I am sick of mis-information, here is the truth of Speed Density cars!
2nd Gear Member
Joined: May 2006
Posts: 329
From: Dallas
RE: I am sick of mis-information, here is the truth of Speed Density cars!
ORIGINAL: Twister
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.
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.
proves that any adjustment to fuel pressure (+/- 25%) will be corrected by the ECM. the o2s work to maintain a 14.64:1 a/f ratio. if you adjust the fuel pressure higher (up to 25%) than the ECM adjusts the pulsewidth of the injectors to compensate (it shortens the PW). alternately, if you lower the pressure the ECM lengthens the pulsewidth. on a dyno you might see gains after an adjustment, but only temporary gains, until the ECM realizes what you've done and adjusts accordingly.
Thread Starter
5th Gear Member
Joined: Jan 2006
Posts: 2,645
From: So-Cal
RE: I am sick of mis-information, here is the truth of Speed Density cars!
ORIGINAL: BCP
I ran an F cam in my 88 GT still SD, it ran great! SD definately rawks for mild setups.
I ran an F cam in my 88 GT still SD, it ran great! SD definately rawks for mild setups.
Thread Starter
5th Gear Member
Joined: Jan 2006
Posts: 2,645
From: So-Cal
RE: I am sick of mis-information, here is the truth of Speed Density cars!
ORIGINAL: TENGRAM
this ford issued document
proves that any adjustment to fuel pressure (+/- 25%) will be corrected by the ECM. the o2s work to maintain a 14.64:1 a/f ratio. if you adjust the fuel pressure higher (up to 25%) than the ECM adjusts the pulsewidth of the injectors to compensate (it shortens the PW). alternately, if you lower the pressure the ECM lengthens the pulsewidth. on a dyno you might see gains after an adjustment, but only temporary gains, until the ECM realizes what you've done and adjusts accordingly.
ORIGINAL: Twister
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.
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.
proves that any adjustment to fuel pressure (+/- 25%) will be corrected by the ECM. the o2s work to maintain a 14.64:1 a/f ratio. if you adjust the fuel pressure higher (up to 25%) than the ECM adjusts the pulsewidth of the injectors to compensate (it shortens the PW). alternately, if you lower the pressure the ECM lengthens the pulsewidth. on a dyno you might see gains after an adjustment, but only temporary gains, until the ECM realizes what you've done and adjusts accordingly.
2nd Gear Member
Joined: Jul 2006
Posts: 236
From: Prince Frederick, Maryland
RE: I am sick of mis-information, here is the truth of Speed Density cars!
ORIGINAL: Twister
what did you do about the vacuum? Alphabet cams usually don't idle well with speed density
ORIGINAL: BCP
I ran an F cam in my 88 GT still SD, it ran great! SD definately rawks for mild setups.
I ran an F cam in my 88 GT still SD, it ran great! SD definately rawks for mild setups.
the car went 12.30s with basically a cam and intake.
I ♥ Acer
Joined: Apr 2006
Posts: 5,116
From:
RE: I am sick of mis-information, here is the truth of Speed Density cars!
just 1 thing to your info.......let the speedo cable break and where will you be
ORIGINAL: Twister
OK, people on here do not seem to have a clue about speed density. 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.
OK, people on here do not seem to have a clue about speed density. 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.
Joined: Jul 2006
Posts: 31
From:
RE: I am sick of mis-information, here is the truth of Speed Density cars!
ORIGINAL: 2 kwik
just 1 thing to your info.......let the speedo cable break and where will you be
just 1 thing to your info.......let the speedo cable break and where will you be
Speed density refers to engine speed not car speed.
