In my datalog for my 86 Trans Am (MAF, 358 with a COMP 8-502-8 cam and 24lb injectors) I am coming across unloading valleys where my BLM is perfect after I let completely off the throttle on the highway where the rpm stays up. Is this normal to see? Picture is included. I was also wondering if my throttle position at idle is reading 0.53V at 160 BLM, and any time I step on the throttle at all, BLM goes back up to 160. Should I be tuning the MAF tables in $6E ONLY when the engine is under load and it will correct itself when not under load? And how much should I step the table scalars up at a time before I start playing with the table values themselves? Very clearly everywhere needs way more fuel if I'm on the throttle at all, how much more exactly should I throw at it? I'm using TunerPro RT V5.0.

 

"I am coming across unloading valleys where my BLM is perfect after I let completely off the throttle on the highway where the rpm stays up. Is this normal to see?"

I can't figure out what your picture is. Not enough info captured and context. When you let off the gas pedal after crusing, decel mode is engaged and integrator (INT) resets to 128 for a bit. You could also enter DFCO mode and INT will reset to 128. In DFCO the INJ PW will be 0. In decel mode the INJ PW will be very low. Also, you end-up changing BLM cell, so it is possible the BLM # will change quickly as you enter another cell.

"I was also wondering if my throttle position at idle is reading 0.53V at 160 BLM, and any time I step on the throttle at all, BLM goes back up to 160."

TPS and BLM don't interact together. If you have 160 BLM at idle you are too lean. TPS has nothing to do with it. If you step on gas pedal while idling, the ecm will change BLM cell as RPM and MAF g/sec increase and will get back to original cell once you release the gas pedal and rpm comes down. If you were at 160... yes you get back to 160, it's normal.

"Should I be tuning the MAF tables in $6E ONLY when the engine is under load and it will correct itself when not under load?"

?????? How can you tune not being under load? That makes no sense.

"And how much should I step the table scalars up at a time before I start playing with the table values themselves?"

That's a complicated topic that I'm not going to get into. Do some searches on this site, lots of info on how tables and scalars interact. @RBob has some good info and explanation. It takes some reading and processing before getting to understand how it works.

"Very clearly everywhere needs way more fuel if I'm on the throttle at all, how much more exactly should I throw at it?"

Again, when you are not on the throttle, you are either idling, decel, dfco or cruising down a hill with very very little throttle. INT could reset to 128 depending on your tune and not update BLM in that cell#. You have to ignore those for BLM tuning. When you accelerate and enter Accel Enrichment (AE), INT could also reset to 128. When CCP is active it also can reset INT to 128 and stall BLM update. When BLM changes (update), INT could also reset to 128 depending on your tune.

To answer your question, you could always change the commanded AFR (0x3D5) which would change fuel across the entire tune.

You DEFENITELY need an AFR gauge to tune Open Loop and WOT PE. Otherwise you are shooting in the dark. However, OEM tunes were quite rich in PE (low 10s), so you might be ok but most likely inaccurate. In open loop, OEM tune were on the lean side, so you probably will feel it on start-up.

 

Okay, I see what you're saying. After doing my research and more datalogging, I realized I had a cylinder with an unplugged spark plug. After I corrected that and did another log, BLM sits around 140-145 and INT sits just around 128 when the throttle is constant. My plan for now is to add 10% fueling in the first 4 tables using the scalar values. I recognize them as hexadecimal values and know how to properly adjust the numbers for only 10% (Convert to decimal value --> add 10% --> Convert back and input). I have provided a datalog file with this message if you wish to make sure that this is the correct way to go about things. From what I can tell that is the way that I should be doing it, at least to start. After finally getting fueling dialed I plan to play with the timing a little to weasel some more performance out of it, but that's a whole different animal that I need to research first. The only other comment I have seems to be more of an issue with the car than anything else, but I'm getting strange spikes in every graph. Bad ground maybe? But I can't find where that would be, as all my dash grounds seem to be in place as they should be.

 

Great
I would not touch timing yet. You need an AFR gauge first to see what’s going on at WOT. If you have a knock sensor, you’ll be surprised how much timing it’s pulling. But that’s a whole other topic.

