Understanding Mass air's transfer function

[lxh89]

Bottom line I see here: Both methods will work and are proven to work.

This is another what's the best color argument. If I had my meter flow tested or modified to overcome the 63.99lb/m EEC-V limitation, then wonderful, I can simply punch the values into my MAF Transfer function. Saving me the time needed to dial it in.

If I'm like a majority of folks out there who incrementally change their combos, I'll stick to using a wide band and altering my MAF calibration to fit new parameters. I bought a Pro Racer package for this exact reason.

One other thing to be aware of, just because a MAF is flow tested, there are dynamic conditions which can still cause problems in the readings such as back flow intake reversions from a big cam, placing the MAF too close to the throttle body, etc.

Calibrating a MAF curve with a flow tester isn't the panacea to all air flow measurement problems.

Tony

[Disturbed One]

jchambers & lxh89. I understand what both of you are saying! I know no one said that a car needs to be tuned everytime a change is made... it's just how it comes out reading through all the posts and replies! (No one in particular)

I myself am trying to learn as much as I can since I like to do things on my own and I appreciate both of you chiming in on this! I figured throwing out what I did would prompt some good discussion and more facts that I can take away from this thread!

Can I atleast ask if what I had posted is correct

I've been reading this and looking into it. It makes sense to me. The Meter has a voltage range upto 5V. If the engine is sucking or getting air forced into it and it's only peak voltage is at 3.75V, There is still more that can be had with that Meter and "tune" in stock form.

The computer will handle air upto that 5V limit before the meter needs to be replaced and the computer will need to be reprogrammed with the new voltage values of the New Meter being installed, so it knows how much air is being brought in at the voltage values.

[Nekasrof]

Originally Posted by Disturbed One

jchambers & lxh89. I understand what both of you are saying! I know no one said that a car needs to be tuned everytime a change is made... it's just how it comes out reading through all the posts and replies! (No one in particular)

I myself am trying to learn as much as I can since I like to do things on my own and I appreciate both of you chiming in on this! I figured throwing out what I did would prompt some good discussion and more facts that I can take away from this thread!

Can I atleast ask if what I had posted is correct
Quote:
I've been reading this and looking into it. It makes sense to me. The Meter has a voltage range upto 5V. If the engine is sucking or getting air forced into it and it's only peak voltage is at 3.75V, There is still more that can be had with that Meter and "tune" in stock form.

The computer will handle air upto that 5V limit before the meter needs to be replaced and the computer will need to be reprogrammed with the new voltage values of the New Meter being installed, so it knows how much air is being brought in at the voltage values.

Correct. The new calibration will include the new transfer function. See the sheets I posted on page 1. With the limitations of our PCM, it's necessary to do the math in order to input those values in the tune.

[Nekasrof]

Originally Posted by lxh89

Bottom line I see here: Both methods will work and are proven to work.

This is another what's the best color argument. If I had my meter flow tested or modified to overcome the 63.99lb/m EEC-V limitation, then wonderful, I can simply punch the values into my MAF Transfer function. Saving me the time needed to dial it in.

If I'm like a majority of folks out there who incrementally change their combos, I'll stick to using a wide band and altering my MAF calibration to fit new parameters. I bought a Pro Racer package for this exact reason.

One other thing to be aware of, just because a MAF is flow tested, there are dynamic conditions which can still cause problems in the readings such as back flow intake reversions from a big cam, placing the MAF too close to the throttle body, etc.

Calibrating a MAF curve with a flow tester isn't the panacea to all air flow measurement problems.

Tony

The point with mass air is that you DON'T have to make changes in the tune when you incrementally change your set up, unless you have reached the limit of the meter or fuel. Once you've exceded the pcm limitations(1739kg/hr, 63.9#/min), additional calculations are needed to match everything up.

Also, keep in mind that revision pulses due to placing the meter too close to the throttlebody is not a fault of the meter. That is improper placement of the meter. And large cams don't affect the meter at all, unless, again, it's right up on the throttle body. Which would also be improper placement of the meter.

