EFI...speed density VS mass air

[MandarinaRacing]

I really don't know much about EFI, this I know because of the little 5.0 knowledge I have. From what I've read mass air systems are way better than speed density because the mass air meter takes actual readings from the ambient air, rather than have a fixed parameter, like speed density. My question is how come all modern cars don't use this system????
Is mass air really better? How come Nissan cars have it and Hondas don't ?
Hopefully some of you can help me to clarify this...

Alex

 

[Anonymous]

Odd, isn't it. Import guy with mass air converts to speed density. Domestic guy converts from speed density to mass air. Bikes rolling with Alpha-N. They are all just different ways to do different things. I wouldn't say one is better than another. Mass Air seems a bit expensive and alpha-n isn't very good at part throttle (and requires a change for even tiny things that even a speed density can take in stride).

Anyone know of an aftermarket fully adjustable mass air system (for any vehicle)?


-=Whittey=-

 

[CobraSix]

Holley 950 system is Mass Air.

Mass air is generally considered better. Most cars I've seen in production now use Mass Air. Why would someone want to go from Mass Air to Speed Density? Speed Density is easier to tinker with as it uses a set ratio of engine RPM vs. MAP to determine how much air is in there. Very easy to change those parameters. The only real thing you can fool with Mass Air is by changing the size of the MAF (mass air flow meter).

But I also think people change just so they sound like they know something and did something. If I have MA and I tell my buddies I switched to SD, then I have something they don't (better or worse) and they wonder if I know something they don't. It's about the grass on the other side of the mountain.

Personally, MA is the only way to do with EFI. So much more accurate.

Slade

 

[Anonymous]

The Holley Commander 950 is a Speed Density system (also selectable Alpha-N).


-=Whittey=-

 

[Anonymous]

AFAIK, Speed Density uses MAP (Manifold Air Pressure), MAT (Manifold Air Tempature), TPS (Throttle Position Sensor), and BAP (Barometric Air Pressure) to calculate required fuel, and then uses rpm to determine when, and how often to inject.
With factory systems (both SD and Mass Air) there is not a whole lot the average individual can do with either of them, aftermarket is another matter.

I personally, am going to build and install the MegaSquirt sytem (Speed Density), as I have read that several people have gotten really impressive fuel mileage gains, even though that was not what they were tuning for.
More Power, smoother running, and better mileage, sounds good to me (plus a new toy to play with).

 

[CobraSix]

Opps...yeah, sorry about that.

Slade

 

[rbohm]

AFAIK, Speed Density uses MAP (Manifold Air Pressure), MAT (Manifold Air Tempature), TPS (Throttle Position Sensor), and BAP (Barometric Air Pressure) to calculate required fuel, and then uses rpm to determine when, and how often to inject.
With factory systems (both SD and Mass Air) there is not a whole lot the average individual can do with either of them

8) the speed density system does not use a bap sensor. the mass are system however does use a bap sensor. the reason is that the speed density does not need to know the outside air pressure to calculate a/f ratios like the mass air system does. mass air needs to know the barometric air pressure, so it knows how much air is actually passing over the sensor wire, not just the speed of the air. both systems can be modified to a fair extent, a lot of 5.0 guys were running in the 10's with stock computers. if you add efi, but plan constant mods, then mass air is best to use as it is adaptable to modding the engine with out reprogramming the computer on a regular basis. on the other hand speed density is a very good system for an engine that isnt modified after the system is installed, or modded very little.

 

[MandarinaRacing]

2 things:

1. How come almost all of the 5.0 guys(86-88 ) switch to MA ? As far as I know it's not cheap. Also almost all of them say that you can't really modify an engine that uses speed density, and expect it to perform well. Are we talking basic bolt-ons or complete build ups??? (heads-intake-cam, etc)

2.Honda guys install turbos on their speed density equipped engines....almost all Honda diehards say that what makes the engines soo great is the technology (VTEC)......is speed density considered technology, has it been upgraded since it's introduction so that it would be at par with mass air...Am I missing something???

So this brings me to ask.....If you were to supercharge/nitrous inject/turbocharge an EFI car, what would you rather have....speed density or mass air ?????? How come the Honda freaks get away with it, while the 5.0 crowd would cringe ??????

Alex

 

[MustangSix]

Mustang guys have always switched to mass air because the EEC IV was so hard to change. There are devices now that allow you to alter code and the code has been hacked so its more understood now.

Either one, as long as it's tunable, but for a turbo, I'd probably pick SD. No air meter to have to place, so I can put the filter and intake anywhere with no restrictions in the inlet tract.

 

[Anonymous]

Personally I like the MAF better that Speed density. Speed density is easier to tune but MAF WILL work better if its tuned right. MAF will also adjust better to altitude, temp, and Baro changes. Naturally asperated both systems work good, but when you add boost to the system I would DEFINATLY want MAF setup (reason for me going with 96' f150 computer/wiring harness for my supercharger) as its more effient since it KNOW how much air is entering the system and NOT guessing like speed density does. With either system its only gunna work as well as the tune is, garbage in = garbage out (but a MAF will work better with garbage as the EEC is adaptive)