I was wondering which ones is better SD or MAF? I have heard good and bad about both.

 

SD is better, in my opinion, but needs to be reprogrammed for your mods.
MAF is more mod friendly until you start going to the extreme.

 

I think MAF is better. It *DIRECTLY* meter's the amount of air entering your engine, and is vastly superior at steady flow metering, as well as idling with big cams. It can flow up to 700+ CFM of dry air in a modified state (although I wouldn't do that unless absolutely needed).

There are only two downsides to a MAF system. *IF* something did need to be replaced, it can be costly, and it's not quite as accurate during "RPM Surges." In other words, if you like to be one of the ***** wanna-be's that sits at a stop light and rev's your engine multiple times (to be sure it sounds "phat"), during that point where manifold airflow is constantly spiking up and down, it's not as accurate....

... then again, I don't think those characters should own a third gen and would be safer in a Honda anyway.

 

The big problem with the MAF system is the computer. Its kinda slow and doesn't refresh as fast as the SD one. In a thirdgen the SD is the way to go IMO. Mostly cause once you have ht puter programmed to where ya want it, it is awesome and the there is much more in the puter to tweek to get everything right.

Kat

 

I guess if I had access to 10 hours of free dyno/wideband time everytime I made a mod, I could live with SD, but I like driving my car more than playing with my laptop. Then I could use that better resolution... in the mean time, I'll let my old, antique of a computer do my minor adjustments while I focus only on the big ones.

 

In theory MAF is the better system, but in the thirdgen it's the older system, so it's not as advanced as the SD system they developed later. Given the choice between equal technology the MAF is clearly the winner, but in our old cars the SD system makes more power.

 

A MAF sensor does no *directly* measure airflow.

It measures it indirectly as it is converted thru the ecm for an expected value derived from the sensing signal.


10hrs of dyno time and a wideband everytime u mod a speed density system?

I'll tell u my latest time frame:

Involves a TPI 383 w/ vortec heads/cam/headers/converter/etc

Started Fri 3:30

Fix minor junk and tweak obvious tune flaws(sat and sun)

Actually work on tune on Mon

PAss IM 240 roller emissions on Teus

Break in Wedns. to Bowling Green for Buick Nats.


I could have done it without using my wideband, most of it was datamaster and VE MAster for the Ve tables.

U can throw parts all u want, until until u learn how to tune it right, its a waste of time

later
Jeremy

later
Jeremy

 

Well, quite frankly 3.8, you can ban me if you want to flex your mod muscle, but you're wrong.

First off, the MAF is placed directly into the path of the air stream. That is a DIRECT measurement, period!

All sensor signals are converted into voltages and read by the ecm. By your warped version of what direct is, are you explaining to us that a coolant temp sensor that is in 180 degree coolant and producing the correct voltage that the ecm would expect to see for 180 degree's is flawed because the ecm is reading the voltage of the sensor and not the tempature of the coolant itself?

So basically you want to argue the whole idea of EFI, since in that case, nothing about EFI would be direct. Yeah, okay.

The MAF is DIRECTLY in the airstream, the MAP is up stream, measuring through a vac line - which can collapse and flex under vac anyways, limiting the over accuracy of a MAP if you really wanted to get into it - being the MAP is not directly in the path of the airflow.

MAF measures the amount vs density of the air entering the engine. MAP can only estimate based on vac. GM reintroduced the MAF in to the fbodys in 94, way before OBD2 was around, for a reason. Steady state fueling, etc etc etc.

Some old arguement, same guys crying about which system is better....


... MAP sucks

 

OK.....third gen MAF sucks ...because it's an antique with an
antique computer

 

I think some forgot to mention that the MAF system is much more problematic. just run a search on all of the posts regarding MAF problems.

 

MAP based systems suck. I am looking into controlling a TBI system with a 165 ecm soon.

 

Isn't that all mid 80 cars in general?? LOL

Yeah, the MAF systems have 1 or 2 extra relays, and the sensor itself... but does that really have much to do with the arguement over which is better overall?

