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acgarib
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What's Considered Too Much MAF Adjustment?

Post by acgarib » Thu Jul 21, 2022 1:34 pm

Hi all,

First off I'll introduce myself - I'm Andrew and I'm new to automotive tuning but have 10 years experience as a process control engineer in oil refining so I'm used to the concepts, but my gasoline lines at work flow 2,000,000 lb/hr instead of 80 haha.

I recently installed a vortech SI supercharger with powerpipe on my 1991 HCI 302 mustang and have been tuning my A9P ECU via a quarterhorse.

I have a draw-through 90mm Lightning MAF in the fenderwell with window screen sandwiched between the cone air filter and MAF and 80 lb Ford racing injectors. Both of these have well defined data sheets that I used as a starting point, with fueling tweaks being performed via the MAF curve only. My issue is that my whole MAF curve is lean by about 10% except for the low end which is 40% lean in the 1 to 1.5 volt range, where I idle and coast around. Is this typical to have to apply a 1.4x correction factor to a LMAF curve when both the MAF and injectors have data sheets that are generally regarded as accurate? I can understand that the 10% part could be my particular intake tract setup vs what was used on whatever flow bench Ford used for the curve, but 40% off at low flow rates seems excessive. The car drives OK except for two tune related problems and one likely non tune related problem


- a slight idle surge when in gear. The surge is confusing me since it continues even if I lock out timing and the ISC. Putting on my controls engineer hat makes it look like CL control has too much integral action and controller gain due to the oscillations in rpm also corresponding with switches on the HEGOs but I don't see any mention of integral action in the GUFB document. Any insight?

- rich and lean stumble during transient conditions right after tip-in when cold which I'm still tuning via transient enrichment tables.

- probably non tune related stumble when at WOT above 5000 rpm with a heat soaked engine. I'm thinking it might be ignition, or a lack of ignition I should say.

In addition, the car always starts out with minimal fuel error after my MAF curve adjustments but after about half an hour of driving and getting ECTs up to near 200 degF the fuel error across the whole curve has increased by a good 10% to the lean end. It's almost like the MAF is reading is affected by underhood temperatures. Is this typical? I don't really see any mentions of this in any writeups. Right now CL is compensating for cruising and I richened the base fuel tables hotter columns so I don't go lean at WOT.

Thanks,
Andrew
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by cgrey8 » Thu Jul 21, 2022 1:52 pm

My experience with MAFs is with old stock 55mm MAFs that came on the early 5.0Ls, C&L aftermarket MAFs that reused those stock MAF's sensors, and stock slot style MAFs. I can't say I've ever noticed MAF accuracy change with air temps. I've definitely seen where engine temps mattered, but generally that's only during early startup and with transient enrichment.Within a minute or so of startup, my engines have always been able to go into Closed Loop without too much trouble. However I did, as a practice, limit KAMRF learning to only running temps above ~160 and after the engine's been running for at least 5 minutes (or maybe 10? I can't remember now).

Regardless, the only numbers you should really take seriously are the temps with the engine warmed up. But even once the engine is warmed up, the differences between cold and warm shouldn't be as drastic as you are describing. A 1.4x difference between Closed Loop cool and steady state is WAY larger than I'd expect. That's almost like something is expanding and letting unmetered air in from somewhere.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Thu Jul 21, 2022 2:12 pm

I should clarify since my post was all over the place - the 1.4x correction factor is what I had to apply to the LMAF transfer curve's 1 volt and below data points. By 1.25 volts I only added a 1.18 factor to the curve. Above 2.5 volts the curve is mostly multiplied by 1.1. this gets my fueling pretty close, but I'm concerned about why I'm having to modify a supposedly well defined MAF curve so much.

The cold vs heat soaked difference is about 10% and CL seems to manage that without issue. I'll look for vacuum leaks again, but on a hot engine since last time I did it on a cold engine. I suppose a vacuum leak might be more evident low on a MAF curve since the absolute airflow numbers are so small.

