Lets talk Maf's and tuning.

[DolSVT00]

A while back, I was reading a thread from a tuner about some experimenting he has been doing with maf housing sizes and different Maf's it was verry interesting to say the least.

Well I've been doing some learning, and testing and wierd things happen. Basicy a calibration for a SCTBA2400 in a fatory housing will work well and get you in range for fine tuning, take that same Maf out of the housing and put it in a larger diameter tube and its way out of range and more changes have to be made to the Maf xfer to get it back where you need it.

Take that same calibration for the SCTBA2400 in the larger tube, and put a 2600 in a stock housing in its place and that same calibration seem's to get you in range for the SCTBA2600.


A larger tube seem's to extend the range of a maf, but at the same time will be in the lower load table's and lean out the tune due to less counts?

I guess I'm kinda confused. I can get any of them right in the tune, thats not the issue i can put the a/f wherever I want it and ramp it however I want without raping fuel tables into submission which is nonsense.

I just want to understand this more, there's gotta be positive's and negetives to both ways, if not basicly what I'm saying is I could use a SCTBA2400 or even a Ford 90mm maf, put it in a big azz tube and run as much HP or CFM as I want without pegging it out. and totally eleminate the need for those rediculiously large maf's like the SCTBA3000 that get all funky on driveability and low end resolution.

Maybe my logic is wrong? I could be wrong, and some of you in the know, feel free to rip me apart, I just want to understand this better.

[slowgreen99]

Put a carb on it!

[ElecTech]

No, you are on the right track.

the card style MAF's (or any MAF with a fixed diameter tube) are very dependant on that diameter for its calibration. If you think about it, the sensor is just "sampling air" and generating a frequency or a voltage (whichever system you want to look at). Its up to the calibration to tell the ECM how much air mass that translates into.

It then becomes a simple relationship between the size of the tube and, if you will, mass per sample.

Still with me?

So, if you do something to increase air volume or mass at a given "sample", it can/will shift the entire transfer curve. Thus the need for proper transfer curves for different intake systems. The older GM MAFs with a fixed diameter and screens intact are much less sensitive to changes in the intake upstream, but they also suffer from lack of range on high airflow situations.

If I read your post right, it sounds like you figured out that a lot of aftermarket Ford MAFs may be nothing more than a stock MAF in a new tube.

Unless something electrically has been done to shift the voltage output signal, like the Diablo MAFia, or a global scalar in the calibration, the tube diameter is the only way to gain range without lengthy multiple table scalings and fudged injector numbers.

The down side to all of this is the finite table range. In the case of the Ford calibration you have 0-5V. As you increase the amount airmass for that fixed range, you lose resolution in that table which is why the curve gets steeper and steeper. Not really a huge deal since most of this is in the higher aiflow areas, it just means the ECM has to interpolate any airmass values that fall between two measured points which increases the importance that the values in adjacent cells is as accurate as possible.


I hope all this makes sense as I just started typing it as my brain was spewing it out.


EDIT: Sounds like the SCT MAF's may have internal electrical offsets to increase the range inthe stock tube, if I re-read your post correctly.

[Harry]

No, you are on the right track.

the card style MAF's (or any MAF with a fixed diameter tube) are very dependant on that diameter for its calibration. If you think about it, the sensor is just "sampling air" and generating a frequency or a voltage (whichever system you want to look at). Its up to the calibration to tell the ECM how much air mass that translates into.

It then becomes a simple relationship between the size of the tube and, if you will, mass per sample.

Still with me?

So, if you do something to increase air volume or mass at a given "sample", it can/will shift the entire transfer curve. Thus the need for proper transfer curves for different intake systems. The older GM MAFs with a fixed diameter and screens intact are much less sensitive to changes in the intake upstream, but they also suffer from lack of range on high airflow situations.

If I read your post right, it sounds like you figured out that a lot of aftermarket Ford MAFs may be nothing more than a stock MAF in a new tube.

Unless something electrically has been done to shift the voltage output signal, like the Diablo MAFia, or a global scalar in the calibration, the tube diameter is the only way to gain range without lengthy multiple table scalings and fudged injector numbers.

The down side to all of this is the finite table range. In the case of the Ford calibration you have 0-5V. As you increase the amount airmass for that fixed range, you lose resolution in that table which is why the curve gets steeper and steeper. Not really a huge deal since most of this is in the higher aiflow areas, it just means the ECM has to interpolate any airmass values that fall between two measured points which increases the importance that the values in adjacent cells is as accurate as possible.


I hope all this makes sense as I just started typing it as my brain was spewing it out.


EDIT: Sounds like the SCT MAF's may have internal electrical offsets to increase the range inthe stock tube, if I re-read your post correctly.

Ya, What he said.:mrgreen:

[slow04]

http://www.sctflash.com/forum/

these folks can help you....just mention my name:hysterical:

[BAD BOB]

SD

[Chillerman]

ElecTech is right on target. If I read your post correctly, please feel free to correct me. Anytime you change the size of the meter or the tube size that's inside, the velocity at which the air enters goes up & down. With only having a 0-5 volt range in the tables really squeezes the algorithms. Thus really screwing with the accuracy of what's it's measuring. Too bad the tables are not based on a 0-10 volt scale. It would leave more room really dialing in your tune. Not being a tuner, I'm not familiar with if there's any adjustability to the proportional gain in the tables.

I hope this helps. If not then just tell me that I'm full of it.

[DolSVT00]

No, you are on the right track.

the card style MAF's (or any MAF with a fixed diameter tube) are very dependant on that diameter for its calibration. If you think about it, the sensor is just "sampling air" and generating a frequency or a voltage (whichever system you want to look at). Its up to the calibration to tell the ECM how much air mass that translates into.