( Maybe I can just say that because I have a spare MAF and a box of relays )

 

Both have their pro's and con's, and both can be enhanced. It all boils down to personal preference, and the owner's situation (time, money etc..).

As for the older, and much slower, MAF's ECM... things are constantly being improved upon. Just take a peek at what "Aeromotive" is doing with that thing from the past, that pre-historic thing, which I think was known as the carburetor. Something now known as a "Float Bowl Sensor".

 

How come all the really fast cars I see run a MAP system?

 

Because you want to spur on an arguement.....

I think that's a pretty had statement to justify. For every fast MAP car there will be a MAF car.....

What you don't realize is us MAP and MAF guys go the rounds with each other all the time and at days ends, each other's cars are just about as fast as they were in the beginning. It's a theoretical arguement for the most part, intellectual jousting if you will. But nice try.

(Something to chew on, if you were actually serious - N10 only came around in 89. G92 only came around in 89. Both options are almost requirements for fast factory cars. 89 was the last year for MAF. So yes, there are more N10/G92 MAP cars then MAF cars - hardly a fair set of standards to compare 5 years of MAF cars, 4 of which didn't have the desired options avaliable, against 3 years of MAP cars in which you could get all the goodies. A 89 G92 will be as fast as a 90 G92...... I know, my 88 Formula has every G92 option besides N10, and w/ my high flow cat, can keep up with MAP G92 cars, mod for mod.)

 

The 165 ecm is slighlty problematic.

The MAF for the 85 oddball and 86-89 MAF cars are basically junk.
As are the MAF.s for the turbo buick cars. I will stand by that, been there done that and will throw them away.

Also if u think a mass air flow meter directly measures are, you need to understand how it works. It is an indirect measurement. If it was a direct measurement it would measure the velocity of the air itself, more akin to like how you flowbench a set of heads where it directly measures cfm/velocity to get an airflow number.

It uses a heated sensing wire and the correpsonding change in voltage needed to keep the wire at "X" is what they use to calculate the airflow. That would be indirect.

Or go read any true engine mamagement book and see what it says if u dont like how I explain it.

New style MAF's in GM land as in say the 94+ F-bodies dont even compare remotely to what our cars came with from the factory. They are superior in every way, from the sensor itself to the factory ecm installed in them. U know, the funny thing is, hey they also have a MAP too. Who would have thought that?

U can even delete the MAF tuning it yourself and they drive every bit as nice as they did with the MAP. From the factory it uses both depending on exact engine conditions and what is occuring.

I just guess I'm clueless, must make my 89 TTA running on a 148 ecm that has been converted to MAP a completely wasted effort now.

later
Jeremy

 

I won't argue with your poor self esteem comments...

Anyways, it's direct, no matter what. The wire is meant to stay at X tempature, and the only factors that affect that are Air Tempature (Mass) and Air Speed..... It's DIRECTLY metering what you need to be concerned about when determining how to fuel an engine.

How can you beat putting a sensor right into the path of consumed airflow that judges BOTH that volume of oxygen in the air, and the amount of air being consumed..... LOL. Not by sticking a vac gauge (the MAP) onto the plenum through a tiny hose can't possibly compete. As far as driveability, my driveability is just fine, after basic mods, with no ECM tuning.... HUMMM

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MAP sucks

 

What he said^^^^!!! The MAP system is simply a guess. Even changing to headers will confuse the system.

 

.Really?

Check out my cardomain site. I ran a stock chip until a month or so ago and the chip was the last mod I made. And I was running a 13.8 before I had the chip burned. I credit finally updating my suspension to some of my new time (13.35) as my 60ft dropped from 2.1 - 2.2 to 1.9.

Drivability issues? I had none before I replaced the stock chip. I do notice that my gas milage has improved considerably though

 

MAP is directly measuring the load on the engine.

