breathment

Im just wondering if u could use the maf readings (gm\sec) to help determain how well ur engine is flowing air with new mods. like exhaust intake etc?? or like porting intake etc.. cause i know my engine doesn't pull anything over 170 gm\sec at about 5000 rpms.. and i was just curious if i ever did any future mods, if i could just turn to the MAF readings to know how much more air im flowing..? i mean i know it doesn't really measure just air flow. but also the density. but still?

also is there anyway to convert the maf reading to CFM's??

Vader

Breathe,

Your MAF measures the MASS of air entering the engine, which, with all other things being equal, IS the intake air flow. The MAF also considers the air density, ignoring barometric and thermal changes. Due to this, the SCFM should be fairly close to that which would be measured by calibrated flowmeter, provided the MAF has not been altered. (We all know that a "gutted" MAF can provide erroneous readings.)

If you are only flowing 170g/S at 5,000 RPM/WOT, you certainly can use your MAF to measure improvements. Realizing that the limit of MAF measurement by the stock ECM is 255g/S, you should be able to use the MAF to that point.

As for calculating the intake air mass at any moment to SCFM, the mass of air at STP must be presumed, and the flow weighted by time (per minute). Understanding that a standard cubic foot (SCF) of air at STP (standard temperature and pressure) has a definite mass, calculations can be made easily.

Standard T & P = Air at a temperature of 68 °F, a pressure of 14.70 psia and a relative humidity of 36 per cent (0.0750 density).

Mass of air at STP = 1,186g/cubic meter = 33.58g/cubic foot.

Therefore, g/S X 60 (seconds/minute) / 33.58 = SCFM,

OR]

g/S X 1.787 = SCFM

Given that, 170g/S = 10,200g/min, or 303.75 SCFM

Obviously, your volumetric efficiency could use some improvement if the MAF readings are correct. Remember that the factory installed a MAF that will flow 544 SFCM, and the MAF measurment capacity is 255g/S, or 455 SCFM. You should be able to use your MAF to measure any improvements to at least that point, or up to 50% more than you're flowing now. Realizing that, you should also clearly see that the MAF itself is not restricting your intake, so don't even go there...

Ace_Murdock

well done vader

breathment

:hail: vader..

well i got bored last night and decided to give it a little test with the scan tool..

with the air intake assembly that comes after the maf. including the filter. 171 gm\sec at 5275 RPMS

with nothing after the maf.. 181 gm\sec.. (which is the highest reading i have ever gotten)

but the MAT readings with no filter etc were 9* higher then with the filter.. i guess its not much of a change but it was fun playing around., now i have to use vaders nifty formula to convert that to CFM's

Vader

So, by your measurement, you improved 17.81 SCFM by removing the filter and ductwork ahead of the MAF. That might be a good place to start, and maybe a low rstriction filter on a sewer pipe would improve the flow. That extra air is certainly good for spme extra power, considering the ECM will maintain a correct addition of fuel up to about double your current intake flows. Maybe that "cam and heads" theory isn't such a bad one after all....

Mkos1980

iTrader: (8)

I wish i was that way. I wish i had room for improment. I max out the maf at the nice 255 at 4,000 RPM's

Rustydawg

Anyone know how to convert from the MAF voltage output to the mass figure?

I'm thinking of using a pair of MAFs from 6cyl cars on a carbureted engine, no ECM to work with. I could put them in line with the cold-air ducting to the dual snorkels.

I'm good with electronics, so I can convert the voltage to something if I know the relative ratio.

Vader

On a stock Bosch MAF from a TPI engine, 5.0VDC = 255 g/S intake flow (measured at the 'C' terminal if I recall correctly). Depending on the year/model, a V-6 MAF could be an analog unit or digital unit. The analog is similar to the stock TPI Bosch MAF, whereas the digital units are 5V P-P, square wave, modulated frequency (duty cycle) to indicate relative air mass. I'd have to know the model to quote the frequncy ranges.

Rustydawg

This particular MAF was from an '86 2.8 litre V6 Firebird. I've seen lots of them similar at the wrecker. The analog version would be easier to deal with.

So long as the output is linear to mass of incoming air, I can do something with it.

I've had a voltmeter on the dash of my Ford monitoring the MAF output while driving and it doesn't seem to be linear.

RBob

iTrader: (1)

Heh-heh, nothing like cross-linking posts:

https://www.thirdgen.org/techbb2/sho...hreadid=139663

RBob.

breathment

nothing like post whoreing

RBob

iTrader: (1)

Need to at least get the spelling correct: that's whoring

RBob.