msims

I often use the manual mode in my auto to downshift and slow down instead of using the breaks. Is this in any way harmful to my Z?

quangquoclu

iTrader: (4)

nope... just waste gas

N74DV

engine braking wastes gas?? nope ... a wives tale, urban legend whatever you wanna call it.... it ain't so.

Rxramon

Im in manual 75% of the time.

The only time im in auto is on the higway or late at night when theres no traffic...

If engine braking is bad.... Good for meeee.....I have a warranty
I proabably want a new tranny in 2years

Rxramon

oh it doesnt waste gas, you are not hitting the throttle or gas pedal, so how are you using more gas....

Your just in a lower gear than the Auto mode would normally be in... One could say it causes more wear on the tranny... (Reason for my above post)

But I also engine brake

msims

I'm not sure I agree with this. To maintain higher RPMs, the engine needs more fuel. Those pistons are moving at a higher rate of speed than they are at idle. The only way they can move at a higher rate of speed is by taking fuel into the cylinders at a faster rate. No where near the amount of fuel the engine consumes when you are accellerating, but definately more fuel consumed per second than when the engine is idling.

N74DV

look.... think about it this way.... if your car ran out of gas as you were engine braking, would the engine suddenly seize and stop?!

no.

fact is no extra fuel is used when engine braking. If your foot is off the accelrator you will not use more fuel. period.

msims

It won't stop, but the spark plugs won't ignite either.

N74DV

the fuel injectors will only deliver fuel if the accelerator is depressed. No two ways about it.

so....explain to me how the hell more fuel will be shot in by the injectors if your foot is off the gas and you are engine braking?

are you saying the pistons will "suck" fuel in?? LOLOL

the bottom line is.... you asked if it is harmful to your Z to engine brake. The answer is probably not. This is not an ordinary auto tranny. It was designed to run hard.

msims

Thats EXACTLY what I'm saying. When you start the car, the car adjusts the fuel intake so that it can warm up (when you turn on the A/C, it does the same thing to compensate for the extra work being demanded from the engine). When you let up off the gas while driving, fuel is still being delivered to the pistons while you are decelerating. There is no way in hell that fuel will ever be cut off to the cylinders while there is still gas in the tank. An engine would not last long under such strenuous conditions (on / off, on / off all the time, not to mention the work load on the pistons while there is no assistance from the spark plugs [can you say engine ping?]) So yes, when the engine is running, and your foot is not on the gas pedal, the engine is indeed sucking fuel into the cylinders while the tranny is generating the resistance needed to slow the car. Ask any auto mechanic, or engineer. I doubt seriously that the fuel loss is signifcant, but there is still more fuel lost during higher RPMs than during lower RPMs.

joust75

iTrader: (1)

You are wrong. Every car manual tells you downshifting to break will decrease gas mileage.

Yes you are using gas when you down shift. Why do you think you can still hear the engine? It does not use a lot of gas but certainly more than if you were to put it in neutral and coast.

AS far as downshifting with an auto, I would not. If you wanted to downshift you should have gotten the 6mt.

Autos have a torque converter and can not be engaged progressively like a clutch. I learned all about this when I burned out my auto trans in High school by driving it like a manual. Downshifts where you go from 5000 rpm to 3000 will shorten the life of your torque converter as will lead foot starts. Thats why I hate autos!

wildone_106

When were you in high school? Maybe they make Auto's better nowadays..!

NeSyO03

First off....why do people get an auto and then always use the manual thingy. Thats just lame, get a manual to begin with. And no its not a hassle for people who think thats a good reason.

Second, the higher the rpms are the more fuel u are using....y do u think people shift at lower rpms alot around town? To save gas. If this wasn't the case more people would be WOT a lot more often, i sure know i would be.

Third, so what ur saying is u only use gas when ur foot is on the accelerator? So if u take it off the accelerator to just coast somewhere u aren't using n e gas? If the car is running, its using gas.

msims

But these autos have a manual mode. They were designed to be shifted like a manual. That's why I asked.

msims

I got one because I could not find a manual in this configuration (pikes peak white enthusiast). Not to mention I was sick of shifting all the time. Then I am now reading where a lot of 6mt owners are on their second and third transmissions before they even hit 12k miles. No thanks, I love my auto, and the shifting ability in the auto is a nice feature, especially when you want to pass someone without plunging your foot into the gas pedal.

I also want to add that people shift at lower RPMs because they save gas NOT necessarily due to the lower RPMs. People don't realize that simple physics comes into play here. Force = mass times acceleration. So the harder you accelerate, the more force it takes, and hence the more energy you consume (i.e. more gas). If you go from 0 to 3000 RPMs in two seconds, you will consume more gas than if you go from 0 to 3000 RPMs in five seconds. That's just the way it works. There is a sweet spot for conserving gas. and that is ... the less your foot is in the pedal, the more gas you are saving ... and depending on how much torque you are demanding from your car, you need to shift at the right points throughout your required acceleration interval to achieve maximum fuel economy for that rate of acceleration. If your stepping on the gas, you need to shift at a higher RPM so that you don't bury the engine in too much fuel (although this was a larger problem with carb engines), but if you are accelerating at a slower rate, then you need to shift at lower RPMs so that you dont suck too much fuel into the engine to maintain that rate of speed at those high RPMs. Its all about power, torque, RPMs, and vaccume pressure from the engine to the fuel line.

Montez

I agree, the car doesnt perform better this way actually worse. The computer can shift it at optimal points better than youcan.

msims

This is not necessarily true. The computer may be programmed for fuel economy as opposed to performance. Also, the computer does not know when I want to take a corner at 60 mph ... so thats why Nissan gave me the option to enter into manual mode, down shift, take the corner, then upshift at my leisure.

N74DV

it's hopeless..... you guys will never get it.


I'm done with this thread.

Mikeb6986

The reason for people buying auto's is cause they arent as much of a hassle to, lets say, a 45 year old like my day who wants a fast car but doesnt want to deal with shifting all the time. My reason is cause my mom cant drive stick and since she is asian, she doesnt want to make an effort to try and learn. I wanted a stick but it was either that or a used 97' mitsubishi eclipse stick. We all know most people would choose the Z.

msims

Which part of the thread is hopeless? The reason for an automatic, or your silly statement that the engine doesn't consume any gas unless the gas pedal is pushed down?