Fuel Cutoff?

[SoL]

Hello, I'm new here, currently driving a 1.5 4AT sedan.

I heard that when going downhill, its better to release the accelerator while in D gear rather than to go down in N, because the engine will cut off the fuel when u release accelerator while in gear.

Is it true? Hoping to save more petrol here. 

[FamilyManz]

Hello, I'm new here, currently driving a 1.5 4AT sedan.

I heard that when going downhill, its better to release the accelerator while in D gear rather than to go down in N, because the engine will cut off the fuel when u release accelerator while in gear.

Is it true? Hoping to save more petrol here. 

how much can u save???

& in the even of a situation where one need to step on accelerator.... one will be too kan chiong to engage back to D

[clarence]

When going down a slope, just release the accelerator and let the car glide down in D. You also have some engine brake for safety.

NEVER drive down a slope in N as it wears out and burns out the gearbox. I read this in an article but cannot remember the exact source.

Frequent shifting will wear out the gear box faster.

[iagree]

how much can u save???

& in the even of a situation where one need to step on accelerator.... one will be too kan chiong to engage back to D

iagree with FM & Clar.

1) not much fuel to save
2) increase of risk if you push it to N gear , you lose control on the accelerator

btr dun do this.

just use D gear as per normal.

even if we stop at traffic light, if can, dun need to switch to N also, but now is habit lah... if wait for 1min at traffic light, then switch to N coz i scare if i let go the brake the car will cheong to kiss the ******** in front. pro & con lah.

[Silver]

can engage parking brake at stops at traffic lights

[iagree]

can engage parking brake at stops at traffic lights

Parking brake?

the "P" gear?

Btr not. Too rush to switch to D to drive off ! too rush.

[david1881]

When going down a slope, just release the accelerator and let the car glide down in D. You also have some engine brake for safety.

NEVER drive down a slope in N as it wears out and burns out the gearbox. I read this in an article but cannot remember the exact source.

Frequent shifting will wear out the gear box faster.

This is true.  Coasting in N for manual is ok.  But it's a NO NO for auto, may ruin your auto gear box. 

[FamilyManz]

can engage parking brake at stops at traffic lights

electronics nowadays is different from yesterday..... by just applying brake will virtually limit/cut off the fuel consumption to almost insignificant level @ short stoppages (traffic light, crawling conjestion etc)......

[SoL]

Apply brake will cut off?
I always thought lifting foot off accelerator will cut off liao. 
Thank you thank you for your help bros!

[Silver]

Parking brake?

the "P" gear?

Btr not. Too rush to switch to D to drive off ! too rush.

yes, the parking brake
drive gear still engaged
so, when need to drive off, only need to release the parking brake

[FamilyManz]

Apply brake will cut off?
I always thought lifting foot off accelerator will cut off liao. 
Thank you thank you for your help bros!

even when u lift off from accelerater.... ur car can still move rite?

[SoL]

But car is already moving ma. I mean when u lift off when car is already moving, not when starting from a stop. 

[darrylker]

Hello, I'm new here, currently driving a 1.5 4AT sedan.

I heard that when going downhill, its better to release the accelerator while in D gear rather than to go down in N, because the engine will cut off the fuel when u release accelerator while in gear.

Is it true? Hoping to save more petrol here. 

Bro, like the other lation's advices, not wise to do it...Firstly, I dont think you'll save much petrol by doing so...worse still you might lose control in times of E-brake...do you previously drive a manuel car? For my previous ride, sometimes i use to turn to 'free gear' at high speed to experiment if can save petrol...but free-wheeling rather dangerous, no engine brake....

From various feedback, our ride is FC rather efficient, think should focus more on your ride foot during acceleration, i.e. dont rev too much, ....my 2-cents worth....

[aerosignal]

Actually somebody got it right in one of the topics before but I too lazy to go find it. Basically, when you don't step on accelerator when car is moving, the fuel injectors cut off (no fuel at all). When the vehicle slow down to a preset speed 20 kph or something like that the fuel injectors turn back on again to keep the engine running.

This was something that confused me initially when I was toying with the scangauge when I was in US. There are times when the display goes 9999 mpg (basically infinite). I thought it was a update error. Later I found out it was because the fuel is cut off during deceleration causin a divide by 0 reading.

In short, when moving with enough speed, engine braking keeps engine moving (no fuel). When car is so slow that engine going to stall, fuel injection turn on again.

