I have heard various opinions and factoids regarding MAF vs. SD. Basically MAF is more adaptable, and fine but SD is better for heavily modified engines.

What are all the differences?

 

This always turns into a stupid flame war filled with a bunch of opinions...
I think MAF cars run just fine. Theres a bunch of very fast MAF cars out there, MAF restriction and all. None of the SD guys have been able to explain that one away, all they do is cry how much faster it would be with SD but none of those guys are running the numbers anyway.
SD cars are easier to tune, I think. The tables make more sense and theres more tuning range available. Seems that 99% of the time, the SD cars run faster. I'd say thats because on a MAF car you might have 500 points of fuel and timing adjustment, and on a SD car you have 1000. Thats just a wild guess number thrown out there but there is more range to adjust a SD car to where it needs to be. Just take a look at the MAF scalar tables and tell me it has alot of range... I think not.

Does it matter? I dont think so. Neither system fires the injectors at the right time anyway, so while the SD guys are screaming about accuracy of fuel tuning, the fuel is sitting at the back of the hot intake valve cooking into a vapor and traveling back up the siamesed (or not) intake and jumping into other cylinders. At least those are the stories I keep hearing...

And to answer the questions about the differences:
MAF runs a MAF (mass air flow) in the air intake to measure the amount of incoming air directly (assumably)
MAP runs a MAP sensor (manifold air pressure) to calculate the amount of incoming air indirectly.
Other than that, there are nuances that arent worth talking about IMO.

 

On another recent post I also read that another reason SD thirdgens are faster than MAF cars (stock VS stock) is that the SD cars came with a better cam. I believe the SD guys are the ones that say they can take LT1 cars w/ very few mods.

 

Bah. L98 cars have basically the same cam. If you are comparing 305 autos, I'd understand but the rest the cams are pretty close, not different enough to make a considerable difference in power. Read around about power gains from removing the roadblock the stock MAF causes. Thats where it is, IMO.

 

I'm not inclined to argue with anyone, just wanna show you where I got the info so I don't look like an @ss.

MAF vs. SD Thread

 

Well, he used to have cam as a reason, but he edited it.

 

You're confusing me here. You say SD is faster than MAF (stock to stock) because you remove the roadblock the stock MAF causes but you say that SD guys are full of BS because they say the car would be faster (even though it is already fast) if the MAF were removed. You don't have to explain it and the last thing I want is to turn this into a flame war. I just wanted to point that out.

But back to the question of the differences. A MAF is a device that uses heated wires that are cooled by air flowing across it. The wires are to be kept at a certain temperature and the ecm applies more power to the wires as the higher airflow keeps them cooler. This is how it measures air flow, by the amount of power being applied to the heated wires. To a certain extent, air flow is air flow so the MAF is more "forgiving".

SD uses the MAP sensor to know the pressure in the manifold to make a calculation to arrive at how much air is in the cylinder. The ecm uses a volumetric efficiency table to look up a number expressed in % at a certain RPM VS MAP. The VE number is constant in the prom unless you change it by prom burning. So if you make a change to the engine that changes it's VE, you need to change the VE tables.

This is oversimplfying the operation but should give some insight. Now, why would I use a 730 SD system over a 165 MAF system is easy. First is of course the fact that MAF is a restriction and a hinderence. No matter what you at least have to make plumbing for it. Two is that the 730 ecm is a better choice since it is more adaptable and has closer ties to other ecms. See, the 730 has been used with MAF or SD, it is also available in a weatherproof package (727), and is a close relative of the SyTy ecm (749) which can handle boost. Oh yeah, and you can find them everywhere so spares are cheap. One other thing is that the 730 has more space available on the PROM for adding custom code. Oh, and the ALDL always works at 8192 baud which is a minor perk, but a perk nonetheless. The ESC module is inside the memcal so less wires outside for a cleaner look. The 730 has fuel correction for air temp, though no spark correction. I'm sure there are other things but they elude me at the moment. Of course if all you want is just a nice stock performing engine, either will do.

 

Dont mean to start up a flame war here...just curious on the differences exactly.

Basically the TPI will be swapped over to my Monte Carlo LS, using the LG4(yea I know, but it has 95k and runs like it has 40k), no smoking even on start up, no leaking, runs perfect. No need to use the LB9 motor with over 200k .

Either way Id use MAF since thats what car Im using, plus I dont feel like incorperatiing VATS if I dont have to, and like mentioned above, MAF is more *forgiving*. I will be doing some minor mods, but nothing severe, as long as Im using a 305 anyways. K&N, Hooker headers/Hooker catback exhaust (should be at 190hp/290ft lbs of torque I think) and then Ill learn more on the MAF TPI mods .

 

Actually, if you look at the cam tech article, you'll see the 88-89 MAF cars have the better cam. 88-89 cams have more duration and very slightly more lift.

 

Yea I see what you are saying, so let me rephrase:
What I said (or meant to anyway ), was SD guys were saying these fast MAF cars would be ALOT faster (I think they were thinking on the order of .5 sec or more, from the numbers I saw thrown around) with SD swapped in. (Side note: I find it funny that the same person who some of those guys were really thrashing on hardcore were using his numbers as evidence to support their claims, even though they thought his car and the numbers they ran were a joke... but thats a different subject.) I've also never seen that to be the case. Thats also based on the assumption that the MAF cars were running stock MAFs with screens and fins intact, which are things all the faster MAF cars I know of do not have. As for stock form, yea the SD cars are faster. They have better programming from the factory, and there arent screens (remember those Torque Plus or whatever intake gaskets with screens in the ports?) and fins in the intake tract. Seems to me the SD cars run around .2 faster in stock form, thereabouts. I think that might be the most you'd ever see swapping from one to the other as well, which IMO isnt worth the effort unless you just gotta have it and you dont have traction issues. Also, unless I am mistaken, I dont think I have seen a direct comparison of a well tuned MAF car that has a seriously modified MAF sensor swapped over to SD.

