I hate cars

[quote=spaceboy;13575642]I have always thought that the higher the rpm the more gas it consumes regardless whether ur foot is on or off the pedal, but ur thought is indeed some interesting info.One question though, why do they set it at 1,200rpm? is it possible to set it lower? (maybe saves more gas at stop light??)

[quote]

I think it was like Swoosh said, 900rpm. My memory sucks. Any lower than 900rpm and it might stumble when the injectors come back on.

You're right, high rpms usually use more fuel under load but if your foot is off the gas and you're above 900rpm, no fuel is being used.

spaceboy

this is definitely some interesting info and thoughts, no wonder MT saves you more gas than AT by allowing you to downshift....so the reason to set it at 900rpm is to make sure the car won't stall??
i no downshifting saves gas, but does it hurt ur tranny??

swoosh

iTrader: (5)

LOL i thought i was the only one who did all that LOL

recently my girl was driving (her car obviously) and we were coming to a light and i was like "why dont u take your foot off the gas and let it coast "

she looked at me like GTFO

I hate cars

Same here. I coast as far back as I can without pissing too many people off. I used to care but I see just about everyone flooring it up to the next light and slamming on the brakes. If it's a route I'm used to like going to work and back home, I know the lights and I know the ones you can and can't make no matter how fast you drive.

swoosh

iTrader: (5)

i think for stall in AT is set to 600-700 odd rpm....so if it dips below that your idle will be rough.....and further lower, your car will stall....

the 900rpm for injectors is for, consider your driving (coasting) and your rpms are dropping from say 2000rpm, the injector are SHUT OFF as the car/engine is not under load....as compared to your rpm sitting at 600rpm then the car is at load.....

hahhhaa i do piss a lot of people off, particularly when taking an exit....i coast to the exit and dont hit the brakes until am 10-20 feet from the light

RaviNJCLs

iTrader: (4)

It's your car....do what you think is right. I personally don't see the logic in what you are recommending. But I'm in the minority. I hardly ever use sport mode.

Typically I drive 80/20 highway/city. I average 27-29 mpg and typically I am coasting at 75-82 mpg. Hell....what do I know....I only drove about 45K miles and spent about $7K on gas last year.

If you're that focused on mpg's then sell the car and get a Civic.

RaviNJCLs

iTrader: (4)

+1. When I am driving between lights I'll coast as much as possible. I'm going to try maintaining that 1200 RPM. But I think I get great mileage out of my TL. I'm doing 14-18% better than my I35.

swoosh

iTrader: (5)

^^^ 900rpm Rav ....

spaceboy

Holy shit....i want that!!!!

RaviNJCLs

iTrader: (4)

OK.

I'm amazed how many of these threads are out there these days. I know I don't know as much as IHC or Inaccurate or some of the other guys. Hell, I get lost reading some of their posts. I just know what seem to work for me. I fill up with 93, keep my fluids fresh, tires at 34-35, speed fairly steady, and avoid flooring it. The power is there when I need it....I just don't need it to race from traffic light to traffic light.

RaviNJCLs

iTrader: (4)

DAMN IT....owned by type O.

Let me try that again....Typically my speed is between 75-82 MPH on the highway. Personally I would have asked for the $7 instead of the 75-82 mpg.

RainSupreme

You could always push for maximum gas mileage

VanyDotK

iTrader: (6)

That's crazy.. I only get about 29MPG on the Grapevine going about 80 with cruise control. If I cruise controlled at about 70 I could probably get a little higher.

djDANNY

You still have to blip the throttle when you downshift, which uses gas. I can't imagine downshifting through all my gears every time I came to a stop. That's pretty impractical. Coast through neutral and save the wear and tear on your clutch and the rest of the components.

spaceboy

well the reason i asked is cuz mine is an AT...

I hate cars

Reset it as soon as you get to the downhill portion going north toward Bakersfield. Keep it in 4th gear and it should maintain about 80mph without your foot on the gas. Put it back into 5th when it levels out and the next 30 miles are slightly downhill. I can usually keep it at >50 until Bear Mtn Rd or whatever its called. Its cheating but you will have a picture of the MID showing >50 for almost an hour.

djDANNY

I was just trying to say that manual transmission cars don't get better gas mileage (in general) than automatics because you can downshift yourself. In fact, I don't know any people who go downshifting through all their gears when they come to a stop in a manual. I suppose you could do it, but at 1200 rpm to downshift to the next gear you would still have to blip the throttle to rev match the engine. It's common practice to just stay in your gear and either engine brake or shift into neutral and coast into the stop using your brakes (though I agree that staying in gear would save gas, but sometimes you don't want to deal with the engine braking and want to get to the stop sign as soon as possible)

There are other factors such as lower weight of the car and lack of losses through the torque converter that probably have a larger effect on the difference between a manual's and an automatic's gas mileage.

I hate cars

You're right. TC efficiency has been brought way up by the lockup clutch inside but that's still a source of mpg loss. It's not always applied, only under specific conditions but when you're going steady state down the freeway you can be it's applied and that's one reason the mpg is close between manual and auto.

