Maf Info

[final5-0]

I've been asked about mafs, inj's, and how a Tweecer makes any maf work with any inj.

Rather than answer in a pm, I wanted to make the reply available to all since we've had a new crop of noobs lately.

While I've given basic info about this subject before, and I've got what I believe is helpful info on my site, the article is a done in a lot of tech speak. I wanna lay it out one more time cause I think I've found a more simple way to present the relationship between all three ... but ... I guess you guys will have to be the judge of that.

I can't promise this will be short
but
I'm really gonna try and keep it ... SIMPLE ... sooooo ... here we go!

I'll answer the easiest Q first.

NO!!! The Tweecer can't make any maf work with any combo.

We all know the GT & Cobra use the exact same maf.

This maf was designed by Ford to report airflow a GT or Cobra can generate with a bit more breathing room up top as well. It just so happens ..........
for THAT amount of airflow ............
you need 19's or 24's.

Notice the maf was designed for airflow and NOT for inj size.

This is where we need to drive home the idea of ... mafs report airflow
and
That airflow is then converted to a voltage which is sent to the pcm

Say you bolt on a blower and you peg that oem maf.

That happened because at say 4500 rpm, you exceeded not only the amount of airflow a GT or Cobra could generate ... you as well exceeded the maximum amount of airflow Ford designed that maf to deal with.

For all practical purposes ... you generated airflow at 4500 rpm that was converted to a maf voltage of 5.0 volts. The pcm can only accept a maximum maf voltage of 5.0 volts.

The Tweecer can do nothing to make the oem maf work in this situation.

You now have to go to another maf that has the ability to
accurately report more airflow.

How about using a different oem maf?

How about using one from a Lightning?

Same kind of deal as above in the fact that Ford designed it to handle the airflow a 351 cubic inch blown motor can generate. Once more, just as in our example above, they did not design that maf to be used for 42 lb inj's. The deal is this ... if you've got a motor that can produce that amount of airflow, you are gonna need that size of inj's to adequately supply its fuel needs.

Here is where we bring in the Tweecer to help us make it all come together.

How we do this is we use data supplied from Ford about the Lightning maf that tells the relationship of airflow to voltage. This data can be called the meter's transfer curve you've seen so much talk about before.

We've now got a maf that won't peg or report 5.0 volts.

You could look at it as ... things are now similar to the original oem setup in the fact that we've got maximum airflow at say 75% of the capabilities of the maf.

Now ... The most important thing to see here is this .........

We've now got all this going on with the additional blowers airflow
and
We are ACCURATELY reporting airflow ........
Just as we did with the little oem meter and oem GT or Cobra motor.

We also will need to use the Tweecer to accurately report to the pcm about our new inj's size such as 36, 42, 55lb, etc.

So now we got the pcm understanding TRUE airflow in a voltage range of 0 to 5.0
and
It also understands that amount airflow will be used with 42's NOT 19's.

Well ... Thats about it!
and
I hope the info was laid out in a fashion that was relatable

At this time ... We'll not go into after market mafs and the method after market maf manufactures employ at an attempt to allow their customers to use their meters without a tune.

If anyone wants go go into that, we can always do it but ... I felt this was plenty to get across for now.

Also ... I used a Tweecer to manipulate the pcm values in this little example cause the Q came from a Tweecer user but other methods such as different self tuning interfaces or chips do basically similar things with airflow and inj values.

Grady

 

[Dan95-5.0]

good post here.

quick question. if i get a lightning maf, install it on my current combo, enter in the maf transfer but keep the stock injectors. this will work correct? because ford MAF's only calculate airflow not injector size settings

 

[rj95svt]

As long as you input the correct transfer curve it shoud work fine. Alot of people actually post they get better driveabilty with the lightning maf because of the better accuracy. The more I think about it the more I think I might buy a tweecer rt and a lightning maf before I do any mods such as a supercharger or H/C/I. I know I will have to learn alot and there will be some bumps in the road but the results will be very rewarding.