Anyway, thats what I meant to say. Sorry for the confusion.

 

Exactly how much harder is it to tune an MAF car? I'm about to get into PROM burning and I'm trying to do everything right the first time. I don't wanna have to relearn everything if I decide some time later that I want to change to SD. Please help.

 

The MAF isn't a "Road block" in a stock engine, the MAF will still flow more air than the engine will ever need. All the F bodies varied in how quick they were even within the same year/engine combos. It is the beauty of assembly lines and wide tolerances in mfg.

 

Could I swap my MAF to SD in my 88 L98 GTA and how hard would it be and what would I need to do...AARON

 

MAF is not too bad to tune.. Its better than a 730 in a blown application, not really better for a N/A application.. The argument can swing both ways, however. One could say that truely measuring the incoming air via a MAF sensor is better than calculating load based on vaccume. Its all a matter of preference.
I've never heard of someone switching either way and gaining anything like .5 though.

Converting it is outlined in the tech area. Go read if thats what you want.

I like to use the "boost" scenario because the only good examples of speed density tuning under boost, have _NOT_ been on the 730, its been on the 749 (grand national, TTA, etc) or variant.

-- Joe

 

The 749 is a 730 with two extra drivers: an extra injector driver and a boost solenoid driver. Going from a 165 to a 749 is just as easy as going to a 730, save for some repinning. What you are trying to do is get rid of the MAF and the ecm's ability to only see 255 grams per second of airflow. The GN and TTA used a 148 ecm, not the 749 which is SY/TY, and also have a 255 g/s airflow limit. The difference is substantial but of importance is the fact that one is DIS so GN guys can't just swap to another ecm like say the 749 as they have no distributor and have no place for it with where the TB is. Maybe with a different manifold. This is most likely why a MAF translator is so popular with these cars. 3rd gen cars have an easy option, swapping to a 730 and a 749 for boost.

As a side note, 255 g/s is roughly about 375 HP. So if you are pushing over that the option you have is to add fuel in the WOT RPM fuel adder table. So while the table may normally add 20% fuel at 255 g/s and under, it'll have to be programmed to add over that % because it can't see any more than 255 or it will go lean. However, under boost and without a FMU, you'll be adding a lot of fuel over that. So PROM burning would be a good idea and a WBo2 would be even better, just to make sure the engine is always in a safe range.

 

Like Ive said before, there is a reason GM went back to MAF after only 3 years, and u dont see the LT1's/LS1's having problems making power. And maf actually measures the amount of air coming in and adjusts the a/f, sd just makes a bunch of assumptions based on rpm/mph, it doesnt know **** compared to maf. Someone correct me if im wrong but this is the way i have been told.

 

MAF doesn't measure the amount of air coming in and sd doesn't make any assumptions. If you look up a few posts you'll see the math the ecm does to convert the MAF output to what it thinks the airflow is. SD also does some math to get the airflow numbers. And BTW, LT1/LS1 cars use a MAP sensor (what the sd uses) to check the MAF readings. If it determeines the MAF is off it reverts to SD. I don't want this to turn into a flame war but you wanted to be corrected. Don't take my word for it or anyone elses. Find a way to read some service manuals or anything you can about the subject.

 

I have an 85 camaro with a 165 ecm (maf) It was originally an 870 ecm and I can vouche for an improvement in the swap by butt dyno measurements, and the additional bonus of it being a more supported ecm for tunability only lead to further iprovements. I have a gtech and assuming my package gets here friday as scheduled I'll be finishing a swap to the 730.

Granted Its been done before (mike davis himself) but I'll as well post before and after changes, because I'm going to be doing this on a gtech and thats food for flamewar in itself im not even going to bother posting the ET, but simply the difference in times, and mph. It initially wont be a fair comparison because my 165 is well tuned and the 730 will be very rough, but over a weeks time of tuning I'll run it again and see what changed.

 

Yeah, GM went back to using a MAF and a MAP so it could have the best of both worlds. Both systems alone have their flaws.

And SD doesn't make any assumptions Everything it does is simple math grounded in real physics, which is why it has earned the reputation of being more tuneable.

The tunability issue is where the idea of assumptions would surface in my mind. You'd think a system that directly measures airflow would be pretty straight forward to work on, but somehow it isn't. Thats because the ECM has to make assumptions based on different MAF readings and RPMs to figure out what the MAF reading really means. If the MAF really did a decent job of measuring airflow, there wouldn't be a need to ever tune a MAF ECM, at least for fuel anyway. Thing is, MAF basically sucks at measuring airflow, so you need the MAF scalar tables to make sense of it. Whereas SD uses simple physics to compute airflow, MAF uses voodoo to change a 'measurement' into a useable number.

 

Read this for more info:
https://www.thirdgen.org/techbb2/sho...threadid=38449

 

Your right I did want to be corrected, I havent looked too much into maf vs. sd cause my maf is workin fine for me right now, I was just going by what my friend who has owned a few third gens has said.