Thanks,
Andrew
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Thu Jul 21, 2022 10:28 pm

I checked for vacuum leaks again and came up empty. This time I also tried checking the lower intake manifold gasket via clamping my PCV hose shut and putting my hand over the oil fill neck to see if I can feel manifold vacuum making it to the lifter valley then to the oil fill neck but I only felt a slight hint of pressurization, no vacuum. I'll have to try making a smoke tester next.

Regardless, I'll focus on physical problems that might be causing my MAF curve to require so much upward adjustment at idle voltages. Spark plugs look ok, compression test looks good at around 150 psi, all header primaries are hot at idle. I also ordered an electronic fuel pressure gauge to replace my little mechanical gauge I have under the hood in case the mechanical gauge isn't accurate and also so I can verify the fuel pressure regulator is behaving in a 1:1 fashion with manifold pressure.

My comp cam XE270HR-12 cam is a couple degrees shy of being an "overlap" cam when looking at the 0.05 numbers - is it possible my idle being in closed loop is forcing too much fueling due to the HEGOs seeing scavenged air in the exhaust and showing up as requiring a big MAF correction, or is that issue typically mild for "street" cams like mine? It looks like I might be able to use a lean HEGO bias to compensate but I'm afraid that might be me barking up the wrong tree.

Thanks!
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by ChsReb » Sat Jul 23, 2022 7:09 pm

I created quite a stir on this topic a while back:
viewtopic.php?f=2&t=23195

Some say a MAF curve is "gospel" equal to the ten commandments. (Thou shall not change! EVER!)

I say it is a dynamic ever changing entity. The best you can hope is to get the MAF close for a given engine at a given time and given state of tune.

OK, so how do you know what to do?

Run the engine in closed loop as much and as long as possible. Datalog KAMUFs, HEGOs, and Lambsees and pay attention to your fuel trims. Your HEGOs must both read together with little variation between the two or you are totally wasting time and gas. Put in new ones if you have ANY doubts. Adjust the MAF to get the KAMUFs as close to one as you can across entire closed loop RPM range. Your final curve should be a very smooth curve with no bumps or flat spots. It ain't easy. Use idle, light cruise (at several engine speeds) and light acceleration staying always in closed loop. The engine must be at steady state temperature. If it Pings under 2500 RPM, find out why and fix it. Outdoor temps 55F-75F give best results. You're less likely to encounter fuel octane issues. I'm a fan of 180 Thermostats. Open Loop KAMUFs are meaningless (and Usually 1 anyway.)

A given MAF curve assumes your engine and the one it was created on are identical. I wouldn't take those odds.
95 GT, CBAZA with U4P0 Base, EEC 56k 1 Bank, 408 Windsor with Trick Flow intake, BBK 75mm throttle body, BBK Shorties, Ford 47 LB injectors, AFR 185 Heads, Custom Comp Cams Cam, Moates QH v1.6, BE 5.122, with Sailor Bob Strategy upgrade, AODE w/SatNightSpl and full TCI Rebuild. 4" Gen 1 Slot MAF with 4" K&N Filter in custom cold air enclosure. Street Use ONLY.

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Re: What's Considered Too Much MAF Adjustment?

Post by cgrey8 » Sat Jul 23, 2022 7:31 pm

What you are describing is where having EEC Analyzer comes in quite handy. I always had filters setup to remove lines from the datalog that represented conditions I didn't want being taken into consideration. I had a bunch of filter conditions for example:
Filter out rows where ECT was below 175
Filter out rows where ACCEL or EFTRFF had a value higher than 0
Filter out rows where the EEC was in Open Loop
Keep rows where the HEGOs were between .1v and .55v

And to account for HEGO lag, would often shift HEGO values (a feature of EA).

I also filtered on any other row where there were null-entries just because those would cause EA to barf and throw exceptions. I think Clint finally got enough checks in to either remove or ignore those lines. But the early versions of EA did not.

