Johnny Bravo

Looking for overall performance. would MAF or MAP provide the best resolution and accurancy for a Turbo charged car.

the Champion Rs4's ran a MAP, but! those cars are 70% WOT through the race track. so its not the best example.

If all things being equal and you could change between the two - what would be ideal for the S4 / A4.

Basically with MAP and RPM you can have a pretty accurate picture of the air entering the system. Humidity doenst play a factor as much in speed density, but it does in MAF. is this bad, or good.

thanks.

cuatrokoop

MAP seems to be easier to tune with...It's what stand-alone systems use for their mappings. Are you thinking of going stand alone? If so, consider the <a href="http://www.034efi.com">034EFI</a> setup.

The IC was pretty much tailor made for you 4cyl guys. The IIC adds a whole lot of extra goodies, including launch control (aka two-step rev limiter, where you program a 2nd rev limit that you can engage via a switch/button at the start line of a drag race or auto-x event, and allows you to build boost while sitting still) and a bunch of other stuff. Customer support is really good too, plus the proprietor is an Audi guy.

xr4tic

MAP is easier to tune, since the MAP signal is the load signal, so you just tune what A/F ratio you want at a given RPM and pressure, assuming the VE table is correct.

Any big changes to VE (cams, portwork, intakes, etc) could require re-tuning in a MAP based system though.

A MAF system can be tuned in the same way, you just need to interpret the Load values into pressure values.

Imolavirus@BuehnEngineering

just track? just strip? street?

Lucas_Gchips

Its not resolution that people may decide to charge from one to the other.
But response and speed.

Essentially a MAF system has the MAF sensor in front of turbo, then there is a distance air that has been measured needs to travel till it gets into the combustion chamber.
Various factors can happen to this meetered air before it is sprayed with fuel and entered the combustion chambers, thinks like BOV, intercoolers, throttle opening/ closing that as MAF system can at time supply the incorrect fuel.
When you are looking at very responsive high power type setups like what most race car setup are, by having a MAP sensor that reads diectly from intake manifold, the ECI is able to calculate exactly what fuel is to be injected, ie it knows what is about to enter the combustion chamber.
The simple example of this is where people install a Blow off valve on a MAF car, then they complain about running rich, Occasional exhaust back fire, etc.
Plus a MAF can also act as a restriction in the intake path.
Tuning with some MAF's becomes complicated at times, as you can modify a car, then you exceed the MAF limit of reading air flow, then you have to start again with bigger maf etc.
Plus MAF units are easier to damage, go out of calibration than MAP units, so my taking MAF unit out and going to MAP. you can are also reducing one potential area of reliability.

xr4tic

I do agree the Bosch MAF sensors are failure prone, but Ford Hitachi MAFs are pretty much bulletproof.

Some MAP sensors are sensitive to mounting location, long signal lines can reduce responsiveness as well.

Personal preference has a lot to do with it, I'd rather have MAP than MAF, but I'm not going to spend $2000 to do it.

Jamez

Do you have yours in front of the TB?

xr4tic

I'm running a Ford MAF though, I wouldn't trust the stock Bosch MAF in that position.

Jamez

I am considering different options when tuning my car. Should I consider a large 80mm housing for stock sensor or rather a ford sensor?

xr4tic

but it does require a sealed system as far as BOVs, crank vents, etc, etc, and it does have a little lag with it pre-turbo, but nothing to be concerned about.

My main reason for doing it was that it was MUCH easier to install it before the TB because I didn't have room to mount it before the turbo.