No Mass-Air or Speed Density?

go to a race track for a REAL race and lemme know how many cars running fuel injection are running a MAF

srtthis said:

go to a race track for a REAL race and lemme know how many cars running fuel injection are running a MAF

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THE TRUF! my eclipse is speed density, a maf is just another restriction and another thing to go wrong.

the old 87-88 speed density cars run hard as hell, when they are right.

Mr. Rustypwnz said:

THE TRUF! my eclipse is speed density, a maf is just another restriction and another thing to go wrong.

the old 87-88 speed density cars run hard as hell, when they are right.

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yup when i go to any type of power adder other then nitrous down the road im ditching the MAF set up and going to a BS3... if i just stick with nitrous in my personal car it will go carbed

As far as I'm concerned, speed density rocks! It made things a lot easier for me.

now not to change the subject any but , i read somewhere if you do mods to the car , the SD cant keep up with it , ie H/C/I , my car is an 88 an i converted to mass air , which is right ?

Speed density is just a way to tune your car that uses manifold pressure and some other variables like RPM, Air temp, load, etc... to determine how much fuel to inject into the cylinder. MAF is a more robust, but also more complicated system that actually measures and uses the amount of "mass air flow" to add the right amount of fuel. Speed density is more or less assuming how much air is entering the engine, and can be very wrong when the computer is not making the right "assumptions."

All that said, you can tune either system to work to perfection on a given car. You are referring to the stock systems. Other guys here are not. When you're close to stock, speed density cars, as stated, will require a retune every time you swap a part that changes the airflow of the engine at any RPM. That can be pretty expensive if you have to pay someone else for a tune. However, if you have your own tuning hardware/software. Tweecer, EEC-tuner, SCT, PMS, or an expensive standalone computer and harness like the guys here that are praising Speed Density, then you can make your own changes until you're happy with the way the car is running. I find that speed density cars are much less complicated to tune than MAF cars, because there are less variables and less confusing tables.

With an MAF car, you can do a lot of things without really needing to tune your car. Adding heads, and a cam would throw the speed density car's tune out of whack and it would require a retune. However, the MAF car will automatically "sense" the change in air-flow everywhere with it's MAF sensor, and it will adapt its tune accordingly. You don't need to do anything except to make sure that the system is working and the car is running right.

That probably makes you wonder why anyone would ever switch back to SD. I'm already talked about simplicity in tuning. Here are some other reasons:
1. MAFs are inherently a disturbance/restriction in the intake
2. MAFs, particularly on the older EEC IV that we run stock are limited in how much flow they can tell the computer is actually entering the engine. So for a high hp/air flow application that exceeds the limits of MAF/Computer, this can result in catastrophic detonation & failure of the engine
3. There is no such thing as "unmetered air" With speed density, you don't run the risk of a large vacuum leak resulting in a poor running engine, or worse - running lean enough to detonate. Speed density doesn't measure the air to determine how much fuel to inject so the tune won't be affected by the extra air that's getting into the motor. It measures MAP (pressure in the intake manifold) and will know that more air is getting into the motor. The MAF car thinks less air is getting in, and sprays an incorrect amount of fuel.

A major consideration here too is that SD systems on the aftermarket stand-alones are much more powerful systems than the stock EEC.

Anyway, to sum things up and kind of get to the pointOf the two stock ford systems, I definitely prefer the MAF with an A9L computer. It's a time-proven system that will meet the needs of 98% of the enthusiasts out there.

My 87 GT is SD and i run a supercharger making 10 psi,locked timing and a stage 2 Snow performance meth kit, car runs HARD,...Before the blower i ran the car last yr,its an GT convertible AOD car with 3.55's all the bolt ons I ran 14.4's with well LOL not knowing were my timing was...1st run out i heard pinging really bad Ran a 15.1 letting off about 1000 ft mark.. i had no way to time it just backed it down..ran 14.4 @ 95mph with a 2.0 60ft on street tires.Who knew where the timing was probably could have ran even better..I think the SD car runs great,,,cant wait to run it with the blower [10 psi] meth kit and the new Drag radials i have for it...see what she does....I was thinking of converting but hey it works so i will leave it alone....

blackened88lx said:

Haha. I forgot why I loved stangnet. "Speed density" is not a physical object that you can see in the intake. Its just a type of fuel injection. It uses just a map sensor rather than a mass air sensor. If there's no mass air then its a SD car.

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I love the feeling when my speed density kicks in. I have it wired to a RED button on my ratchet shifter.

1991notchbackLX said:

I love the feeling when my speed density kicks in. I have it wired to RED a button on my ratchet shifter.

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Damn, so now you have SD and VTEC? I bet if you hit both buttons its like a huge shot of naws.



MAF has it's downfalls for sure. SD does too but SD is still used today in most vehicles. For cammed EFI cars, MAF is better. I've known people with stand alone PCM's that have deleted the MAF and the O2 sensors and just run off a fuel map. Can be hit or miss and isn't emmissions friendly but it sure seems to work.