[VizorSRF]

Hello! Do you have anybody transfer function for this MAF?
I think it's from 2002 Mustang 3.8 with 70 mm housing

I found calibration for A9L, W4HO and F-series from EEC Analyzer, but this MAF used for E-series and 02 mustang 3.8

[ChsReb]

Here is a place to start: http://efidynotuning.com/. He has wiring Diagrams there to under "MAF". Look under "MAF transfer curves".

Remember a MAF and/or MAF curve is only a "drop in" for the same PURE stock vehicle it was installed in, and even then the older (My Stock '95 Curve was a joke.) Stock MAF curves were way off. (Closed Loop is a great Fudge Factor for a "One size Fits All" MAF .) Anything you do to change the way air moves through the engine alters the MAF curve. Even going from a stock air filter to a K&N will alter the curve. (In this case it leans it out. The engine breathes easier.)

[ChsReb]

Here is a place to start: http://efidynotuning.com/. He has wiring Diagrams there to under "MAF". Look under "MAF transfer curves".

Remember a MAF and/or MAF curve is only a "drop in" for the same PURE stock vehicle it was installed in, and even then the older (My Stock '95 Curve was a joke.) Stock MAF curves were way off. (Closed Loop is a great Fudge Factor for a "One size Fits All" MAF .) Anything you do to change the way air moves through the engine alters the MAF curve. Even going from a stock air filter to a K&N will alter the curve. (In this case it leans it out. The engine breathes easier.)

[Jtab]

Here is a place to start: http://efidynotuning.com/. He has wiring Diagrams there to under "MAF". Look under "MAF transfer curves".

Remember a MAF and/or MAF curve is only a "drop in" for the same PURE stock vehicle it was installed in, and even then the older (My Stock '95 Curve was a joke.) Stock MAF curves were way off. (Closed Loop is a great Fudge Factor for a "One size Fits All" MAF .) Anything you do to change the way air moves through the engine alters the MAF curve. Even going from a stock air filter to a K&N will alter the curve. (In this case it leans it out. The engine breathes easier.)

From my understanding, that is incorrect. The transfer (conversion as I am used to saying from my job) is the output of a particular sensor-housing combination. A different air filter will not alter the curve, though it may alter the relationship between throttle and airflow.

[ChsReb]

Jtab,

We'll agree to disagree.

I originally thought EXACTLY as you do until I proved to myself otherwise. Buy One MAF and housing. Make sure it is big enough and never change the curve again? Right?

The filter effect will be small, (It may be hardly noticeable) but a K&N replacing the stock air filter will lean things out. You'll see it mostly at cruise conditions.

My Challenge:

Get a dirty stock filter and a new K&N and try it. Watch your KAM's in closed loop during cruise. (Adaptive s Off, Kams Reset) You'll see them go leaner with the K&N, and YES your gas mileage will probably increase. I've seen a Honda Accord 4 Banger gain 2 MPG during cruise with just the addition of a K&N because the K&N leaned things out during cruise.

Anybody putting headers on a stock car with no other adjustments, will see the engine will lean out. You have to increase the jet sizes on a carburetor car, thus altering the fuel-air relationship. (And what is a MAF curve again?) This is same effect as the Air Filter, but the headers have a larger net effect.

I've been working this from a fuel economy angle for quite some time now. I'm still testing, but running a lean cruise mixture definitely gains MPG during cruise. (TO A POINT.) The Timing is extremely important with lean mixtures as well. With Biden Jacking up the cost of gas, I decided to be as preemptive as possible, because gas prices aren't going to decrease anytime soon.

[Paulie]

My experience has been similar to ChsReb. What is before and after the MAF does effect the transfer function.

[cgrey8]

From a theoretical standpoint, I can't say that this makes any sense at all. However reality has a way of putting our theories in their place. For instance, clocking the MAF shouldn't have any affect on it at all, but it sometimes can particularly if the MAF uses an edge-detection sensor. And based on the sheer characteristics of laminar flowing fluids, it does make sense that if you increase the density of the fluid by reducing the restrictions (e.g. changing the filter), you could end up with more flow than is being measured which would result in a leaner mix AND a change to the MAF curve to compensate/correct for.

