MAF vs. MAP

DBR

Member
a mass air flow (MAF) sensor and manifold absolute pressure (MAP) sensor are two different ways of feeding fuel to an engine. some cars use a MAF and some cars use a MAP, but i get the impression a MAP system is preferred for turbo use. can anyone explain why?

here's some comments from the SDS standalone computer site:

http://www.sdsefi.com/tech.html#FAQ


Q. What is a MAP sensor and why are there 3 different ones?

A. A MAP sensor senses the pressure in the intake manifold. When combined with rpm information, it allows the ECU to compute airflow and supply the correct pulse width to the injectors.

We sell 3 different MAP sensors to cover engine applications with different boost levels.

The 1 Bar sensor is for naturally aspirated engines.
The 2 Bar sensor is for engines running up to 15 psi boost.
The 3 Bar sensor is for engines running up to 30 psi boost.

Map sensors are referenced to an absolute vacuum internally so they compensate for altitude and barometric changes automatically. MAP sensors simply connect to your intake manifold with a length of vacuum hose.

Q. Can SDS use an airflow meter?

A. No. Since SDS is fully programmable and designed to work on almost any engine, we decided to use the speed/density method of load sensing. Installation of airflow meters on many vehicles, especially turbocharged ones, is often awkward because of their size. Airflow meters also represent a flow restriction which is not conducive to making hp on performance applications.

any supporting/contrary comments? thx.
 
Yes, but isn't a MAF more accurate?

(Don't get me wrong, they have their issues and most days I wish I didn't have one, but if the MAF worked for the full range of air flow. . .I don't see the problem.) On that note, is the Mazdaspeed MAF different? Why does ours max out if the MSP doesn't? Or does ours not max out. . .damn, I apparently have confused myself. . .I know not what I say. . .
 
Kooldino said:
What kind/where from?

Not sure I will have it yet....I must wait and see. The system I am getting will also be able to use the stock sensors.
 
Last edited:
sure a maf is more accurate but aftermarket computers are usually designed to use map (for the reasons below) and they are much better at it now than they once were.

try finding a maf that a) is big enough to cause no flow restriction, and b) doesn't mind if you have a bov venting to atmosphere....

if you vent to atmos with a maf, heaven help you - measuring flow at the maf which doesn't get to the engine, what happens then? very annoying i'd imagine....

oh, and afaik, map sensor specs are for vacuum as well as boost, so two bar = 1 bar each side of 0, three bar is for up to two bar boost etc.....
 
MAF is the only way to go for any street car and should be used race cars. The MAF will read how much air is going into the motor. The MAP has been seen as the end all for years due to the fact that OEM meters were small. For over the last 15 years the 5.0 Ford market has lived with MAF meters and it opend the door to making big power without all of the problems that came with aftermarket computers. With 100,000s of Fords on the street with MAF meters the aftermarket was forced to that a look and do something about it. You then saw a few companies start making larger MAF meters. Some were junk and they are no longer around. With the G-M running MAP sensors they were forced to use aftermarket computers for big power. With the Ford you could still keep the stock EEC-IV or the EEC-V.

We built and ran a Ford Ranger ProRWD truck for the last two years. It had a 2.3 Turbo that would have made over 1000hp if it could be tuned right. One of the main sponsors is Electromotive. They did all of the tuning for us on and off of the track. The TEC-III will not work with a MAF so we stuck and had to take a trip back in time and use a MAP sensor. They would tune it this week and next week the air got colder and the tune was off. After a retune we would go back to the track in a few weeks and this time the air was hotter, now it needs to be retuned again.

This is a very common problem with the MAP system and aftermarket computers. The MAF meter will read the airflow into the engine. If it is a hot day the air is different they on a cold day. The same is true on a dry day or a rain day. All of the factors will be seen by the MAF but not the MAP. Once you dial in a MAF system you can leave it alone. With the MAP you will need to retune as the weather changes.
 
What is the hangup with BOVs. You can get by-pass valves for upto 40lbs of boost and 500hp. Also a by-pass will help spool the turbo faster when you shift. How much are you looking to run?

We stock two Mazda meters that will work from 300 to over 425hp. How much are you looking to make?

We sell an aftermarket computer that does use a MAF sensor, it will run upto 12 injectors, 4 coils or your stock Mazda coils, boost control and turbo launch control. It also has Windows based software and it is easy to tune.

Thanks again


Later......Nick
 
stef_nz said:
sure a maf is more accurate but aftermarket computers are usually designed to use map (for the reasons below) and they are much better at it now than they once were.

try finding a maf that a) is big enough to cause no flow restriction, and b) doesn't mind if you have a bov venting to atmosphere....

if you vent to atmos with a maf, heaven help you - measuring flow at the maf which doesn't get to the engine, what happens then? very annoying i'd imagine....

oh, and afaik, map sensor specs are for vacuum as well as boost, so two bar = 1 bar each side of 0, three bar is for up to two bar boost etc.....

Yup, 'tis all true, AFAIK. Long time no see, stef. WB.
 
