Ideal Idle AFR and Spark

[WS6_LOU]

Hello, everyone, happy saturday

I have a question; when it comes to setting up idle AFR I was told that you should always shoot for 14.7 or the stoich equivalent to the fuel youre using. I noticed on my car that it idles okay at 14.7 afr but it seems to have a muffled sound to it. I have noticed that if the AFR is somewhere around 16-16.5 the idle seems crisper, doesnt stumble as much, and chops much harder. I was wondering, is there any issue to running a leaner idle AFR than 14.7? Because I am really tempted to set idle AFR to 16-16.5:1 but I dont know if that would cause any long term issues. Also, my idle timing is set to 15 degrees because I noticed that had the best map reading and smoothest idle. Is that too low?

I have no issues really with drivability other than for some reason my car wants to die when coasting and going in to neutral. Although I suspect it has to do with my cracker tables. I still need to do more research on that because I dont understand it fully.

My Mods:

LQ9 stock internals
LS3 heads
BTR Stage 4+ NA cam (240+ durations)
1-7/8 headers
Dual 3 in exhaust
Deatschwerks 65 lb LS3 Injectors
Walbro 525 lph fuel pump
LS3 Intake Manifold

[bk2life]

when it comes to setting up idle AFR I was told that you should always shoot for 14.7 or the stoich .

who said this? factory narrow band o2 sensors say lambda is stoich and thats what it should be...according to who? EPA? All vehicles will run better at a leaner afr. -but you cant lean it out with narrow bands, they will conitnue to adjust fuel to get stoich. If you go open loop and dont use narrow bands, you can set your afr wherever you want it. But, it depends on your situation and ablility to adjust and make your VE perfect.

I still need to do more research on that because I dont understand it fully.

start with the RUSS K idle (google it) and then report back once its all done.

[WS6_LOU]

Thanks for the reply bk2life. I have done the Russ K idle config, so I know thats not the issue. Im more leaning towards the cracker table or adjusting the idle proportional and integral since I noticed increasing the proportional and integral idle airflow tables makes the issue worse so ill probably have to lower them below the factory setting. Ill mess with that later though.

From what ive been reading, everyone suggests an idle AFR target of 14.7 or 1.00 lambda but my car idles much better at a leaner AFR, typically around 16.5 or so. Its literally night and day. The chop is more aggressive and the idle sound is much crisper without sounding muffled. As of now I am forced to run open loop only because my o2 sensors are not sending signal to the ecu for some reason and I really dont want to be tracing wires right now. My VE table and MAF tables are spot on, though, and at WOT im at around 12.7 afr. I was just wondering if there were any long term effects for running such a lean AFR at idle.

[SiriusC1024]

Running lean in idle and cruise won't hurt anything. Leaning out AFR and increasing spark advance is the 'lean cruise' function. Lean cruise is disabled on US cars due to EPA regulations on NOx emissions.

[WS6_LOU]

Thanks for the info, SiriusC1024. Since im running OL exclusively due to a potential wiring issue with the o2 sensors, I went and adjust my open loop EQ ratio to be .9 under 70 kpa and between 122-212 F, 1.00 in cells above 70 kpa and between 122-212 F blending in neighboring cells assuring smooth transitions. Im wondering if the large overlap is causing an issue with the income air being mixed with exhaust gases and setting a leaner idle helps it run smoother. I appreciate the info guys.

[SiriusC1024]

Im wondering if the large overlap is causing an issue with the income air being mixed with exhaust gases and setting a leaner idle helps it run smoother.

That's an excellent deduction. What's typically done for overlap is to lower the O2 switching voltage at idle. This will make the AFR there trend towards the lean side.

Engine>Fuel>Oxygen Sensors>Rich/Lean vs Airflow
Set Bank 1 and Bank 2 to something like 375mV (high numbers are rich, low are lean) in the 0 airflow mode column.