 

[final5-0]

Note: mods pasted here for my convenience with reply

MODS: Full bolt-ons, Ported Typhoon intake, Fully Ported E7's, 2031 cam, Cobra 1.7's, 70mm Fox TB Conv., March Underdrives, Street Edge 3200 Stall, Transgo Shiftkit, B&M Hammer Shifter, 3.73's, T/A girdle, Subframe connectors, Full Mac exhaust, EGR/AIR delete, GSS340 255lph, Autometer Phantoms, TWEECER R/T, Innovate LC-1

good post here.

quick question. if i get a lightning maf, install it on my current combo, enter in the maf transfer but keep the stock injectors. this will work correct? because ford MAF's only calculate airflow not injector size settings

Well Danny

Glad to see you found the info interesting.

Your answer first ... Yes you could do that

Would that be in your best interest to do that ... Not necessarily so

Please answer the following Q's so we can have an idea of which
direction we could go with our reply that will be best for your combo.

1) Are you now using the oem meter with the above combo?

2) What are the the values you see in your dlogs under the conditions
of WOT in second gear at maximum rpm

rpm
mafv
afr

The Q's are to get an idea of how far you are pushing the meter

From looking at your combo .......
I'd say you are asking too much from those little 19's
and
That is not considering these factors which would ask for even more fuel

1) Your auto trans places more of a load on the combo
2) If you are using stock fuel pressure

I suspect you have considerable more need for fuel than a meter

Now about this here ..............

because ford MAF's only calculate airflow not injector size settings

Its not that Ford leaves out anything
or
Its not that the after market boys offer anything additional

Danny ... my friend......

You have access to the pcm
This gives you options
In order to maximize those options
You need to think differently than the masses who don't have pcm access

I'm trying to show they are forced to play the whole silly game of ........
A meter must match the size of the injector
and
You do NOT have to deal with ANY of those issues all that can cause

Look ... It is just simply that .............
A meter reports airflow
and
Has nothing to do with fuel

The pcm takes that airflow info and mixes it with other data such as .......
ect, battery voltage, act, spark, and ... yes ... inj size as well
And Then .........
It uses all those inputs to arrive at the final af ratio

The amount of airflow the combo generates dictates the size of inj needed
absolutely, positively ... N O T ... The meter

Once you can get your head around that fact ...........
Mafs ... no matter if they be Ford, ProM, C&L, etc ...........
The whole maf/injector thing ... will all make so much more sense

I gotta tell you ... It took me a good while to see how they work together

anyway ... find the answers those few Q's
and
lets get more into all this stuff.

I know this has been long but it is so very important
and
Its more important to us 94-95 folk than the Fox boys
cause
We have pcm's with a focus on load where they don't
and
Guess what determines the load ... The Meter

Sooooo ... have just a bit more focus with all this ....
and look at ... yet ... a little more info

Endure just a bit more reading so a working knowledge can be
in place about the issues with mafs, inj's, modded combos,
and using Tweecs to make the pcm & combo play nicely with
each other once more.

Here is basic info explaining about the after market maf "Cheat Method"

I would ask you to please tell me it it makes sense
or ... in other words
Can you see what those after market boys are trying to accomplish

Assumptions for this document are that you own a TwEECer or EEC-TUNER
and that you are running larger than stock injectors and/or Mass Air Flow
meter (MAF).

First lets start with a little theory. The way the ford EEC series
processors determine the amount of fuel and calculate load values is by
measuring the amount of air that is flowing into the engine via the Mass
Air Flow (MAF) sensor. The MAF sensor works by heating a wire inside the
sensor. As air flows past the wire it cools the wire. Depending on how
much the wire cools and the radius of the MAF sensor you can calculate the
physical volume of air flowing through the sensor. This measurement is
sent to the EEC processor as a voltage reading between 0 and 5 volts.

The EEC has a 30 point table pre-programmed into it that references a
voltage reading to an amount of air in kilograms per hour (KG/HR). For
simplicity lets pretend it is only a 5 point table and use simple round
numbers to make calculations easier. For example:

5 volts = 1000kg/hr
4 volts = 700kg/hr
3 volts = 500kg/hr
2 volts = 350kg/hr
1 volts = 250kg/hr

The way the EEC works is to reference the voltage signal to a row in the
table. If the voltage falls between two readings it calculates a value
using the surrounding numbers. So if the MAF was sending a signal of 3
volts you would have 500 kg/hr of air flowing into the engine. If the MAF
was sending a signal of 2.5 volts you may expect 440 kg/hr (the scale is
weighted with larger increments in the higher voltage range).