However I'm wondering if a center-flow measuring MAF, such as the slot style MAFs, would be as sensitive to these changes? My guess is there are other factors at play so it may still be affected, but would it be affected as much as an edge-sensing MAF would be?

My point in this is not for us to end the discussion with both sides thinking "I know what I know and I don't know what you are smoking", which doesn't further the topic or help others that are just following along. And BTW, I'm not saying anybody has done that. So far, I haven't witnessed that. So please don't think I'm trying to call anybody out.

What does further the discussion is to share theories as to why this might be happening and then we can hopefully come to some reasonable conclusions as to when this happens and when it doesn't.

For example, the reasons behind why changing the air filter and installing headers appears to lean the tune are likely two completely different reasons. They may both have the same procedural fix (update the MAF) but understanding the situation, not just knowing how to fix it would be far more valuable to me as a reader of the thread.

My possible explanations on these two scenarios are that a change of the filter changes the inlet airflow across the sensor altering how the sensor measures flow enough to necessitate a slight adjustment to the curve to compensate for.

Upgrading to a header improves exhaust flow & scavenging which could result in more fresh-air blow-thru during valve overlap causing O2 sensors to "think" the mix was leaner than it actually was. Depending on how aggressive the overlap on the cam is would be a factor in how likely this would be and by how severe the detected leanout would be. It's also possible the improved flow is now causing exhaust backflow/reversion from the CAT(s) to reach the O2 sensors which would definitely result in a leaner reading especially if the vehicle uses a smog pump or fresh-air injection to aide the CATs. People don't realize just how much backflow their is in an exhaust system. We tend to think of the exhaust flow as this even-flow of gas that only goes in 1 direction. Not true on either of the engines I installed in my truck. When I held a shop rag over the exhaust pipe at idle, I was dumbfounded as to how far up in the exhaust pipe the reversion would pull the rag. I have a video of it happening somewhere. DynaTech actually makes a "muffler" specifically designed to minimize reversion in an effort to improve low-RPM torque. It's more of a resonator or rather anti-resonator than it is a muffler. If you look at how it is made, it doesn't look like it'd do much muffling:

[ChsReb]

All good points. The one other Programmable thing screwing with the MAF sensor reading nobody is mentioning can be summed up in one scalar:ITHBMA

1.) The PVC valve is there to vent the crankcase gases that get by the pistons and rings. On a cold motor, especially a forged one, these gasses are likely somewhat higher than on an engine at operating temperature.
2.) The above positive PCV gas flow condition is most pronounced under high engine vacuum. I.E. Idle and Cruise.
3.) As the engine ages, bore sizes increase and rings wear. That means more gases in the crankcase and more flow through the PCV valve.

Bottom line: The ITHBMA setting greatly influences the bottom of the MAF curve. Mine is set for .6 Lbs/Min (16.3 Kg/hr). Look at the values on the bottom of your MAF curve. Neglecting that adjustment can have a huge effect on AFR at idle and light cruise. ( Now setting ITHBMA is a royal pain in the...)

Now the really bad news: Since ITHBMA keeps changing as the engine ages, so does the MAF curve. The MAF curve is a constantly changing (Usually SLOWLY) entity. You just have to decide how often you need to check it.

Now throw in a defective or changing due to wear spark plugs, smog pump and EGR valve and you get a dynamic MAF puzzle.

[ChsReb]

Guys, I agree theory supports the “One Size Fits All” thinking. I beat my head against the wall for days trying to understand what was going on. I’m a Degreed Mechanical Engineer with some technical training in ICE.

I finally rationalized it all this way: Be it jets or sensors, operating at the edge of design always allows additional error and variation to take place. Those Low flows are subject to statistically increasing errors with decreasing flow rates.