[WS6_LOU]

Unfortunately my O2 sensors are not able to send signal to my ecu for some reason. They read 440-450mv constantly and I?ve read they do that when they are not sending signal to the ecu or are unplugged. I verified that no wires were damaged and I know they are getting power, but there is no signal reaching the ecu. If you don?t mind me asking, how exactly does altering the oxygen sensor voltage in the tune file affect the car?

[SiriusC1024]

"Closed Loop Proportional Base vs. Airflow Mode: This table returns the base proportional % fuel change. Proportional base rate table is the primary amount of fuel needed to drive the closed loop fuel control into oscillation. Proportional fuel acts like an on/off switch to keep the fuel moving around the current O2 Rich/Lean vs. Mode table set point. The values on the Proportional Table add or subtract to the base fuel rate depending on the previous fuel condition (i.e. if rich then switch lean, if lean the switch rich). The amount of fuel to add or subtract increases with the airflow mode and should be based on injector size and % fuel switching needed."

[Hondaeater]

Unfortunately my O2 sensors are not able to send signal to my ecu for some reason. They read 440-450mv constantly and I?ve read they do that when they are not sending signal to the ecu or are unplugged. I verified that no wires were damaged and I know they are getting power, but there is no signal reaching the ecu. If you don?t mind me asking, how exactly does altering the oxygen sensor voltage in the tune file affect the car?

Until you get the O2 sensors fixed changing anything on your oxygen sensor switching voltages is not going to help when running OL. If the mV are reporting when you're at speed with hot exhaust flowing but not at idle then I would definitely look at the wiring, especially if extensions used for long tubes, check the heater circuit wiring. I've seen extensions have reversed wires end to end.
Your cracker table can have a big impact when you clutch/ coast with speed. Anything other than stopped in P/N idle, your cracker table is used. The Idle Follower and Idle Cracker channels must be logged. While driving,... BOTH channels should have air adder populating. As soon as you lift throttle, Follower airflow should start decaying rapidly, and then only Cracker air is what is providing the airflow while the TB is closed and depends on speed vs rpm Axis and you can get an idea where you want to add air to prevent the dip. Add 1 g/s in those cells. If you get a cruise control effect in gear coasting or rpm hangs clutched in as you return to idle then reduce some. Trial and error at various rpm vs speeds is needed to find what it wants. Raise the enable speed where it transitions from cracker to idle routine too. All the air adders must 0 out to go into idle routine.
Do you have drive by cable or drive by wire throttle body?
That is a big cam. What type of fuel pressure regulator do you have?

[WS6_LOU]

So something rather interesting. My best map reading of .32 happens when my idle spark is 0 degrees. Ive never seen that. It fixed my car wanting to die when pressing in the clutch, now it returns smoothly back to idle quickly without wanting to stall. Although it does surge quite a bit right now so im trying to figure that out. Have any of you seen that before?? Seems outrageous to me but my idle is noticeably smoother.

[SiriusC1024]

Get the O2's fixed. They're like 20 bucks. Quit trying to tune around it.

[WS6_LOU]

O2 sensors are brand new AC Delco ones, so it?s not as easy as simply replacing the sensors. I did that already. The O2 sensors not working is a separate issue not for this topic. I just want to get some insight on my idle timing because I just can?t believe it idles best near 0 degrees of idle timing. I ran it for a few minutes and it idled really well but I noticed that my engine generated much more heat. I didn?t have a log for it at the time, I will be getting one today, but my clusters temp gauge was sitting just below 210. My floor board next to the trans tunnel was very warm, as to be expected considering how everything is routed.

Also, I have an issue with idle surging. It seems significantly worse at speed, fluctuating between 800-1300 rpm, and gets better the closer to 0 mph you go. During idle it fluctuates about 100 rpm. I?m in the middle of a power outage right now and am typing this on my phone so once the power is back on in a little bit I?ll be able to upload my tune. Would appreciate some insight and help with my idle timing since I have no experience with it being this damn low.