I would not add 10%. Don’t rely on the BLM numbers for accuracy. Start with maximum 5%. Like I said though, changing commended AFR is way easier. PE would not be affected. Again, you need AFR gauge for open loop to see what’s going on.

I’ll take a look at your log when I get a chance

 

It's only pulling about 2 degrees when it decides to pull anything at all, and it's currently running a little lean, why would I lean it out? My plan was to richen the fueling by 10% since BLM is showing the ECM is adding about 12.5% fuel by itself.

 

Yep! Brain fart this morning. I corrected post.

 

Deleted

 

Just quickly looking at your data there. The glitches are a pain in the b***, so ignore them. Convert your XDL file into an Excel spread sheet by using the "Export Log File" in Tuner pro. Way easier to analyze data. Your timing was pulled by as much as 8.5* at some point when you were in PE with 100% TPS (sample#47-69). Also you have a stored code #32. Your commended AFR in PE was low 12s. So if you apply the 10% too lean logic, you are low 13s in PE. Did I say you need a AFR gauge for WOT tuning lol.

I like the 91mph... I "can't drive 55" song in my head

I'll post more when I review your data.

 

This is the log file from when I went full throttle for the first time in the car. I wasn't used to having as much power under my foot as I do now. 8.5* seems like a lot, but if it's running leaner than expected, it could cause some knock, could it not? So fixing the base fuel mixture should help with that at least a little bit. Is my logic sound there?

I also am not getting a check engine light for the code and I never noticed it before this log. Every piece of the EGR system was replaced when I did the engine swap recently, so hopefully it's just a fluke error that was since corrected after I tightened down the spout on the back of the smog pump.

The Excel file is attached

 

Few things I noticed from your log:

1)EGR is enabled and a code 32 is stored. If you still have EGR, there is something wrong with it. If not, you have to disable it. You can uncheck Flag 0x1DE bit 3 or zero-out table 0x26F EGR – DC Multiplier vs CT.

2) Your BLM boundaries (Cell#) are probably stock. The problem is when you get into PE, INT goes to 128 but BLM will go to 128 only if it was under 128 before PE, otherwise it will display whatever number is over 128. Stock BLM boundaries are messed-up. You end-up with huge cell#15. So, it makes tuning WOT AFR difficult. I usually dedicate Cell #13-14-15 to WOT so it stays 128. Here’s an example for a bone stock 305 TPI:



For your 355TPI, you might want to push 116 a bit as you registered 123g/sec @ 2800 rpm (sample#46) while in PE at WOT and that's with MAF table being lean. It could be more.

Here’s the problem you will create. If you correct MAF tables 1 to 4 only you will correct BLM towards 128 in cell #15 (all good intention). However, table 5-6 will stay the same and they are mostly use in WOT. So, when you will go into WOT and cell#15 kicks in, you will be quite leaner… not so good. Right now, your log shows BLM 147 at WOT in cell#15. But remember, in PE, BLM&INT are not updated as the ECM is shooting in the dark. So that 147 number means nothing. The only way to find out what is going on in PE (WOT) is with a AFR gauge.

3)Cell#0 is dedicated to warm idle. You are obviously super lean. BLM is maxed out at 160 (by your tune) and INT is in the 130-140. Not good! If you have changed your MAF from the factory Bosch, that could be the cause. If it’s the case, read this (post#7): https://www.thirdgen.org/forums/tech...t-ok-then.html

4) Your BLM are definitely too lean. What could cause that? It depends on what tune you are using, what psi your fuel pressure was set at and injector size. First off, you have to make sure fuel pressure is set at 43.5 vacuum disconnected. Then you can set the injector size into your tune (0x3D7 & 0x3D9) to match what ever injectors you have. After that you can adjust your BLM.

Here’s your average BLM score:

 

Read post #10 and 12

 

It appears you had a knock detected when you entered PE WOT at sample#47 and it threw an 8.5* knock retard (KR). Your RPM went from 2175 to 4100 rpm in half a sec. I suspect an AT downshift. The rest of your WOT run had no other incident detected. The problem is the 8.5* took 4.5sec to recover. That hurts power!!!! Could your transmission downshift get the knock sensor to ring? Search TGO, I believe it's possible. There is ways to fix that.

UPDATE: Check around sample #666, you had another similar incident near WOT in PE with a downshift. It took 3* KR.

You're not running stock heads obviously. Are you on 93 octane?