Having these filters in place, really made the analysis results much less noisy and made tweaks based on the logs far more likely to be accurate/beneficial.

I know a lot of people don't understand EA and thus don't use it. But it is a FAR more powerful tool than people give it credit for. The filter-alone is worth the money. Add in the fuel calculators, MAF calculator, and Injector Parameter calculator, and it is a novice tuner's best friend. Expert tuners probably don't need these features nearly so much. But without experience, those tools really make visualizing the data far easier.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Sat Jul 23, 2022 9:30 pm

That's similar to what I've been doing, but I do it the painful and slow manual way due to not having BE/EA.

Early on I decided not to touch the injector settings since people seem to have more faith in the Deka 80's than MAF curves to be true to the data sheets. I'm always open to change however, as I'm far from experienced with automotive tuning.

What I've been doing for fueling is I go for long drives and purposefully try to drive in a style that produces long stretches of steady state operation at many different MAF values at both a high RPM and a low RPM. I then look at the log and pick times where the engine is warmed up but not totally heat soaked, about 190 degF ECT, to collect my data. If I collect data after I've been stuck in traffic with the AC blasting when ECTs are 200+ degF then the next day fuel trims will be cutting a substantial amount of fuel,-10% or so, until the engine gets toasty hot again and fuel error is back to +/- 3%.

I also make sure the HEGOs are switching and the wideband is at a lambda of 1, fuel trims are steady, MAF is steady, TPS is steady, and there's no transient fueling going on. If I meet all those conditions then I write down the fuel trim value that closed loop decided was appropriate and update that MAF curve point. Rinse, lather, and repeat for the next drive. I haven't found there to be any substantial difference in fuel trim at a particular MAF value for low vs. high RPM so I feel that my low vs. high slopes are generally ok.

I'm not so sure about the breakpoint though. My MAF curve correction factors have a dip in the middle (see attachment) so I'm wondering if I should raise the breakpoint to the point where the dip disappears. My reasoning is - raise the breakpoint, ECU thinks it needs a shorter injector pulsewidth, HEGOs report lean, I fatten up the "dip" in the MAF curve such that the whole MAF curve error factor is a flat line, except for the extreme bottom end which will still be way different from stock. Although I'm not sure if there's any benefit other than making my MAF curve correction factors more of a straight line instead of a curve.

Overall I feel that the fueling is fairly well dialed in for steady state operation - I'm just concerned about the huge difference between my LMAF curve and what a stock LMAF curve is for the <=1 volt range and if it indicates any sort of problem or if that's something typical to see for a modified engine. Cgrey8's vacuum leak suggestion is still on my mind and I'm working on making a smoke machine out of a glass pickle jar since my carb cleaner isn't revealing anything. The problem is the jar has lots of pickles in it and I can only eat so many pickles in a day. :lol:

My fuel pressure gauge arrived yesterday and I plan on installing for the next cruise to make sure fuel pressure is
- at 39 PSI at zero vac
- following manifold pressure 1:1 from decel up to 10 psi boost (might be hard to do since I can't log it... considering using a Ford diesel truck MAP sensor to replace the BAP so I can log boost)
- overall pressure isn't drifting down as my engine gets hotter so I can rule fuel pressure out for my "lean when hot" issue

Just as an update - the issue of missing at high rpm under boost I first mentioned in the first post seems to be fixed now. I lowered spark plug gap from 0.032 to 0.026 inches. In case people are wondering, I have a completely stock 1991 mustang ignition system.

My next issue to tackle after I rule out vacuum leaks is transient fueling and lean tip-ins. I only get one shot a day at cold engine transient fueling so it's a slow process. I might give up on this and use the famous OL lean idle since many people here seem to have success with it.
Attachments
7-22-22 MAF correction Curve.PNG
7-22-22 MAF correction Curve.PNG (17.71 KiB) Viewed 2361 times
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Sat Jul 23, 2022 10:13 pm

ChsReb wrote: Sat Jul 23, 2022 7:09 pm I created quite a stir on this topic a while back:
viewtopic.php?f=2&t=23195

Some say a MAF curve is "gospel" equal to the ten commandments. (Thou shall not change! EVER!)

