Stop/start? What we need is drive/neutral....for massive MPG savings
- Thread starter MarkDavis
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Assumed it was to do with balance/grip - having nothing to regulate the speed of the driven wheels. Thought that might effect traction.
That and that you aren't really in control of the vehicle until you are in gear.
I think it's just more the fact that it isn't conducive with good car control.
If you're used to engine braking, you may end up going quicker than intended and have to brake more sudden. If you need to accelerate out of danger or make a quick maneouver then you have to get back into gear, so will delay that. Also more brake wear due to no engine braking.
Yup, getting 42mpg from periods of coasting definitely saves more money than continually staying in gear and getting 30mpg.
The octavia iii dsg does this if its in 'eco' mode, there must be some science behind the reasoning for this, although it seems its broken a bit on the vrs spec as it struggles to re-engage the correct gear if you go to accelerate again, unless you dab the break first? which i guess if your town driving is ok, but on the motorway sounds ropey.
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Errrrmmmm.....yes you do have nil fuel usage, as in ANY car with a catalytic converter the injectors shut off (therefore do not put fuel into the cylinder) when off the throttle and in gear in order to prolong the life of the cat, so because ZERO fuel is being put into the cylinder then you are using ZERO fuel, and a synonym of ZERO is NIL therefore NIL fuel usage
meanwhile the engine is being kept running by the wheels turning the drivetrain which in turn keep the engine turning over.In neutral the engine is not connected to the drivetrain therefore fuel is required to keep the engine turning over hence you are using fuel. Seriously go and look up how an engine works
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Well it was English, so I can't really help you further if you've 'no idea' what I said. My post is still there if you feel like having another try later
Errrrmmmm.....yes you do have nil fuel usage, as in ANY car with a catalytic converter the injectors shut off (therefore do not put fuel into the cylinder) when off the throttle and in gear in order to prolong the life of the cat, so because ZERO fuel is being put into the cylinder then you are using ZERO fuel, and a synonym of ZERO is NIL therefore NIL fuel usage
In neutral the engine is not connected to the drivetrain therefore fuel is required to keep the engine turning over hence you are using fuel. Seriously go and look up how an engine works
Not sure that's entirely true. If absolutely all fuel was cut, surely the engine would be almost silent?
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In theory some recent BMW's including my F30 have sail mode as part of Eco pro which effectively drops the auto box into neutral, the manuals have a more manual approach called the clutch pedal. I have never known mine to engage this mode so I'm not convinced by it!
It's still turning you know, why would the noise stop?
The engine is still running though?
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as said above the engine is still turning over therefore would still be making noise
You're wasting your time guys, its hard to argue with cold, hard evidence like this
On a significant downhill, you lose some momentum through engine braking vs coasting. There's a fine balance. Sometimes it's more efficient to have the fuel cut off. Sometimes it's more efficient to maintain momentum.
Coasting with the engine off is more efficient than either. You use no fuel and don't lose speed because of the engine braking effect. I'd say it's dangerous in most cars and isn't welcome on public roads though.
About the most efficient and legal you can do is using engine braking downhill to hold to the speed limit.
On my 2010 Honda Insight, light throttle pressure pressure on a gentle downhill overrides engine braking. With very light pressure it engages a cylinder shutoff mode, where the electric motor keeps the engine turning but no fuel is used. It will do this fairly happily at 70mph given the right gradient and conditions. Remove throttle pressure entirely and it switches to a simulated engine braking, which charges the battery.
Given that regenerative braking is not 100% efficient, it's usually more efficient to hold in cylinder shutoff (essentially engine off coasting) without much electric assist or engine braking / regen, allowing the speed to gradually bleed off rather than use the regenerative braking.
Edit: When cylinder shutoff happens, it's quiet but there is a very quiet mechanical noise from the engine continuing to turn. By comparison, I've driven a Prius and when that runs in electric mode the engine isn't actually turning. In both cases road (and sometimes wind depending on speed) noise is louder than the engine / motor.
Coasting with the engine off is more efficient than either. You use no fuel and don't lose speed because of the engine braking effect. I'd say it's dangerous in most cars and isn't welcome on public roads though.
About the most efficient and legal you can do is using engine braking downhill to hold to the speed limit.
On my 2010 Honda Insight, light throttle pressure pressure on a gentle downhill overrides engine braking. With very light pressure it engages a cylinder shutoff mode, where the electric motor keeps the engine turning but no fuel is used. It will do this fairly happily at 70mph given the right gradient and conditions. Remove throttle pressure entirely and it switches to a simulated engine braking, which charges the battery.
Given that regenerative braking is not 100% efficient, it's usually more efficient to hold in cylinder shutoff (essentially engine off coasting) without much electric assist or engine braking / regen, allowing the speed to gradually bleed off rather than use the regenerative braking.
Edit: When cylinder shutoff happens, it's quiet but there is a very quiet mechanical noise from the engine continuing to turn. By comparison, I've driven a Prius and when that runs in electric mode the engine isn't actually turning. In both cases road (and sometimes wind depending on speed) noise is louder than the engine / motor.
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Because the fuel has stopped exploding inside the cylinder?
So no, saying silent was silly I grant you. But surely it's not unreasonable to assume that with fuel cut to nil, all combustion stops, therefore the engine would become noticeably quieter...this is not something I've ever experienced when coasting in gear.
You mean the only one that agrees with your theory. Porsche need to implement things like that to meet CO2 targets, IIRC automatics have nowhere near the engine braking effect compared to a manual anyway.
I prefer engine braking anyway, car doesn't increase in speed when going downhill and I don't end up reducing the effectiveness of my brakes by overheating them. Infinite MPG in certain conditions and improved car control especially in slippy conditions. If you drive smoothly and anticipate traffic flow you can greatly increase economy, there's no real need to coast ever.
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