_DAN_

Why is it as far back as the 1980s Cossies had MAP Sensors?

Yet Evo Imprezas even Skylines run MAFS?

Anonymous

Cause MAP = innacurate
and MAF = accurate

loosely speaking

Jim Galbally

map guesses the airflow (well, calculates )

maf actually bothers to measure it

pee vee

small turbo esc cos has MAF sensor

Jay,

iTrader: (4)

so why do most remove the maf?

pollocks

yeah why do a lot of ppl go fro a map based management system :S

Jay,

iTrader: (4)

this is it poeple think that scoobies are very weak but most times they blow up is because the maf goes tits up and leans the motor out ?

Anonymous

MAP = easy and cheap to tune on a one off basis

MAF = great for economy on production vehicles where you need exact measurements

Jim Galbally

because from an electronics/ecu point of view map is FAR easier

Anonymous

Also, MAF is better at handling changes.

Bolt a set of lairy cams into both engines and see which one melts!

Jay,

iTrader: (4)

so maf is better than map in a comunication way and measuring but as for working reliably as in consistancy map is better?

DelboyTurbo

MAF is a more accurate way of measuring airflow, as said. Its nicer for manufacturers to keep within emission requirements etc.

The beauty of MAP sensors, is that there is no intake restriction....its a simple way of doing things. Alot of aftermarket ECUs dont calculate the airflow at all, they just take the values with the MAP reading on one axis. Its simple and easy to work from.

ECU Monitor Enthusiast

iTrader: (1)

MAP can be as accurate a MAF if set up correctly.

Chip is right, a MAF equipped car will adjust to changes such as cams
air filters, porting etc... (to a limit)

MAP sensors are used as they are cheaper to buy and install.

MOST cars that have MAF will have a MAP sensor aswell if turbo charged
such as the escort cossie small turbo.
(Some early scoobys and evo's dont have both and only have a MAF)

MAF sensors restrict airflow to the engine.
MAF sensors have an ultimate airflow/BHP limit due to these restrictions.

At the end of the day, either sensor will produce near identical results
if set up correctly but only directly control the cars fuelling 50% of the
time anyway due to transient changes in load.


My personal choice will be MAP every time for turbo cars !

Stavros

As per what Simon says, MAF is fine on standard cars, but once start tuningthen its MAP all the way, as MAF becomes a pain in the arse.

Look how many race (or just mega power) cars runs MAF. Pretty much fuck all as they all run MAP.

Anonymous

Race cars generally dont have it cause economy isnt an issue.

I bet a lot of the le-man cars do though?

DelboyTurbo

hmmm.....surely MAP can only be as accurate if the car stays at the same height (above sea level)

Map sensors accuracy will deviate as a car goes up a hill (i mean a big one lol). MAF will always compensate for this as it measures the mass of the air. Thats why manufacturers (especially japs because of their environment) tend to use MAF sensors.

Or so i would imagine.

For tuning, you couldnt give a flying fuck about emissions.....power all the way, which means you go for a MAP sensor.

DelboyTurbo

Nah, it will make a negligable difference to economy i'd have thought. Mainly for emissions as theyre so strict now. Japan is mountainous...MAF is better for that surely.

reality

DelboyTurbo Decent ECU's have barometric pressure correction built-in which answers your sea-level point..

Most modern turbocharged cars use the MAF for all the base fuel map.. contrary to popular belief, n/a cars with MAF's only tend to use them on certain part-throttle areas of the map..

MAP is handy sometimes because you instantly know if you have a problem with the car (when you stick your wide-band on).. With MAF, it's tricky because if for some reason your car isn't flowing as much air, it'll still be fuelling right but you'll be down on power..

Horses for courses really..

Stu @ M Developments

iTrader: (12)

This is another subject that i will do a serious essay on one day. Mass Airflow Vs Speed density.

MAF is better, end of story really.

You will find that nothing could be further from the truth actually. Right at teh top of teh tuning tree, F1 tuners pay massive attention to efficiency and run motors so lean you wouldnt believe it.

Anonymous

Indeed, more energy released per kg of fuel, so less kg's needed per race.

Jay,

iTrader: (4)

so in f1 then this is why the engines let go so easy as cooled by ambient airflow in hot climates, you hear brundel comment if theres a restart or a long pitstop it could cause probs in the race as they heat up so quickly and i spose lean mixtures dont help

Anonymous

The engines are specifically designed to last the exact amount of time that is required of them, they are run up on the dyno and the entire race (well now two races) are played out, the idea is that the engine should pretty much have expired as you cross the finnish line on the second race, if the engine gets more use (due to a restart) then potentially its now going to expire too soon.

Formula 1 is all about things being *just* up to the job thats asked of them, and utterly no more, or its weight you dont need to be carrying or power you arent using that you could be.

Ironically the "1 engine for 2 races" rule was introduced to try and make it cheaper, but in reality i think the opposite has happened as although less engines are used in the racing, im convinced more are used in development now!

Jay,

iTrader: (4)

cosworth have tested the series 6 engine up to 4 race distances that like a 1000k balls out the stress and energy must be amazing on that unit

Kev.H

sure there was aguy with a frs who damaged his maf fitting a filter and it caused his engine to go pop

Dave Henshall

if the MAF sensor uses a hot wire element for sensing the airflow, then yes, fitting an oiled aftermarket filter (piper corss , K&N etc) the oil can stick to the hot wire, contaminating it and making it 'think' there is less areflow than there actually is - thus the engine fuells acordingly when is then lean and ...pop.. melted pistons

Anonymous

At the end of the day, no matter what techology is employed on an engine management system the determined idiot will ALWAYS come up with a way of making sure it doesnt fuel properly in the long run.

No matter how idiot proof you make something, a better idiot always seems to evolve

foreigneRS

depends if the MAP sensor measures just the pressure that it sees (known as the guage pressure), or includes the atmospheric pressure too (known as absolute pressure sensors).

even in the case of gauge sensors, when the ignition is switched on before the engine is cranking, the ecu can do a quick reading of the MAP sensor to effectively read atmospheric pressure and compensate for it. however, if you drive up or down a big hill, or into a storm or whatever, without switching the ignition off and on to recalibrate then it will not be able to compensate for the pressure change.

RichardPON

Happens quite a lot with the scooby lot I believe.........

Oil coated filter, messes up the AFM etc etc........

Has actually happened on my MR2 thanks to a pony HKS filter.......

Kev.H

quote of the week

Porkie

iTrader: (1)

Please remind my fooking Skyline that

Porkie

iTrader: (1)

They also Idle at about 12,000rpm and run probably Rads that are just big enough and need air pushed through them constantly I would imagine.