XLR8NSS

iTrader: (4)

Good question....I don't know.

Another_User

If I may... It is not superior to a ported stock piece. There are a few simple facts:
- an aftermarket MAF cannot make more power than a ported MAF of the exact same size, with computer tuning. an aftermarket MAF does not magically flow more air, nor does it magically make extra air and fuel appear in your engine.
- an aftermarket MAF cannot magically account for changes in your intake, such as a lid or aftermarket air intake, which means that it probably is not making your MAF readings any more accurate based on your induction type.

Aftermarket MAFs fill a niche in the aftermarket market for people that do not want to go to spend the money for and/or be bothered with computer tuning.

XLR8NSS

iTrader: (4)

Get on it.

SScam68

iTrader: (20)

When you make a physical change to a MAF, ala porting, you are also changing its transfer function. The transfer function bascially is a mathmatical description of a phsyical property of a system. Crack open any controls engineering book and you'll see it's definition Before software was available the only way for compensating was an aftermarket MAF that had the compensation worked in in the form of resistors and would bring the readings back "in line". A point you touched on at the end.

At this point in the game an aftermarket MAF is a moot point, or is it? This is the reason for my questions and its rare an actual manufacturer gets on a forum to share info which is what I am trying to take advantage of

What baffles me, and what I am trying to understand, is why people change their MAF tables to compensate for fueling when it is nothing more than an input sensor like an IAT, O2, thermometer etc etc. Am I missing something here?

SScam68

iTrader: (20)

Just to add a little more, I do agree with Granatelli in that a MAF is a great tool that can be used in engine management to compensate for many variables that are experienced in the real world that a strictly SD tune can't, but I also have limited experience with both.

So back to Granatelli's original question, how does the stock PCM compensate for a temp change once the SD is dialed in?

NicD

iTrader: (7)

You change the MAF transfer function because air is not flowing across it like it was calibrated for when you use aftermarket lids and fittings. If you have your VE set correctly and you plug the MAF back in and it skews things you obviously have an improperly configured MAF transfer function... or a vacuum leak or other mechanical issue I suppose.

NicD

iTrader: (7)

This all is correct. A MAF just tells the computer how much air is going into the motor. It isn't some magical horsepower maker, nor does it remove the hard coded limit in the PCM. Now if the aftermarket maf is calibrated for an aftermarket airlid I can see how it would help, slightly. But based on what I have seen, the stock MAF isn't terribly thrown off by an aftermarket lid anyways. We are talking less than 5% here which is fairly easy to change in the transfer function. If it's larger it can obviously flow a bit more air, but the stock maf isn't really much of a restriction until you get up a bit in horsepower.

Z1500

It's so nice to see that map go up to 300kpa.
Speed density is the only way to fly.

Kevin

SScam68

iTrader: (20)

How so? The MAF doesn't need to be compensated, that I know of, after installing a lid, ported TB etc. Its just a measurement device. The reason for the foil, at least best I can figure, is to increase the velocity across the sensors for improved readings.

The only thing it can do is measure airflow irrespective of whats before or behind it.

NicD

iTrader: (7)

Only if the airflow was flat/laminar across the entire area it would work that way. The airflow through a mass air meter is never flat and will always be "spotty". Different airlids, etc will change that throwing the calibration off. This is basic stuff.

SScam68

iTrader: (20)

Right, and the reason for the "honeycomb" in front of it, straighten flow out.....

something else I am still overlooking?

slow

iTrader: (7)

If you have lots of expierence with ford stuff, you will see easily see the effect of different intakes on the maf output. Install a cold air kit with a bend in it, and your maf x-fer function is 5-7% off.

Ryan

samz28

why do you want the maf? its just another intake restriction. Just hack the code to use speed density with fulltime wideband support, that is more logical. i'd bet if you exceed the maf range you would then default to SD mode anyways, its only logical.

NicD

iTrader: (7)

Yes, you are overlooking the simple fact that changing the intake in front of the MAF changes how air flows across the sensor honeycomb or not. Look at the differences between the calibrations for the Z06, trucks, etc. The MAF is the same, the transfer functions are different. Like I said before, this is pretty basic.

SScam68

iTrader: (20)

....hmmmm

Sorry to derail Magnus

Kudos to you guys for the new feature and giving us an option

NicD

iTrader: (7)

I for one like the fact that with the maf the PCM will adjust accurately to many differing weather conditions, altitude, etc. If I had a race car or a large cam I would use speed density. I have tuned several cars in speed density and I do know its benefits. Heck, all standalones that I program I just use speed density. But for me and my daily driven car I want a very stable weather adaptive program in place that I don't have to constantly adjust and tinker with and speed density just drifts too much for my liking. As always, just my opinion...

NicD

iTrader: (7)

No doubt, I will be using this new feature on cars in the very near future.

SScam68

iTrader: (20)

Right, but the ZO6 MAF is a different diameter and I believe 02+'s come with no screen and an IAT sensor as a part of it compared to the truck MAFS.

Different physical body, different flow characteristics, different calibrations.

The actual circuitry of the MAF is nothing more than a Wheatstone bridge, hence the resistor adjustment in the SLP MAF's to compensate for the missing airfoil.

The transfer function is, in part, locked into the actual physical characteristics of the MAF itself. Hence if you descreen or port the MAF you throw off the TF. There is a set physical airflow through that set physical orifice for a given set of conditions. You map out the output by using controled conditions i.e. a flow bench. Hell, don't take my word for it MM&FF did a write up on how a MAF is calibrated.

You keep bringing up changes in airflow, even with a completely stock car your going to get turbulent and laminer conditions under different driving conditions. How do you know you are not smoothing airflow out by adding a lid, or bellows? Does it change the TF, nope. Does it change airflow, yes.

yes it is simple.......but people don't understand or maybe there is something that I am missing but nobody has yet to post a legitimate reponse on how a Transfer function can change by changing a lid etc.

not trying to rib you the wrong way , its been a long time since I have looked at anything controls related, 3yrs to be exact, but the best that I can recall this is how a transducer works.

Frank

time to do some research......

Z1500

My .02 for what it's worth.
When you need a very wide range (0-800+whp) of 'perfect tune, street manors' SD is IMO the only way to go. What we need is idle nice, not stall on decel, cruise smooth at low throttle, and get good gas mileage. The problems I've had with MAF's is if they are large enough to read up to 800-1000whp they loose counts or generally have horrible idle/ stalling problems. And if you use a MAF small enough to maintain good idle and street manors, it max's out at XXX hp.
I have no problem SD tuning street cars that run 22psi everyday and 30+psi on weekends. They drive like stock, pass emissions, perfectly tuned at all times, get better mileage than stock. Adjustments for air temp are made by the IAT sensor, the map self adjusts for altitude. You can drive a well tuned SD car around the world with no problem. I have never heard of anyone wanting to change away from SD to go with a MAF. Only the OEM wants to use MAFs so the customer can modify or have a half broken car and it will self adjust by reading actual air mass entering the engine. One down side with SD is every time you change something on the car you have to retune.

Kevin

NicD

iTrader: (7)

Arg... seriously they are the same MAF. Look at the part numbers, hell just look at them side by side they are the same, with the exception of the no screen part # for an 02 Z06.

This is not true. Like I said, look at all the different cals out there for the same MAF in different applications.

Yes, it will change the transfer function, period. I obviously can't explain this any better than I already have.