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Hvad er fordelen ved MAF ??
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Forfatter:  ae86 [ 27 jan 2008, 13:56 ]
Titel:  Hvad er fordelen ved MAF ??

Da bilfabrikanterne på nogle biler stadigt bruger MAF så må da der være en fordel ved det ... og det er ikke prisen da denne løsning kun kan være mere bekostlig end MAP.. så hvad er det der gør at MAF ikke høre fortiden til lige som vingemåleren ??

Forfatter:  ae86 [ 27 jan 2008, 14:07 ]
Titel: 

tror jeg fandt lidt af svaret her::________________
bits from a discussion skrev:

feel free to clean up...

<mcell> it requires a lookup table (MAF signal is usually logarithmic) and a division in fuelcalc
<mcell> pw = const * flow / RPM * lambdacorr
<hackish> well I knew it would need to be divided by RPM.
<mcell> but other than that division, it's similar to MAP
<mcell> however MAF is not a good idea: slow
<Jorgen> If we make an alpha-N like setup but that use the MAF instead of the TPS as an input it will work.
<mcell> yes, of course: with the table (MAF, RPM ) it's easy
<mcell> I think we can make WBO2 adjust even when EGR is applied (EGR is nice both for economy, emissions and ALS-substitute or ALS-helper)
<hackish> as I understand there are 2 main reasons for MAF in factory cars...
<mcell> hackish: yes: "lame" "design"
<Jorgen> With MAF RPM is optional.
<hackish> a) more accurate b) better transient response c) more adaptable to manufacturing differences (mods)
<mcell> they get more money when servicing the car
<hackish> er I guess that's 3
<mcell> a) is bullshit
<mcell> b) bullshit
<mcell> c) true
<mcell> MAP has much better transient response, and better accuracy
<mcell> what we have in MAP (25..250 kPa) and RPM (500..8000 RPM) is stuffed (multiplied) into one MAF signal
<mcell> 12500 .. 2000000
<mcell> notice the dynamic range difference
<Jorgen> MAF is used to allow the engine to work even when it is aging and to allow for engine tolarances.
<hackish> good point jorgen.
<mcell> yes, but the WBO2 is better than MAF in that
<Jorgen> Definately.
<hackish> yes, most cars do not come with a stock wideband.
<mcell> so MAF is a dinosaur from the time when WBO2 did not exist
<hackish> interesting.
<mcell> I would only use as a veryfication of speed-density (+limp-home)
<hackish> I'd like to get some limp code in there too...
<Jorgen> Limp home must be mapped, but if we are willing to do that we can look at Autronics application.

Forfatter:  Morten VJ [ 27 jan 2008, 15:10 ]
Titel:  Re: Hvad er fordelen ved MAF ??

ae86 skrev:
Da bilfabrikanterne på nogle biler stadigt bruger MAF så må da der være en fordel ved det ... og det er ikke prisen da denne løsning kun kan være mere bekostlig end MAP.. så hvad er det der gør at MAF ikke høre fortiden til lige som vingemåleren ??

Det kunne måske være forde den måler luftens masse, som motoren suger ind.
Og ikke behøver en ekstra sensor for at kompencere for lufttryks ændringer, eller kompencere for luftfugtighed. ups det kan et map baeret system ikke.
Eller slid på motoren, og det kan et map baseret system, heller ikke, lige umiddelbart.
Et map baseret system er bare meget mere gennemskueligt hvis man selv skal justere på det.
et maf system, er væsentligt sværere at gennemskue..
Men tæl selv, Maf systemer er i klart overtal hvis vi taler OEm.

MVH

Morten

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