Now if I make it easier on the engine at idle or cruise, it needs less air and less fuel to perform the same function as before the change. That lower power requirement means a more closed throttle and a higher engine vacuum. That means a higher leakage past the throttle body and any emission system will likely have a higher flow as well. Throttle blades are far from linear in there response as well. (If you want a technical discussion on this: http://www.diva-portal.org/smash/get/di ... TEXT01.pdf)

Bottom line: the further you get from designed maximums, the greater the errors and deviations you can expect. What goes on that is not under control of the throttle body and thus measured by the MAF, has and ever increasing error from what is expected. Any errors experienced are almost certainly not linear. The software allows you to account for this, ( ITHBMA ) but it definitely isn’t “Plug and Play.”

To see this, Set the car on cruise on a level road with no traffic. Datalog MAF and Throttle Position. The datalog will cycle both up and down. This is caused by those low flow errors and variations.

[indy2000]

ChsReb

Can you explain how a K and N filter will make a maf transfer function, lean?

[cgrey8]

ChsReb

Can you explain how a K and N filter will make a maf transfer function, lean?

I'm curious to know the how on this too. I'm not doubting it's a real phenomenon. I'm just curious how it manages to pull this off.

My assumption is that it changes how the air approaches the sensor as compared to factory enough that at mid to low airflow conditions, the readings end up being leaner. However I wouldn't think that higher flow conditions would be as affected. But being I don't understand the problem and have no 1st hand experience with the problem, I have no confidence I'm even close to right.

[ChsReb]

In a sentence: Lower Differential pressure drop across the filter. The engine breaths easier at the same throttle opening. Same thing with headers on the back end. If I make it easier to breath, I get better cylinder filling. Better cylinder filling produces more HP at the same throttle opening. Now I need less HP for the same load, thus a tighter throttle opening. Now a lot of this is reflected in ITHMBA as well. A more closed throttle means a higher flow past a supposedly closed main throttle body, and a higher PCV flow when open. That PCV flow is totally unmeasured. I believe my ITHMBA is set for .6 Lbs/Hr. That is a huge error at Idle and cruise if unaccounted for. In addition, All this is not linear. It is a damped sinusoidal. Put the car on cruise and datalog the MAF. The output cycles up and down. In the words of my control theory book, “It is always hunting. Never fixed.” The flow error goes up and down. No doubt the cycling O2 sensors, don’t help this condition, but I’m running mine in open loop for better gas mileage and it still is sinusoidal.

To relate this to HVAC, the quickest way to burn up an HVAC compressor is to never change the filter. It jacks up the head pressure on the compressor, and makes it use more power.

[ChsReb]

Your MAF curve is a relationship between fuel and air based on a known air flow based on a SPECIFIC volumetric efficiency.

It is all about cylinder filling and exactly how and with what you fill the cylinders.

Another way to look at it, let’s suppose I had a terrible exhaust system. The result of combustion is most probably going to be rich because of charge dilution. The O2 sensors will see that and lean the mixture out. The net result: Low Power, Low NOX, and the cat cleans up the wasted fuel. Sounds like the 70s and 80s to me. Higher fuel consumption and low power.

OK let’s suppose that the previous power is adequate for that condition. I fix my exhaust, now the cylinder fills completely, more power is produced, and now I can go to a lower throttle opening. But wait, that tighter throttle now needs more fuel!

Back to the pre-80s: A carb is a “Mechanical” MAF. The jet sizes depend on the quality of the cylinder filling. Changing jets alters the mechanical MAF “Curve”.

[ChsReb]

My original contention remains: Anything done to alter the way the engine breaths alters the MAF curve because you alter the volumetric efficiency of the engine. A MAF curve is only accurate for a specific complete drive train.

Actually I’m being really generous with that statement. My stock MAF and It’s associated curve was extremely lean.

[cgrey8]

I get how mechanically driven devices, like VAMs and Carbs are affected by changes in engine characteristics. However MAFs are not the same as those. They measure the mass of air flowing, not the volume of air flowing. So static OR differential pressure differences should not affect a MAF like they would a carb or VAM.

So I'm still not hearing a reason why the MAF curve would be affected by changing something like an air filter (or any other part of the engine) unless something is changing with how the air flows across the sensor causing the sensor to incorrectly detect the flow. For example non-uniform flow patterns across the sensor.