I say it is a dynamic ever changing entity. The best you can hope is to get the MAF close for a given engine at a given time and given state of tune.

OK, so how do you know what to do?

Run the engine in closed loop as much and as long as possible. Datalog KAMUFs, HEGOs, and Lambsees and pay attention to your fuel trims. Your HEGOs must both read together with little variation between the two or you are totally wasting time and gas. Put in new ones if you have ANY doubts. Adjust the MAF to get the KAMUFs as close to one as you can across entire closed loop RPM range. Your final curve should be a very smooth curve with no bumps or flat spots. It ain't easy. Use idle, light cruise (at several engine speeds) and light acceleration staying always in closed loop. The engine must be at steady state temperature. If it Pings under 2500 RPM, find out why and fix it. Outdoor temps 55F-75F give best results. You're less likely to encounter fuel octane issues. I'm a fan of 180 Thermostats. Open Loop KAMUFs are meaningless (and Usually 1 anyway.)

A given MAF curve assumes your engine and the one it was created on are identical. I wouldn't take those odds.
I read through that thread and I agree installation details can definitely alter the MAF's accuracy. My MAF hasn't had a screen for the 12 years I had it on the car until now. I installed it a few weeks after I installed my supercharger since I was noticing the engine running a little "choppier" vs. when I was N/A, presumably from the new less ideal intake routing. Unfortunately it didn't help with the choppy MAF signal during decel, but fortunately it did lower MAF voltages throughout the entire rev range, to the point I'm not pegging the MAF meter as bad at WOT. The screen made me run lean and I had to add about 2% to MAF voltages 1.25 and up, and 17% at my idle voltage of 1V, putting overall MAF correction up to 1.4x at idle! I don't feel that the screen is a restriction since after re-dialing in the MAF curve, the calculated airflow remained the same during WOT runs, it's just now at a lower voltage. I can only imagine airflow is more evenly distributed in the MAF housing vs. before it must have been concentrating on the MAF element.

My left and right HEGOs almost always agree with each other, even during misfire events. I used closed loop for dialing in non-WOT fuel from the beginning since I like the KAMs calculating my MAF corrections for me. :-) For WOT I relied on my wideband since I was afraid to run 11 PSI boost at 1 lambda.

This community has been a great resource as I taught myself about EEC-IV and how to tune it.
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by Paulie » Mon Jul 25, 2022 11:45 am

I'll just share my experience. I have a Vortech and a UPR power pipe on my car. I originally had an SCT BA2400 maf which is similar to the lightning maf. I had issues with transient fueling and consistent dashpot behavior. I switched to a PMAS 90mm MAF which is a newer style slotted maf. While I won't say it solved all my problems, it was definitely an improvement for me.
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

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Re: What's Considered Too Much MAF Adjustment?

Post by ChsReb » Mon Aug 01, 2022 5:07 pm

My BIGGEST screw-up to date: Ignoring ITHBMA. My second biggest screw-up: Assuming the fuel filters were clean.