MAF doesn't meter the airflow directly, it measures it by cooling the wire. If it was directly metering the air, there would be an impellor in there spinning as the air entered the MAF. And it doesn't measure the amount of oxygen or the air consumed.

And why do you keep talking about the tiny hose attached to the MAP?

 

Why do you think the OEM use both now. They both have their advantages and disadvantages. But as far as steady state going down the road the MAF setup is much better. The only reason the MAP is on the newer engines is for AE. Other than that MAP sucks.

The wire in the MAF is heated but that also helps determine air mass. Cool air is denser which needs more fuel (cools the wire more).

The MAF sensor is a direct reading of airflow into the engine as it sits in the middle of the air intake.

True that the MAP sensor measures engine load but it is still not as accurate as MAF. The MAP is terrible for low rpm fuel metering just like a carb. The MAF sensor is measuring airflow which is very low at cruise.

 

The MAF takes a reading that is directly proportional to the airflow. The current needed to maintain a constant temp above ambient air temperature is what determines the output. This airflow is only as good as the calibration in the ecm. As long as the calibration is good, then the readings will be reasonably accurate over a wide range of temps and flows without any compensation.

One really isnt better then the other. They both have pluses and minuses, which is why they both are still used today. Alot of cars use them together. My taurus does, although it seems to idle/run at P/T fine and not even set a code for a short time without the MAF, so its unclear to me the extent that each is used.

As for the load, you can sort of guess what it is by using the airflow (LV8), but its not as good as map IMO.

 

Dimented- doesn't your camaro still use both?

I know on the later model 305 and 350 vortecs and probably 4.3 for that matter the MAF is the main sensor and the MAP is used for AE, spark, transmission control and backup. It uses the MAF almost extensively for fuel control. With the MAF it will run a LT4 Hotcam in a 350 vortec without even setting a code. Has great throttle response and good torque. No different in the driveability department than a stock 350 vortec. That combination is in my dads 1997 Express 1500. (Broke a rod @ 50,000) Its the only Express I have seen that is actually express and has a lopey idle to it. I know it could probably even run better with some tuning but for now it is fine.

The same could not be said if that cam was stuck in a SD TBI setup without tunning. Hell my LT1 cam confused the ECM enough that the idle logic puked and it would surge between 400 and 1,400 rpm. Any amount of throttle would make the engine fall on its face.

 

It's kinda pointless to argue which is better......to me it comes down to ease of tunabilty. On my car I run 165 MAF, it works fine but I will convert it over to a 730 SD set-up this winter. The reason I am converting it is because I have now tuned a few customers cars with the 730 and I like what I see. To me, it seems a little more refined and more intuitive. However, like I said, the MAF works fine too.

 

Yeah, When I finish with the $0D Im thinking about trying to blend the two together, or maybe use the MAF for PE and the SD for p/t. Still not sure yet.


As for the ecms, given the choice between a stock 165 and the 730, Id take teh 730, its definatly the better of the two.

 

It's already been addressed, but I will go over it again.

Colder air is more dense. The density of air is a valued way to determine the amount of oxygen in a given unit of air.

Slow traveling air will cool a warmer object. Air at the same tempature, but moving faster, will cool the object more quickly.

Therefore, the rate at which a wire is cooled by air passing by will determine both the mass (tempature, cold = more oxygen) and velocity (speed of passing airflow) of the cconsumed oxygen which is the element required for combustion.

If GM used the same MAF on a 16 bit system this wouldn't even be an arguement, MAF is simply a superior form of metering. Even with it's antique of an ECM, it still works great.

 

being thirdgen.org I thought that the relavent argument of MAF vs SD is only based on OUR thirdgens. So the only argument here should be "Which one is better on out thirdgens?" not which one is best overall.

 

Actually, the poster asked with is better, SD or MAF systems, not which ECM is better from the factory....
... which begs the question - is there a 16 bit MAF GM ecm out there that we can use on our cars.... hummmm

Oh well, I'll still take the 8 bit 255gm/sec limited ECM over the computer controlled vaccum gauge.


