Oh, what a night. On saturday evening we met with some friends at a club. Beer (I didn't drink), singing sailors' songs, shouting, dancing, partying. Got home as the eastern horizon was getting light. I put the Wife to bed, crawled into the car and went coastdown testing. I had a paraphrased version of the Beach Boys' Surfin' Safari in my head:
"Let's go coastin' down
Everybody's learning how
Come on and coast down with me
(come on and coast down with...)"
At 04:30 I was filled up and ready to start. Since the car was already "dressed up", this was the 'A' of 'A-B-A'. So 'B' is the standard car, as the factory made it (only tire pressure was 50psi instead of 36psi), while 'A' has:
- removed roof rails
- lower grille opening totally covered
- Kammback
- rear wheel skirts
- folded passenger side mirror
The air temperature during the 3 hours of testing was between 8-11*C (recorded every 15-45min.), humidity around 70%, pressure reduced to sea level about 1020 hPa. No wind. I estimate the car with me and a full tank, but without rear seats, weighs about 1550kg.The test track was a 4 lane (w/ median) road going east from the Warsaw city limit. Elevation about 100m. Unfortunately, central Poland is supposed to be as flat as a pancake, but pancakes have lumps, and this pancake was made on a crooked frying pan. As I found out during testing, the road slightly slopes down towards the west (river basin), giving a 20% difference between E and W runs
The test track has a 2km stretch between urban zones, with a speed limit of 100 km/h. At each end is a turnaround, a few hundred meters further intersections with lights. Since this is one of the most important transport routes, there are a lot of cars, trucks and busses. Sunday morning at 5am would be the best (and only) time to try to do tests here. Unfortunately, towards the end of testing there was more and more traffic, so I only did the bare minimum. On the last few passes I would have to wait up to 30 seconds to turn around, and then wait on the side for a hole in traffic to allow me to not get in the way, and vice versa. On a few occasions a passing car or truck may have effected the trial
First I did the 'A' coastdown with a webcam aimed at the GPS.
Instead of fooling around with recording each run separately, I left it on while turning around. Six passes (3 in each direction) took about 17-18 minutes. I have yet to go through the data for coast downs, so I'll post that later.
After coasting I did cruise control. I set the CC to the right speed using the GPS instead of the speedometer. I did two passes at 70 km/h (one in each direction) and four passes at 100 km/h. I'd turn the CC on earlier so that it stablizes and reset the fuel gauge at the beginning of the 2km test track. I know that my built in gauge is a little low compared to at-the-pump calculations (about 0.5 l/100km), but until I get a SGII this is the best I have.
Next I took off all of the mods, put the roof rails on, opened the side mirror and did coast downs and CC for 'B' data, then put everything back on and did another round of CC testing. By now it was 07:00 and too much traffic for coastdowns. Because of traffic and time constraints I had to resign from testing each mod individually
Note The first 100km/h pass is missing b/c I had trouble setting the CC.
Here is the raw CC data in l/100km:
Speed(km/h) W E
A:
| Speed(km/h) | W | E |
| 100 | --- | 4.6 |
| 100 | 4.2 | 4.3 |
| 70 | 2.4 | 3.1 |
B:
| Speed(km/h) | W | E |
| 100 | 4.2 | 4.9 |
| 100 | 4.0 | 4.8 |
| 70 | 2.7 | 3.3 |
A:
| Speed(km/h) | W | E |
| 100 | 3.6 | 4.4 |
| 100 | 3.6 | 4.6 |
| 70 | 2.6 | 3.1 |
| Average@100km/h | W | E | Both |
| A | 3.8 | 4.5 | 4.15 |
| B | 4.1 | 4.85 | 4.5 |
| Average@70km/h | W | E | Both |
| A | 2.5 | 3.1 | 2.8 |
| B | 2.7 | 3.3 | 3.0 |
So removing the roof rails, folding one mirror, adding a grille block, Kammback and rear skirts improved FE by just under 7% @70km/h and under 8% @100km/h. This is less than I was hoping for (at least 10%). Maybe I'd get better numbers if the test track was flatter, with less traffic, and if the fuel instrumentation was more reliable. I also would have liked to make more passes, but traffic was increasing with every minute.
I didn't use my LED DRL's in the test, since when I started the test it was too dark for them and I decided to keep the normal lights for the whole test.
During the runs I had the radio off, but when taking off/putting on mods I listened to music.
On the way home I filled up again. I used 6.5 liters of diesel, the total distance was 130-140km between 04:00 and 07:30. On the way home, the night finally caught up with me, I started feeling sleepy, but it wasn't bad enough to effect my driving.