freddofrog
won 16.4k on Euro lottery :)
I found a book in the house of my (recently deceased) father (a Chartered Mech Eng).
It had a lot of info on the "coastdown" method for finding the coefficient of drag (Cd) and the coefficient of rolling-resistance (Ad + Bd)
I had an idea that maybe we could all try some tests on each of our Accords, and determine if there was a relationship between the coefficient of rolling-resistance and the mpg that we get.
To begin with, I collated the 7th gen data from the 7th gen ESM
DIMENSIONS CL7/CL9/CN1
Overall length 4665 mm
Overall width 1760 mm
Overall height 1445 mm
Wheel base 2680 mm
Track - Front 1515 mm
Track - Rear 1525 mm
DIMENSIONS CM1/CM2/CN2
Overall length 4750 mm
Overall width 1760 mm
Overall height 1470 mm
Wheelbase 2720 mm
Track - Front 1515 mm
Track - Rear 1530 mm
WEIGHT CL7/CL9
Curb weight - 5MT 1301−1418 kg
Curb weight - 6MT 1386−1450 kg
Curb weight - 5AT 1357−1483 kg
WEIGHT CN1
Curb weight 1463−1533 kg
WEIGHT CM1/CM2
Curb weight - 5MT 1462−1545 kg
Curb weight - 6MT 1508−1582 kg
Curb weight - 5AT 1494−1610 kg
WEIGHT CN2
Curb weight 1575−1647 kg
Using the above data for my car, I did some coastdown tests to get the Cd and (Ad + Bd) but I found it very difficult to get a consistent Cd .....which should not change at all, and since I didn't know what it should be, I decided to search online for the Cd values and I found some values on some sites.
for 7th gen saloon (e.g. CL9), the "claimed" Cd = 0.26 ....but wikipedia has an excellent list with a more believable 0.30 --> https://en.wikipedia.org/wiki/Automobile_drag_coefficient#Typical_drag_coefficients
for 7th gen Tourer (e.g. CM2), there was an "estimated" Cd = 0.34 ....I can get close to this in the tests using my car
By retesting several times, I have managed to get as low as Cd = 0.36, but with an alarmingly high value for (Ad + Bd = 0.22) , which may well account for the poor mpg that I get.
I don't have the time to go into this further at present, but I will add more, time permitting
edit:
brief explanation of coastdown here --> https://www.quora.com/What-is-coastdown-testing
It had a lot of info on the "coastdown" method for finding the coefficient of drag (Cd) and the coefficient of rolling-resistance (Ad + Bd)
I had an idea that maybe we could all try some tests on each of our Accords, and determine if there was a relationship between the coefficient of rolling-resistance and the mpg that we get.
To begin with, I collated the 7th gen data from the 7th gen ESM
DIMENSIONS CL7/CL9/CN1
Overall length 4665 mm
Overall width 1760 mm
Overall height 1445 mm
Wheel base 2680 mm
Track - Front 1515 mm
Track - Rear 1525 mm
DIMENSIONS CM1/CM2/CN2
Overall length 4750 mm
Overall width 1760 mm
Overall height 1470 mm
Wheelbase 2720 mm
Track - Front 1515 mm
Track - Rear 1530 mm
WEIGHT CL7/CL9
Curb weight - 5MT 1301−1418 kg
Curb weight - 6MT 1386−1450 kg
Curb weight - 5AT 1357−1483 kg
WEIGHT CN1
Curb weight 1463−1533 kg
WEIGHT CM1/CM2
Curb weight - 5MT 1462−1545 kg
Curb weight - 6MT 1508−1582 kg
Curb weight - 5AT 1494−1610 kg
WEIGHT CN2
Curb weight 1575−1647 kg
Using the above data for my car, I did some coastdown tests to get the Cd and (Ad + Bd) but I found it very difficult to get a consistent Cd .....which should not change at all, and since I didn't know what it should be, I decided to search online for the Cd values and I found some values on some sites.
for 7th gen saloon (e.g. CL9), the "claimed" Cd = 0.26 ....but wikipedia has an excellent list with a more believable 0.30 --> https://en.wikipedia.org/wiki/Automobile_drag_coefficient#Typical_drag_coefficients
for 7th gen Tourer (e.g. CM2), there was an "estimated" Cd = 0.34 ....I can get close to this in the tests using my car
By retesting several times, I have managed to get as low as Cd = 0.36, but with an alarmingly high value for (Ad + Bd = 0.22) , which may well account for the poor mpg that I get.
I don't have the time to go into this further at present, but I will add more, time permitting
edit:
brief explanation of coastdown here --> https://www.quora.com/What-is-coastdown-testing