Adam raised a really profound thought in the X-Flow Variances post this week. I thought I'd follow it up with some details.
Note: Wheels used a Stewarts Dyno, and it was fairly well calibrated. It was used for many yearas untill front drive cars started jumping off the rollers. Last test was 1981. The tests were corrected for temp and pressure, and the cars were tested at the Castlereagh Drag strip from the early days untill 1983 when it closed. The cars were always tested two up, with at least half a tank of gas, timed by the same Mike McCarthy for years and years.
March 1979 Wheels
Quarter mile with a 250 auto 4.1 XC without A/C was 18.6 seconds.
May or June 1979 Wheels
It was 18.5 seconds as an 4.1 XD with A/C. The fuel figure above was for an A/C XD.
The Alloy head XD gave 18.3 secs
The XE Alloy head gave 18.0 secs as a Ghia 2-bbl with another 116 kilos of 'fruit and veggey' options, and gave 22 mpg plus.
The dyno figures came from Wheels 1979, and the XC was dyno tuned as having 62.6 rwkw (84 rwhp) at the wheels, a loss of 1.46. Thats 123 hp down to 84 hp.
A TE Cortina 4.1 six, tested on the same dyno, same day, with a poor state of engine tune, gave only 57.0 rwkw (77 rwhp), and couldn't even break a 18.2second quarter!
The difference was power loss of 1.60. That's 123 hp down to 77 hp.
I went through the old issues of Street Machine and Wheels, and found that 1.26 was a common power loss from flywheel hp to rear wheel horsepower.
I saw another article from Wheels Feb 1980. In it, TE Cortina 2.0 4-speed, with a factory 9.2:1 86 hp 65 hp at the rear whhels, a loss of 1.31. It did 18.9 second quarters. See, the Falcon 250 could loose a lot more with an auto transmission . There clearly must have been huge torque converter slip.
This is a characteristic I find on all production Ford autos before 1991. The manual 250 Falcons did easy sub 18's. A good 1983 XE carb will do 17.6 seconds all day, while the 4.1 auto has it hard doing better than 18 seconds flat.
A badly tuned Cortina x-flow won't beat a well tuned manual Falcon x-flow.
Note: Wheels used a Stewarts Dyno, and it was fairly well calibrated. It was used for many yearas untill front drive cars started jumping off the rollers. Last test was 1981. The tests were corrected for temp and pressure, and the cars were tested at the Castlereagh Drag strip from the early days untill 1983 when it closed. The cars were always tested two up, with at least half a tank of gas, timed by the same Mike McCarthy for years and years.
March 1979 Wheels
Quarter mile with a 250 auto 4.1 XC without A/C was 18.6 seconds.
May or June 1979 Wheels
It was 18.5 seconds as an 4.1 XD with A/C. The fuel figure above was for an A/C XD.
The Alloy head XD gave 18.3 secs
The XE Alloy head gave 18.0 secs as a Ghia 2-bbl with another 116 kilos of 'fruit and veggey' options, and gave 22 mpg plus.
The dyno figures came from Wheels 1979, and the XC was dyno tuned as having 62.6 rwkw (84 rwhp) at the wheels, a loss of 1.46. Thats 123 hp down to 84 hp.
A TE Cortina 4.1 six, tested on the same dyno, same day, with a poor state of engine tune, gave only 57.0 rwkw (77 rwhp), and couldn't even break a 18.2second quarter!
The difference was power loss of 1.60. That's 123 hp down to 77 hp.
I went through the old issues of Street Machine and Wheels, and found that 1.26 was a common power loss from flywheel hp to rear wheel horsepower.
I saw another article from Wheels Feb 1980. In it, TE Cortina 2.0 4-speed, with a factory 9.2:1 86 hp 65 hp at the rear whhels, a loss of 1.31. It did 18.9 second quarters. See, the Falcon 250 could loose a lot more with an auto transmission . There clearly must have been huge torque converter slip.
This is a characteristic I find on all production Ford autos before 1991. The manual 250 Falcons did easy sub 18's. A good 1983 XE carb will do 17.6 seconds all day, while the 4.1 auto has it hard doing better than 18 seconds flat.
A badly tuned Cortina x-flow won't beat a well tuned manual Falcon x-flow.