The EEC then uses this table to calculate the pulse width for each
injector to supply the proper amount of fuel to feed the measured air.
This calculation is based on the values in LOW_INJECTOR_SLOPE and
HIGH_INJECTOR_SLOPE (more on these settings later). For now assume that
both are set to 20 to represent a 20lb injector.

Now lets assume you ordered a new MAF meter from Pro-M and had it
calibrated for 40lb injectors (remember, these are all made up numbers).
You installed a fresh set of 40lb injectors and bolt on the meter. How
does the meter make the 40# injectors work with the stock programming? It
does this by reducing the voltage from the MAF meter to represent a
physical volume of air equal to the factory injector size divided by the
new injector size (in this example 20/40 or ½). NOTE: It is NOT reducing
the voltage by this percentage, this is very important to understand. The
reduction in voltage is precisely engineered to make the EEC believe it is
receiving intake air - reduced by this percentage. This means that if
1000 kg/hr of air is actually flowing through the meter it will signal the
EEC with 3 volts (from our table above). This tells the EEC that 500 kg/hr
of air is flowing into the engine and the EEC opens the injectors (that it
still thinks are 20# injectors) for long enough to feed 500 kg/hr of air.
Since the injectors are actually bigger (twice in this case) the amount of
fuel injected is actually proper for the 1000 kg/hr that is flowing
through the meter.

You can also do the math in reverse. At the same voltage reading from the
stock MAF and the new MAF your actual airflow will be new injectors
size/old injector size (in our example 40/20 or 2). So, if the voltage is
3 volts from the new MAF which corresponds to 500 kg/hr of airflow when
you look at the stock transfer table at 3 volts you would see 250 kg/hr of
airflow.

This works fine for most tuning needs but does mess with other
calculations in the EEC like load values. You also don’t have the ability
to accurately scale fuel unless your MAF table accurately represents the
meter and if you plan on data logging it is nice to have the log show you
actual airflow.

For all these reasons and more it is recommended you tell
your EEC what is actually going on by entering actual flow numbers and
actual injector sizes using the TwEECer or EEC-Tuner.

Well ... There you have it!

Long ... I know ... but ...
I felt it necessary that the article be available if anyone was gonna
get much of anything out of my offer to discuss a subject that is critical
to being accurate in order for our 94-95 Stangs to drive nicely as
possible with mods.

Not only to Danny ... but All members .............

My offer to help is not just all about ... Me

SN Friends ... these days, we have so many peeps on our site who
know their way around this subject and they've got the fruit of
successful combos to prove their expertise.

Why not take advantage of this resource at hand ... who knows .......

Some just might go to the next level of their knowledge database
when it comes to modding their Stang.

Grady

 

[HISSIN50]

Very good stuff Grady. This should help unbrainwash what the aftermarket MAF companies have done in terms of the deductive reasoning folks use about how things work. I found it confusing at first too (since I didnt have any tuning/theory background, but rather just saw how the cheat methods worked. This is where most of the confusion comes from I fear).

You are helpin some folks out. Matter of fact - if there's some kind of FAQ in the Tuning sub-forum, I think this should go there if it's useful to guys starting out with tuners (and it seems that it is).

 

[final5-0]

Very good stuff Grady. This should help unbrainwash what the aftermarket MAF companies have done in terms of the deductive reasoning folks use about how things work. I found it confusing at first too (since I didnt have any tuning/theory background, but rather just saw how the cheat methods worked. This is where most of the confusion comes from I fear).

You are helpin some folks out. Matter of fact - if there's some kind of FAQ in the Tuning sub-forum, I think this should go there if it's useful to guys starting out with tuners (and it seems that it is).

Thank you JT

You are always so kind my friend :Word:

I don't wanna admit to how much time I spent on this whole subject
but lets just say it this way

I knew it was important for me to understand
and .. even though it didn't make a lot of sense to me at the time
I just kept hosing around
On all the forums
Until I finally got it

I just thought I could help more than one person this way
and
Offer to share my part in a discussion if others wanted to get into it

I know ... You know ... This is one of those subjects where Fox applications ......
Just don't 100% apply to our 94-95 Stangs

I mean ... Yes ... Some of that Fox stuff about mafs is OK to take as valid
but
Not all of it
so
The half truths will most likely always be around
to
Muddy up the 94-95 water ... so to speak

I was like 50 50 about putting this junk in tech or tune
and
I felt more would see and benefit from it in tech

besides JT ... You know how all those tuning folk are

They're just a bunch of nerdy eggheads
and
Nobody reads that stuff they put in there anyway

Hey ... I was told ......... All they know how to do is type on a laptop
and
I even heard they're afraid to get a little grease under their fingernails

Grady

 

[Dan95-5.0]

thanks for that reply. you really cleared up some things for me. when searching through the forums, i try to completely ignor all FOX related stuff.


to answer your questions.

