shifting from 'D'to 'N'
 

i heard from somebody that u can save gas by shifting from DRIVE to NEUTRAL when yer goin downhill or approaching a stop sign/red light. basically when u take yer foot off the acceleration. i thought about it for a while and it didnt relly make alot of sense soi decided to search online. some people on other forums say that it relly doesnt save a noticeable amount of gas and that its actually bad for the tranny. other people said that its actually worth it and the damage to the tranny is barely any or none at all. i was just wondering wat u guys think bout this.

I think I'd rather pay the extra dollar for gas than the "barely any damage" required to save the dollar.

^^^^yea. this applies if u have a manual tranny. u dnt want to F up ur auto tranny for the .5% ur gonna save on gas.

Well, there's been plenty of discussion on it, and people tend to have one of two opinions:

Camp A - Shifting into N is good for the tranny. It lowers the RPMs while you're coasting.

Camp B - Keeping it in gear is better. When the car is in gear and decelerating, the engine is being turned by the wheels, and although it is at a higher RPM, the fuel is being cut off.

:rotz:

why would shifting in and out of drive cause transmission problems, unless you go WOT in neutral and dump it into drive?

either way, i really doubt it is going to save that much gas

If your car is engine braking, then you're not saving any gas at all basically. So just leave it in drive. Think about it, while in neutral, your car is basically burning as much gas as at idle. When the car is in gear and engine braking, you're using even less gas because the wheels are causing your engine to cycle and your injectors don't have to fire.

i dont know about that

i haven't heard a single car go silent when braking (not taking hybrids into account)

Go install a wide band and look at the readings while decelerating in gear... the car still makes noise yes, but you are not burning gas...

Wide band measures Air / Fuel Ratio... during Decel you are reading off the chart... 25+ when normally you read around 14 - 15 A/F... the sensor basically cuts off because no fuel is being burned...

how would the car have an exhaust note if NO fuel is being burned?

Engine is still cycling so there is still an exhaust note. There was a big debate about this on the Lexus forums and some of the techs basically confirmed this.

On hybrids, doesn't the gas engine totally shut down when the electric motor takes over? As in it is no longer turning?

so the sound of air compressing is the same sound as i hear when i take my foot off the gas?

FWIW GM has a system on the new astra that automatically shifts it into neutral when at a stop in order to save gas. yes it is only a .5 savings, but in the interest of CAFE they did it.

Let me see if I can find a link. But to answer your question, yes. At least that's what the techs say.

At idle, yes it would make a difference. Because on an auto; at idle in drive, the engine is loading against the transmission and brakes. ie, the only thing keeping you from moving is your foot on the brake. But in neutral, there isn't a load on the engine so it would burn less gas. But while coasting downhill, the engine wouldn't be loaded while in D.

i've met plenty of techs that dont know a damned thing :laugh:

there are some computer programs (depending on they type of car you have) that have a Decel Fuel Cut Off (DFCO) feature, but most actually have decel fuel maps

According to the FSM on my IS350, if you release the gas pedal all the way and the engine is turning faster than 2500 rpm, fuel is cut entirely. Fuel turns back on once rpm's drop below 1000. This is the same way for most other modern cars due to emissions, not CAFE. And it's not a new method, some cars since the 1980's have done it. I guess someone could check the Maxima FSM and see if it holds true.

Nissan's (A32/33) don't cut fuel entirely, but the IPW is VERY small, my wideband goes offscale when decelerating like Merlyn's.

http://forums.maxima.org/showpost.ph...2&postcount=32

so i should basically juss leave it in DRIVE and not shift back and forth between DRIVE and NEUTRAL. thanks for your thoughts.

It easier to look at it this way. Think of the engine as a large air compressor. On an air compressor, most of the noise you hear is the movement and compression of air. The engine is the same. Fuel/combustion does play a part in the noise, usually it intensifies the sound. So yes the motor will sound like it's still running, but it doesn't need fuel to make that noise.

I also agree that it's best not to put it in neutral. You really don't save much of anything unless you're coasting down a hill that is like 10 miles long, and even then, it's a very small savings.

S

Yes, leave it in drive. You'll burn less gas.

Not this discussion AGAIN...

Sigh... :rotz:

https://img514.imageshack.us/img514/...shutoffhh6.jpg


During deceleration, while IN GEAR, you are NOT burning any fuel. You waste more gas by putting it in neutral. :nono:

/endthread.

Unless you shut the engine off at stop lights and coast down hills. In which case, you will get excellent mileage.

Stop complaining!! You think you're being hit hard by petrol prices. I own two Maximas and I fill them both up once a fortnight. It costs me around $92 for each car because I use 98 octane fuel.

In Australia, in my home city Townsville, I saw at the pump this morning for REGULAR (same as your 88/89) $1.57 a litre. That's $5.95 per US gallon.

Little old New Zealand is $2.10 a litre.. yes that's right.. that's equivalent to $7.96 per US gallon. That's double what you're paying.

How do these people do it? We just do. If we can't afford it we bike, bus, walk.. you name it.

That's the global oil crisis. It's very real people and pretty soon you'll be joining the rest of us.

I'm certainly not. I don't like it, but rising gas prices will lean out traffic and get some of the craptastic drivers off the road. However, the non-a$$-hole part of me thinks gas prices are a bit ridiculous.