This page is about getting the best fuel economy.
If you have some experience or know-how please let us know.
Admittedly, injector divider was never ment to be changed with running engine.
- theoretically the best fuel economy (for any RPM and load) can be reached with injector divider=1 , and no reason to switch to injector divider=2
- if there is a case (engine, conditions, RPM, load) where injector divider=2 results in lower fuel economy than what is reachable with injector divider=1, that should be investigated (and tuned so same fuel economy is reachable with divider=1).
- Beware: do NOT depend on the shown fuel consumption to compare these cases: because the actually injected fuel at low pulsewidth is known only approximately (the "injector opening" data is not sufficient for this), the shown fuel consumption is uncomparable for inj divider=1 and inj divider=2, so don't get cheated. (seperate calibration would be needed, which is lengthy process to get sufficiently precise for this comparison)
- Also note that injector divider=2 will not "skip every other injector output" just detune the good sequence (eg. useful when a factory harness has 2 injectors connected in parallel).
- skipping every other injection (could be done by tweaking injgroups: also not ment to be changed with running engine!) would likely make fuel economy worse (because of "charge robbing": charge injected to cyl1 but inhaled by cyl2) going wires pa (doing so would risk leaving an injector output activated
Volvo turbo 4 cyl. Sequential
Audi s2 5 cyl. Sequential
We did test the too cars by setting the injector settings to divider by 2 and it is actually working pretty good.
This function is only for cruising when the car is up to speed cores lack of power.
We need a strategy how to improve this function.
Did a lot of testing on this with a 5 cylinder Audi - 1.2.16. Program B is the same as A, except that the injector divider is 2. Currently, I activate the function with a switch.
Car stutters violently when I swap in low gears, but from 90-140 km/h in 5th and 6th, it actually works.
I wanted the car to switch back and forth on its own, but I end up getting into an endless loop.
Example: I want the car to turn off every other injection (change to program B) between 2500 and 4000 rpm. Changing one way is easy, but the problem is that I can't get it to change back from B to A because that would need two windows, i.e. idle to 2500 AND 4000 to 7000.
Would it be possible to move the output parameters away from the part that is specific to A and B, so that it would swap back as soon as the revs are NOT 2500 to 4000?
Or possibly thange the divider in response to outer conditions, so I wouldn't have to swap programs?
Another neat feature would be to let the output react on throttle movement. If the throttle is moved quickly, the program should always go back to A and run on all cylinders.
Cool thing is that the same cylinders aren't passive throughout (like on late model Audis that always switch off the same cylinders). It actually seems to turn cylinder 1 of every other time, making the sequence 12453124531 => 1X4X3X2X5X1
Won't run as smoothly as on the new cars with variable valves, but it works. Must run even better on a 6 or 8 cylinder car.
I am hoping to save 3-4 % fuel this way, reaching 800 km on one tank :-). As long as the car runs this way, consumption is 50-60 %. Not exactly 50 %, though, because you open the throttle a bit more (not sure about that) in response to the lack of power. Can't measure that well because lambda gets messed up from the fresh air that is pumped through by the "empty" cylinders.
eg. by Leaner mixture
Some methods can improve fuel economy, often by allowing leaner mixture (or allow engine built to higher compression):
- E85 fuel (70-85% Ethanol content)
- LPG (propane - buthane gas)
- EGR (exhaust gas recirculation
- Canister Evaporator Valve does not allow leaner mixture, but saves a few drops of fuel during summer (marginal saving)
- water injection: also little effect (and can be problematic eg. in winter)
- Apply a gearbox / differential with slightly lower RPM in highest (5th or 6th) gear.
- unfortunately factory gearboxes are a bit "short" for fuel economy. And, sadly, the 6th gear in my 6 gear audi gearbox was not significantly "longer" (if at all) than the 5th gear in the 5 gear gearbox.
- stratified combustion: requires direct injection (beyond reach for most diy-ers, at least more complex than using a max 20-30kW, higher compression engine for cruising )
Less shaft power:
- Alternator excitation: charge battery when breaking or coastdown (or when really needed), not constant (eg. 14.5V) all the time which usually wastes amperes (10 ampere needs appr 200W shaft power, which is appr 1.4% of the shaft power needed by a Cd=0.32 normal vehicle at 90-100 km/h )
- inflate tires a bit (beyond limits, of course)
- and carry as little weight as needed
- remove roof-mounted gizmo when not in use
The average (1.6 - 3 liter) engine is just not optimal for cruising
- (appr 14kW power required, but the drag power is roughly proportional to v^3 because drag force is proportional to v^2)
- so 20-30kW engine would be better (30kW engine seems to be applied in some concept electric hybrids).
- maybe, by valve timing tuned to reduce valve overlap (VVTI cylinder head might help so engine becomes responsive at higher RPM too), lower RPM might be reached (higher MAP, less pumping loss), with modified gearbox
Volvo 960 B230FT. 18 dec. 2013
I tried the table config switch, and fuel divider set to 2.
When running 3000rpm part throttle cutting out 2 cylinders of 4 is to much. It is difficult to keep up speed, but cutting 1 cylinder might work fine.
It could be interesting to try, if I just could cut 1 injector event at every 8 ignition event (or 12 or 16).
This is only when at part throttle, of course.