[WS6_LOU]

Here is my tune so far and my mods;


LQ9 Iron Block
LS3 821 Heads
LS7 Lifters
BTR Stage 4 NA+ Cam (233/248 - .630"/.615" - 111.5LSA)
Deatschwerks 65 lb LS3 Injectors Stock Regulator and rails
Walbro 525 fuel pump
LS3 Intake Manifold
BTR .660 Dual Springs and 7.4 Push Rods
1-7/8 headers
Dual 3 inch exhaust


If you see something else I did wrong in the tune, please correct me. I want to learn as much as I can.

[SiriusC1024]

I've never tried below 17 degrees so I really don't know.

[Alvin]

Hello, everyone, happy saturday

I have a question; when it comes to setting up idle AFR I was told that you should always shoot for 14.7 or the stoich equivalent to the fuel youre using. I noticed on my car that it idles okay at 14.7 afr but it seems to have a muffled sound to it. I have noticed that if the AFR is somewhere around 16-16.5 the idle seems crisper, doesnt stumble as much, and chops much harder. I was wondering, is there any issue to running a leaner idle AFR than 14.7? Because I am really tempted to set idle AFR to 16-16.5:1 but I dont know if that would cause any long term issues. Also, my idle timing is set to 15 degrees because I noticed that had the best map reading and smoothest idle. Is that too low?

I have no issues really with drivability other than for some reason my car wants to die when coasting and going in to neutral. Although I suspect it has to do with my cracker tables. I still need to do more research on that because I dont understand it fully.

My Mods:

LQ9 stock internals
LS3 heads
BTR Stage 4+ NA cam (240+ durations)
1-7/8 headers
Dual 3 in exhaust
Deatschwerks 65 lb LS3 Injectors
Walbro 525 lph fuel pump
LS3 Intake Manifold

There is a point where the narrow bands will not function as they should be cause the cam is too big. You are at the point were at an idle you might not be able to trust your wideband also. Sounds like you've already tested this.. IF the engine idles better leaner than let it have that. You cannot hurt it at low load/idle running lean. I wouldn't go by how it chops as a super lean idle willl often chop really hard but will start to have hesitations and stumbles.

Also the stalling coming to a stop is often a rich decel/idle situation far more often than it is something to do with throttle cracker/follower. People will cover it up with cracker but the problem is just a rich decel.

[WS6_LOU]

Thanks for the reply, Alvin. I really dont know what the hell is going on. So I went for a drive again after letting the car come up to temp. For whatever reason my wideband is reading out 20-22:1 at idle and is really bad and transitioning out is worse. I really need some good guidance because Im becoming incredibly frustrated trying to tune this pos. Cold start drives fine without issues. Once it gets up to operating temp it goes extremely lean and wants to die coming to a stop. Its terrible to drive without an insane amount of bucking at low speeds and low throttle and now has a hanging idle while moving at around 1800 rpm but once I come close to stopping it dips down to 5-600 rpm almost in free fall before catching and correcting itself. I have attached my tune and a couple logs. Log 2 is the main one and Log 3 was just an idle test in MAF only to make sure the issue wasnt just with the VE table and it did the same thing. I know my MAF is very good, much better than my VE for sure. So if anything it should have ran much better but ran just as terrible. The logs do not have AFR because for whatever reason it keeps disappearing everytime I start logging which is yet another issue im having. Seems like everything is wanting to go to shit apparently. If you could help me out and take a look at my tune and log and give me a bit of guidance on what to do next id really appreciate it.

[SiriusC1024]

- MAF fail frequency is 50Hz. Set back to stock for running MAF.
- Re-enable STFT.
- VE is way too high for NA. Be sure you did your VE tuning procedure correctly. MAF unplugged, Fail frequency 0Hz, P0102, P0103 SES checked and set to MIL on first error, disable DFCO and PE (STFT won't correct during PE. High load areas can be more safely tuned by re-enabling PE and using a wideband for fueling error in those zones.). Set VE table to stock before you begin because it's going to be much closer than what you've got in that table. Tune VE using the narrowbands.
- Looks like you modified the spark tables at low RPM/low airmass. 18 is a little low for 1200rpm. Put that stuff back. 18 degrees is fine for idle zones.
- Set idle spark drive and park to match spark tables so there is no bucking on the transition set at Base spark.
- Put Idle Adaptive Spark Control back to stock settings then increase values 25-50%.
- Contrary to purpose of spark smoothing, I've had better results with it disabled on my manual car. Try it both ways see what it does.
- Be certain that spark dwell settings are for your coils. Reference respective stock tunes for data.
- Make rolling idle speed match base so that there is a smooth transition. Base is 850rpm, so set 0mph starting point to 850rpm.