1) Are you now using the oem meter with the above combo?

answer: yes, stock meter. thinking about a 80mm lightning or something else cheap enough to sell later on and that wont pegg with my current combo.

2) What are the the values you see in your dlogs under the conditions
of WOT in second gear at maximum rpm

answer: i actually just installed my Tweecer R/T about 10min ago. finally got around to it and it only took me about 2 slow and easy hours to do. i left the switch on the #5 position for now untill i get my hands on a laptop. started without a problem on the first try.

i took your previous advice and sold my kirban regulator and bought some 24lb injectors.

i have a set of 24lb injectors arriving in a few days and when they go in, i'll load a j4j1 tune to see how it likes it.


ever since i installed my H/C/I combo, i've never gone WOT in fear of pegging the maf, overworking the injectors, and running lean. i keep it under 4,000 RPM as hard as it is to do but the torque around 3,000 RPM feels great so it keeps me happy for now.

 

[final5-0]

thanks for that reply. you really cleared up some things for me. when searching through the forums, i try to completely ignor all FOX related stuff.


to answer your questions.

1) Are you now using the oem meter with the above combo?

answer: yes, stock meter. thinking about a 80mm lightning or something else cheap enough to sell later on and that wont pegg with my current combo.

2) What are the the values you see in your dlogs under the conditions
of WOT in second gear at maximum rpm

answer: i actually just installed my Tweecer R/T about 10min ago. finally got around to it and it only took me about 2 slow and easy hours to do. i left the switch on the #5 position for now untill i get my hands on a laptop. started without a problem on the first try.

i took your previous advice and sold my kirban regulator and bought some 24lb injectors.

i have a set of 24lb injectors arriving in a few days and when they go in, i'll load a j4j1 tune to see how it likes it.


ever since i installed my H/C/I combo, i've never gone WOT in fear of pegging the maf, overworking the injectors, and running lean. i keep it under 4,000 RPM as hard as it is to do but the torque around 3,000 RPM feels great so it keeps me happy for now.

Good to know that info Danny

Even though you are just getting started we can look at your situation
and make some headway with your concerns.

We now know you are using the stock meter

It is almost certain ... You are not gonna peg that meter

Before doing anything like changing inj's or trying to use a different
cal file ..... I'd do something along these lines .......

After you feel comfortable with how the Tweecer .........
moves data back and forth
captures data for later analysis
accepts data from your wideband
yada, yada, yada

Make several test runs while datalogging for a baseline of reference

In second gear, do a wot blast up to say 4500 and look at the
maf voltage which of course is not gonna be close to 5.0 volts

Just work your way up to your redline with other runs at about
500 or so rpm intervals to see how close you come to pegging
that little meter.

You wanna be doing this with your wb outputting to the Tweecer .....
This will give you a clear understanding of whats what
as far as the WOT fuel ratio goes

I did not understand you were just getting started so I kinda
jumped the gun in my attempt to help you

Sorry about that
and
I hope I've not over whelmed you at this point

Never the less ... Just get comfortable with it all and have fun
When you're ready you can do all that other stuff and more

Grady

 

[blksn955.o]

I read the first comment about getting any maf to work with any combo...and kinda looked at the statement from a diff. angle.

You can get any maf to work with any combo...just you will either reach that meters limits quicker or end up not using the potential of the full transfer (like a meter that you will even at WOT never see above 3v).

YES- a meter needs to be thought out as far as flow needs just like the inj size.

After a good bit of searching and going over numbers and what have you...I went with a 98gt meter on my combo. Now that I seem to have the BIG bugs worked out with cal-edit - will run a DL tomarrow actually to make a more finalized tune- the maf is working flawless...and I must say even with the BUGS it has been great as far as drivability goes.

 

[HISSIN50]

I read the first comment about getting any maf to work with any combo...and kinda looked at the statement from a diff. angle.