(psssp ator - not everyone here runs the stock ecm that came with the car from the factory.)

 

sd is a little more then that If the temperature compensation, VE, etc. are set up properly, it can be both accurate and precise. Teh stock thirdgen maf systems are accurate, but by no means precise do to the way theyre set up.

 

Computer controlled vacuum gauge..you must be referring to the Accel Gen 6 DFI crap...not the factory piece.

 

Who cares? Because this was the original question

Now being that this is strictly a 3rd gen forum who cares which aftermarket or non-original ECM your running.

Bottom line is, which is better that ORIGINALY came with our cars, this is the TPI section of the 3rd gen forum, not a general car/engine forum.

 

You know what's really cool - when you are just so dead set about argueing with someone that you have to break up the quotes just to be sure you have proven some peonic point....

Well, I think I've contributed to this thread enough anyways...

GM went to the MAF as the PRIMARY sensor for fueling and the MAP only for diagnostic purposes in 1994. The MAF's are WAY different then ours, the ECM's are different as well, but the fact that in a business where HP sells cars, and .001 gallon per mile, or .05 greater CO emissions can cost millions... I'll just play follow the leader and hold out with my "ALIKE" Primary fueling sensor.

Besides, ALPHA-N systems are gaining popularity, and after 255gm/sec, that's basically what a 165 becomes.

 

MAF does have the sensor sitting in the intake tract, but it uses a set of scalars, and tables to translate the measured electrical readings into a value the ecm can use. BOTH the MAP, and MAF readings need to be translated into values the ecm can use. The MAF measures airflow, and needs to be converted to a load reading, and MAP measures vacuum, which compared to RPM is a load reading. 6:1, half dozen of another..........

One of the problems with MAF is that in tansistional/ accleration areas, it over reads the air flow. How can that be?, well the plenum operates in a vacuum, so as manifold vacuum drops, some of the air measured by the MAF is not actually used by the engine, it's just used to adjust to the new manifold vacuum level. The MAP that is directly reading the vacuum, is immune to that error.

Starting with OBDII, the MAP is used for low throttle openings, and transistional engine operation, and MAF for WOT. There are a series of calculations with in the OBDII diagnostics where the values are compared, and used for diagnostics.

To properly cal a MAF, or MAP system with the oem resolution tables means adjusting about 250 points within the various fuel tables. Doing either type calibration takes about the same energy for an tuner experienced in both.

Now when you get to timing and MAF systems, they have to do a LV8 calculation to figure out what the actual engine load is, and then that's used for the timing table. Trouble is, that's another set of calculations that are prone to rounding errors.

Emerald, and Motec, which seem to be the world class leaders in ECMs for the exotics, both use just MAP.

In the future, the're probably be a better system that uses both, in a blended way, available to folks. BTW, even a primitive version I tried years ago ran pretty well.

 

..

 

I said I was going to leave the topic, but finally Mr. MAP himself arrived.

You said that above phrase numerous times Grumpy, and have always justified it with the same logic that there is almost an "Airflow stall," as too much air enters the plenum that creates a drop in manifold pressure under sudden throttle changes that would inherently create an overfueling, and *Possibly* and perceivable delay in response.

The problem I have with the logic, while sound for the most part, is that it does not take into account that an internal combustion engine will use all air available until internal component failure if enough air is available. Under load or not, with no rev limitation in check, an engine will spin higher and higher until either

A - all easily accessible air is being consumed at the maximum rate it can be gathered by the suction created within the bore, to that point that not enough of a vacuum is being created - to in hand create the energy required to pull anymore air through whatever track it came through. (such as at idle - only Y amount of air is permitted through)

B - internal component failure from force/load/speed.

It is plain as day, and what "Rod throwing" contests are based on. If you've never heard of a rod throwing contest, it's were they take a few cars, bet which will break first, and stand on the gas pedal for 10, 15, maybe even 20 seconds until something breaks first, and that's what the bets get paid out on.