If you haven't done so already, dial in ITHBMA. http://efidynotuning.com/ Has an excellent write up on how to do this, (Under "Idle Air") HOWEVER this is NOT a "One and done" as you'll be adjusting your idle air and probably the lower end of the MAF as as you go. The write up says dial in the MAF FIRST. With all due respect, I had to adjust the MAF, Idle Air and ITHBMA to get it right. A REALLY slow process, but well worth it. Go slow, starting from the stock settings and slowly increase or decrease in .1 Lb/hr increments. DATALOG after every adjustment paying special attention to idle KAMUFs and LIGHT throttle tip in. (If the engine won't idle after an adjustment, drop to a smaller adjustment.) If the EGR is leaking by, you have a vacuum leak, or the PCV valve is having issues, you'll know pretty quick. You may have to fix something and start all over again, It took me a DOZEN+ rounds to get mine close but it made a HUGE difference in idle and part throttle from idle response. Mine turned out to be .6 lb/min. If you look at the lower end of the MAF curve, that can be a huge error if left at zero. My 408 has NO EGR and NO crankcase bypass hose after the MAF. Replace EVERY vacuum hose before you begin.
95 GT, CBAZA with U4P0 Base, EEC 56k 1 Bank, 408 Windsor with Trick Flow intake, BBK 75mm throttle body, BBK Shorties, Ford 47 LB injectors, AFR 185 Heads, Custom Comp Cams Cam, Moates QH v1.6, BE 5.122, with Sailor Bob Strategy upgrade, AODE w/SatNightSpl and full TCI Rebuild. 4" Gen 1 Slot MAF with 4" K&N Filter in custom cold air enclosure. Street Use ONLY.

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Mon Aug 01, 2022 8:33 pm

ChsReb wrote: Mon Aug 01, 2022 5:07 pm My BIGGEST screw-up to date: Ignoring ITHBMA. My second biggest screw-up: Assuming the fuel filters were clean.

If you haven't done so already, dial in ITHBMA. http://efidynotuning.com/ Has an excellent write up on how to do this, (Under "Idle Air") HOWEVER this is NOT a "One and done" as you'll be adjusting your idle air and probably the lower end of the MAF as as you go. The write up says dial in the MAF FIRST. With all due respect, I had to adjust the MAF, Idle Air and ITHBMA to get it right. A REALLY slow process, but well worth it. Go slow, starting from the stock settings and slowly increase or decrease in .1 Lb/hr increments. DATALOG after every adjustment paying special attention to idle KAMUFs and LIGHT throttle tip in. (If the engine won't idle after an adjustment, drop to a smaller adjustment.) If the EGR is leaking by, you have a vacuum leak, or the PCV valve is having issues, you'll know pretty quick. You may have to fix something and start all over again, It took me a DOZEN+ rounds to get mine close but it made a HUGE difference in idle and part throttle from idle response. Mine turned out to be .6 lb/min. If you look at the lower end of the MAF curve, that can be a huge error if left at zero. My 408 has NO EGR and NO crankcase bypass hose after the MAF. Replace EVERY vacuum hose before you begin.
I've been going down the vacuum leak rabbit hole and I either don't have any or haven't been able to find any. I already replaced just about all the vacuum lines other than behind the dash and inside the fenders and I noticed my charcoal cannister purge line looked suspect during the latest round of vacuum leak snooping so I replaced it but there was no change in my KAMs. Clamping off those other lines had no effect so the remaining old ones should be fine. I don't have EGR anymore so I don't have that as a possibility. I also am using a PCV valve from a TurboCoupe with the crankcase vent hose plumbed in between the MAF and supercharger inlet so I don't have any vacuum leaks from incorrect crankcase ventilation either.

I've been following the efidynotuning writeups with a big focus on the fueling section and I'll definitely put more focus on ITHBMA and idle air, incrementing ITHBMA up and down. I've noticed I sometimes have a small idle surge when in drive even when I lock timing and ISC duty. I noticed my wideband, narrowbands, MAF, and RPM all oscillating when this happens so I'm trying to see if the MAF curve is possibly leaner or richer at slightly lower or higher idle flows, causing an air/fuel ratio induced oscillation but so far I'm not making progress on that front. Family comes first so tuning time is limited.

I've also verified my fuel pressure with a digital gauge and it's 39 psig with zero vacuum. My next step is to record my boost/vac gauge and fuel pressure gauge while driving, both cold and heat-soaked, to make sure fuel pressure follows manifold pressure 1:1 at all times. I'll replace the fuel filter if it looks like my fuel pressure isn't keeping up at higher boost.

I also want to try dialing in my injector timing at idle. I have a zero overlap camshaft so I don't think I have much to worry about if I set the injector to fire onto a closed intake valve, however I'm not expecting any miracles.

