, then scale it towards rich a bit'. my best behaved tunes for ee have ended up with trims in low 120s. the o2 sensor can take it the rest of the way just fine.. but more importantly, i think it may yield a bit of extra fuel during transitions or whatever which aren't tuneable in ee (yet). finally in cases of inaccuracy in tools or changes in fuel quality, i'd rather it started richer than leaner.

as you've learned, you can't just throw a wideband in and expect it to be 100% accurate in all cases, and narrowbands aren't perfect either. don't obsess with getting it perfect, you can't. it'll run happily with a bit less or a bit more fuel.

I suppose I need to tune on the ve tables, now that I kind of have an idea how. As of now the only thing I did was adjust the entire high table more rich by a percentage because it was pretty lean with the maf unplugged but now its pretty close to right. But I need to actually tune it.

you should tune it, but also be aware that on ee, the ve tables don't do much when the MAF is active (definitely no real effect on cruising and PE), but there do appear to be a few states of operating when it's used. there are very few tuners that adjust the VE table on ee when using a maf, as a rule it's left alone, and if you do want to play with it, i'd spend time getting everything else dialed in first. what you've just done to your ve table already (enrichen the top end by a bit) is exactly what i've been doing for tunes on other people's cars.

[zoomo]

ok I still have a lot of questions, but im going to try and take this one step at a time so i dont get overwhelmed and confused.

First im going to try and tune the maf table the way steveo suggested.

once i set the entire open loop table to 13.5 do i leave it there?

and just to make sure i understand correctly, im going to go drive it and tune my maf to get the afr i want on my wideband at this point?