But the one that I suspect is probably the most likely culprit is changes in reversion or at least in the pulse-waves produced by reversion. In a theoretical world, the airflow across a MAF would never be backwards. But pulsing of airflow could cause shock-waves through the air that affect the MAF's detection of the airflow. So while the air isn't technically moving backwards, the pulses are pressure waves that would alter the detected mass of the air. So a backward flowing pulse through otherwise forward flowing air could cause the sensor to read certain sections of the air as heavier or lighter than what's actually going into the engine thus causing the sensor to report higher or lower amounts of air than actual. Again, this is just a theory. I have no clue if it is backed up with fact. But it's the only thing that makes sense to me.

[skunk]

Not to be contentious or contrary, I do agree with most of what you are saying regarding volumetric efficiency affecting fuel required.

However..... The MAF is just a sensor. It only reports a voltage based on airflow. If volumetric efficiency changes, the airflow past the sensor should change respectively. Im not saying it won't need some modification to the curve but if you need to alter fuel...the MAF is not the place to start. Adjust injector parameters first since its something you CAN control being the direct means of fuel delivery just like you described when dealing with jetting a carb.

Saying that....the only concern you should have regarding the MAF is are you going to peg it if its too small and are you going to have enough resolution down low if its too big. As with most sensors accuracy tends to stray at the extremes of their measuring ability.

I think you definitely provide some great detail in your posts.... thank you!
John

[ChsReb]

All Good points guys. A interesting an insightful discussion.
To follow up on a point by point basis:
1,) Is turbulence at the MAF sensor an issue. YES, Definitely!! Going back to my HVAC days, we always chose a point to drill the hole for a Pitot tube or Hot wire, 8-10 duct diameters down from the nearest turn upstream and three diameters from the nearest turn down stream. We can't do that here. Not enough room under he hood.
2.) Is reversion an issue? Probably! Especially with a stock smog pump. I dunno how to check for this except for watching the O2 sensors.
3.) In my case I bought a slot MAF and a housing. The slot MAF knows velocity. It doesn't know how big of a housing I have installed it in until I scale my MAF. The MAF sensor has a Temperature sensor. Using Temperature and Velocity the computer knows air density and Mass Flow per unit area.
4.) Every sensor (Computer, Automotive, HVAC, Process) I've ever used is most accurate in it's upper measurement range and least accurate at the lower limits of it's range.
5.) The changes I make in my MAF curves only have significance below 1.5 Volts, meaning light cruise and Idle.
6.) ITHBMA, in my program, is set for .6 Lb/Min. That unaccounted for can be a 20-25% error during idle and light cruise. That number was set at idle. I used Decphia's website methods to set it. It required several Idle air and MAF adjustments to get it right. Light cruise would likely be a lower ITHBMA value due to the slightly open throttle. We can dramatically enhance this discussion with a full tutorial on how this value affects the calculations here. Anyone know?
7.) Single blade throttle bodies are extremely NON-Linear air flow controls. In my HVAC days, I've seen slightly cracked parallel Dampers flow 10-15% of total flow and a 40% open blade flow upwards of 70% total flow.
8.) Volumetric Efficiency is a huge player in modified engines. (I won't beat that horse again.)
9.) Could you adjust fuel by altering injector settings? Yes, but I wouldn't recommend it. Injection accuracy at low flows my be lacking as is low flow accuracy across the MAF.
10.) I put a K&N on the wife's 4 banger Honda Accord and picked up 2 MPG! Honda's use differential pressure for air flow calculations. My contention here is I improved the engine's volumetric efficiency.
11.) OK so why alter a MAF curve in the LOWER Range?
A.) I'm adjusting for VE.
B.) I'm adjusting for MAF Sensor low flow errors.
C.) I'm adjusting for Injector low flow errors. The bigger the Injector the greater the low flow errors.
D.) I'm adjusting for errors in ITHBMA. LOAD induced or calibration induced.
E.) I'm adjusting for EGR errors or leakage. (If Present.)
F.) I'm adjusting for Smog Pump (If Present) flow Reversion or general exhaust gas reversion.
G.) I'm adjusting for MAF air stream turbulence errors.