 

[QUOTE=TheMagikMan;6487828]I also am not getting a check engine light for the code and I never noticed it before this log. Every piece of the EGR system was replaced when I did the engine swap recently, so hopefully it's just a fluke error that was since corrected after I tightened down the spout on the back of the smog pump./QUOTE]

Clear the code and see if it comes back. Sometimes they store them but won't throw SES.

 

Interesting facts.
This is not to brag or talk you down, it's just for comparison and where you are with your set-up.

If your speedometer is accurate, it took you 7.2secs from 61 to 91 mph at WOT.

My latest test with Camaro 89, 305TPI bone stock, 5 speed, 3.08 gear with my own custom tune went from 61-91mph (3400-5000rpm) in 6.6sec on road with slight grade, 3rd gear (1.34), no wind, sea level (103-104 MAP) with speedometer verified to be accurate. Before my custom tune, it was 7.0sec!!!! The biggest factor in the tune was adjusting AFR at WOT with a gauge. It went from 10:1 to 12.8 average. GM had injectors opening at 95%DC, just crazy. Timing adjustment did not make much difference. 0-60 went from 7.0s to 6.6s. Quarter-mile went from 15.0@91mph to 14.7@93mph.

So you have potential there I would say

 

I am running 93 octane on 370 casting double hump heads that were intended as an over the counter replacement for factory 1969 Z28 cars. Compression is sitting at about 10:1. As for gearing I have 2.77 gears in the rear end. It does feel sluggish to me but I don't really have the means at the moment to get an AFR gauge. Camquest tells me that this particular setup ideally tuned should make right around 400hp/490tq. It doesn't feel anywhere close to that. I'm reading through all your info right now. I greatly appreciate the help!

Edit: I also have 24lb injectors and the values in the tune are set at 24lbs, and the MAF is completely stock. This is currently running on a tune that was made for me by Tuned Performance.
I have added an image of what I believe I need to change, but I am not sure. I am running in $6E and I can't really see in TunerPro where I would change up my cells, or how to increase fueling in table 6, as the scalar is set to FF and the table values go to max at 4.80 Volts.


BLM cell adjustment? This seems very out of whack

 

No problem! It's my passion.

400HP/490TQ I doubt with a stock TPI. My mild 383 with FIRST TPI gets that. Richard Holdener has an interesting comparison of 383's TPI vs Mini ram etc. Max he gets with TPI set-up is 465HP on 383. Maybe you can get 400 on a 355 but not with stock TPI. I believe if you search the internet or TGO you'll find some impressive 350TPI making lots of power.

My Firebird 1991, again flat road, no wind, sea level, 3.89 gear, 6 speed, 3rd-4th gear shift (1.43-1) gets 61-91mph in 4 secs. That's at 400HP... and it's slow for a 383 . 0-60mph in 4.5sec on a good day, 1/4mile 12.5@111mph.


https://www.motortrend.com/how-to/su...tpi-induction/

 

Re you post #15
Yes your images are ok. That's what you need to change.
As far as MAF tables and scalar it's a bit touchy like I told you. Why don't you just changed commanded AFR from 14.69 to 14.00 for a start. This won't affect your WOT AFR, no chance of running lean.

Your injectors are way to small for 400hp
I calculated that they were opening at 74% DC during your WOT pass, so you are getting to the 80% threshold. For a 355 cammed and 24lbs/hr opening that much, your car should be faster.

 

I just got to think here since this tune was made by Tuned Performance. Are you sure your 02 sensor is accurate? I thought you were running on a OEM tune but if it was made by a professional, that is weird. If your 02 sensor is faulty, it could make the ECM believe it is lean. You better call Tuned Performance and check with them.

 

This tune was originally designed with lower compression, 87 octane, and about 300hp in mind, but during the engine build it snowballed a bit and ended up with a much stronger motor than necessary. The O2 sensor is brand new OEM equipment. I want to learn to do the tuning myself so it hasn't had any iterations at all. Should I edit those values to be the break values between the cells in that table that you sent earlier? The OEM one? Higher/Lower? They are Bosch D3 injectors so realistically peak flow is up to 27lb/hr according to South Bay.

 

Ahhh I see. Yep correct those boundaries and change commanded AFR to 14. Start with that and go for a data log. See what happens. One step at the time.