Keeping the above in mind, idling at the traffic light burns gas for nothing (0 mpg). Stepping on brake to slow vehicle drains energy to heat. The energy was obtained earlier when you were accelerating. So, as far as possible, reduce acceleration and use engine brake as much as possible (9999 mpg).

[aerosignal]

Another interesting observation. It was interesting playing with the MPG gauge because it has a gallon per hour function. I was able to play with the consumption of various items. For example, aircon increases comsumption by 20% when car is idling. This was in the U.S. where it was relatively cool (winter-spring). So can expect quite alot more here. Headlights increase consumption by about 5% during idling.
Idling consumes about .4 gallon/hour (~1.6L/hour).

Another example about aircon. When I used to work in tuas, I leave at 6-630 and aircon will usually be lowest speed ( I set 27). FC is 17km/L. When I go ICT, I leave at 5.30 and car gets really hot. Aircon will full blast for about 5-10 (sometimes 15 mins) mins to cool down to 27 degrees. My FC during ICT will drop to 15.5 km/L. Driving pattern remains the same because camp and work place in same area.

[SoL]

Hey aerosignal, so disregarding the human safety aspect, its not harmful to the car if I coast on Neutral with my engine on?

As in, it won't spoil the transmission? Latio is not flat-towable mah.

[aerosignal]

Hey aerosignal, so disregarding the human safety aspect, its not harmful to the car if I coast on Neutral with my engine on?

As in, it won't spoil the transmission? Latio is not flat-towable mah.

Er that one I don't really know. Effect to car, coasting at neutral is related to the transmission, not the engine.
At neutral, you have to burn gas because your engine is no longer driven by your wheels.
With engine brake, you may slow down abit. However, I find that on ben shears, I can sustain 80 kph coming down without steppping on accelerator at all. This means that I am burning 0 fuel when coming down the bridge.

I think you got the neutral coasting idea from hypermilling sites where they do at times coast at neutral. However, most of these people drive hybrids and it works very well for U.S. roads where they have long stretches of roads with gentle incline. In our case, the slopes are usually steep and if you go to neutral, you will accelerate  down the slope so much you have to use your brakes to slow down (traffic). As mentioned before, everytime you step on brakes, the energy you created goes into thin air, wasted as heat.

For what it's worth, I wouldn't try coasting at neutral myself because I don't think I can save more that way. Just accelerate less so you brake less.

[xuan511]

Er that one I don't really know. Effect to car, coasting at neutral is related to the transmission, not the engine.
At neutral, you have to burn gas because your engine is no longer driven by your wheels.
With engine brake, you may slow down abit. However, I find that on ben shears, I can sustain 80 kph coming down without steppping on accelerator at all. This means that I am burning 0 fuel when coming down the bridge.

I think you got the neutral coasting idea from hypermilling sites where they do at times coast at neutral. However, most of these people drive hybrids and it works very well for U.S. roads where they have long stretches of roads with gentle incline. In our case, the slopes are usually steep and if you go to neutral, you will accelerate  down the slope so much you have to use your brakes to slow down (traffic). As mentioned before, everytime you step on brakes, the energy you created goes into thin air, wasted as heat.

For what it's worth, I wouldn't try coasting at neutral myself because I don't think I can save more that way. Just accelerate less so you brake less.

I always practice brake less. Onli no choice den i brake, normally will try my best not to press any brakes.
You can also try looking far, the furthest traffic condition or the next traffic light, den decide to press acc or dont press anithing, until u are close enuff to a stop den press brake.
When approaching a red light, I will aim for the shortest line and release acc and not braking onli when close, coz incase it turns green I still have some inertia with mi, so can move off much easier

Just 2 cents

[aerosignal]

I always practice brake less. Onli no choice den i brake, normally will try my best not to press any brakes.
You can also try looking far, the furthest traffic condition or the next traffic light, den decide to press acc or dont press anithing, until u are close enuff to a stop den press brake.
When approaching a red light, I will aim for the shortest line and release acc and not braking onli when close, coz incase it turns green I still have some inertia with mi, so can move off much easier

Just 2 cents

[Ying]

Actually somebody got it right in one of the topics before but I too lazy to go find it. Basically, when you don't step on accelerator when car is moving, the fuel injectors cut off (no fuel at all). When the vehicle slow down to a preset speed 20 kph or something like that the fuel injectors turn back on again to keep the engine running.

True, When I see red light far ahead and no car behind me, I just left go acc. The car will slow down to ~20kmj then there is a sudden slight rush forward guess the car decide to pump some oil to engin at that time. I am driving a CVT so the rush is not due to gear change. Did not change to N