All adjustments were made using Lambse and Kamrf readings during idle, cruise, and VERY light acceleration. The goal was to get as close to a Kamrf of 1 as possible. I generally tried to get plus or minus 1.5 for a set of KAMRF readings. Generally I picked the bank with the most responsive O2 sensor. All I'm really doing by changing the MAF curve is lying to the computer about how big the MAF housing is under about 2500RPM. There are two videos on YouTube explaining how I made these adjustments.

Does it work?

25-26 MPG @ 65MPH (and as much torque as my 454 LS7 Chevelle) with my 10.25/1 compression, aluminum headed 408 on 87 Octane gas! The 8" tires break loose at 2800 RPM on wet pavement, Unconditionally!

And I ain't done yet...

[cgrey8]

This post most people will probably tune out on as TLDR. And that's fine. For those that do read it, I'm genuinely interested in any thoughts that might improve my understanding of things. Feel free to disagree with me. I'm not always right, but I do learn from others by expressing what I think, and then hear other's reasons for disagreement and determine if it makes sense enough for me to understand where I might've been wrong.

...1,) Is turbulence at the MAF sensor an issue. YES, Definitely!! Going back to my HVAC days, we always chose a point to drill the hole for a Pitot tube or Hot wire, 8-10 duct diameters down from the nearest turn upstream and three diameters from the nearest turn down stream. We can't do that here. Not enough room under he hood...

Measuring airflow on the front of an engine is far from an ideal environment. Whether there's turbulence or not, the pulsed aspect of intake air means that the sampling rate on the sensor has to be far higher so the readings can be averaged.

...2.) Is reversion an issue? Probably! Especially with a stock smog pump. I dunno how to check for this except for watching the O2 sensors...

I'm not sure how much smog pumps add to the mix. Fortunately most people on this forum are probably taking those off or disabling them at the very least. Watching the O2s & WBs are our only way of detecting inaccuracies with fueling. But I don't know how useful they are at gleaning any conclusions about the presence or affects of reversion. Reversion creates pulses that are at the frequency of the engine RPM x the number of cylinders / 2. Even at relatively low RPMs, that's still way faster than stock EECs and datalogging devices can sample at to "see" the waves of reversions on the MAF.

...3.) In my case I bought a slot MAF and a housing. The slot MAF knows velocity. It doesn't know how big of a housing I have installed it in until I scale my MAF. The MAF sensor has a Temperature sensor. Using Temperature and Velocity the computer knows air density and Mass Flow per unit area...

I'm going to be a bit nit-picky and pedantic here, but when talking technical issues, it is important to be as accurate as possible.
I'm not sure that the MAF knows velocity. That's exactly what a Pitot tube is measuring. But MAFs measure mass, not differential pressure. I agree that it is possible to correlate mass-flow to a velocity knowing the current atmospheric pressure and density of the air, but density is not a constant. You could have 35kg/hr of airflow at a multitude of different velocities depending on the pressure of the air. N/A engines, this is not that big of a deal since atmospheric pressure doesn't change that much. But in a blow-thru boosted application, the air pressure can be 2-3x higher than atmosphere. Thus mass-flow and velocity are not linear or even directly related in these situations. Add an inner-cooler, and suddenly the same pressure has a much denser airflow for the same pressure.

The MAF does have a temp sensor to compensate for temp. But interestingly, there's another aspect the MAF does not have the ability to measure. And that's humidity. At high ambient temps (e.g. 90degF), a high humidity adds a non-trivial amount of mass to the air. And the only thing that compensates for this is the EEC's ability to adjust the mix (and learn those adjustments into the KAM).

...4.) Every sensor (Computer, Automotive, HVAC, Process) I've ever used is most accurate in it's upper measurement range and least accurate at the lower limits of it's range...

This is true for most analog sensors whether it be voltage, airflow, light, or anything else. Most sensors are more accurate when there's "more" of whatever it is measuring to measure. The company I work for differentiates itself in the Industrial HVAC industry by making VAV controllers with a MUCH more expensive differential pressure sensor than most of our competition so that our controllers operate more accurately at low-flow conditions.