Update: DON'T go WOT as cell#14-15 will be 128 instead of 147. That is going to lean out.

 

Okay. I have updated the tune with the AFR at 14.00 and changed the BLM cell breakovers to match the OEM table you shared above. I'll load the tune and go for a drive tomorrow. As long as I don't go WOT I should be okay with those corrections, right?

 

Yep! put 125 instead of 116 on last boundaries.
I would stay away from WOT until you have a AFR gauge.

update: actually I was wrong earlier, PE AFR will be enrich also by around 5% so it would go from 12.2 ave to 11.6, however, BLM will go from 147 to 128, so it will lean out but not as much

Man that is a lot to think 🤔
Thanks for you patience hahaha

 

I have a small issue. With moates recently closing their website I can't get the spider to put my chip into the burner anymore and it didn't come with my Burn 2 for some reason. So I am unable to load any new tunes.
Edit: I seem to need the Moates HDR1 adapter to be able to do it and I don't have one of those.


The chip won't come out of the bus without ripping some of the pins out of the housing, so I can't seem to plug that in directly either. Is there a special way to remove the chip without breaking the housing?

 

RE post #23

Nope it won't come out. It is soldered, it will brake.

You need a EPROM header (HDR1) and Memory adapter. Check on ebay or online. There are still some for sale. If you could get your hand on a Moates Ostrich 2.0 that would be nice

Attach your .BIN so I can take a look at it. Just curious.

 

Just a few pointers:

Look like your peak torque is around 3500RPM
Remember your MAF will max-out at 255 g/sec. But that is just an assigned number. It will actually max-out in terms of voltage and that is more concerning. You can data log your MAF voltage but that necessitates some mods to your BIN and ADX file. I always rely on MAF voltage and not assigned g/sec number.

See post#11: https://www.thirdgen.org/forums/diy-...scellanea.html

Also, lots of info in the PROM Tuning guide: https://www.thirdgen.org/forums/diy-...uide-book.html

 

I missed your attach the .BIN message. It's attached here for you. Original_Safe is the name of the tune that tuned performance made for me when I was starting the build, and Rev_0.1 is the one with changes applied. My spider is supposed to get here on the 27th so I'll be able to put the new tune in the car then. I also had the ability to turn down the temperature threshold for highway mode, so I kncked it from 186 degrees to 170 because it's a 180 stat now so it likely never enters highway mode with the threshold set at 186deg.

 

Great
Will study your .BIN and post if I find anything.
I always disable Highway mode. Just don’t like it lol. Not accurate enough. Specially with a mod engine. Unless you have an AFR gauge there is no way to know how lean you get. GM had it disabled on later models I believe.

 

Your .BIN appears to be a copy of AUJM (89 F-car 5.7TPI auto with 3.27) with minor mods to it.

 

What was the original engine in your car?

 

Corrected a mistake in your scalar #4 table that was set at 141 instead of 131
Also, zeroed out your ALDL spark adder.

Make sure your fan#1 is operating correctly as S17-5 has been flipped by Tuned Performance (compared to AUJM)

That's your SA curve at WOT PE based on RPM & LV8 with CT at 180Deg.F

 

It still weird why you are so lean. If your 357 sucks more air than the original AUJM 5.7TPI, the MAF should pick it up and compensate. Why would the MAF scale be so offset? Might be an answer that is beyond my knowledge.

 

The fan is operating correctly. I very much appreciate the input. What program are you using? It doesn't look like TunerPro RT V5. Can you explain why you zeroed out the ALDL spark adder? My original engine was a MAF small block 305, not a 350. But we transferred over the factory TPI intake so it matches the car guaranteed.

 

I use Tuner Pro RT V 5.0 and I have my own Excel spread sheets with database and calculators to help with emulating INJ BPW, Commanded AFRs, SA, etc.. The graphs are generated by Excel. I have my own custom XDF.
I always zero out ALDL spark adder because it's useless and it could affect your data logging. Search the TGO forums for more info. I corrected your MAF scalar #4 because it had messed-up your MAF tables.

"My original engine was a MAF small block 305, not a 350. But we transferred over the factory TPI intake so it matches the car guaranteed."
Soooo, you reused the factory 305 TPI with the 357? You are aware that the knock sensor and and its module are different for a 350?

