Justin_Bradley

What's the difference? I know that pre-'89 ('88 California) was speed density. But like what purpose do each of them serve? Is the MAF just a better way to get done what the Speed Density did before it, or do they each do something completely different?

Predator

I am sure other people will give you the big long posts about what the difference is, but basically, air (speed?) density is based off of a few variables (I think engine rev, angle of accelerator and maybe something else) to determine how much air SHOULD BE GOING TO ENGINE. This makes it really suck when it comes to modifying, because it just does (other people will most likely explain why).

MAF cars measure the amount of air comming in and adjust the mixture of air and fuel to this. It is many times more accurate, and when it comes to modifying an engine, MAF is the way to go. From what I remember about other threads, the MAF uses electricity to heat a wire at a constant temp; and based on how much electricity it needs to put into that wire to keep it at that temp, the computer measures how much air is going to the engine.

In short

Air density = lame for modification

MAF = adaptable, so mods work better

roundman

speed density control uses all the various engine mounted sensors to "estimate" the air flowing into the engine and the ECU is programmed for the stock cam and injectors only so they don't allow any major mods without runnablility problems.
the mass air system replaced speed density as it is much more accurate as it actually measures the air flow entering the engine and is not guessing based on the sensors. this system uses a different ECU and is much more adaptable to major mods like cam changes and heads, etc. the only drawback to mass air sytems is that the mass air flowmeter (MAF) puts some restriction in the air flow in order to measure the air entering the engine but this is easily taken care of by upgrading to a larger diameter MAF when you make mods.

Justin_Bradley

So both are just ways of getting the air/fuel mixture right?

Tims 88GT

yep, also the 88 Cali car was mass air and anyother mustang was not it was only cali car, and it worked really well so from then on they were all mass air. sd tends to bitch at you a little when tuning a little rich or a little lean it seams never to be right, but it worked ok for me.

Justin_Bradley

What? LOL I don't understand what you are saying...

roundman

Yes but the mass air system is much more accurate since it is actually measuring the intake air flow into the engine and the ECU can be more easily modified with a tunable chip to allow changes for mods like bigger lift, more duration cams, etc. while the speed density system is not nearly as flexible when it comes to trying to tune it to match up with non-stock mods. the mass air system also utilizes an inlet air temp sensor which the speed density system does not which makes it just that much more tunable internally in the ECU to respond to changes in engine demand as you drive down the road.

Tims 88GT

justin, sd is not as easy to tune, thats y i said it can be a bitch, i think it only worked ok for me is because my cam is not really really radical.

Scottsat

I have speed density in my Capri 5.0, I always understood that I can make external mods to increase HP (bigger throttle body, Phenum(spelling???) spacer, removal airbox, etc) but nothing internal like Cam, etc.

I have heard the MASS type is much better though, that is why along with better heads(truck) they made the change in '87

later and good luck,