In essence, dynamic conditions causing bad readings on the mass air meter are caused by either improper placement or improper calibration. Ford chose to advance to mass air from speed density due to its acuracy and repeatability in all conditions(hot, cold, humid, dry, low altitude, high altitude). The meter reads the mass of air and all calculations are produced from that calibration being exact. It's very simple actually.

[lxh89]

Originally Posted by Nekasrof

The point with mass air is that you DON'T have to make changes in the tune when you incrementally change your set up, unless you have reached the limit of the meter or fuel. Once you've exceded the pcm limitations(1739kg/hr, 63.9#/min), additional calculations are needed to match everything up.

Also, keep in mind that revision pulses due to placing the meter too close to the throttlebody is not a fault of the meter. That is improper placement of the meter. And large cams don't affect the meter at all, unless, again, it's right up on the throttle body. Which would also be improper placement of the meter.

In essence, dynamic conditions causing bad readings on the mass air meter are caused by either improper placement or improper calibration. Ford chose to advance to mass air from speed density due to its acuracy and repeatability in all conditions(hot, cold, humid, dry, low altitude, high altitude). The meter reads the mass of air and all calculations are produced from that calibration being exact. It's very simple actually.

Not quite sure why you are driving that point home. It's pretty well known mass air systems (if operated within range) can adapt to changing air flow conditions (elevation, barometer, humidity, temperature, artificial pressure)

The fundamental argument here is whether to rescale the MAF when the limit is exceeded or tune the MAF transfer. The latter is the most convenient in my opinion. That's subjective so no need to debate it.

You do whatever method floats your boat, it's a free country.

Tony

[Nekasrof]

For additional understanding regarding mass air meters and their function, here's another excellent discription. If you've read post #1 and #4, then this will be additional information.

To be clear, we're not talking about messing with the mass-air sensor itself -- that's a piece of hardware plugged into the MAF air-tube. The tube + the sensor is called the MAF meter (so we have our terminology straight). The MAF meter (specific sensor in a specific tube) has specific flow characteristics. No MAF meter is 100% linear (for various physical reasons: shape, sensor flow-interference patterns, non-linear turbulence at different air flow rates, etc). If the meter (sensor-in-tube) response curve was 100% linear a tuner could calibrate it correctly by programming a straight line function from zero flow to maximum capacity is because linear response = a straight line curve -- from 0 to 5v. In reality, the [MAF] meter curve programmed into the tune must adjust for this – ie: reflect *real* flow across the rpm range. This is done, in essence, by every small voltage increment representing ever more flow -- but the flow increments mapped against voltage are a NOT LINEAR function -- a curve.

If you think about it, it makes perfect sense. If you pull air through a tube of a fixed configuration starting off slowly, every time flow doubles the effort needed to pull twice the air will *more* than double -- it's a curve, not a straight line function. And the more doubling, the greater the slope change of the curve. Additionally (as mentioned above) the specific size, shape, interior tube obstructions (the physical sensor itself is a major one) all affect flow in a non-linear way as flow varies from zero (no air movement) to maximum defined flow (where the sensor returns 5 volts to the ECU) . However, each voltage increment must represent a different AND NON-LINEAR amount of flow to ACCURATELY reflect the PHYSICAL flow going through the tube at any given instant. That is the SOLE AND CRITICAL PUSPOSE OF THE MAF in all mass-air cars (Ford and GM use different sensor and ECU communication logic, but the MAF engineering rationale is indentical).

So, in the Ford system (voltage based; GM uses frequency) it should be apparent that it's critical that the return voltage correctly maps to actual physical flow once interpreted by the ECU logic, else the ECU will be doing things to the engine it doesn't really intend to do. The mass-air meter curve (alternatively called the MAF transfer function) is how the tuner programs that relationship (flow as a function of voltage) into the tune so that the ECU always knows EXACTLY what the true air flow is at every instant -- critical because only then can ALL the other functions in the tune logic work properly because virtually all of the logic is affected by the MAF because air flow = horsepower and the correct fuel must be inserted into the port consistent with precisely how much air is going past (the injectors us pulse width modulation, essentially the time that an injector is 'open' is varied since the injector itself always flow the same amount when 'on' so what is varied is how long it's on per intake stroke). If the MAF is not accurately calibrated to flow, the tune will push control into and out of dozens of tables at incorrect entry and exit points and the operation of the engine will not be accurate and, under untested conditions, it will be less safe (or worse).