 

The factory knock sensor was not used, instead we used the proper one for the 89+ roller cam block that's in the car now. The knock sensing system is proper for the new engine.

 

Interesting fact about HWY mode.

In your tune, HWY SA has been disabled from factory. GM put 0X17B at 304.25Deg.F so HWY SA will never engage. Also, for HWY AFR, 0x43C is set from factory at 140 LV8 which seems to be high for cruising on overdrive (4th). In fact HWY mode may never engage!!!!

For HWY AFR, you have to meet all criteria for more than 10 secs:
LV8 over 140
CT over 170.60Deg.F
Speed over 55mph
HWY SA is disabled

Personally I would disabled all that.

 

I know it's a lot of posts but as I study your log and .BIN, things come to mind. This is interesting:

At warm idle, your MAF seems to read normal at 575-625rpm, around 5.75-6.10 g/sec. With 24lbs/hr injectors, BPW should be around 1.6msec before voltage compensation. Yet, the ECM wants 2.3msec (40% more). That is a lot at idle! I suspect there is something wrong with the O2 sensor feedback or could be fuel pressure or wrong size injectors (smaller, but I doubt). The ECM believes it's lean but is it really? Only an AFR gauge would tell you.

Like I said, being so lean across the board with a MAF system that SHOULD adapt from an OEM TPI 350 to a cammed 357 TPI raises a flag. Something is up... but NOT with the calibration.

You might want to research about cammed engine fooling the 02 sensor.

 

I'll be working on it now. The spider just got here. I'll load that new revision and do some datalogging once the weather dries out in the next couple days.

Something I noticed in the tune by tuned performance is that the fueling for 0.00V was set to 6.00g/sec then went down for the next step, then up again. Could that be causing the idle rich condition? If I return it to 0.00 as a stock tune has it, would that maybe fix the problem?

 

I have never had luck with this system "adapting" on anything. Changes to even a stock displacement engine resulted in the need for tuning changes. Even a simple 214/224 @ 0.050 cam and headers made an 86 TPI 305 practically undriveable. I swapped the junk MAF for a MAP and tuned with 165' ECM with Australian Holden speed density code.

1.6 msec is LOW IMO for 24 lb/hr injectors being fired in Batch. In SFI mode my 24 lb/hr injectors on my L31 were at 4.8-5 msec. Since batch fires 2x as often, that makes them equivalent to about 2.4-2.5 msec at idle using the TPI firing method. In TBI mode my LT4 injectors on my 355 in my G20 fired about 1.8 msec. TBI mode fires 2x as often as TPI mode. In MPFI mode the LT4 injectors were at about 3.4 msec at idle. The cam in that engine had a fair bit of overlap and alot of the idle fuel was getting pulled directly into the headers and exhaust. As you add overlap the pulsewidth will increase to maintain the same air/fuel ratio in the cylinder. Actually, the overlap issue is one of the reasons I love the P01 and P59 running a SBC. The SFI setup allows injection timing to be adjusted and optimized in relation to the exhaust valve closing point. By altering the injection timing, I was able to make the same pulsewidth of fuel delivery shift the fuel trims to -10 to -15% to which I then removed that much fuel from the calibration.

First thing I am going to hammer into a tuners mind. INJECTOR DATA, INJECTOR DATA, INJECTOR DATA, INJECTOR DATA. Not only that but the base fuel pressure needs to match what the correct injector data was gathered at. Attempting to dial in with unknown injector data is going to drive you crazy.

PS- I do WOT PE tuning by narrowbands 95% of the time. Very seldom put a wideband on a vehicle. When I do the WOT air/fuel ratio is very close to what I am targeting. Wideband 02s were not super common when I started tuning and I figured out the narrowband voltage vs wideband AFR of a GM 02 sensor a long time ago. As long as you are between 11:1 and 12.5:1 there is nearly no power difference. I target 12:1 near peak torque and 12.5:1 near peak HP. I can put the air/fuel between 12 and 12.5 at WOT every time with the narrow bands only. TBI, TPI, LT1, Vortec, LS1, it does not matter.

 

Setting 0V to 6.00 g/sec is merely to enable the engine to idle if the MAF becomes disconnected. The airflow will never be at 0.00V with the engine running. It should not change your idle as I am sure your MAF Voltage is well above Zero at idle.