I feel like I'm 90% of the way there - I just need to finish dialing in accelerator / transient fueling to fix the lean tip-in / post-tip-in with a cold engine, figure out the slight idle surge in gear, and try to figure out if this huge increase in MAF flow at idle is real or me masking some other problem.
Paulie wrote: Mon Jul 25, 2022 11:45 am I'll just share my experience. I have a Vortech and a UPR power pipe on my car. I originally had an SCT BA2400 maf which is similar to the lightning maf. I had issues with transient fueling and consistent dashpot behavior. I switched to a PMAS 90mm MAF which is a newer style slotted maf. While I won't say it solved all my problems, it was definitely an improvement for me.
I may end up needing a new MAF, depending on what my airflow readings are in colder weather. I'm right on the hairy edge with my LMAF. If I end up needing a new one, I'm definitely curious to see I I'll need to fatten up the low end of the new curve as well. I'd think that would tell me the MAF curve is the wrong tree to be barking up.
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by AuroraGirl » Thu Aug 04, 2022 7:21 pm

at your above 5k thing I would be asking what your distributor, wires, plugs, dielectric interface, routing, and then routing relative to eachother
WHAT KInd of spark plug

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Thu Aug 04, 2022 10:37 pm

AuroraGirl wrote: Thu Aug 04, 2022 7:21 pm at your above 5k thing I would be asking what your distributor, wires, plugs, dielectric interface, routing, and then routing relative to eachother
WHAT KInd of spark plug
I'm using Autolite 3923 plugs gapped to 0.026, a stock distributor with the original TFI and PIP, Ford Racing spark plug wires, stock ignition coil, auto parts store cap and rotor with brass terminals, no dielectric grease anywhere, and the wires routed to not be resting on the headers, but with no regard for particular cylinders' wires to not touch. No ignition boxes or anything. The wires and plugs appear to be in good shape.

I used to have the plugs at 0.032 inches and dropping gap to 0.026 seems to have fixed the high rpm stumbling. I wouldn't have thought only 11 psi of boost would cause spark blowout issues but a single 31 year old ignition coil compared to modern coil on plug setups must just not be up to snuff.

Another thing I fixed was my DRBASE idle not pushing DSDRPM above 816 rpm no matter what I set it to. The issue was GPAS clip limit being too low.

As I've been tuning my idle, I've gone from setting idle timing in the teens in the beginning, to all the way up to 30 (which was great for keeping engine temps low with the AC on in the summer heat stuck in traffic), back down to 24 due to not having enough reserve torque at 30 degrees and the idle feeling like it could conk out at any second. I feel the idle is much more stable at 24 degrees than 30, but I'm hoping to get higher advance for better efficiency by messing with the advance vs rpm error function some more.

Overall I'm just working on the driveability part of the tune for now and just ignoring the 40% extra fuel I have to add at idle since I'm out of ideas on that one. Both the wideband and narrowbands say I'm good so I'm rolling with it.
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by AuroraGirl » Fri Aug 05, 2022 2:18 pm

I would stand your wires off eachother and watch the routing, crossfire on the cap and induction along runs are fairly common issue
But that spark gap... why such a long spark?

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Sat Aug 06, 2022 11:28 pm

AuroraGirl wrote: Fri Aug 05, 2022 2:18 pm I would stand your wires off eachother and watch the routing, crossfire on the cap and induction along runs are fairly common issue
But that spark gap... why such a long spark?
I thought typical spark plug gaps were around 0.05 inches and that having to drop gaps to 0.026 was pretty small, but I'm new to the forced induction world so maybe I'm worrying about nothing.

I'll buy some more spark plug wire holders to keep the wires off of each other and other engine components just to be safe.

