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8.000 km with the new gear and it works great so far. The results are good, I've never exceeding 3 l/100 km although driving sometimes a bit faster or with traffic jam. The gain is about 7,5% but I still have to calibrate accurately my flowmeter to measure it. The problem is that the calibration factors of the 2 flowmeters are not the same strangely. The flow was counting down with the same factors, I'll do the bucket test for the return line and then calibrate the supply line according to volume at gas station over several fillups. 7,5% is about 60% of the gearing change (12,7%) which is what I expected.
Performance in 5th gear is of course worse. I did a max speed test and recorded the data on a GPS (attached file). The graph shows speed, altitude (left scale) and grade (right scale). The red line is 0% grade. It's a good road to test max speed because it's reached quicker with a downhill before a flat part. The max speed is averaged between the 2 marks.
Average speed : 144,54 km/h
Average grade : -0,23%
Air density : 1,223
Wind : <5 km/h tailwind
Calculated max speed with 0% grade and 1,204 density is 143,5 km/h at 3420 rpm (32,6 hp).
Another thing is that the gearing is bigger than expected because of the tire circumference. I always took the theoretical figure which is smaller than measured.
1710 mm for a half-used 155/70 R13 (approx. 1740 for a new one) which puts my 5th gear exactly at 42 km/h per 1000 rpm.
I mounted the 145/80 R14 tires (with inner tubes because of poor sealing). They are 1870 mm big which makes an expected 7,4% increase. I tested them yesterday about 20 km and it's not that great:
-They are not well balanced, the car shakes pretty bad from 105 km/h on.
-Bad cornering stability maybe due to the high 80 ratio.
-Gearing might me too big. I have now nearly 46 km/h per 1000 rpm, even though I coundn't test the max speed due to the shaking, I had a hard time reaching 120 km/h.
I'll test them on my daily commute and the conditions to keep them is to be able to pass all "hills" (which are never steeper than 4%) in 5th gear and of course to have better FE.
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