The argument of MAP vs. MAF has been going on for what feels like forever. Not too long after Ford went from MAP to MAF on the 5.0 V-8, GM proclaimed their preference of going from MAF to MAP, though they have only done this on some cars, not all.

They both have their pluses and minuses. False signaling is a problem with both solutions. MAP is "realtime" but the maps are sensative to engine modification and a pain to configure. MAF is more forgiving, but not as accurate, plus can be an intake restriction. Just some examples.

Neither solution is an absolute solution to reading in air intake; in either case the amount of incoming air is calculated/extrapolated and there is no assurance of accuracy, only a best effort.

As for not being on high-end vehicles, that is not correct at all. Many tuners prefer MAP, almost all aftermarket performance injection systems default to MAP (not just because it's appealing as a slightly lower cost offering) , and many, many high-end race cars use MAP (Alpha-N is only desirable for some limited applications).

Some cars are hybrid, like the LT-1/LS-1/LS-6 GM's; the ECU computes signals from both the MAP and MAF sensor in a significant way, the MAP is not just a secondary input.

My personal project will start out as a MAF solution, using the OEM Bosch Mototronic solution for my 928 engine; however, my other "off-road" 928 engine will be a MAP solution. I am pretty sure they will both fare pretty well.

Good luck.
Abdul

 

VU, good points in your post.

This was a thread about L-Jetronic, 951 is Motronic and has TPS where L-Jet has just an idle and WOT switch. I looked into MAP for L-Jet, it won't work. MAF on top of L-jet works like a champ, but requires you to do a lot of homework.

If a computer is configured for MAP it will work, but on these older systems (i.e. L-Jet) it simply would be a band aid attempt. Again, I am not talking about the 951, that is a different system totally.

L-Jet is 1970s technology and requires an air mass or airflow measurement device to work properly.

 

John..

About how long did it take to tune the converter brain for unboosted conditions?

 

Abdul,

Nice balance, I tend to lean like most race teams (MAP). You're right of course, there is still a place for MAF, and MAP does have its own limitations. I just see the tech for MAP getting better and MAF is kinda stuck. That and MAP gets much easier, the more computing power you have available. Computing gets better/faster/cheaper everyday - hence my heavy lean towards MAP. But certainly one can make some sort of case for MAF, or at least, some sort of MAF corrected MAP scenario.

John/VU,

I think that if you examine the I/O on an L-Jet, look hard at how the AFM I/Os, and do a some MAP d/a, you might rethink your position on not being able to retrofit MAP on L-Jet.

It can be done, really. Just not with what's out there now (and damn, they stick it to you on some of that retro-MAF stuff, ouch!). Almost as laughable as some of the money some charge for management stuff.

Greg

 

westcoastprshe, anytime you change the backpressure on the engine, you change the VE. If you start doing some turbo modifications, you can very easily change the backpressure on the engine, and send the computer's fudge factors all wrong.

Guru Raceing is an intersting site, and it's exactly what I said would be needed, assumeing it works. It is a computer that takes engine rpm, and Manifold, absoulte pressure and turns it into a flow rate useing a ve look up table. I belive they make up for the problems with backpressure by fine tuneing the ve curve to be releltivly close, and a little rich. The best way to "make up for it" is to put another pressure transducer in the exaust manifold, and then develope a curve of the effect of backpressure on ve, and use that to modify the ve curve of te engine.

However, the price tag is deffently up there. 890 dollars for the stage one kit, 1195 for the stage two kit, and an additional $100 for the boost controler. That ain't cheap by any streach of the mind. Plus, you still need the hand held programer to get the fuel curve right on eighter kit. Add $290. So you buy the kit, all told, about 1500 for the best version. You then install the kit, or have someone install it for you, then you tune. How much was the stand alone engine management system again? And with a stand alone kit, you get to control so much more.

Anyways, just my thoughts on that.

John, the motronic TPS, is like the unit on the LH-jet cars tells the comptuer 3 things. Idle, cruise, and close to or at WOT, exactly the same as the microswitchs in the L-jet cars. However, the TPS is a more compact, similer, more elegent, and cheaper way of doing it.