Scaling MAF for Intake

[footlong70]

Hey guys, I know this is nothing ground breaking or new but I think it's some good food for thought for guys playing with their own tuning, or something to inquire about when getting custom tunes written.

I just finished my next portion of mods. Turbos, manifolds/pipes, valvetrain, intake mani, No Limit intake and hotside pipe, and a bunch of other things... Same HS 300 File. Anyways, prior to the No Limit intake I ran an S&B for 3 years. First test drive after the full install was very pleasing for the most part however I noticed some slight flatter power lower to mid rpm. Definitely slower spool, needed more throttle to get the same seat of the pants feel. Just a slight less seat of the pants feel rolling into the throttle until about 40-50%. Even a bit less smoke down low spooling which should be the opposite with slower spooling larger turbos. Don't get me wrong, the truck felt like a monster, but so much of it was up top. My truck spends a lot of time down low with 38's and 3.55's so it's pretty important to me. I know its not very scientific but I know my truck VERY well. I pressure tested the hell out of everything (even the intake on the heads) so I know leaks were not an issue. With so many changes and larger turbos though its kind of a long shot to pin point the change low-mid range rpm. Most would guess bigger wheels, more lag, that's life... However I did get thinking about the No limit intake and the diameter size change. I've dealt with MAF adjustments on gas motors plenty which are a must with piping changes. So I thought for sure the canned tuning needs scaling. I took some measurements:

Stock intake diameter at MAF: 4.125" = 13.36"squared area
No Limit Intake Diameter at MAF 5" = 19.63"squared area
19.63 - 13.36 = 6.27 difference / 13.36 = 0.4693 x 100 = 46.93% increased area at the MAF.

So there is clearly alot of air the MAF/PCM are not seeing. Therefore were running lean initially. The MAF tables do max out up top so it doesn't matter after so much air is flowing however down low-mid flow is going to run lean, slowing spool/less power potential low-mid spool.

Using MCC I took the MAF rate map and multiplied the entire map by 1.4693 to get my 46.93% increase. Loaded her up, took her for a spin, and mission accomplished. The sensitive, powerful throttle feel down low is back and drives just like prior to the mods, just much stronger. Rolling into the throttle really throws you back low-mid spool. Lag feels identical to stock, so very quick to light. No real increase in smoke, truck runs ridiculously clean. Also Mileage wise, I did a 200km trip prior to Map increase, and the same 200km trip the next day after the adjustment and the mileage according to the Lie o meter was the exact same, even within a couple tenths better(It's not a perfect method to determine mileage I know but it will give a guy a decent basis for increase or decrease). So I'm very impressed with the adjustment and pleased I didn't pay a couple hundred bucks for custom tuning that took 5 min. I'm sure gearhead or any of the other renowned custom tuners know this and it's old news but for those that like to mess around with their own tuning. Also since so many are running No Limit intakes I would think this should be common knowledge for everyone. Hope this helps some people.

 

[tbsimmons]

Scaling the MAF is a normal thing to do in gas tuning. I was sure tuners would do it in the diesel world I guess not when I spoke to one of them about if the tunes changed with bigger than stock compounds and was told no.

 

[ncollins64]

Good info

 

[ckrueg]

Interesting. I wouldn't think it would have much of an effect, as the fueling is independent of air on a diesel as long as it's below the low boost fueling table. At least I haven't seen any tables where the fuel depends on air mass.

 

[drunk on diesel]

If you look at your MAF activation map, you'll see that they aren't even looking at it at high load. It's monitored right in the area you're looking for gains

 

[Nick284]

soooo, i should do this? ha...I read it twice, second time made alot more sense to me. i believe this theory is true, makes sense. im no tuner or anything, but im going to do the same if the writer of my single tune doesnt mind doing it for me.

 

[footlong70]

Scaling the MAF is a normal thing to do in gas tuning. I was sure tuners would do it in the diesel world I guess not when I spoke to one of them about if the tunes changed with bigger than stock compounds and was told no.

Yeah for sure. The H&S 300 tune does not touch the MAF map from stock. I wouldn't think any of the canned tuners would touch the map unless it was suggested. The MAP would not have to be changed for different sized turbos. The only factor affecting the MAF map would be the change of area based on the I.D. at the MAF sensor itself.

Interesting. I wouldn't think it would have much of an effect, as the fueling is independent of air on a diesel as long as it's below the low boost fueling table. At least I haven't seen any tables where the fuel depends on air mass.

