Diffrence between MAP and MAF

[WILD VR CLUBBY]

Hi guy's been hearing a far bit about MAF sensors lately and i just want to know what the difference between a MAP sensor and a MAF sensor is? And im also geting the impression that one gives you more power then the other is this right?
And which one is better?
so if any one can help me with this it will be good
Thanx

[Cheap6]

MAP - Manifold Absolute Pressure. Measures, as the name suggests, the pressure present in the inlet manifold and, together with engine speed, manifold air temperature and a value in the ECM for volumetric efficiency at that engine speed, calculates the mass of air drawn into the engine. The delivered fuel desired is based on that. The 'absolute' refers to the fact that it is referenced against a vacuum rather than atmospheric pressure.

MAF - Mass Air Flow (meter) directly measures the mass of air flowing into the engine. In Commodores this is done by measuring the amount of electrical energy required to maintain a (heated) wire in the air flow at a constant temperature.

In terms of power potential produced by the engine there is no difference between each type of system. Each does have advantages. MAF systems, by directly measuring airflow, have a greater flexibility in adapting to modifications that alter volumetric efficiency but may represent a (small) restriction to airflow.

MAP, also known as '(engine) speed - (air) density', systems don't have an airflow meter in the intake path but, relying on a 'map' (as in plot) of volumetric efficiency to calculate the air flow into the engine, are less able to adapt fuel flow to large alterations in volumetric efficiency.

[klaw81]

Good answer, very comprehensive.

It's worth noting that in most cars, the MAF does present a substantial restriction when attempting to increase the engine's output considerably. The common solution to this problem is to install a larger MAF capable of flowing a greater volume of air, or to remove it entirely - hence the MAFless tunes you see referred to in these forums. Engine tuning on many cars relies heavily on MAF inputs, so the ECU must be reprogrammed to rely only on MAP inputs.

[WILD VR CLUBBY]

so if i was turboing my car which of the two would be more better to use

[WILD VR CLUBBY]

also do VR's even have a maf sensor coz i got no restrictive airflow sensor looking thing.
thanx

[vt1538]

No the VR runs on map.

[Cheap6]

OK, fair comment klaw81 re. restriction with considerable increase in output.

WILD VR CLUBBY:

No, VR's don't have a MAF sensor. For that reason, and that MAF meters, particularly large ones, are generally more expensive than a MAP sensor, I would suggest that a MAP system would be better for what you are asking. 2-Bar (able to read up to 2 atmospheres of pressure vs the standard 1-Bar) are available relatively cheaply as factory parts from many GM US models (Buick GN Turbo, GMC Syclone and Typhoon for example, same part). A complete remap of the PCM will be required in any case for a turbo set up.

[Cheap6]

Sorry to repeat re MAP vs MAF in VR. I type too slowly.

[klaw81]

A lot of modern turbo cars don't even have a MAF from factory, relying on MAP data only. MAF is usually capable of giving more accurate fuelling, so it is popular with manufacturers who have an easier time achieving emissions compliance and optimum fuel economy.

There are no real downsides to only using MAP - fuel economy may suffer slightly due to the slightly less accurate airflow data but I'm guessing that with a turbo on the agenda, fuel consumption is not a high priority. Finding a MAF capable of flowing enough air for significant power output would be quite expensive and/or difficult and would give no advantage at all.

You will almost certainly need to upgrade the MAP sensor on your car to one capable of reading boost (positive pressure) since the factory one would never see any more than atmospheric pressure and would not give an accurate reading.

Do you have any idea what sort of engine management you plan to be using?