It then becomes a simple relationship between the size of the tube and, if you will, mass per sample.

Still with me?

So, if you do something to increase air volume or mass at a given "sample", it can/will shift the entire transfer curve. Thus the need for proper transfer curves for different intake systems. The older GM MAFs with a fixed diameter and screens intact are much less sensitive to changes in the intake upstream, but they also suffer from lack of range on high airflow situations.

If I read your post right, it sounds like you figured out that a lot of aftermarket Ford MAFs may be nothing more than a stock MAF in a new tube.

Unless something electrically has been done to shift the voltage output signal, like the Diablo MAFia, or a global scalar in the calibration, the tube diameter is the only way to gain range without lengthy multiple table scalings and fudged injector numbers.

The down side to all of this is the finite table range. In the case of the Ford calibration you have 0-5V. As you increase the amount airmass for that fixed range, you lose resolution in that table which is why the curve gets steeper and steeper. Not really a huge deal since most of this is in the higher aiflow areas, it just means the ECM has to interpolate any airmass values that fall between two measured points which increases the importance that the values in adjacent cells is as accurate as possible.


I hope all this makes sense as I just started typing it as my brain was spewing it out.


EDIT: Sounds like the SCT MAF's may have internal electrical offsets to increase the range inthe stock tube, if I re-read your post correctly.

It does, and that's somewhat on track with my findings. I actually asked the question to find out why I was able to tune it and why it gave me soo much range when normally some of these maf's would be pegged out in their stock housings.

http://www.sctflash.com/forum/

these folks can help you....just mention my name:hysterical:
That forum is of no help, usually the answer's send you in the wrong direction, Im not having trouble tuning it, its the exact opposite, I can tune it no problem, I'm just wondering why people buy all these stupid maf's when I can get perfect resolution with a stock ford 90mm and a larger tube.

That and the fact that a 2600 is nothing more than a 2400 in a larger tube. I imagine its the same with the 3000.

[gearmesh, inc.]

A further complication of having a MAF big enough to flow what you need on a healthy boosted application, is that there will be a weak airflow signal at idle airflow conditions through such a big bore. By nature, a built for boost engine with a lower compression ratio will have an even lower idle vacuum signal through the sample tube than a higher compression N/A engine.

No wonder most big time turbo setups just go ahead and and bite the bullet and go speed density from the beginning.

Back on the MAF subject, didn't Pro-M back in the day have a blow through MAF with a 360 degree sample port? Anyone know how that unit worked out?

The neat thing about a blow through MAF is that it can be placed right before the throttle body which enhances the response time of the MAF signal when compared to the rise of the TP signal. Most boosted intercooled setups have a lot of air volume in the plumbing that takes time to get moving when the throttle is whacked open. If your MAF is on the suction side of your power adder, your TP voltage spikes right up immediately when you whack the throttle. Meanwhile, all the air in the plumbing has to get moving before the MAF can register more airflow, thus a delay in air measurement, resulting in a corresponding bog in response. To help this out, the tuner can program in a big "accelerator pump" shot through the injectors to bridge the gap in response, albeit a less precise way of solving the issue.

[1iron]

SD

X2

[blubyu87gt]

Quick question on this subject that maybe one of you guys can answer for me.

Currently I have a Pro M MAF on the Fiveslo with the stockie 19lb hr injectors. I have some 24lbers that I was going to install but first am courious. Would it be best to send the MAF to Pro M and have them re-calibrate (100 bucks) or take it and have it put on the dyno and calibrated with a tune (if that's even possible for a shop to do the calibration for bigger injectors) and save the 100 since I want to get the Mustang tuned anyway.
As always thanks for the info guys.

[DolSVT00]

Quick question on this subject that maybe one of you guys can answer for me.

Currently I have a Pro M MAF on the Fiveslo with the stockie 19lb hr injectors. I have some 24lbers that I was going to install but first am courious. Would it be best to send the MAF to Pro M and have them re-calibrate (100 bucks) or take it and have it put on the dyno and calibrated with a tune (if that's even possible for a shop to do the calibration for bigger injectors) and save the 100 since I want to get the Mustang tuned anyway.
As always thanks for the info guys.

What are they tuning it with?

[1998ta__1991rs]

is there any way to do a 2.5 or 3 bar map sensor on those trucks and going SD? this way works a lot better than maf's do with GM's computer system

[Carlrx7]

:poke: Zac
SD is for the guys that can't figure out how to tune a MAF.

[slow94]

As long as you don't use ford SD. Try tuning that!!!!

[DolSVT00]

I guess I'm not telling anyone that tune's a Maf setup anything new, but when looking at a maf transfer table, the larger the tube the farther down in the table you modify to get your commanded fuel, you can't just modify the entire table and think that the changes will be linear, I've got a large enough tube that the top 4 readings on the transfer table are completely useless, because the maf never even see's those counts.

I also had to mess with the bottom 4 readings more more than normal, because the larger tube seemed to make the maf loose a little bit of resolution down low, wich would cause driveability issues if not properly adjusted.

[blubyu87gt]

What are they tuning it with?

I haven't decided on a place yet so I dont have an answer for that. (any suggestions would be awesome by the way)

I have just been getting info on some shops and going off word of mouth from some people around the area as to where to go. I just moved to Ladson Rd area and people have said some good things about The ShowZone so was thinking of taking it there as its also about a half mile away from me.

Was more just a general can it be done and is it worth it question as I dont know too much about MAFs. The big issue with sending it in is the week or so that I would be without the car. Its my DD so not really an option right now.

[Lurch]

Jim sr can tune this with 60lb injector's to over 7,000 RPM's, Just did one with his help. Lurch