...7.) Single blade throttle bodies are extremely NON-Linear air flow controls. In my HVAC days, I've seen slightly cracked parallel Dampers flow 10-15% of total flow and a 40% open blade flow upwards of 70% total flow...

Very true. I recall some mfgs guide the throttle cable around a cam mounted to the throttle blade shaft so that movement of the throttle at low-flow conditions doesn't move the blade as much as the same throttle movement at higher airflow positions. That makes off-idle control of the engine RPM so much easier to control. With modern throttle-by-wire, they can compensate for this in far more sophisticated ways than a cable-cam.

...9.) Could you adjust fuel by altering injector settings? Yes, but I wouldn't recommend it. Injection accuracy at low flows my be lacking as is low flow accuracy across the MAF...

This is one of those areas where my experience has been so radically different than most others here on the board. Both sets of injectors I've ever had to tune for, the stock values I used were trash. I heavily relied on EEC Analyzer to help me tweak my Injector Slope/BP values. So while it may not be recommended for the average person to go messing with those values without a clear understanding of what they are, I would always recommend someone at least check their Slope/BP values against EA just to see how close their values are to what the datalogs are showing...particularly if they've already paid for the EA license. It's like why not?

...10.) I put a K&N on the wife's 4 banger Honda Accord and picked up 2 MPG! Honda's use differential pressure for air flow calculations. My contention here is I improved the engine's volumetric efficiency...

I've never had this experience with an air filter change. The only difference I've ever seen is increase in HP due to less resistance to airflow at the higher end. At lower flow conditions like cruise, the throttle plate is already restricting airflow. The resistance a dirty or less-than-optimal filter might add is going to be minuscule compared to the resistance the throttle plate is applying to the airflow. But the conditions on the engine should not have changed. The engine needs X amount of air/fuel to push the vehicle a certain speed. I'm not seeing, logically, how a freer-flowing filter alters the engine's need for air/fuel or even eases it's burden in any way that would improve its efficiency. Lets say a dirty filter was causing less air to flow. This just means the throttle plate would have to open a little wider. A cleaner filter would just require the throttle plate to close more to produce the same airflow to the engine. But from the engine's perspective, the resistance necessary to result in the airflow required to produce the power needed is the same. Likewise the intake manifold pressure should be the same at those same cruising conditions. So like I said, I'm just not seeing where the increase in efficiency to account for an improvement in fuel economy came from.

Note I'm not saying it is not possible to happen. I just don't understand how it can happen. So for those that have seen it and swear it is true, I'm not questioning that it is a thing (so don't get defensive). I just don't understand it and have no explanation as to how it is happening.

...11.) OK so why alter a MAF curve in the LOWER Range?..

Here are the ones I agree with:

...B.) I'm adjusting for MAF Sensor low flow errors.
C.) I'm adjusting for Injector low flow errors. The bigger the Injector the greater the low flow errors.
D.) I'm adjusting for errors in ITHBMA. LOAD induced or calibration induced.
E.) I'm adjusting for EGR errors or leakage. (If Present.)
F.) I'm adjusting for Smog Pump (If Present) flow Reversion or general exhaust gas reversion.
G.) I'm adjusting for MAF air stream turbulence errors.

As for my setup, it's probably not as dialed in as yours. But I'm also not working with the same caliber of engine. I went into my build knowing the highest HP I would possibly make would be 300hp. And I MIGHT be 270hp at the crank on a good day. But with high compression, 3.27s, lean-tuning at cruise, and a very torque-oriented build, I'm roughly 25MPG on the road (65-75 MPH), 20-22 on the daily commute if I keep my foot out of it. Keep in mind this is a relatively heavy and boxy shaped truck, not a sleek sports car. Without dropping the clutch, it can break the tires loose in 1st. But that's the only gear it can do that. There are limits to what stock ported heads and intake can do.

[indy2000]

ChsReb,

I thank you for trying to explain why you think the MAF xfer needs to be changed if you put in a less restrictive air filter. However, I dont see anything you have typed that validated your argument. All I can conclude from your explanations, is that had to alter your xfer to satisfy your Kamrf need to be 1.0. Your 02 reporting could be the issue, where it is in the exhaust, so you are merely making your xfer fit your location, can you see how this is problematic, ie introducing another variable?