I was able to go on a test drive and I recorded my boost and fuel pressure gauges while driving and found some interesting fuel pressure behavior. The regulator is not behaving 1:1 and at idle with manifold vacuum at -14 inHG I would expect 32 psig but I'm seeing 34 instead. With no vacuum I'm dead on at 39. At 10 psig of boost I'm seeing 43psi. It seems like the regulator is only partially compensating for absolute manifold pressure on both the high and low ends. Some of this could be parallax error from recording the gauges at an angle though.

Are fuel pressure regulators typically better at actually being 1:1 with manifold pressure, or is what I described the best I can expect?

I'm also analyzing my logs for my cold engine transient misfires and it really seems like my transient fueling is way too short lived when looking at the HEGOs going lean right after transient fueling finishes so I just tried 3x my time constants in FN1322 from 1.5 to 4.5 to see if a slower decay will help. The hard part is discerning what the HEGO delay is so I know if I'm looking at something real or not, plus discerning actual lean vs. reading lean from a rich misfire. I'm pretty much just guessing and seeing how the change helps for the next drive. I might also try lowering the numbers for the lower load rows in FN1321 so there's a bigger transient fueling effect for off idle transitions, but I'm going one step at a time.
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by jsa » Sun Aug 07, 2022 1:15 am

For forced induction, plug gaps get closed up as boost rises. Set them to what works.

Coil on plug can have widest gaps.
Wasted spark less.
Coil and dissy the least gap.

A decent FPR will keep pressure very close to 1:1.
Cheers

John

95 Escort RS Cosworth - CARD QUIK COSY ANTI / GHAJ0
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Re: What's Considered Too Much MAF Adjustment?

Post by cgrey8 » Sun Aug 07, 2022 7:44 am

Transient fueling can be your saving grace or your downfall.

One of the problems I've always had with Ford's logic is that it doesn't lock-out Closed Loop operations while accel/transient fueling is engaged...or a the very least prevent it from reducing fuel. Normally accel/transient enrichment sustains for such a short period of time that there's no real harm it can cause. But when you go increasing the time component of transient, that's not the case. You can get into a situation where the transient enrichment is doing its job holding the mix rich. But then when it disappears, Closed Loop has adjusted to lean out the mix. Then when transient disappears, now you are left with LAMBSEs too lean. So all you did was delay a leanout, not prevent it.

If you do increase the time component, you'll likely also want to decrease the enrichment you get. Ideally, you'll want the transient enrichment to be just barely adequate such that the HEGOs actually report lean WHILE enrichment is occurring so that Closed Loop action doesn't lean out the LAMBSEs. Most engines are tolerant of being just slightly lean at lighter loads...just not heavily lean hence how engines are able to run fine during the lean-switches of a HEGO. The trick is to get the mix lean during these transient conditions at all RPM/Load conditions that matter. That's easier said than done. So this trick may have to be just one technique in a combination of techniques to get rid of lean-stumble during tip-ins.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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EDS50
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Re: What's Considered Too Much MAF Adjustment?

Post by EDS50 » Mon Aug 08, 2022 6:32 pm

Your corrections for your combo is typical. You are using a maf "calibrated" / Intended to be used with 42# injectors with 80# injectors installed on an ecm calibrated for 19# injectors. If you still have adaptives enabled you will just be pissing up a wet rope trying to dial in your fuel and the rest of the tune. Everyone has a different approach to tuning depending on their skillset, knowledge base and experience and can tend to overcomplicate things. My recommendation would be to disable adaptives and force open loop in your tune after clearing the kamrfs and start from there. Hardware wise I would recommend a calibrated meter like a Pro-M MAF for your injectors and ecm at your level and which will make tuning much easier as you're starting out. Having a supercharger installed prior to learning tuning basics can be a recipe for disaster if you're not careful with the changes you make in the tune and how you have your mechanicals are set up. You will need more than a 255 lph in tank pump as well with upgraded relay/wiring harness with your combo. Its usually recommended to learn basic tuning fundamentals naturally aspirated first. If you haven't done so already, post your tune so we can better help you.
1992 Mustang LX - 25.1c Chassis, Vortech Blown Dart 333 on Meth, Lentech Trans, TRZ Backhalf, A9P Tune, Moates QH/SL v1.9, BE, EA, TunerView

2003 Mach 1 - Core Tuning RYAK1/ZYA2 QH Tuned, Borla Atak Cat Back, Pypes X-Pipe, Twin 65mm TB, K&N CAI, ICT Billet Intake Spacer, Eibach Pro Series Plus Suspension, Steeda Adj. Upper/Lower Control Arms, QA1 Bump Steer, Steeda Short Throw Shifter, 315/35/17's.

