MAP vs MAF

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MAP vs MAF

Postby Hardwyre » Wed Apr 20, 2011 2:58 am

My neighbor has a Ford MAF sensor he just wants to get rid of. Says it was virtually new off of a wrecked car (it looks pretty clean itself). I noticed that we have MAF functionality. I'm curious what the benefits of this might be. One forum said that with the MAF you don't actually need a VE table. Is this true? If it was, I'd expect more people would have gone this route.
My Datsun is powered by: Pick'N'Pull, Cadillac, BMW, Ford, HomeDepot, Volvo, etc, etc.
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Re: MAP vs MAF

Postby elaw » Wed Apr 20, 2011 4:35 am

Well, people will have a lot of differing opinions on that, but let me give you my perspective...

I switched my car from MAP-based to MAF-based operation a couple of months ago and have been very happy with the results. I think the best way to sum it up is that it makes tuning *much* easier. I had been dealing with a lot of the issues you see on the forums here like IAT heat soak and AE/EAE tuning difficulty, switching to MAF basically made those issues go away. I'm actually not running any AE at all (regular or enhanced) and the car drives wonderfully. I also was having a bear of a time getting the mixture right around idle, especially as the engine warmed up, and with the MAF sensor those issues disappeared.

Downsides are that it takes some messing around with .ini files to make it work, especially with VEAL. You probably can avoid some of that since the data for the Ford MAF sensor is already in the system, unlike that for the Bosch one I'm using. The MAF sensor does create a small restriction in the intake which could make a difference if you're trying to wring the very last horsepower out of the engine (also using a large sensor helps). And while theoretically you don't need a VE table, in practice you probably will. When I made the switch I started out with an "empty" table (all values set to 100), and it ran reasonably well... after half an hour with VEAL it ran *really* well.
Eric Law
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Re: MAP vs MAF

Postby Kurt A » Wed Apr 20, 2011 8:57 am

The other thing you really need to be carefull of using MAF is that you have absolutley no vacum leaks. A vacum leak ever so small can really disrupt MAF as it does not get counted in to the fueling equation.
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Re: MAP vs MAF

Postby elaw » Wed Apr 20, 2011 10:23 am

Good point!

Also air/fumes coming in via the crankcase ventilation system (if fed in after the MAF sensor) can make things interesting, usually at idle. Canister purge too.
Eric Law
1990 Audi 80 Quattro with AAN turbo engine: happily running on MS3+MS3X
1997 Saab 9000 Aero: self-tweaked stock engine management (and stock engine)
1986 Audi 4000 Quattro: R.I.P.

Be alert! America needs more lerts.
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Re: MAP vs MAF

Postby Hardwyre » Wed Apr 20, 2011 11:19 am

Interesting, excellent thank you! I think I'll grab the sensor from him since he's just going to throw it in a box of parts to give to the local Pick'n'Pull otherwise. I'm getting the Z dyno'd tomorrow so I'll see how it runs then, but it'll be good to have on hand incase I ever feel the itch. Actually I've got her running what I feel is fairly decent after a couple rounds of the VEAL (VE AnaLyzer right?). Before I did the first round she would stumble without AE, now, hardly.
My Datsun is powered by: Pick'N'Pull, Cadillac, BMW, Ford, HomeDepot, Volvo, etc, etc.
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