At idle and under low load the O2 sensors' stoich switching is used to dynamically adjust A/F. This is known as closed-loop operation. At high load and WOT, fuel is commanded based solely on tables, not the O2s. This is called open-loop operation and this is the mode the tuner focusses on. However, the ideal A/F is not a static requirement across rpm because, even at WOT, load and cylinder pressures vary with rpm. If it didn't, your dyno curves would be flat. Different load demands different A/Fs to be safe. The more load, the more fuel for a given quantity of air is needed to be safe. At low load A/Fs of 14.6 to 14 (idle to low load) are fine. More importantly, less load permits less fuel with the same amount of intake stroke air. Why? Because less fuel is required to prevent detonation under less load. This is yet another reason not to mess with the MAF transfer function (curve) except to make it reflect 100% accurate flow because there's no point in a flat A/F curve. It needs to be what the engine load is demanding and the only way to achieve that accurately FOR ALL CONDITIONS (not just the conditions the day of the tune) is by basing the whole tune on an accurate MAF meter.

So, why is it bad to target A/Fs? Well, achieving good A/Fs isn't bad at all, but tweaking or damaging the MAF's calibration to artificially target them is bad. And that is why a tune is then needed if a mod is made...because any mod will throw the A'Fs off if it was done the wrong way. Why? BECAUE THE TUNE IS THEN NOT ACCURATE FOR THE FULL RANGE OF THE METER -- 5V. So a mod that makes more HP pushes the tune into unchartered and necessarily inaccurate territory -- SO WILL ANY CONDITIONS THAT YIELD A HIGER ALTITUE DENSITY THAN THE DAY OF THE TUNE.. That is a real problem lurking to bite you -- maybe when you go to a different track either at a different altitude or a day with really "good air" (better than the day of the tune). If the MAF is correct, you could change a pulley or exhaust or intake or operate at different altitude-densities and NO TUNE would be required (up to meter range and pump capacity, etc) -- even tho those mods and/or conditions produced substantially more HP than the day of the tune -- because the A/Fs WILL BE ACCURATE FOR THE FULL RANGE OF THE CORRECTLY CALIBRATED METER.

Not surprisingly, that is the whole point of a mass-air car. It's why Ford ditched the old speed-density approach 20+ years ago. It's just nutty to defeat the whole purpose of mass-air engineering by distorting the curve and then trying to 'fix' dozens of other settings to compensate for that on the day of the tune. It should be clear that only serves to *potentially* put the engine at greater risk under myriad real-world conditions that didn't exit the day of the tune (better altitude-density as explained above) and to have the customer come back (or datalog, etc and email changes) for every little mod/change. Even then, it's still less safe under improved altitude-density conditions because it has essentially defeated how a mass-air car properly works and the entire tune is therfore slightly inaccurate because it's always necessarily making inaccurate assumptions about true air flow at all rpm -- even at idle.


This is sticky-worthy material. While some may attempt to dispute the importance regarding proper tuning procedures, others have found out what it means to have an improper tune installed in their car. It doesn't take an exhaustive search to find issues just on this board alone.

[j rick kirby]

I'm just getting on board with this and what I think I am learning is that no tune is required until the fuel system or the MAF's capacity is exceded as the system will compensate for the mods. That being the case what are the limits of the stock fuel system and MAF?

[lxh89]

Originally Posted by j rick kirby

I'm just getting on board with this and what I think I am learning is that no tune is required until the fuel system or the MAF's capacity is exceded as the system will compensate for the mods. That being the case what are the limits of the stock fuel system and MAF?

To be more prescriptive here, any changes made before the MAF (CAI/RAI/Bigger Air Filter) do influence the flow characteristics and measurements by the MAF.

Changes such as heads, exhaust, under drive pulleys, ported intake or bigger throttle body have no direct bearing on the function of the MAF.