I do agree however I believe there is a map we don't see on mcc or equation the pcm uses that would probably limit fuel to a point based on current airflow. A map hardcoded meant for stock tuning to help emissions numbers and reduce soot. Really when you think about it, there is no way the fuel injection event would be based solely on a throttle position and boost. That would really take away efficiency potential and mileage. The PCM could use sensors such as barometric, intake temp, boost, pyro, and back pressure to estimate the amount of air coming in to make an efficient burn but nothing will be as exact and quick as an actual air flow sensor. FWIW I leave my low boost fueling at 5 which is "no limit".

soooo, i should do this? ha...I read it twice, second time made alot more sense to me. i believe this theory is true, makes sense. im no tuner or anything, but im going to do the same if the writer of my single tune doesnt mind doing it for me.

Do it, I can't see why they wouldn't recommend it anyways. Maybe you can get 2 tunes with the map untouched and modified for the time it takes. Then you can see for yourself first hand if I'm full of it.

 

[Nick284]

hes going to send me a tune with the new maf eqaution. i just matched yours, even though my intake is slightly bigger. but it should be the same scenario and work like you say. im pumped to try it!! des make sense about running lean etc...

 

[drunk on diesel]

I messed with this back when Kind was first posting about it and asked H&S to give access to the map.

On a stock turbo truck, I just noticed what seemed like more bottom end fuel. If felt like it could be replicated with more bottom end fuel, but I never adjusted it back down to see if it was more responsive at a given soot output

 

[Dzchey21]

i had to just do the same thing on my 6.7

6.4s dont seem to be as sensitive to MAF changes as 6.7s but i am glad you figured that out.

 

[tbsimmons]

Yeah for sure. The H&S 300 tune does not touch the MAF map from stock. I wouldn't think any of the canned tuners would touch the map unless it was suggested. The MAP would not have to be changed for different sized turbos. The only factor affecting the MAF map would be the change of area based on the I.D. at the MAF sensor itself.

I disagree from tuning, every MAF and intake even stock is different. You tune to MAF then power enrichment.

I do agree however I believe there is a map we don't see on mcc or equation the pcm uses that would probably limit fuel to a point based on current airflow. A map hardcoded meant for stock tuning to help emissions numbers and reduce soot. Really when you think about it, there is no way the fuel injection event would be based solely on a throttle position and boost. That would really take away efficiency potential and mileage. The PCM could use sensors such as barometric, intake temp, boost, pyro, and back pressure to estimate the amount of air coming in to make an efficient burn but nothing will be as exact and quick as an actual air flow sensor. FWIW I leave my low boost fueling at 5 which is "no limit".

From gas engines, even for boosted engines, you tune off a few sensors, one being the MAP for boosted, more so if you switch to a 2-bar sensor. But even for NA that MAP tells you a lot, not as much as the MAF for fueling, but a lot in NA.

 

[drunk on diesel]

i had to just do the same thing on my 6.7

6.4s dont seem to be as sensitive to MAF changes as 6.7s but i am glad you figured that out.

ahh, good to know!

 

[footlong70]

I disagree from tuning, every MAF and intake even stock is different. You tune to MAF then power enrichment.

I also agree every intake is different and a true scaling needs to be done on a bench. However after inspecting the stock/no limit intake at the maf, there are no bends at the maf, both are round/straight(several inches in front and behind), maf sensor depth into the intake is the same, same maf sensor, and both filters would send air in very evenly. The only significant change would be diameter at the sensor. So simple logic is, pulling the same volume of air through 2 different size straight pipes will change the speed the air flows through. Larger I.D. would be slower than smaller. Therefore the same volume of air flowing through (regardless of plumbing/turbos after the MAF) would move slower through the No limit intake making the Maf think less air is moving through even though its the same. It's not going to be a prefect scaling but I'm will to bet it's damn close, and better than leaving it untouched. Sorry if I'm telling you what you already know and I'm not trying to sound like a know it all ass but I'm just not totally sure what all your disagreeing with.

From gas engines, even for boosted engines, you tune off a few sensors, one being the MAP for boosted, more so if you switch to a 2-bar sensor. But even for NA that MAP tells you a lot, not as much as the MAF for fueling, but a lot in NA.

Yes sir I agree. NA motors rely heavily on MAF input for fueling and timing, been there done that. At least ford motors do. Boosted diesels not as much but still utilized during basic dd driving for more efficient burn. Like I said originally though, I noticed a significant difference so something is working in my favor after just changing that MAF map.

