lower final drive mod - no difference in MPG

[night9]

Next step Areo mods???? It would be useful to take advantage of the new gearing.

[ever_green]

yes I did use gps. I do have a baseline but I ignored it because its hard to get same variables as wind down/up-hill grade, pavement type, tire pressure and other factors. I havent made a new chart for cruising mpg yet though to compare against baseline. still I dont see how that matters if my mileage for past 2000km has been very very close to before. I even tried a lot of pulse and glides on this tank to no avail. I almost completely avoid engine loads below 60% now with pulse and glide as there is no more cruising. but exactly thr same mileage (pulls hair out).

one thing I noticed is now it takes longer to pulse due to lower rpm. I spend most of my time below 2000rpm now.

[RedDevil]

If you are at 10% higher load for 12% lower revs you apparently gained 2% already plus whatever the higher efficiency at higher load may bring.
I would be surprised if it brought you more than 5% net gain. And that's just cruising at speed. It will not affect city driving at all.
If you spend 80% of your miles in the city, you'd get just a 1% gain all over.

The effect may get bigger if you reduce air resistance or highway speed, as then the load decreases and will be ineffective in the OEM setup.

The higher load also means less need for and less effect from P&G.

Colder weather will have a big effect. Is it colder in Toronto now than when you used the OEM setup? That's the likely answer then.

[HypermilerAX]

If he's at 10% higher load with 12% less revs, it means that the conditions were not the same.
Power = torque*rpm so if you lower rpm by 12% you will necessarily increase torque by 12% to have the same power. With a higher gearing, you only gain with the second thing you mentioned: efficiency.

My 2 re-gearing experiences showed that MPG gain is about 55% of the gearing change (based on averagely geared cars, not too high nor too low originally). This is valid at cruise speed in final gear. 10% would translate to about 5.5% gain. But when driving always in 5th gear. Try to estimate how much you use the last gear in regards to the total distance.

[jedi_sol]

It's October, perhaps gas switched over to Winter blend...hence any gains in lowered gearing was lost due to the swtich in gas formulas?

[ever_green]

maybe, but my winter gas mileage is much worst than this. its not cold here about 20 celcius. the thing I love about this mod is that I can drive to work and back without exceeding 2000rpm while keeping up with traffic.

[RedDevil]

Originally Posted by HypermilerAX

If he's at 10% higher load with 12% less revs, it means that the conditions were not the same.
Power = torque*rpm so if you lower rpm by 12% you will necessarily increase torque by 12% to have the same power. With a higher gearing, you only gain with the second thing you mentioned: efficiency.

Ah, no. One effect of lowering the revs is reducing the power needed to spin the engine. If the load goes up by just as much as the revs go down there is no gain.
It is obvious that you need less power to rotate the engine at a lower rpm. There should be a lesser load increase.
The better efficiency at higher loads makes up the rest.

Btw. the discrepancy between rev reduction and load increase is not 2% (as it might seem to be) as one cannot subtract addition and subtraction percentages from each other (I am at fault here for bringing them up).
Instead, multiply total values so 88% times 110% makes 96.8%.
Reducing the rpm means you need 3.2% less power to maintain the same speed.
Again, better FE at higher load means the total gain is bigger than that.

[ever_green]

some raw data I collected today vs. Baseline:

Cruising:

consumption---Speed---BASELINE
5.6L/100km 40mph
6.0L/100km 45mph
6.6L/100km 50mph
7/100km 55mph
7.2L/100km 60mph
7.4L/100km 65mph
7.6L/100km 70mph
8.0L/100km 75mph
8.3L/100km 80mph

consumption---Speed---CURRENT
5.2L/100km 40mph
5.8L/100km 45mph
6.4L/100km 50mph
6.8/100km 55mph
7.1L/100km 60mph
7.3L/100km 65mph
7.6L/100km 70mph
7.8L/100km 75mph
8.0L/100km 80mph

Acceleration:

In order of Worst TO Best:

CURRENT:
consumption---LOD------RPM
12.7L/100km....95% ....~3500rpm
12.3L/100km....100% ....~4000rpm
11.2L/100km....70% ....~2500rpm
11.0L/100km....95% ....~2500rpm
11/0L/100km....80% ....~2500rpm
10.7L/100km....80% ....~3000rpm
10.7L/100km....70%....~2500rpm
10L L/100km....60% ....~2000rpm

BASELINE:

Run....Load(%).....Shifts(RPM)...Consumption(L/100km)...Acceleration Time(s)...

A.........WOT.............5500RPM...........15.8L. 100km
B.......+90%.............3000rpm............13.3L/100km
C.........80%.............2300rpm............12.3L/100km
D.........60%.............1800rpm.............12.1 L/100km
E.........80%.............2300rpm.............12.0
F.........80%.............2500rpm............12L/100km
G.........90%.............3000RPM............11.9L/100km
H.........90%.............3000rpm.............11.9
I..........60%.............1800RPM............11.5 L/100km
J..........60%.............1800rpm.............11. 5


so lower final drive definitely helps. also looks like 60% load is still the king at 2000rpm...it's very difficult to do engine lugging with such short gears and I also don't want to damage the powerplant. Also there is not much torque below 2000rpm in this boxer oversquare engine:

http://ecomodder.com/wiki/images/d/d...-ej22-bsfc.png