In terms of determining the limit of the stock MAF, it's 46.166 lb/min or 648 CFM. At 6800 rpm and assuming 117% VE, this equates to around 488BHP or roughly 407rwhp. It's just enough headroom to do some decent NA modifications in airflow and still have the ability to compensate for density altitude changes (elevation, temperature, humidity, etc).

As for your fuel system limit, impossible to state without knowing the brake specific fuel consumption of the combination, fuel pressure, etc. In example, the BSFC of a nitrous combo will be significantly lower than a Supercharged combo. In other words, you make more usable power on nitrous than you can with a supercharger if the fuel system is the limitation.

Tony

[chijess]

whoa in plain english to people who know nada about all this and dont care will a stock mach1 need a tune with just a jlt ram air (was told no tune nessary) threw no code also catback and possibly headers need a tune? please give me an easy answer as i am not as informed as you all

[lxh89]

Originally Posted by chijess

whoa in plain english to people who know nada about all this and dont care will a stock mach1 need a tune with just a jlt ram air (was told no tune nessary) threw no code also catback and possibly headers need a tune? please give me an easy answer as i am not as informed as you all

If you want the easy answer, install whatever you want and your mileage may vary. If you have an interest in making your car faster, start reading, buy books, educate yourself. I wasnt born with this knowledge and it's not my job, only a hobby.

You install a new cold air kit and the car may run just fine. A tune isn't necessary but if your like the original poster who seems very concerned about the accuracy of his MAF, then you should get it re-tuned or send your whole intake setup to Pro-M to be flow tested then get it tuned. There's always a possibility the car may run slightly richer or leaner from factory calibration; however, the factory tends to make enrichment conservative so it shouldn't swing things so much that it places the engine in significant risk. However, I won't tell you that's the case always or I'd be lying.

[j rick kirby]

Originally Posted by lxh89

To be more prescriptive here, any changes made before the MAF (CAI/RAI/Bigger Air Filter) do influence the flow characteristics and measurements by the MAF.

Changes such as heads, exhaust, under drive pulleys, ported intake or bigger throttle body have no direct bearing on the function of the MAF.

In terms of determining the limit of the stock MAF, it's 46.166 lb/min or 648 CFM. At 6800 rpm and assuming 117% VE, this equates to around 488BHP or roughly 407rwhp. It's just enough headroom to do some decent NA modifications in airflow and still have the ability to compensate for density altitude changes (elevation, temperature, humidity, etc).

As for your fuel system limit, impossible to state without knowing the brake specific fuel consumption of the combination, fuel pressure, etc. In example, the BSFC of a nitrous combo will be significantly lower than a Supercharged combo. In other words, you make more usable power on nitrous than you can with a supercharger if the fuel system is the limitation.

Tony

Good to know. I'm planning on a freshining of my motor soon and will leave stock with the exception of a little head work so it sounds like all I need to do is screw it all back together and have fun. No tune required.

[chijess]

thanx, bought the new jlt directly from jlt and they told me no tune but would gain more hp with tune? same with catback?

[Nekasrof]

Originally Posted by lxh89

To be more prescriptive here, any changes made before the MAF (CAI/RAI/Bigger Air Filter) do influence the flow characteristics and measurements by the MAF.

Changes such as heads, exhaust, under drive pulleys, ported intake or bigger throttle body have no direct bearing on the function of the MAF.

Correct. However, bends or tubing size changes within 6" of the meter, on either side, will also affect airflow and more than likely require a recalibration due to turbulance. In an FI condition, this will become extremely important. See the 2 transfer functions I posted on the first page. They are from the exact same meter but you can see the differences between the 2 calibrations. Turbulance from that set up necessitated a recalibration.

Originally Posted by lxh89

In terms of determining the limit of the stock MAF, it's 46.166 lb/min or 648 CFM. At 6800 rpm and assuming 117% VE, this equates to around 488BHP or roughly 407rwhp. It's just enough headroom to do some decent NA modifications in airflow and still have the ability to compensate for density altitude changes (elevation, temperature, humidity, etc).

