just curious, how does the SD system work differently from the MAF?

------------------
Stock 2.8 MPFI auto w/ Flowmaster ?? Series (dunno what my dad put in), More to come......
New Pioneer Head Unit
Targa E-910 7-Band Equalizer w/ crossover
2x 10" Pioneer subs powered by 300 Watt Jensen amp
2- 6x9" Pioneer (rear)
More to come..... (hey, i dont got a job yet)

 

Well, to my understanding, MAF is more interactive with it's environment. MAP measures pressure at the manifold, then goes to intornal, pre programmed fuel charts. MAF on the other hand, creates it's own fuel curves as it goes. Sound about right to anyone that knows for sure?

-Reno

------------------
'88 Firebird LB8
"Cerberus"
-Supercharged Hybrid LB8/L32 Project-
"Got a green light, got a red light, no cop, no stop, man I don't care, every one of you could be the same, every one of you could play this game, got a green light, got a green light but you're going nowhere..."
http://www.angelfire.com/il/Firebird28/index.html

 

i bet TomP knows alot about this... i wonder what he has 2 say......

------------------
Stock 2.8 MPFI auto w/ Flowmaster ?? Series (dunno what my dad put in), More to come......
New Pioneer Head Unit
Targa E-910 7-Band Equalizer w/ crossover
2x 10" Pioneer subs powered by 300 Watt Jensen amp
2- 6x9" Pioneer (rear)
More to come..... (hey, i dont got a job yet)

 

Reno pretty much nailed it! MAF is a better system, since the computer calculates air flow. With SD (using the MAP), the computer "looks up" air flow.

The arguement used to be that a speed density car wouldn't respond to out-of-the-ordinary (cam, headwork, etc) mods as well as MAF... hardcore mods were supposedly "off the charts" for speed density, and the computer couldn't look up a value. Glenn's one of the guys on here that says the SD tables -can- handle harder mods.

It seems the reason GM went from MAF to SD was cost; the MAF sensors were fragile, and when they broke, it cost big bucks. In fact, some of the MAF-equipped 2.8 A-bodies (Oldsmobile Ciera, Buick Century, Chevy Cavilier, etc) had a GM recall out- the recall involved a new chip, some wiring modifications, and a MAP sensor. It converted the MAF system to SD.

I think when I hunt down a V8 in the future, I'll be looking for a TPI motor that uses a mass-air system instead of speed density... but that's just me.

[edit] Oh, heck, why not: Our 2.8's use a different MAF sensor than the V8 f-bodies. The 2.8's use the AC/Delco "frequency film" maf. These have an flat rectangular piece of orange-colored film inside. The film vibrates at a certain frequency when air travels over it: High freq=high air flow, low freq=low air flow. The V8 guys use a Bosch "hot-wire" sensor. This involves a wire that stays "constant" at a certain temp. The airflow is measured by using the voltage required to keep that hot wire fixed to it's temperature. Obviously, more current = more airflow, less current = less air flow. The AC/Delco MAF's use a 3-pin connector, part #85111 from Motormite (pep boys/autozone/etc). The Bosch MAF's use a 5-pin, I think it's 85259? I forget. I dug those part #'s up a while ago in the tech section.


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

[This message has been edited by TomP (edited April 16, 2001).]

 

so say, a MAF car would get a more noticeable gain from a K&N airfilter vs. a SD car? but then if u replace the cam of a SD car, the gain would seem greater than on a MAF car?

------------------
Stock 2.8 MPFI auto w/ Flowmaster ?? Series (dunno what my dad put in), More to come......
New Pioneer Head Unit
Targa E-910 7-Band Equalizer w/ crossover
2x 10" Pioneer subs powered by 300 Watt Jensen amp
2- 6x9" Pioneer (rear)
More to come..... (hey, i dont got a job yet)

 

MAF on an LT-1/LS-1 is a better system. The MAF on thirdgen's was GM's first stab at it and it leaves a lot to be desired.

Quite frankly, BOTH systems are overly rich IMO. The MAF just continues to promote this "overrich" behaviour on minor mods. At least with SD, you are getting closer to the proper mixture.

I won't get into this discussion as this has been bashed far too many times. I will say that as a "prom burner", I prefer the SD system as I have better control and can make my engine run far better. MAF (3rd gen) doesn't react as fast as the SD system (which is damn near instantaneous).

Regardless of the system, both benefit from tuning. For the average guy, it is easier to get MAF reasonably close, but you will have difficulty in obtaining 128/128 perfection. But, once you play with SD, you can get it much closer to 128/128 perfection.

The biggest disadvantages of MAF is the 255 gm/sec air flow limitation, lack of precision, lack of reaction speed and it does present a restriction in the intake. MAF systems present tuning problems for guys with power adders or that increase the displacement of their motors. Also, the eprom is only 16K bytes big and there is absolutely no room to add additional programming if you want to "improve" the acutal GM programming. That MAF sensor (or relay) also seems to have problems and is damn expensive to replace

The disadvantages of SD is the tuning time and learning curve involved in getting it "precisely tuned" (but this is easily overcome) and it too is not "power adder friendly" (though you can trick it to accept a 2 Bar MAP). The eprom is larger (32 K) and there is plenty of room for expanding the code/tables. Also, you can at least enlarge the engine and it will recognize that. The cost of a MAP sensor is really cheap compared to a MAF sensor.

Unless you are making a large displacement engine or producing a lot of HP, there is generally no reason to convert from MAF to MAP. (Converting to the 89 ARAP BIN MAF is generally sufficient). But if you are going to make big power (and displacement), a lot of guys do convert to MAP.

For a V6, I wouldn't bother and just work with what I've got.