 

[footlong70]

i had to just do the same thing on my 6.7

6.4s dont seem to be as sensitive to MAF changes as 6.7s but i am glad you figured that out.

Cool! Did you notice a significant difference in response or even power? I would have to agree that the 6.4 is not as MAF sensitive from what I've seen but still utilized low-mid flow rates.

 

[tbsimmons]

Sorry if I'm telling you what you already know and I'm not trying to sound like a know it all ass but I'm just not totally sure what all your disagreeing with.



Yes sir I agree. NA motors rely heavily on MAF input for fueling and timing, been there done that. At least ford motors do. Boosted diesels not as much but still utilized during basic dd driving for more efficient burn. Like I said originally though, I noticed a significant difference so something is working in my favor after just changing that MAF map.

The only factor affecting the MAF map would be the change of area based on the I.D. at the MAF sensor itself.

I have not tuned a diesel. But every MAF vehicle I have I have tuned without a MAF first and then with one then to power. I am sure the diesel uses the MAF somehow for fueling or to talk with the MAP, other sensors.
Easy way to test this theory, put a 0 in all the MAF scales and see what occurs.
What you are seeing is what I was talking about scaling a MAF. Every MAF is different meaning each one will give a different Hz number the computer reads for a given gram per second of air. Now I have never seen just an intake change the tuning, the sensors usually adjust enough for that, unless the intake is sp poorly done in the first place. What I see when the MAF really needs adjusting, change in power, more air, like your turbo. More or less air at low throttle angles. For taht given throttle angle the PCM is used to seeing this amount of air, well that changed. In my opinion is why you felt a difference not because of the intake. I bet if you put the stock intake back on at low throttle angles the truck would feel the same as it does now.

 

[footlong70]

I'll have to agree to disagree. I'm not sure we're on the same page here but the MAF is JUST measuring air passing the sensor as you said. Turbos and plumbing changes after the sensor does not need maf scaling. The sensor is just going to see more or less air passing it based on what you changed behind it like you should. So for example installing some new massive compounds that is going to pull tons more air than stock is going to do just that. Pull more air in which the sensor will see as its suppose to. It's see more air passing so the pcm takes it from there.

The part that gets skewed is a change in area in the plumbing at the maf itself. If the motor for example pulls in 100cfm in x amount of time of air in two senarios. One with the maf in a pipe at 4" and one in a pipe 5". Which scenario will have faster moving air even though the same total volume is being moved in the same amount of time. The 4" obviously. So when you have a maf/pcm scaled to read in a 4" pipe, then change just the piping size to 5" without adjusting the maf map, the sensor is going to see a velocity drop with the same 100 cfm. Translating into a lower gram/hour as far as the pcm is concerned even though it's not true. The engine is still using the exact same volume of air but the maf/pcm is not seeing all of it.

Just to clarify. I did not mean the larger intake changes the maf map or any of the tuning. It just not reading the correct values anymore.

I've tuned NA motors that would not or barely run just from a 2.75" pipe to a 4" at the maf. Even a motor that would barely stay running with a 30 degree angled cone filter that was pointed up instead of down, just because the filter threw air away from the maf thermocouples. It's definitely a useful sensor that should always be kept tuned for size of pipe it sits in.


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[Kind]

Scaling the maf for my triples was all the difference in the world! I added a very non scientific guess of multiplying mine by 120% for the two larger then stock intake tubes. It made the truck responsive again and quick spooling. For awhile I was wondering what the dig deal of triples was cuz mine were leggy as all sh!t... And they aren't even big. But once I rescaled the maf it was everything I thought it would be.

Reading this tho I should probably multiply it more. My 2 5" intakes are probably closer to 190% more volume if a single 5" is 46% larger.

 

[footlong70]

Scaling the maf for my triples was all the difference in the world! I added a very non scientific guess of multiplying mine by 120% for the two larger then stock intake tubes. It made the truck responsive again and quick spooling. For awhile I was wondering what the dig deal of triples was cuz mine were leggy as all sh!t... And they aren't even big. But once I rescaled the maf it was everything I thought it would be.

Reading this tho I should probably multiply it more. My 2 5" intakes are probably closer to 190% more volume if a single 5" is 46% larger.