Not quite. When calculating hp from the stock transfer function(1256.4461kg/hr), you simply divide by 2, divide by 1.5, multiply by .85 and that'll give you rwhp(stick trans) @ 5v. Running at 5v is dangerous as it gives you no room for error on a really good altitude density day. That's the reason for the calculation in post 19 which will give you room, just in case.
The factory Mach 1 meter(no change to transfer function) will support 355rwhp @ 5v before the meter needs to be recalibrated.
In the hp calculation from the meter, fuel does not play a part at all. The only thing you need to know is what the 5v calibration is and you'll want to stay at least 10% under that for your hp target provided you aren't interested in any additional mods. If you're going to change to FI or nitrous and your target is say, 500rwhp. You simply get a meter flowed for 800hp and call it a day. Always go larger on the calibration as we all know xxxhp is never enough!

Originally Posted by lxh89

As for your fuel system limit, impossible to state without knowing the brake specific fuel consumption of the combination, fuel pressure, etc. In example, the BSFC of a nitrous combo will be significantly lower than a Supercharged combo. In other words, you make more usable power on nitrous than you can with a supercharger if the fuel system is the limitation.

Tony

Yep. Trek on over to pages 202 - 204 in the Ford Racing catalog.

Originally Posted by chijess

whoa in plain english to people who know nada about all this and dont care will a stock mach1 need a tune with just a jlt ram air (was told no tune nessary) threw no code also catback and possibly headers need a tune? please give me an easy answer as i am not as informed as you all

If I am not mistaken, you can use the factory meter with that JLT, right? If so, leave the screen in. The screen is designed to cut down on turbulance. If you must remove the screen, recalibration may be necessary - if you want it 100% right.

Originally Posted by j rick kirby

Good to know. I'm planning on a freshining of my motor soon and will leave stock with the exception of a little head work so it sounds like all I need to do is screw it all back together and have fun. No tune required.

Yep, no tune required.

Originally Posted by chijess

thanx, bought the new jlt directly from jlt and they told me no tune but would gain more hp with tune? same with catback?

Do a before/after dyno pull to see what/if you gain in hp on the JLT. Get the data log for the before and after pulls for comparison.

[lxh89]

Originally Posted by Nekasrof

Not quite. When calculating hp from the stock transfer function(1256.4461kg/hr), you simply divide by 2, divide by 1.5, multiply by .85 and that'll give you rwhp(stick trans) @ 5v. Running at 5v is dangerous as it gives you no room for error on a really good altitude density day. That's the reason for the calculation in post 19 which will give you room, just in case.

If I understand your math, you used STD (aka STP or Standard Temperature & Pressure) conditions to convert kg/hr into cfm. Technically it's 2.0447 but you rounded down. I used SAE conditions to convert which equates to 1.94046 kg/hr equal to 1 CFM. Your MAF is calibrated based on SAE conditions, not STD.

Therefore, 1256.4461kg/hr (your number) / 1.94046 = 647.4990981519846 (~648 CFM)

The division by 1.5 is presumption that 1 horsepower requires 1.5 CFM. Without knowing the true VE of the engine, very difficult for that conversion to be correct. I used ~1.34 CFM = 1 HP which assumes a VE of 117% (e.g. some kind of positive pressure present).

Finally, your .85 conversion presumes a 15% drive train loss to find rwhp. In my calculation, I used 20% drive train loss.

I think the many variables required to give this a truly accurate answer aren't present so generalized assumptions have to made. We really need to understand compression ratio of the engine, brake specific fuel consumption, and brake mean effective pressure to get more accurate.

Originally Posted by Nekasrof

If you're going to change to FI or nitrous and your target is say, 500rwhp. You simply get a meter flowed for 800hp and call it a day. Always go larger on the calibration as we all know xxxhp is never enough!

Yes, agreed you want headroom but the question was what's the limit, not what's the safe limit :P

If that's true about Nitrous and my stock meter is limited to 355rwhp or even 407rwhp by my calculation, can you explain how my car made 465rwhp on nitrous with the factory MAF? I know the answer to this already, but I'm curious if you do.

