Speed density is a form of controling the air/fuel mixture by pre-set codes in the computer. YOU CAN MANIPULATE THEM WITHOUT A CHIP!
Speed density was the first form of air management for the multiport EFI Mustangs. It was used into the 90's in trucks and non-H.O. 5.0's, such as Lincolns and T-Birds. For the Mustang, it was used in all 5.0's in 1986, 1987 and all 88's except for the ones sold in California.
All and all, you can do anything that you want to do to a speed density car except for a large cam. Speed density requires vacuum, at least 19 inch pounds. Stock 5.0L HO cam's advertised specs are 266°/266° duration, 0.444"/0.444" lift, Iskidarian makes a cam that works well that is 252°/257° duration and .465"/.480" lift. The reason why the cam works well is that the lobe center is 112°, good for vacuum.
I am currently running a speed density 1986 5.0 with a 65mm Accufab throttle body, a REAL Ford Cobra intake, GT40 Y heads, the cam listed above, equal length headers, a custom X-Pipe and Dynomax Ultra Flow mufflers. My fuel system is a Walboro 155 lph pump, an Accufab adjustible fuel preasure regulator and FRPP 24 pound injectors.
The trick to running speed density is to have a cam the produces enough vacuum, and to adjust the fuel and air flow correctly. As you increase the air, you will have to increase the fuel in equal ratios to stay within the factory programming. Some will tell you that this is not possible, but it is. The best thing to do is to work with a shop that has a dyno and can read air/fuel exhaust ratios. I daily drove my 86 with this combo for over 50,000 miles without issue.
thanks go out to
Twister for this great write-up[sm=smiley20.gif]
speed density info