Then report back with a log.

[Alvin]

Thanks for the reply, Alvin. I really dont know what the hell is going on. So I went for a drive again after letting the car come up to temp. For whatever reason my wideband is reading out 20-22:1 at idle and is really bad and transitioning out is worse. I really need some good guidance because Im becoming incredibly frustrated trying to tune this pos. Cold start drives fine without issues. Once it gets up to operating temp it goes extremely lean and wants to die coming to a stop. Its terrible to drive without an insane amount of bucking at low speeds and low throttle and now has a hanging idle while moving at around 1800 rpm but once I come close to stopping it dips down to 5-600 rpm almost in free fall before catching and correcting itself. I have attached my tune and a couple logs. Log 2 is the main one and Log 3 was just an idle test in MAF only to make sure the issue wasnt just with the VE table and it did the same thing. I know my MAF is very good, much better than my VE for sure. So if anything it should have ran much better but ran just as terrible. The logs do not have AFR because for whatever reason it keeps disappearing everytime I start logging which is yet another issue im having. Seems like everything is wanting to go to shit apparently. If you could help me out and take a look at my tune and log and give me a bit of guidance on what to do next id really appreciate it.

I typically avoid working on someone else's tune because it's critical for everything to come full circle.. You know if the basic config isn't right than it will have fueling/spark problems, if the injector stuff is off i'll be hunting for the problem in VE, if the VE is off I'll be chasing idle issues, if its got idle issues I might chase idle airflow stuff.. IF the VE is off than the MAF will not turn out right. All of these things can be rooted back to a error in the tunes basic config or injector stuff.. You see what I mean? When I get involved with them I go completely back to stock and start from the ground up.

I offer help by looking for errors or issues you might not be aware of. Offer guidance that has come with experience. etc. I like to lead people down the right path so they can be successful.

Situations were you see a bunch of people chiming in with tuning edits could not be a worse way to tune a car IMHO. Who knows if the people chiming in have the right ideas or even just ideas that mesh with the next persons.

[WS6_LOU]

Thanks for the suggestions Sirius. I went back and started fresh from a stock trans am tune and will be working on transferring over what I need to get it to hold idle today. Im waiting on a depin kit to come in the mail so that I can depin the O2 signal high and lows and check the wires. And if the wires are no good ill just run wires and repin them at the connector so I can actually have working o2 sensors. And most importantly so that I can hardwire my wideband through the ecu so I no longer need to use the usb port because for some reason it keeps disappearing and HP Tuners customer service isnt much help. Because as of right now I cant even work on my VE table.



Thanks for the reply, Alvin. I totally get you, no worries. I just wanted someone that knows a lot more about tuning than me to provide any tips on how to get tuning in the right direction. As previously stated, I tried to find peak timing at idle by using the scanner to set timing at a certain degree and see where you get the best map. Seems like a pretty common practice since multiple people suggested it, but for some reason I had the best map reading of .32 at 0-3 degrees of idle timing. Stock idle timing is in the 20s. Have you personally experienced something like that? I noticed the idle was smoother and the engine no longer shook. But I could not find anything online where anybody had luck with putting it that low. Seems like most people need to increase it on a large cam, but I had to severely decrease it.

[Alvin]

I'm not a fan of that method.

Keep the timing at idle reasonable.. that way you can jump up to the 28+ degrees to save a idle dip. Think of it as keeping some reserve torque. Timing is your fastest correction to idle. airflow is the slowest.