Tony

[Nekasrof]

Originally Posted by lxh89

If I understand your math, you used STD (aka STP or Standard Temperature & Pressure) conditions to convert kg/hr into cfm. Technically it's 2.0447 but you rounded down. I used SAE conditions to convert which equates to 1.94046 kg/hr equal to 1 CFM. Your MAF is calibrated based on SAE conditions, not STD.

Therefore, 1256.4461kg/hr (your number) / 1.94046 = 647.4990981519846 (~648 CFM)

The division by 1.5 is presumption that 1 horsepower requires 1.5 CFM. Without knowing the true VE of the engine, very difficult for that conversion to be correct. I used ~1.34 CFM = 1 HP which assumes a VE of 117% (e.g. some kind of positive pressure present).

Finally, your .85 conversion presumes a 15% drive train loss to find rwhp. In my calculation, I used 20% drive train loss.

I think the many variables required to give this a truly accurate answer aren't present so generalized assumptions have to made. We really need to understand compression ratio of the engine, brake specific fuel consumption, and brake mean effective pressure to get more accurate.

Again, we are talking about the mass air meter here. Nothing after the meter matters to the transfer function(except bends within 6”) for proper operation. It won’t matter what the CR is, what cam you put in, what blower type you install, what size injector, what headers you put on, porting or polishing, etc. As long as you have designed the tubing to minimize turbulence(which you’ll see right away), then the input of the proper transfer function will yield the correct basis for your tune. We have discussed the importance of this meter and the reasons for exact calibration. When the meter is calibrated correctly, your tunes will be easier to build and you won’t have to work thru hiccups within the tune, in essence, bandaiding. Issues that arrise will be hardware issues and very apparent. If you‘ve chosen your meter/fuel correctly, no changes to your tune will be necessary, minus a possible change in dashpots for an overlapping cam, for mods. (I have excluded shutting off rear O2s for o/r x or h pipes as this is an ‘understood’ action)

The best example I can give as to why you must have the proper transfer function/meter curve and NOT fool with it is this: Suppose you put a light fixture in your kitchen. In the fixture, you put a 25watt bulb. You turn it on and realize it isn’t bright enough. Would you simply go out to the meter and jack up the voltage coming into the house? (We’re not getting into the specifics of electric meters here or the feed from the pole). If you jacked up the voltage into the house from 120v to say, 14ov or 160v, the lightbulb would certainly be brighter. But how would that affect the rest of the lights, appliances, tvs and all other items plugged into the outlets? You would have to reduce the voltage to every item using the ‘120v’ outlets. That is what you are doing when you move the meter curve/transfer function. That transfer function is the basis for all calculations in the tune. Not the other way around.

Originally Posted by lxh89

Yes, agreed you want headroom but the question was what's the limit, not what's the safe limit :P

If that's true about Nitrous and my stock meter is limited to 355rwhp or even 407rwhp by my calculation, can you explain how my car made 465rwhp on nitrous with the factory MAF? I know the answer to this already, but I'm curious if you do.

Tony

I will wait for someone to run above the 355rwhp limit with the factory transfer function calibration WITHOUT nitrous. But we’ll agree to disagree here.

I am not a nitrous guy. But you use a wet system. The reason you can crest the mass air 5v limit is that it has its own fuel injector working in conjunction with the Nos injector, directly into the manifold. From there, you set the proper mixture for a target AFR. It won’t be dependent on the mass air meter after the 5v limit, as the fuel/nos mixture must be regulated properly to hit your specific afr(11 in an na application, if I am correct). I know this is a generalization of what goes on, but it's close....See my 1st sentence in this paragraph.

As a student of mass air, I started this thread because the mass air meter is THE most misunderstood meter on the car. This misunderstanding is evident in tuners who have just started as well as tuners who have been in the business for 20years. CAN you tune by moving the meter curve? Absolutely. It’s done every single day. But I guarantee that once you tune by NOT moving the curve, with a properly flowed meter, you’ll never go back to that way again. No tweaking necessary for mods except in a few conditions that most won’t see. When the meter curve is correct, you don't get all those issues we've seen documented from a tune...unless you have a hardware failure.

There ARE tuners around who tune without moving that meter curve. You just have to find them and depending upon your application, it may mean sending out the meter and the tubing to be flowed.