Ok since MAF sensor don't like BOV because they vent air into the astmosphere why don't they move them post BOV and elimiate that problem... I know it sounds too simple but I'm not understanding the difference between MAP and MAF
 
MPNick said:
MAF is the only way to go for any street car and should be used race cars. The MAF will read how much air is going into the motor. The MAP has been seen as the end all for years due to the fact that OEM meters were small. For over the last 15 years the 5.0 Ford market has lived with MAF meters and it opend the door to making big power without all of the problems that came with aftermarket computers. With 100,000s of Fords on the street with MAF meters the aftermarket was forced to that a look and do something about it. You then saw a few companies start making larger MAF meters. Some were junk and they are no longer around. With the G-M running MAP sensors they were forced to use aftermarket computers for big power. With the Ford you could still keep the stock EEC-IV or the EEC-V.

We built and ran a Ford Ranger ProRWD truck for the last two years. It had a 2.3 Turbo that would have made over 1000hp if it could be tuned right. One of the main sponsors is Electromotive. They did all of the tuning for us on and off of the track. The TEC-III will not work with a MAF so we stuck and had to take a trip back in time and use a MAP sensor. They would tune it this week and next week the air got colder and the tune was off. After a retune we would go back to the track in a few weeks and this time the air was hotter, now it needs to be retuned again.

This is a very common problem with the MAP system and aftermarket computers. The MAF meter will read the airflow into the engine. If it is a hot day the air is different they on a cold day. The same is true on a dry day or a rain day. All of the factors will be seen by the MAF but not the MAP. Once you dial in a MAF system you can leave it alone. With the MAP you will need to retune as the weather changes.

The problem would be corrected if you tune the car to standard day, and run all your pressure and speed corrected to standard day.
 
I am a little lost as to what you trying to say. Do you mean that if you tune on a prefect day the car will always be in tune?

Thanks again


Later.........Nick
 
people have done that to other cars before.... the issue is whether the MAF can read that much air

TiGrayMsp716 said:
Ok since MAF sensor don't like BOV because they vent air into the astmosphere why don't they move them post BOV and elimiate that problem... I know it sounds too simple but I'm not understanding the difference between MAP and MAF
 
thanks Kooldino, nice to be back, i've had a wee break while i collect info and bits for my project.....saving for the autronic now (then i'll have everything) and hope to do my engine swap just after new year.....my, how there is a lot to learn ;)

as far as having to retune map-based tunings all the time, all i can say is "if you pay peanuts.....etc". any decent aftermarket system will have a built in atmospheric and temperature compensation in line with what YuYuRena said.

MPNick, if you tune your car on a certain day, your computer should use that as a reference and adjust accordingly when the conditions change. like i said before, if your computer isn't designed to do this (link is one i can think of), then you'll have good days and bad days with your tune :rolleyes:

oh, and by the way, the "hang up" with BOVs Nick, is that many, many people like the sound of them. personally i'm not one of them but there you go......
 
Last edited:
How does the Link system or any other system that only has a MAP sensor adjust for humidity? How does the Link or any other system that only has a MAP sensor know that you are at 15psi of boost @ 3,000 ft or 15psi @ sea level?



The MAF sensor can and that is why it is the most accurate way of knowing how much air is going into the engine.

Thanks again


Later..............Nick
 
Here's an excerpt about corrected parameters. I use this everyda for large turbo. It's long, just a warning.

The essence of corrected parameters is the elimination of outside ambient conditions (pressure and temperature) on the performance of engine. As you know engine especially FI is suspectible to ambient conditions. By correcting the "actual" measurements of pressures, temp, and so forth it is possible to judge and analyize another similar engine ran in a different ambient conditions.

Standard day is the answer to be able to level the measurement uncertainty to an acceptable level for comparison. Standard day is therefore derived from meteorologists from 1800-2000 conducting research and measurements to the point where a standard average annual pressure and temperature are defined.

AT SEA LEVEL
Standard day temp: 59 deg. F
Standard day pressure: 14.696 psia

Now there's a curve for both temp and pressure related to altitude, but you can look up the curve.

Humidity also affects the performance of the engine. It can messes with flow and for what I'm used to standard day is 0% humidity. So you can also correct back to that as well.

I hope this answer your question. The computer we now have are smart and fast enough to do these calculations, cuz they're simply curves and computer just read the curve to get the values. It's tunable and very feasible to tune to standard day condition and use that in reference in other weather. Now it won't be perfect, cuz we all know how screwy weather can be sometime, but at least this can be a baseline for further detailed tuning for specific ambient conditions.

Don't you agree this is a good method?
 
MPNick said:
The MAF sensor can and that is why it is the most accurate way of knowing how much air is going into the engine
Later..............Nick

How can MAF adjusts for turbulence in the intake tract? Turbulence can give you the wrong mass flow reading like spiking to overrichen the engine. Although, Hotwire is a very sensor for MAF.

Also how do you adjust for larger intake tract? For example if your intake pipe is 100inches? I know I'm exaggerating, but if you have a MAF to accurately cover that, how big would that MAF have to be?? And how much flow blockage is that going to cause?

MAF is very good sensor and it's good for small scale, but I think for larger pipe MAP offers a better choice.
 
Back