[ChsReb]

I once too believed the MAF curve was the 11th Commandment- "Thow shall not change!". That is until I proved to myself otherwise. One size fits all as long as it is big enough, right? ( I had to create mine because I bought a slot MAF and uncalibrated housing.)

I'll post some before and after MAF Transfer functions shortly. (EXACTLY the Same MAF, housing, and air filter used on two Different Engines, A 302 and a 408. Yep, I bought the Hardware and put it on the 302 FIRST, thinking I'll get the curve just right and I'll be done with it. Just tighten the clamp, plug in the sensor, and drive off into the sunset, right?) Even if you reject my Volumetric Efficiency Arguments, the need to adjust things for ITHBMA remains. That's unmeasured "Something" coming in from the crankcase via the PCV valve.

The next argument would be: "Yeah, but that is all accounted for in the calibrated MAF I bought." Engines wear. Blow-by increases with age. Unless your car is exactly like the car used for calibration, some things will change. Those changes can really effect light cruise and idle.

Could the O2 sensors be off? Possibly! They are in a stock location in stock exhaust piping with stock mufflers, so there isn't much I can do other than change them. The signals are both consistent, so I trust the sensors.

Now, I go with what they're telling me and evaluate the datalog of the results. (Actually the engine is running in OPEN LOOP so I can lean out the mixture for better cruise gas mileage.) Gas Mileage, Idle and tip in performance are all as best as I could hope for. It Starts right up from 28 to 95F, doesn't surge, and Idles like a stocker. I've got all the seat feel of as much torque as my 454 Chevelle. I've even got to be careful just how much throttle I use at stoplights even with the 8" tires!

If you're totally happy with what you have, fantastic! Happy motoring!

I'm just passing on what has worked for me!

[indy2000]

The fact that you have chosen a MAF that was not supplied a xfer function, is what i believe has made you gone down this path. I see why you are 'building' a maf xfer now.

That was your choice. I do not see why you would insist in running in open loop, is this just for building your maf? Also your understanding of the PCV, is not correct. The air leaving the crankcase is being replenished by metered air from the intake post maf.

[ChsReb]

I’ll post my “One size fits all” MAF response shortly.

As to my contention on the PCV valve, from Wikipedia: https://en.m.wikipedia.org/wiki/Crankca ... ion_system

From Summit Racing: https://help.summitracing.com/app/answe ... alve-do%3F

From an Auto repair site:
https://www.camarilloindy.com/what-does ... 020-09-16/

As to lean fuel mixtures:
https://ls1tech.com/forums/pcm-diagnost ... r-mpg.html

[cgrey8]

...As to my contention on the PCV valve, from Wikipedia: https://en.m.wikipedia.org/wiki/Crankca ... ion_system

From Summit Racing: https://help.summitracing.com/app/answe ... alve-do%3F

From an Auto repair site:
https://www.camarilloindy.com/what-does ... 020-09-16/

I looked at each of these and they seem to detail the purpose and point of PCV correctly. I don't see that anybody has disagreed with how PCV system works that would give you "contention."

It is true, the engine pulls air from the crankcase into the intake so blow-by gasses can be re-burned as well as preventing backflow in the event of a backfire or a boosted application. However the amount of air being pulled in from the PCV valve is WAY more than the blow-by. Thus the engine's crank case has to have an intake of fresh air. Old engines just put a breather on the valve cover and pulled in air from the atmosphere. However this is problematic for computer controlled systems since that would be un-metered air that the computer isn't accounting for. So modern systems plumb the crank case (usually via a valve cover) to the intake air path between MAF sensor and the Throttle body so the air being pulled into the engine crank case is "measured" by the MAF. The Explorer 5.0Ls had a PCV intake tap right on the oil filler neck, which mounts to the valve cover:


A rubber hose went between that port and connected to the big rubber air intake snorkel that connects the engine to the MAF.

