mass air vs. speed density

1fastsn95 · Aug 28, 2006

Ok, I got this bone stock 87 LX Im wanting to put a cam in. Not so much for power, but for the sound! Nothing sounds better than a cammed 5.0! Anyway, can anyone tell me "why" i have to convert to M/A to do this. What would happen if I didnt convert to M/A?? Also, what is the cheapest, most economical way of converting to M/A?? Thanks guys!! Chris

Mustang5L5 · Aug 28, 2006

Because Speed Density takes vacuum readings to determine how much fuel to inject. The cam messes with the vacuum and the computer basically can't figure out how to run the car.

Cheapest way to convert

Ebay
stock MAF
Stock rubber intake tubes (there are 2)
A9L (5-spd) or A9P (AOD)computer
IST Mass Air Conversion Harness
http://www.mass-air.com/Products.htm

Of course you could go for a larger aftermarket MAF or a CAI of some sort, but that should get you started. If you don't have factory CC, you'll need a VSS setup as well

Lang · Aug 28, 2006

you can change cams AND stay speed density...i'm sticking with sd cuz it's cheaper, simpler for my simple mind, and is quicker on a less heavily modded car cuz no maf restriction an more aggressive computer...here's a link on SP cam options; http://www.50tech.com/viewtopic.php?t=50694
rock on

1fastsn95 · Aug 28, 2006

ok what is cai, and vss?? I dont have cruise, and its aod. thanks

795.0pacecar · Aug 28, 2006

Lang said:
you can change cams AND stay speed density...i'm sticking with sd cuz it's cheaper, simpler for my simple mind, and is quicker on a less heavily modded car cuz no maf restriction an more aggressive computer...here's a link on SP cam options; http://www.50tech.com/viewtopic.php?t=50694
rock on

This may be true on a stock engine but not on anything the least bit modified. I doubt my 80mm pro-m presents any kind of restriction considering that after converting to mass air my car's throttle responce is better and it feels a bit more powerful. If the SD computer is more agressive it is only by a very small margin and most likely unnoticable. Mass air has much greater accuracy in metering air intake and thus is much more accurate in providing the correct amount of fuel to the engine.

CAI = cold air intake, VSS = vehicle speed sensor. From what I've read you need a VSS with manual transmissions so the engine wont die on decell.

1fastsn95 · Aug 28, 2006

Duh! on my part! I shoulda known what CAI was haha. But Ive never even heard of VSS! Looks like I need to make the swap though. Will the A9P comp swap right in? Is this a factory computer from a M/A car? Thanks again! Chris

65ShelbyClone · Aug 28, 2006

Yes, the A9L is from a manual trans mass air '88-93 5.0 HO. The A9P is from an automatic. Doesn't seem to matter which you get.

795.0pacecar said:
Mass air has much greater accuracy in metering air intake and thus is much more accurate in providing the correct amount of fuel to the engine.

I don't know that I would call it more accurate, but perhaps more flexible. The temperature compensation is better and it can accommodate changes in airflow better. On the other hand, SD is more involved tuning-wise, but IMO equally capable. Now that I know how much less difficult chipping an EEC-IV is that I first thought, I wouldn't be afraid of going with a radical SD EEC setup.

795.0pacecar · Aug 28, 2006

Without tuning mass air is superior. I have seen the tables and how SD and MAF calculates air flow, mass air is much more accurate.

canesstangnitro · Aug 28, 2006

I am doing a conversion on my car right now

The mass air is going to help you a lot on performance over the speed density. I have the same car you have. red, 87' lx no cruise and speed density and I am converting my car right now too. I bought my conversion kit from a guy on ebay and got it cheaper. you can buy the conversion kits from summit and pay like 540 for the kit. I got my kit for 300. you are going to have a red, black, brown, and blue wires. you have to run them to the new computer. Also, we dont have cruise control so we have to get the speed sensor, electrical connector, and a speedometer cable. your computer will not work w/o these 3 things. you will also need to splice 3 additional wires in pin 19, 3, and 6 on the computer. they run to the fuel pump and speed sensor. you can buy the speed sensor, electrical connector, and speedometer cable as a separate package from ford or interactive systems & technologies. (706)-692-2018. I hope this helps you on your conversion

795.0pacecar · Aug 28, 2006

If you get the FMS conversion harness like I did it makes everything 100x easier. It took me no more than 10-15 minutes to convert to mass air.

This is what I have.
http://img.photobucket.com/albums/v625/Steve79stang/PICT0238.jpg

mattmcdan · Aug 29, 2006

795.0pacecar said:
If you get the FMS conversion harness like I did it makes everything 100x easier. It took me no more than 10-15 minutes to convert to mass air.

This is what I have.
http://img.photobucket.com/albums/v625/Steve79stang/PICT0238.jpg

I have the same kit he has, It was hassle free and works perfect.

795.0pacecar · Aug 29, 2006

Well I didn't get the kit. I bought the harness off a guy in the mustang club. I sourced my own mass air meter and computer.

Pro Mod · Aug 29, 2006

My car didn't have cruise or VSS... when I converted I didn't mess with the VSS and it ran/idled just fine. I did hook up the fuel pump monitor wire, and switch around the 2 wires in the main harness plug in though. I used the piggyback harness from Pro-M/IST. It worked like a champ. I also used an AOD EEC (can't remember my calibration code though). No problems with the car at all.

Having said that, if I had it to do all over again, I would have just chipped the Speed Density. The only problem with that, is that anytime you do a major mod you must re-chip it. Mass-Air grows with your combo much better. But with all the pros/cons, I wish I would have stayed with Speed Density and got it dyno tuned.

1fastsn95 · Aug 30, 2006

I appreciate all the help guys!

cj99 · Aug 30, 2006

i need help too. MAP sensor

I need help too please, i have a 86 GT that has been MAF converted. and the car has been down for a year, and i just got the engine back in it and running..sound great, but i have not drove it yet, still doing odd's and ends to it. here is the question i see what looks like a MAP sensor, and it looks like it is hooked up, but there is no vacuum line going to it. I dont remember if i took this off or not ? the car starts good. but i dont know if it was taken off for the MAF convertion ? or if i did it. should i hook this up to a vacuum line or not ? anyone know if there's is hooked up ?
thanks
chad
:SNSign:

cj99 · Aug 31, 2006

just trying to move tread to top again. still need help thanks

795.0pacecar · Aug 31, 2006

There should be no vacuum line going to the MAP sensor when you convert to MAF. When you converted, your map sensor became a Barometric pressure sensor.

cj99 · Aug 31, 2006

cool thanks, its just been so long i forgot if it was hooked up or not

mass air vs. speed density

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