You can get any maf to work with any combo...just you will either reach that meters limits quicker or end up not using the potential of the full transfer (like a meter that you will even at WOT never see above 3v).

YES- a meter needs to be thought out as far as flow needs just like the inj size.

As I read it, Grady's post was simply about the theory of what works and how. Just raw info to say that one can get just about any meter to work because of how the puter works. Being so blatant helped individualize the meter's purpose (instead of thinking it's siamesed with the injectors).



If Grady went on, he'd say that while anything works, just because someone can doesn't mean someone should. But in theory, about anything can be made to work.

And now in your retrofit, you're now talking about an actual application. Kind of a continuation of what might be discussed once one goes from theory to choosing a meter and making it work.

Good stuff. Not so much even from different perspectives, but different stages of thinking (as I see it).

 

[Prince95GT]

yes or no, can I throw 24's in and still run the factory maf I have in there now?

 

[final5-0]

Greg and JT

I see what you guys are saying

Yes JT ... I was trying to stay kind of generic with my info.
I was gonna get more specific IF there was some interest shown

Its such a shame how over the years, I've seen many peeps spend
money for meters & injectors for their 94-95 Stang and base that
decision upon info that is not completely valid.

Some of the time ... I saw their gain was nill or tiny
and
Some of the time ... they ended up with nothing but drivability issues
So ..........
that goes to show ... lots of misinformation is still out there
and
I've gotten a good bit of pm's asking about the subject

Yet ... It seems like the subject is taboo or something
cause
Usually ... you don't see much of a response from a thread such as this

Speaking about specifics

I've had some things on my mind about the maf subject
and
I've seen others kinda elude to the fact ... those things might be valid

Take the issue of pegging a meter ... NOT a C&L btw

Heck ... lets just use me as a guinea pig
I can take it if I make a fool out of myself
by
Thinking out loud on a public forum

I went to a ProM 80mm meter caled for 30's
I worked with its curve, fuel table, and wide band so I could simply
enter the af ratio of my choice in the row that pertains to WOT.

I say this to show ...........
I did have to change the kg values in the curve cells a bit.

Now ... in this optimization process ... I noticed something

There was a place or two in the maf transfer curve where I could
not obtain the same af ratio value as the rest of the curve

The objective here was of course .............
A nice flat af ratio curve all across from the start of the OL part of the
maf curve to maximum airflow my combo would generate

Not a big deal really as I was working with only a tiny fraction
of the curve and I'm only talking about a tenth or two when
the curve spiked or dipped.

Little side note here
this is nothing like the af display you see on dyno charts
which have filtering in place
In this case ........
the raw data provided here is much more detailed

Sorry for that little diversion ... and ... back on track now

But Still ... We all know how those tuner types are
They always gotta know why and will strive for perfection

The deal was ....
If I was trying to knock down a spike .....
I would adjust the transfer curve point before it
and
it would go down too much
or
The same thing would happen with the next point

It was like ...........
I needed a transfer curve point or cell ... in-between for more control

Hey Greg ... You ever ran across that kind of thing

Here are my thoughts about that
and
A possible work around

My combo generates WOT airflow on my meters 12.75 to 1.00
optimized transfer curve that tops out at around 4.1 volts or
transfer cell point #24

You could say I got 9/10's of a volt
and
6 cell points of the 30 point curve to play with
however
I've always seen it said you don't wanna hose with points 1 & 30
so
I guess I only got 5 points to play with

A long time ago in a far away galaxy while working to get that last
bit airflow from my little oem meter, I stole a point or two as I recall
from cell 2 or maybe cells 2 & 3. My memory is fuzzy but the point is
I had more than cell #1 with a zero kg value.

Now back to the present time and galaxy ... if you please

Why O Why

Could I not do the same with just a different little twist

Since I got a few cells on the top of the curve I don't use ......
I could take like say #29 and use it for that in-between
trouble spot in the curve I talked about above for finer
resolution in that part of the curve.

I can see no reason it would not work

Thoughts ... Anyone

Grady

 

[final5-0]

I thought some of you might wanna see what I've typically worked with in
the past to optimize my WOT fuel ratio

A thought or two about the image you're looking at

This was my first attempt with the larger meter
so
It is a bit dippy & spikey
Again ... The typical dyno curve has filters to smooth things

The target af ratio was 12.5 to 1.00

The added notes are present on this image because I've used the file
in the past to help noobs relate.

