MAF vs. MAP and MAF vs MAP Theory

[WhiteRaider]

I was doing a little bit of research on the Megasquirt forums and came across a link for the description of different systems. I've got an ECU from a 1995 Buick Century which is a MAF only ECU and was trying to determine the advantages of using it over a MAP system (other than SFI) in my upcoming swap.

I came across a webpage link from the MS forums and thought it was pretty interesting.

http://thegebharts.com/mswhys.html

It lists the pros and cons of each system. For the MAF, it's advantage is:

Direct measurement of airflow allows system to be self-healing. Will tolerate signifigant changes to engine VE without being retuned.

and it should be used when:

When an engine needs to always have optimal tune with no user intervention and possible neglect or modification.

If this information is accurate, then it would seem that as long as you're using the proper injectors, that the system will not require any tuning for things like intake manifold porting or a larger throttle body in a general NA engine. The ECU will compensate automatically. This would be good news for people who want to put the better flowing post '00 intakes on their vehicles.

Does anyone know if that information is true or if there are other advantages/disadvantages that are not listed on this page?

[SappySE107]

RE: MAF vs. MAP and MAF vs MAP Theory

I haven't seen a MAF setup yet stock that was perfectly tuned. I haven't found MAF to be self healing either. To me, MAF and MAP both need tuning with engine changes. MAF should be used when you have no vacuum, and thats pretty much the main issue I see so far with MAP. When you have no vacuum at idle, your resolution for tuning is real small. Stock 3.1 for example idles at .35 on a 0-1 scale. This leaves the .45-75 range for normal cruise and light acceleration, and higher for WOT and lower for decel. Easy to tune with MAP. Add high compression, a pretty lopey cam, and a larger TB and you have a recipe for trouble with MAP. I have tuned a few cars like this and was able to make it work well with MAP but I was sure wishing it was MAF.

There are other advantages/disadvantages, which I had posted before but it may have been on GMF for all I remember. MAP measures pressure, which gives it more accurate readings at the valve vs MAF which is before the throttlebody. MAP is faster to react to changes as well. MAF is more accurate for incoming air and doesn't car about vacuum though which is good for tuning some of the more extreme setups.

I used to be pro MAP, but now im neutral. I would say that the above post is wrong though, with no needed tuning with porting and larger manifolds. I haven't seen it work that way yet anyway.

[WhiteRaider]

Thanks for the real-world experience about this. Not tuning when making engine changes sounds too good to be true anyway.

I guess for the gearhead who would do the modifications, tuning the engine is probably something that they would want to do to make sure they are getting every last little bit out of their engine.

I'll be able to test how this works a little bit when I do the engine swap since I'll be using one of those 94-95 Century MAF only computers on an '02 Century engine. There is only a 15HP difference between the engines so stock tuning shouldn't be too bad anyway. I'll be using the Multech I injectors for this.