-Why would I say all of this?- Inevitably, the engines break, which validates the above conclusion to air made available will be used, even in a transitioning situation. They are taking intakes, cams and heads, and making them provide airflow at 8000 and 9000 RPM... obviously if there's enough energy to do that, there's enough energy to create a greater than normal VE during a transition, which is the key that I don't think your idea accounts for. That being the case, the idea of "Hampered" transitioning in the MAF sending a signal to over fuel is flawed, even in the shortest time span of milliseconds....

I'm sure you have data logging to back up the idea that you've worked with over time, but it would be irresponsible to account a spike in AFR, or a dip in Manifold Vac to overfueling, and overfueling alone, when you are forcing a change in piston speed, momentum, and other associated energies.

That's all but it has carried weight with several others that I've spoken too in the Import area as well.

Which bring up the next topic, who's gunna do a VAF setup

 

Obviously not you so get lost!

 

didn't read the whole post sorry if I repeated anything

MAF is more mod freindly than SD with out touching the prom

MAF is not as reliable and its not cheap if your maf goes

but 1 major advantage to MAF is you can buy a MAF's for third gen that allow you to adjust the calibration with a screw on the side

so if your running alittle lean or alittle rich all it take to change the mixture is a screwdriver


MAF can't be all bad the LT1 and LSX motors use it

 

I concur. Ive seen 70-100 g/s spikes when I slam it down.

Has this really been confirmed on the software side of the new OBD-2's? Do we have a link? Just curious...

One nice thing about the MAF is that its independant of the engine to an extent, so it doesnt need to be messed with as much when you mod.

 

Instead of trying to restate what I've said, which BTW, you've managed to twist into something I haven't, you ought to actually try comprehending what I posted.

I noticed alot of I thinks, and I guesses in you posting, maybe you ought to try getting really familiar with both systems, so you can talk about things with some experience under you belt instead of trying state opinion as fact.

BTW, have you actually done any code developement?, ie ever really tried to understand what an ecm does?. Again, maybe if you had some ecperience in what your professing to know, you'd be more knowledgible in the matter, and not have to use the *I think*, mode of **logic**.

BTW, I noticed this completely exscaped your comprehension:
* In the future, the're probably be a better system that uses both, in a blended way, available to folks. BTW, even a primitive version I tried years ago ran pretty well. *
That kind of puts the cabosh on your Mr MAP, nonsense.

As far as the 32 or 6E (3rd Gen V8 MAF codes) code goes they also don't bother using the IAT/MAT in correlation with the timing, which is a disadvantage. Again, another shortcoming of the stock MAF code.

 

Only if you ignore the timing end of things, make much in the way of any changes, and the timing still needs redone.

True.

I've set to see one of the screwdriver adjustable ones allow for getting the timing corrrect, so again one still needs to do PROM work.

They use **BOTH**. You can run the OBDII in MAP only mode, by flipping a *switch* in the code (Using Tunercat).

 

Scot Sea, has posted about it. I beleive it's in the PROM Board here.

Oh, and one other issue is reversion, which depending on intake tract design can foul up the air flow reading, since a MAF can read air going in either direction. And at Turbobuicks.com some time ago there was a posting showing the air flow error of a stock TR MAF.

Shall, we also mention how a vacuum leak like the PCV or Brake Booster also introduce errors into the MAF readings since both or none metered air sources?. And how does one allow for more of an error as the rings go, and introduce even more of an error?.

Again, both have their strong points and it'll take a blending of them, to really get things right.

Just as a FWIW, I've run MAF, MAF with some MAP compensation, and MAP, all with the same base code, and can state things from a matter of experience, about how the 3 systems work.

 

So, did DF get his answer? It appears that he's had several. The information is all there, and he can decide. The rest of the opinion can only add confusion.

Thanks for the clarity, Grump!