[lxh89]

Originally Posted by Nekasrof

Again, we are talking about the mass air meter here. Nothing after the meter matters to the transfer function(except bends within 6”) for proper operation. It won’t matter what the CR is, what cam you put in, what blower type you install, what size injector, what headers you put on, porting or polishing, etc. As long as you have designed the tubing to minimize turbulence(which you’ll see right away), then the input of the proper transfer function will yield the correct basis for your tune. We have discussed the importance of this meter and the reasons for exact calibration. When the meter is calibrated correctly, your tunes will be easier to build and you won’t have to work thru hiccups within the tune, in essence, bandaiding. Issues that arrise will be hardware issues and very apparent. If you‘ve chosen your meter/fuel correctly, no changes to your tune will be necessary, minus a possible change in dashpots for an overlapping cam, for mods. (I have excluded shutting off rear O2s for o/r x or h pipes as this is an ‘understood’ action)

When you want to understand the horsepower limits of the mass air meter for sizing purposes, you most certainly do need to understand what's going on after the meter. An efficient engine will produce more horsepower per kg/hr of air than a less efficient one. Now it's clear that both our answers are neither right or wrong, they are approximations based on a set of assumptions.

Originally Posted by Nekasrof

I will wait for someone to run above the 355rwhp limit with the factory transfer function calibration WITHOUT nitrous. But we’ll agree to disagree here.

I am not a nitrous guy. But you use a wet system. The reason you can crest the mass air 5v limit is that it has its own fuel injector working in conjunction with the Nos injector, directly into the manifold. From there, you set the proper mixture for a target AFR. It won’t be dependent on the mass air meter after the 5v limit, as the fuel/nos mixture must be regulated properly to hit your specific afr(11 in an na application, if I am correct). I know this is a generalization of what goes on, but it's close....See my 1st sentence in this paragraph.

I had a dry nitrous system. Fuel isn't really a factor in solving the MAF riddle given this scenario. The reason why I produced 465rwhp on a MAF that could never measure that much air is because the MAF never measures the nitrous. You spray it post-MAF (although the GM folks like to spray pre-MAF, but that's another discussion entirely). The key to this is, the nitrous brings its own oxygen into the equation (~36% Oxygen by mass). I just need to have enough injector and/or fuel pressure to deliver the necessary fuel for that extra oxygen to burn and make power. Same priniciple with a wet nitrous system...the nitrous is delivered post-MAF along with fuel into the intake.

Originally Posted by Nekasrof

But I guarantee that once you tune by NOT moving the curve, with a properly flowed meter, you’ll never go back to that way again. No tweaking necessary for mods except in a few conditions that most won’t see. When the meter curve is correct, you don't get all those issues we've seen documented from a tune...unless you have a hardware failure.

If I had a 30-point flow curve in hand for the MAF on my car, I'd use it in a heart beat rather than **** around logging A/F ratios and comparing against commanded fuel to set my MAF. As I said before, it comes down to practicality and preference.

Tony

[Nekasrof]

It’s assumed in this conversation and I’ve stated again and again that proper meter selection(tubing size)/calibration is necessary. Once that is done, nothing after the meter matters UNTIL you’ve hit the 5v limit. Then, you either get that meter recalibrated(if it’ll efficiently flow to support the higher hp target) or, you purchase a larger meter with the proper calibration.

As far as efficient or non-efficient is concerned. The kg/hr measurement will be right on target every single time you data log. It won’t matter what AFR you are seeing(lean or rich), you can calculate the hp right off the data log. If the dyno is reading 510rwhp(we wont even get into dyno set up between dynojet and mustang dyno), you’ll be very very close to 1800kg/hr. Of course, on the Mach 1 pcm, you’ll be seeing 900kg/hr as you’ve halved the transfer function to input the values correctly in the tune.