PCV_intake_pipe.jpg

The assumption being made by the control strategy is that the air being pulled into the engine is equal to the amount of air pulled into the engine. It's an incorrect assumption since the air going into the engine will be LESS than the amount of air passing through the PCV valve into the engine since the air supplied by the PCV valve will be a mix of the fresh air and blow-by. Although the difference isn't that much. So despite the inaccuracy produced by the bad assumption, it's close enough. It's certainly a way-more accurate account of the intake air than than if the PCV intake air wasn't metered at all.

[ChsReb]

I 100% agree with both of you that the DESIGN of the PCV system is you pull metered air in after the MAF has measured it thru the engine and back out thru the PCV valve.

My only argument is that as the engine wears, blow by increases. Over time the negative flow into the engine decreases and at some point it may go positive both at the bypass hose and the PCV valve. Those gases will be oil vapor and exhaust gases by their very nature. With increased blow-by comes more unmeasured crankcase fumes entering the manifold. Some of it will burn. Some will not. All of it diluting the incoming charge making it burn rich because the flame front isn't as efficient during ignition.

Same thing with the EGR. As it gets older, it carbonizes and doesn't seal as well. Any leakage increases ITHBMA.

[ChsReb]

OK, here are my experiences that made me advocate for adjusting the MAF Curve.

I bought my Quarterhorse and Binary Editor and decided it learn to tune on my PURE stock engine. The stock car was a dog! Clearly it was running extremely lean as any throttle opening past 1/4 throttle elicited loud pinging under the hood. Clearly I was getting lean detonation. After over a month of MAF curve tuning (proceeded by new plugs, wires, coil, fuel filter, and thoroughly cleaning the distributor cap), I considered the engine ready to tune. (We're talking about a 100,000+ plus mile motor here.) After a couple months (Yeah, LLLLLOOOOONNNNNNGGGG learning curve.) work, things were really looking up. I could even squawk the tires if I wanted too, and with comparative ease! Good gas mileage was back as was a clean stable idle. It was just like driving a new engine!

OK, now I'll just buy the new MAF and air filter and just put it on the 302. After I get it right, it'll just bolt right in there and that part of the new engine tune will be done, Right?



(The black stuff is a high temperature insulation and the open filter are faces the fender opening just like the stock setup. This way I get cold fender air instead of under hood air. There is plenty of room to get your hand around the filter. This just couples nicely to the stock elbow ahead of the (old and new) Throttle body, so everything remains in the stock location.)

Did it work out that way?

Not Quite!



Really, not at all! The 302 curve with the NEW MAF (B Column) was way to rich for the 408 (NEW MAF C column). It took another couple weeks to get to the curve I'm running now.

OK, so what caused this? Three suspicions: 1.) Injector fouling 2.) Low Fuel Pressure 3.) Fuel pump inlet issues. When I decided to change the fuel pump, (Ahead of putting in the new engine.) I found out the pump fuel sock was so varnished parts of it would hold gasoline! In effect I built in my 302 fuel delivery issues into the MAF curve! Now, remember the old 302 was getting good gas mileage and even capable of stop light tire spins with the stock automatic!

Now admittedly this is an extreme example. A new car with a calibrated MAF created on a NEW car with everything installed in the same locations will yield far more favorable results.

So what is different on your car from the calibrated MAF on the test car it was created on?

[indy2000]

you could always log fuel trims, pcv and no pcv, if you feel there could be a problem in your case. I can assure you, running open loop is not what you want to do.

[ChsReb]

After a couple test datalogs over a predetermined route, I can find no real difference in fuel mileage by running open loop utilizing lean AFRs over closed loop. I left the timing unchanged both in open and closed loop. My cruise ignition timing is still advanced like a vacuum advance would do in the old days. Yeah, my ignition curves are highly customized to maximize fuel economy.

Now does that mean running open loop is a bad idea?

Well, Now I know my fuel tables are REALLY close and if a HEGO is suspect, I just flip the scaler and find out for sure.

Now does that mean my ignition timing is optimal as well?

I wouldn't say that. At least not yet.

25+ @ 55+ cruising MPG and a 408 and I ain't done yet. Yes, I still datalog LAMBSEs and KAMRFs and adjust the MAF Transfer as required. I definitely gotta be in closed loop to do that.