That's awesome. I did go threw some of your old threads regarding the triples and scaling as well. Good info. Very cool build too btw. And yes I would agree if your using two 5" pipes that are pulling air equally then it would be a 193.7% increase needed using the stock maf in straight plumbing. But of course yours is a pretty extreme example so a live maf tuning would be much more accurate. I wouldn't think you'd have much of a map left after an increase like that since values max out lol!


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[drunk on diesel]

there are certainly calculations going on behind the scenes

it may be effecting much more than just "bottom end fueling". there may be transitional timing tables that we're unable to view, etc.

I was careful to caveat my statement with the fact that I'm on stock turbos

 

[tbsimmons]

I'll have to agree to disagree. I'm not sure we're on the same page here but the MAF is JUST measuring air passing the sensor as you said. Turbos and plumbing changes after the sensor does not need maf scaling. The sensor is just going to see more or less air passing it based on what you changed behind it like you should. So for example installing some new massive compounds that is going to pull tons more air than stock is going to do just that. Pull more air in which the sensor will see as its suppose to. It's see more air passing so the pcm takes it from there.

I will have to disagree with that statement and not a agree to disagree. It has to do with how much air the engine is digesting. Put the stock intake on. If your theory is correct and mine is wrong the truck should run totally different, as in worse at low throttle angles. In my opinion you are just getting the MAF scaled to the air flow at low throttle angles, nothing with the volume of the intake. You would have a bunch of extra fuel down low because you have told the PCM that now when the MAF is reading this frequency expect this much air. Another way is to put a tune in your truck that has more fueling down low and put the MAF tables back to stock. The truck will have more power down low because of the low throttle angle fueling. I didn’t notice one bit of difference in power in my truck from the a drop in AFE to a No Limit Intake with the stock chargers.
MAF has more than just measuring air, temp also.
If say at 5% throttle the tables are used to supply X amount of fuel.
Now at 5% you are getting more air into the engine and the same X amount of fuel is supplied the vehicle will run different, be it gas or diesel.
Now with bigger turbos you tell the MAF that at this 5% of throttle angle you need Y amount of fuel the truck will run different than with X amount of fuel. Which is what the MAF tables do, add or subtract fuel based on air.

The only way to get more air into the engine is build a motor or bigger chargers. An intake is not going to change the intake air requirement of the engine. It might not supply the required amount but the intake is not what determines air flow.

The part that gets skewed is a change in area in the plumbing at the maf itself. If the motor for example pulls in 100cfm in x amount of time of air in two senarios. One with the maf in a pipe at 4" and one in a pipe 5". Which scenario will have faster moving air even though the same total volume is being moved in the same amount of time. The 4" obviously. So when you have a maf/pcm scaled to read in a 4" pipe, then change just the piping size to 5" without adjusting the maf map, the sensor is going to see a velocity drop with the same 100 cfm. Translating into a lower gram/hour as far as the pcm is concerned even though it's not true. The engine is still using the exact same volume of air but the maf/pcm is not seeing all of it.

The only way the MAF would need to be scaled for the same amount of airflow would be if (2) intakes Y together and are of equal size and the MAF is only on one of the legs of the Y. If not the engine is taking in the same amount of air then the MAF would not have to be scaled. Look at the size of the inlet of the Turbo, that is staying the same. What you are saying above is partially correct but has to do off grams per second and the frequency the MAF sends to the PCM for fuel. The only way that can change is with a bigger turbo sucking more air at a given throttle angle. The above yes a 4” will have more velocity than a 5” but the air requirement of the engine is still the same.

Just to clarify. I did not mean the larger intake changes the maf map or any of the tuning. It just not reading the correct values anymore.

I am taking that you need to scale the MAF for an intake, I thought that was the point of the dicussion.

I've tuned NA motors that would not or barely run just from a 2.75" pipe to a 4" at the maf. Even a motor that would barely stay running with a 30 degree angled cone filter that was pointed up instead of down, just because the filter threw air away from the maf thermocouples. It's definitely a useful sensor that should always be kept tuned for size of pipe it sits in.


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Many reasons could have been used for the 2.75-4”. One is the injectors were way to big and the injector constant was not adjusted. With the vehicle idling it was thinking it was seeing a load and dumping fuel. The other was that the MAF tables were so far out for the given load that it was either pulling a bunch of fuel or dumping it. MAF is usedis for fueling (Along with MAP, injector size, etc.) before the vehicle sees a load bigger than whats programmed to switch into the fueling for power. Closed Loop to Power Enrichment or Open Loop for a gas engine for example.