The hydraulic pump is the other item that takes a little power and mpg.

I don't think most people downshift each gear. If you wait until the rpms come down to around 1,200 or less, downshifting two gears isn't going to put the rpms that high. It is personal preference though. My father is very against this practice so I would do it just to get at him when I was driving.

vietxquangstah

iTrader: (7)

Just to clarify... With the automatic TLs, it's safe to downshift while in sport shift mode to save gas? From what I've read in previous posts I always heard people say that you shouldn't down shift unless you are trying to pick up speed (i.e. pass a car on the highway, going on the merging ramp). If you are coming up on a red light or a stop sign or traffic slows, I read that you should just let the tranny automatically downshift itself for you because if you manually downshift constantly it causes stress to the tranny so it's best to let it do it on it's own...

If that's not the case, can someone give me a simple example on when it's safe to down shift (no stress on transmission, and also benefits MPG even if it's slightly)

I hate cars

If we're talking strictly mpg, only downshift when your foot is off the gas. Downshift just enough to keep the rpms above 900rpm. Repeatedly downshifting 2-3 gears going from 1,500rpm to 6,500rpm is not the best thing for the trans (it won't hurt it but it puts a little more wear on the clutches), downshifting from say 4th to 3rd, 1,200 to maybe 1,800rpm is not bad for it at all.

Thunderrr

Most threads I have read have not given any useful info on balancing semi sporty driving in SS mode, and MPG. I am sure most people see the SS mode as a GG mode gas guzzling mode. But the point of my post (witch i see was completely missed) was.. it is possible have your cake and eat it too by knowing how to shift.

.... So if you know the best rpm to shift at you can get a little more fun out of driving without killing your MPG and actually improving it.

Maybe I should have bought a manual.. but when my gf would likes to hold hands when I drive (not because she is scared i am going to total the car)

Thunderrr

+1 I would probably put it in N when coming to a light if i wasn't addicted to SS.

I hate cars

I think that's a great idea, you should put it into neutral and use more gas then just leaving it in D. Maybe you can drive with the brakes on as well to lower mpg even more.

I hate cars

I can't help myself, what is the "best rpm to shift at"? What is it and why does it improve mpg? I can't wait to hear this.

djDANNY

I think all of this is situational dependent. I live in SF where there are tons of hills. If I accelerate up the hill and then pop it into neutral about half way up (more or less depending on how steep the hill is), I can easily coast into the stop sign and let gravity bring me to a stop. If I were to stay in gear (above whatever the fuel cutoff rpm is) the engine braking would slow me down too much and I would have to add gas to make it up the hill. So in that case, shifting into neutral and coasting makes more sense.

If I were going down a hill, then it would probably make more sense to go down the hill in gear above the fuel cutoff point (as long as the engine braking doesn't slow me down too much). Besides the fact that it's always safer to be in gear rather than coasting in neutral in case you need to speed up quickly for any reason.

swoosh

iTrader: (5)

^^^ ok so here is what i understood from the thread:

when you pop it in N the rpms fall below 600 and your injectors are ON....hence you shudnt do it.....

if you stay in gear and leave your foot off the gas and just downshift around 1200 rpm, the rpms stay over 1000 and hence injectors stay OFF and better gas mileage....

whyTF is this soo hard to understand.....am glad some on ya'll didnt try to become rocket scientist....

djDANNY

the point is that you can't make such grand generalizations as if that's going to happen in the real world 100% of the time. Sure, if i could magically stay above 1000 rpm and maintain speed without having to get on the throttle, that would be ideal. The fact is that doesn't always happen... there are things that we call friction and gravity that prevent that from happening.

So to say that you should never shift into neutral because it uses more gas isn't a hard and fast rule. In certain circumstances, that's correct... in others... by staying in gear you'll actually end up having to use more gas to maintain speed. make sense?

there's a balance between when to coast in neutral and when to stay in gear. if you have common sense you should be able to figure out when to do one versus the other.

swoosh

iTrader: (5)

^^^ well this is for coasting to a stop....

if you want to maintain speed coming down a hill....stay in gear with a light tap on the gas as and when you need it....and stay off the gas when you dont....

and yes the rpm's do stay over 1000 magically....unless you push into N....

I hate cars

That, I agree with. One of the keys as well is if you're downshifting, downshift just enough to keep the rpms high enough to stay in fuel cut. You don't want to downshift to 4,000rpms where it's going to slow you down quickly, if you get used to it, you can usually keep the rpms between 1,000 to 1,500 so downshifts are smooth and it doesn't slow the car down that much.

lil12002

IHC I browse the forums a lot and see your informative posts, could you explain the driving on SS a bit for me? I live in los angeles and drive on the 405 quiet a bit, I also have a physical disability so shifting is difficult which is why i bought an auto, i never drive in SS... any info to help improve gas millage would be greatly appreciated.

justnspace

iTrader: (1)

Please, go back over the thread.
I learned what the injectors do at a certain RPM just by reading this thread.