 

Could you maybe educate me on how you use the narrowband for WOT? If I can avoid spending the money it'll help me dial it all the sooner

 

RE post #38

TheMagikMan, the 2.3msec INJ BPW I was talking about is before voltage and offset Low BPW correction. So the 2.3msec I was talking about is in realty 3.4msec with your actual tune at 13.5volts on your warm idle at the end of your log. 1.6msec gives you around 2.7msec. So if you want to compare INJ PW between different engines, EFI systems and data logs, etc. Just make sure you compare same data... Final INJ PW.

TheMagikMan, you might want to read this https://www.thirdgen.org/forums/tech...t-ok-then.html regarding MAF voltage issues. That's why the MAF table is higher at 0.00V. But there is also a default calculation if MAF becomes defective and sends no voltage to ECM. I always data log MAF voltage.

AFR gauges are nice to have for open loop tuning as well. Good luck tuning WOT on narrow band

I assumed Tuned Performance modified AUJM using your new injectors data??? It seems the Voltage compensation was increased compare to OEM injectors. Hopefully the injectors datasheet was used. The Low BPW table was not modified.

RE post #10 "First off, you have to make sure fuel pressure is set at 43.5 vacuum disconnected". Did you ever verify that?

 

I was unable to verify that information due to lack of tools. I have personally never worked with EFI or an electric fuel pump before.

 

Assuming your fuel pressure is set correctly, Injector data was entered properly in your tune, MAF is functioning properly (sending a voltage) and O2 sensor is functioning properly, here's a tune for you. I adjusted your MAF tables which requires some sort of calculator to be precise (Excel spreadsheet). It's not as easy as one might think. I added 10% to table #2-5, between 12-21% for table #1 and 0-10% to Table #6 which now maxes out at 4.62volts, 255g/sec. Your max g/sec on your log was 194g/sec at WOT which was MAF at around 4.30 volts. So you should be fine for now. I adjusted your INJ rate at 24 instead of 24.4 and disabled SAM and HWY mode (both pain in the a***). I lowered your fan to accommodate your 180 stat (I assume you have aluminum heads). I put back 14.69 for AFR. You should be fine at WOT as the calculated BPW will be roughly the same with MAF tables and INJ rate adjusted... so same amount of fuel as your first tune.

I expect your BLM to come down a lot. You might get a bit rich. Your idle might still be lean, but not like it was. You could always fine tune later. Don't obsess over the BLM being right on 128. You will give yourself panic attacks. BLMs will vary depending on outside temperature, CT, MAT and voltage.

Why do I do all this for free. Just to help like I was helped MANY MANY times over the years by TGO, specially RBob, 84Elky and many famous names. Also, you don't beg, seemed to do your home work and you are not entitled. It also could help another TGO fellow later and hopefully you will help someone one day.

Anyone can come here and criticize, boast, brag or write dissertation about stuff that gets you no where. Hopefully this will help you. It's not perfect but it's a start for you. Tuning with these ancient systems is hard and complicated. Don't let anyone tell you otherwise. I spent thousands of hours trying to understand how it works with hundreds of hours data logging. The fact of the matter is these ancient systems are inaccurate and slow. They are time consuming to tune and frustrating as data is inaccurate or limited at times. No one really has a perfect understanding of them. As time goes by, some new info comes out and gets shared.

And if one little piece of hardware is not doing its job or is malfunctioning, the whole system can behave badly. Remember, they were not design for high performance in mind. That's why, some resort to go after market with modern EFI systems. I had a chance to work on a mega squirt system for a race car and let me tell ya... It was soooooo muchhhh easier. No MAF crap!

Have fun, Happy Holidays and go easy on the WOT lol

 

No worries. If everything is stock, one can assume fuel pressure is ok. But that is just an assumption. There is a Shrader valve on the TPI fuel rail (search TGO for info). If you could get yourself a fuel pressure gauge (borrow if you can), and test fuel pressure that would be great. Being lean can be caused by not enough pressure or too much at idle.

 

02 Voltage at WOT is pretty consistent even with Narrow Bands. It may shift up to ~20 mv higher when the sensor is really hot after running at WOT for a long period of time but that is not the end of the world.

