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chrisoverson · 04-19-2012, 07:20 AM

I suppose anything you can do to encourage the engine to use less fuel on idle would give you an advantage in that case, because you can then keep everything working perfectly and not have the risks of no power assisted brakes or steering.

Or if the 5th gear RPM is low enough to not add significant load onto the engine during gliding, the safest thing would be to leave it in gear. It does slow you down but you'd use zero fuel. I suppose all that depends on the car in question though...

Perhaps in an ideal world you could keep the driveshaft spinning and turning the pulleys but not pump the pistons up and down, minimising the parasitic load as well as engine wear.

I did have an idea for a hydraulic system of pistons rather than using a solid piston rod, which could allow easy cylinder deactivation and also (my favorite bit) change how far the pistons moved up and down on the fly, allowing you to effectively change engine displacement and compression ratio whenever you wanted. I don't know how you could design such a system, but if possible it would be very interesting. I very much doubt anybody could make that at home though, would have to have a lot of time and money invested by a car manufacturer.

I, Christopher J Overson hereby claim this idea as mine, on 19/04/2012. Just incase nobody's already thought of it

Anywho, for the mean time we need to determine which is best for pulse + glide:

1. Engine in neutral, still running as normal for safety (shift to pulse)
2. Engine in neutral, fully turned off to save fuel (bump start to pulse)
3. Engine in gear, injectors off and throttle closed for least effort (apply throttle to pulse)
4. Engine in gear, injectors off and throttle wide open for lower pumping loss (activate injectors to pulse)
5. Engine in gear, fully turned off (turn key to restart + pulse)

I'd guess that how much the engine slows the car down on zero throttle depends on the engine size. Mine is a 1.8 inline 4 cylinder engine, but I expect someone here with a big 5l v8 would see much bigger losses from leaving in gear...

Ultimately I want to add such things as regenerative braking and a mini motor to assist the engine, but I don't know what kind of motor to use or where to aquire batteries.

The other question is, which is more important? Reduced fuel during pulses, or increased glide duration... I suppose if either is significantly improved then its a win win, but which is likely to acheive more with least effort?

04-19-2012, 07:20 AM	#20 (permalink)
chrisoverson The Mad Technician Join Date: Apr 2012 Location: Devon, England, UK Posts: 31 Rover - '98 Rover 218 iS Thanks: 0 Thanked 1 Time in 1 Post	I suppose anything you can do to encourage the engine to use less fuel on idle would give you an advantage in that case, because you can then keep everything working perfectly and not have the risks of no power assisted brakes or steering. Or if the 5th gear RPM is low enough to not add significant load onto the engine during gliding, the safest thing would be to leave it in gear. It does slow you down but you'd use zero fuel. I suppose all that depends on the car in question though... Perhaps in an ideal world you could keep the driveshaft spinning and turning the pulleys but not pump the pistons up and down, minimising the parasitic load as well as engine wear. I did have an idea for a hydraulic system of pistons rather than using a solid piston rod, which could allow easy cylinder deactivation and also (my favorite bit) change how far the pistons moved up and down on the fly, allowing you to effectively change engine displacement and compression ratio whenever you wanted. I don't know how you could design such a system, but if possible it would be very interesting. I very much doubt anybody could make that at home though, would have to have a lot of time and money invested by a car manufacturer. I, Christopher J Overson hereby claim this idea as mine, on 19/04/2012. Just incase nobody's already thought of it Anywho, for the mean time we need to determine which is best for pulse + glide: 1. Engine in neutral, still running as normal for safety (shift to pulse) 2. Engine in neutral, fully turned off to save fuel (bump start to pulse) 3. Engine in gear, injectors off and throttle closed for least effort (apply throttle to pulse) 4. Engine in gear, injectors off and throttle wide open for lower pumping loss (activate injectors to pulse) 5. Engine in gear, fully turned off (turn key to restart + pulse) I'd guess that how much the engine slows the car down on zero throttle depends on the engine size. Mine is a 1.8 inline 4 cylinder engine, but I expect someone here with a big 5l v8 would see much bigger losses from leaving in gear... Ultimately I want to add such things as regenerative braking and a mini motor to assist the engine, but I don't know what kind of motor to use or where to aquire batteries. The other question is, which is more important? Reduced fuel during pulses, or increased glide duration... I suppose if either is significantly improved then its a win win, but which is likely to acheive more with least effort?