Maf

badtmpdgoat · 01-13-2005, 04:40 PM

What is the screen for? wouldn't the filter keep what ever junk was in there out?

GTO TOO · 01-13-2005, 06:26 PM

The screen is in there as a flow straightener. Airflow has a density profile as it changes velocity in the induction system. The screen helps to keep the meter readings repeatable. Some will say remove it for more airflow. The truth is the screen is not a restriction in the system. The stock MAF will flow more air than the head/cam/ valve area. What will happen when you remove the screen is you will change the airflow characteristic of the meter. All MAF's are not generic "MassAirFlow" devices. They do not "measure" mass of air. How they do work is at a specific airflow ( airflow is not MASS ) the meters are calibrated to output the reading to the ECM that is converted using a very large 3D table to input "MASS" into the fuel calculation. If the meter is not calibrated with a known induction system the output is NOT MASS OF AIR, but merely a relitive reading of airflow. All production systems have some amount of "learning"(feedback form calculated MASS IN to measured oxygen out, from the O2 sensors ) and what is learned is an offset correction that is stored. That stored memory is also a 3D table of memory.

badtmpdgoat · 01-13-2005, 10:58 PM

If the flow of air is greater than the intake and others, than why do people replace these(MAF's) before other mods are done? and can the stock MAF remain in place for most mods?

Napalm · 01-14-2005, 09:50 AM

The MAF is the car uses heat transfer to measure the mass of air ingested by the engine. The rods at the back of the MAF and electrically heated, then cooled by the incoming air stream. The air temp and the temp of the rods is used to calculate the mass air flow by the computer, more air flow cools the rods more and etc. This is use by the computer the meter the fuel. The screen on the MAF is not to calibrate the MAF but as a last line of defense to keep crap out of the engine. The calibration is in the computer. Mass air flow sensors are sized to the throttle body.

Other car makes use a VAF (volumetric air flow) sensor which is a spring loaded vane in the air stream. The more air the more the vane move backwards. The computer then uses the air temp, looks up the density for air at that temp, then with air volume calculated mass.

This system add the most restriction to the air stream to get the same data.

Sorry for the long post, but if you have a good CAI and are comfortable that no matter can get through the filter, remove the screen. If you are not comfortable don't the power difference is minimal

GTO TOO · 01-14-2005, 05:40 PM

napalm,
Not to argue. But the size of the screen compared to the airfilter size...The screen would hardly stop a fly. What it is, is a flow straighter. The calibration indeed is in the computer, but one of the elements of the PCM software IS THE AIR METER calibration. It is specific ........

Oh never mind, you're right. I forgot. All component suppliers and vehicle manufacturer's are always trying to add every do dad they can to increase costs. THE ONLY REASON IT COULD possible be in there is to catch all the large stuff that manages to get past the airfilter element.... and to restrict airflow to limit horsepower so every shade tree "engineer" can show those clowns that design engines for a living how to get alot more output at "no cost".

It's the same reason they put those restrictive airfilter elements and complicated induction parts on a production system when a straight pipe and K&N filter can do a much better job at half the cost. Those clowns are always worryin' about throttle body icing and water intrusion. Man I bet their even a little anal about DUST!! What harm can there be in that. Heck a little water in the combustion process will actually cool combustion and MAKE EVEN MORE power..What?? durabilty and engine life...NOOOOO we don't need no durablity !!! any good engine tinkerer can tell you how to make MORE power with absolutly zero unintended consequences....

Just one question if you change the MassAirflow at given engine speed, what other engine variables are effected?

badtmpdgoat · 01-14-2005, 10:36 PM

did not want to start an argument here so put your cocks away

neither one of you have answered my question? Is the MAF to be changed before or after any mods are made?

GTO TOO · 01-15-2005, 06:35 AM

Here are ALL of your questions.
" what is the screen for?"

The last time I asked the MAF design engineer that question, I told you what his answer was.

NO one has their D%^& out. However, I have found answers are normally only as good as the questions asked. And If you ask a question on an internet board be ready for an answer because some folks figure if you don't know, any answer is good enough. I have stated before on this board I would try to answer question to which I know the answer. Facts are more enlightening than opinion. But it always seems opinions are more fun. P.S. there are very few facts shared on most of these boards.

Why do people replace them first? They are not engineers.

When appling general knowledge of how something works, without specific knowledge of how it really works, most poeple use trial and error. If you wish to experience the error part of that equation, believe everything you are told on these "tech" boards.

Your last question was can a stock MAF handle "MOST MODS". How much will you increase airflow with " MOST MODS"? If unhooking the heated coolant lines to the throttle body and removing the screen, or installing a PCV tube for a cold air intake is "most mods" the answer is YES

Ask Groucho how big the airplane wings need to be for MOST PLANES......

BigJim · 01-15-2005, 10:50 AM

01-18-2005, 06:53 PM

i would post something here but i dont know what im talking about but i do know a goat will eat an eagle!

BigJim · 01-18-2005, 07:33 PM