What’s amazing is that some will spend an enormous amount of time fooling with that transfer function, back to fuel, dashpots, trasnfer function, fuel, etc, rather than just sending the meter out to be flowed to support the hp level they wish to achieve. The original transfer function I posted was simply a 3.5” ProTube flowed to 5v. It’ll support 1100+hp due to the calibration. The car will NEVER need another meter, unless that one gets damaged because neither the fuel system nor motor are capable to support that hp limit. And no reason to touch the transfer function for any reason other than the initial halving to put it into the tune. Of course, there were other parameters that needed to be adjusted to match the meter halving. But you should know what they are. That halving applies to Ford pcms ’04 and prior, including the Ford GT. This is the transfer function as it appeared in the tune, prior to the turbulence:

You can see where SCT is incorrectly telling you to move the transfer function to attain AFR. Here's the screenshot right off the transfer function parameter. And that last line is where ya get into trouble.

I am NOT saying don't use SCT software. NOTHING wrong with the software at all. Just disregard that last line in the above instruction screenshot. Turbulence will be seen and will be evident. Reflow the meter and tubing to correct it. Then, you continue with your tune. Better yet, in a custom install, simply get the meter/tubing flowed right from the begining and downtime will be minimal.

One huge issue is the CAI producing companies tell you that you bolt on thier CAI and gain hp. However, you pull the meter itself out of the factory maf and bolt it into their tubing, thier tubing is usually larger than the factory Mach 1 maf tubing. That results in MORE air flowing thru the tube and the meter can't pick it up. What do you see on your AFR gauge? LEAN. Why? Because the factory transfer function is telling the pcm you are flowing x air. When in fact you are flowing more air than x. The fuel calculation from the factory transfer function is telling the pcm it needs to inject x amount of fuel to match x airflow. That fuel injected isn't enough to match the ACTUAL airflow into the engine and you get a lean condition. I know it sounds crazy because nobody does it...but the proper way to address this is to have the CAI tubing sent out and reflowed. That transfer function gets put into the tune and you MIGHT have to do some tweaking on the fuel side. Done.
Why don't you simply add fuel instead of sending out the tubing to be reflowed? Because you won't know exactly how much air is flowing past the meter without the proper calibration. Again, ALL calculations are done from that meter being properly calibrated/flowed. And as more air flows past the meter without being properly read, load is calculated lower and spark is calculated higher. That combination also results in detonation. Then you get burnt pistons or worse.

[lxh89]

Originally Posted by Nekasrof

As far as efficient or non-efficient is concerned. The kg/hr measurement will be right on target every single time you data log. It won’t matter what AFR you are seeing(lean or rich), you can calculate the hp right off the data log. If the dyno is reading 510rwhp(we wont even get into dyno set up between dynojet and mustang dyno), you’ll be very very close to 1800kg/hr. Of course, on the Mach 1 pcm, you’ll be seeing 900kg/hr as you’ve halved the transfer function to input the values correctly in the tune.

A supercharged engine making 510rwhp will require significantly more airflow than a naturally aspirated engine making 510rwhp. According to you (based on your statement above), I could take a MAF from a naturally aspirated motor making 510rwhp and put it onto a supercharged engine also making 510rwhp and I should still see 1800kg/hr. In reality, that supercharged combo is likely producing up to 100BHP more than the naturally aspirated ; however, the parasitic losses from the supercharger result in less power to the wheels.

Originally Posted by Nekasrof

What’s amazing is that some will spend an enormous amount of time fooling with that transfer function, back to fuel, dashpots, trasnfer function, fuel, etc, rather than just sending the meter out to be flowed to support the hp level they wish to achieve. The original transfer function I posted was simply a 3.5” ProTube flowed to 5v. It’ll support 1100+hp due to the calibration. The car will NEVER need another meter, unless that one gets damaged because neither the fuel system nor motor are capable to support that hp limit.

Too much headroom on a MAF can be just as bad as not enough. What I mean by that is, you lose resolution on measurement between points. You only have 30 points to define so if the KG/Hr measurements between points are too wide, your car's computer is left to fill in the blanks. By your own statements earlier, the MAF curve is not linear. With poor resolution, you get drivability issues at part-throttle or certain loads.

Originally Posted by Nekasrof

Better yet, in a custom install, simply get the meter/tubing flowed right from the begining and downtime will be minimal.

This discussion is getting circular now as we're rehashing what's already been stated.

Tony