This is really close on the numerous GM vehicles I have tested it on. That being said shoot for 880-930 MV at WOT which is in the safe rich area and you will not make 2 hp playing with the fueling getting it perfect with a wideband. Unless you are towing a house up a mountain at WOT the added fuel use between 12:1 and 13:1 at WOT is minimal. Given that there is no individual cylinder correction on many GM platforms it is better to stay a little rich at WOT because the leanest cylinder could be up to a full point leaner than the average. I target 12:1 near peak torque and 12.5:1 near peak power and then read the spark plugs. It would be even safer for a beginning tuner to target 950 mv and read the plugs. The plugs will be a little sooty after a WOT run if everything is working as designed. At that point, reduce the fueling a little, drop the 02 voltage to 930, then 900, then 870 looking at the plugs after each hard WOT run. At some point you will find that a cylinder or two will be leaner than the rest. At that point it is time to increase the fuel a bit from that point.

830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1

Under 830 mv you are too lean, over 950 mv you are too rich.

These are the plugs that came out of the LH bank, Bank 1 on my ~500 hp 383. RH, Bank 2 plugs looked the same. Nice and clean, not too rich and not overheating from being too lean. No aluminum specs indicating detonation either.

 

As you can see in this video it takes a BIG air/fuel ratio change to impact power and also a substantial timing advance change to hurt power. Typical stock GM Iron headed engine I run at about 30-32* of timing at WOT. The 3 hp it loses compared to 36-38* is not worth the added potential for detonation on a hot day. Same with the trying to push the air/fuel to the lean side at WOT. On a stock TPI engine with a conservative tune that was done using narrowband 02 only, I will make within about ~5 HP of what someone makes that has it on the edge of blowing it up with a wideband. I fix alot of these 13:1 WOT air/fuel across the board and completely maxed out timing curve type of tunes. Tuning a LS1 it is actually the first thing I look for. The typical dyno tune seems to be 30* of timing and 13:1 a/fr on a LS1 and they do not like it on the actual road much at all.

 

I give these cars what I call the screwdriver test. Any vehicle that uses this style of mass air flow sensor is prone to failure. The Turbo Buicks, the TPIs, and even the mundane 3.3L and 3.8L Buick front drivers. Nearly 20 years ago when I first started messing around with GM EFI these cars were a lot more common than they are now. As knowledgeable people disappear so do the base pool of knowledge on the platforms. The screwdriver test is simple. With the engine idling, take the handle end of the screwdriver and lightly tap on the MAF. Don't go crazy and smash it as if you were driving a nail, a few light taps is all it takes. If the car hesitates or stumbles the MAF has a loose resistance grid. It was a very common failure to see when these cars were still plentiful.

 

830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1

Just compared these to my last chassis dyno on a 383 TPI with AFR Gauge. Using these I would have estimated AFR richer by 0.7:1 average and as much as 1.0:1 at peak power. We were actually a bit lean on the dyno after beefing up the exhaust. Using these, it would have told us everything was fine at 12.3 when we recorded 13.3.

However, last stock LB9 I tuned showed low 10s high 9s on AFR gauge at WOT (from factory). O2 MV was definitely over 930mv but not that much. After tuning it back in mid to high 12s with AFR gauge, average O2 was 880mv which would give us 12.5:1 according to above scale. Not bad!

Going from low 10s high 9s, we shaved 0.3-0.4s on 0-60 and 2mph on 1/4 mile without touching timing

Having said that, @TheMagikMan, your log shows average O2 of 902mv at WOT, what ever that means.

Bottom line is use the above scale as a gross guidelines. Nothing replaces AFR gauge, specially for Open Loop tuning and monitoring Closed loop.

 

From the thread I suggest: https://www.thirdgen.org/forums/tech...t-ok-then.html

"I could not get the MAF to not send a signal. I tapped on it while engine running and nothing"

I did not use a screw driver thought, I think it was a small wrench, so maybe I should try with a screwdriver!

 

Nothing replaces being able to properly read a spark plug. I have found many widebands have substantial error even following proper free air calibration. My Innovative LM1 was not as accurate as a cheap AEM. The biggest key is knowing where your air/fuel ratio is in respect to the instrumentation. Unless you have a wide band in each header tube you are looking at the average of at least 4 cylinders.