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Tue Aug 09, 2022 8:38 pm

EDS50, I increased the time the engine stays in OL after a cold start so I can adjust transient fueling without also fighting closed loop. This is definitely easier to analyze when looking at logs and doesn't seem to impact drivability in any way. 8) I used to transition to closed loop pretty quickly, such that I used to be in closed loop practically before I get out of my driveway.

I was finally able to take a quick test run on the new tune with longer decay time from FN1322 and that change alone didn't help. However what helped when combined with the FN1322 change was reducing the values in the FN1321 cells that I idle at, which is around 30% load when the engine is cold and 25% load when hot. This allows the wall wetting calculations to calculate a larger increase in fuel sticking to the intake manifold walls as the engine load increases right after tip-in, causing transient fueling to be greater. FN1322 having larger values made the increase in transient fueling stick around longer.

CGrey8, I stayed on the leaner side during transient fueling so my lambdas still climb into the 1.15 range and that seems to be rich enough to prevent stumbling but not so rich that I'm fighting closed loop if the ECU goes closed loop. I still have at least one more round of tweaking to do since I really only get one shot per test due to the engine warming up, but at least I don't have a lean misfire or stumble after tip-in anymore. I'll find out for sure when I can drive the car with a cold engine again.

I think my transient fueling issue came from my MAF curve having a 1.4 correction factor applied at idle. This puts my calculated airflow significantly higher than "normal" which makes for a high load calculation at idle. There is a very large difference in FN1321 when comparing low loads vs. high loads, however there is a much smaller difference when comparing my particular idle load of 30% to a high load so I won't get as much transient fueling when using a stock FN1321.
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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Re: What's Considered Too Much MAF Adjustment?

Post by acgarib » Tue Aug 16, 2022 9:35 pm

Just another update:

I testest tip-ins on a cold engine again due to my last round of changes being performed after the engine had partially warmed up, and I was able to cause a brief stumble with an aggressive tip-in so I further reduced the values on the 30 Load row of FN1321 for colder ECTs and now I have no more hesitations / stumbles / lean misfires after tip-in on a cold engine. FN1321 needs a little more dialing in still but it's 90% of the way there.

I'm still working through the FP regulator not acting 1:1 with manifold pressure, and once I figure that out I'm hopeful the MAF corrections I made in the upper end can be dialed back closer to a stock LMAF curve. Unfortunately it doesn't seem like it'll help my crazy high corrections on the low end though since the issue is actually helping me by keeping FP higher at idle. The engine also still leans out when heat soaked but closed loop handles that no problem. At this point I'm really just chasing things that are causing deviations from that stock curve and am happy to no longer be dealing with actual drivability problems.

Thank you everyone for your help.

Another update on my pickle jar smoke tester - see the picture! It helped me find a small vacuum leak on the throttle body blade shaft but it seems to be very minor. I also saw a poorly sealing brake booster vacuum line where it connects to the booster check valve and I fixed that but it was minor as well.
Pickle Jar Smoke Tester
Pickle Jar Smoke Tester
IMG_20220816_221346.jpg (210.34 KiB) Viewed 1556 times
1991 Mustang, AOD transmission, stock small block,Twisted Wedge heads, Track Heat intake, XE270HR-12 cam, Vortech SI at 11 psi with power pipe, 255 lph fuel pump, 80lb injectors, draw-through 90mm LMAF, A9P EEC-IV with Quarterhorse

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