Grady

 

[final5-0]

yes or no, can I throw 24's in and still run the factory maf I have in there now?

No

Now .......

I'm gonna just say this ... just in case anyone wants to know ... why

The pcm has no knowledge you stepped up to the next size inj

It is now trying to control 24's with the same info it has about 19's

The end result can be none other than .............

Things are gonna be too fat
cause
Each pulse width now squirts about 25% too much fuel.

Grady

 

[blksn955.o]

I didnt want to repeat the info given and sound alike a broken record...so I thought adding my real world testing of a diff. factory meter to go along with the theory would be a nice progression.

DAMN good info so far... and lots of it.


From looking at alot of diff. factory meters I have come to some conclusions/my own theorys about some things ford did diff. with the newer mafs vs. older 5.0 mafs.

1. The last data point is not some far out voltage number like 16v. I think Ford realized that even hitting 5v's knocks the eec around and it see's the maf is pegged and treats it as a fault/error/out of range. So ford on its 4.6 year mafs now have max. volt ranges of 5.1 or so.

2. The last data point is a repeat of the max 5v value (in air flow). I can see NOT wanting to change that as the last one is an absolute not possible value...so that second to last value of 5v...is prob. a good idea not to change. Same with the first 2 points. The have a base line that is repeated in some cases (like the 98gt meter) 5x's and the 6th is the same airflow but showing volts (first five at 0 volts).

3. With all the data points being bunched up in the lower volt range I would delete one of the repeated base line values and use that one to fit the range further up were you seem to need more details...

4. I think ford added the repeating numbers for maybe control of the wot part of the transfer to keep it not so detailed...better drivability low and probably alittle softer up top to keep breakage down. I also think they gave themselvs room to play/learn/work out any bugs- my thinking comes from the hit and mis drivability issues that were found with the 99 and 00 gt's for instance they would stall at weird times and almost feel (SOTP) to have a 2 peak power curve...one kinda early then another slowly building to the redline. I would like to get a read eec from a 03 or 04 gt and compare the maf transfers to the 99/00 gt transfers...I think they may have done alittle moving around of values as you really dont seem to hear about the later year new edges having the hit or mis drivablity thing...

I would start by adding that value within the curve as close as possible to the spike but as close as possible to the curve and go from there...but I am just probably backing up your feelings on the matter and not re-inventing the wheel with that idea.

 

[blksn955.o]

With my logs I am treating everything as if it was currupt...the new tune is 100% either a fresh j4j1 or off a read eec. I exteneded this idea to the logs as well. So I am not going off any of the data I have collected so far or putting any merit in what I saw.

I am going to make a trip tonight and plan to datalog a nice chunk of it, I drove it again last night about for about an hr and 15min to an hr and a half so things should be nice and stable as far as KAMFR and such to log.

 

[final5-0]

OK Greg

I know you've spent a good bit time with oem meters

Good stuff
and
Based upon what you said from your findings

I gotta think I'm not way out there in left field with my thinking about this subject

Thanks for sharing

Grady

 

[Dan95-5.0]

i have a maf question.

in a centrifugal blower application, the maf is placed in between the air filter and the blower headunit.

when the bypass valve opens, and does its thing (recurculates the air before the blower into the powerpipe), wont the reading that the maf originally found be wrong with whats actually going into the throttlebody to the motor?

the reason this question came up is because ive been reading all of these "you cant run a BOV with a vortech blower" because of the maf setup. i found some info that you can actually but i would like some info about the bypass and MAF setup.

thanks

 

[final5-0]

If I understand your application ..............

You are dealing with metered air and only metered air so all is fine.

Grady

 

[fkloss]

I know this is an old post. We are thinking about using the stock maf for 95 gt with 30 lb injectors using tweecer rt. We have been using a summit calibrated meter but we think it is toast. So for an experiment we want to try the stock meter and see if the car will run with all
given parameters being the same in scalars and injector offset ,etc. Mind you we are running a v-2. So pegging this meter wll probably be a no brainer. However for an experiment and wanting to see if it will run and do low rpm acceleration and fatten up calibration . Grady what do you think since you have done more research on this than others?
Thanks,
Fritz