A-Spec*

Howdy AZiners i dont know if this has been talked about mayb it has sorrie if it has but me and my buddy have been arguing sayin that downshifting wastes more gas ....i didnt think so cuz i always downshift while drivin comming to a stop or to slow down for a turn.... soo can som1 please tell me whos rite?????

01tl4tl

downshifting waste gas
every time you raise the revs it uses gas- while coasting allows the computer to sense what is going on and the revs are kept very low- not looking for traction in the system.

Downshifting is to be in the right torque band for accellerating off the apex and out of the corner!
Otherwise- for normal driving leave it in D5, or D4 if stop and go traffic as that keeps it from hunting back and forth between 4 and 5/top gear at low speeds- which saves more gas for you!

A-Spec*

SHAME!!!! i always thought if your not pushing down on the gas it wouldnt waste as much gas......guess i gotta change the way i drive

01tl4tl

Use the brakes to slow down-that is their the whole purpose in life!!

the transmission is very expensive to replace- perhaps you have heard
of the gen2 failure problem??
Brakes are easy to replace and have a relative low cost for what they do--
keep the car the same OE length as it left the house each day~
ask my wife

phee

iTrader: (5)

you also shouldnt downshift to slow down, thats what brakes are for.

01tl4tl

drive and watch the tach - your way and the other way suggested- see what happens.
Also traffic permitting- brake early- say from 40 to 20 approaching red light, you coast towards it and it may go green- saving you gas as you are already at 20 and get back to cruise speed while the guy who raced to the red light sits there and then jumps on the gas, making 4000 pounds get moving- who do you think wins in the end? besides big oil?

A-Spec*

Sweet now i know not to downshift when i dont have to lol...... i suppose i should be using my new brembos more

01tl4tl

you have brembos and you use the trans to slow down!!!!!!
- may I suggest you take a hi-performance track day school at your local roadrace track for about 250 dollars
They will help you learn how to really brake the car- turn in -gas out and go fast and smooth
cant go fast without the smooth

A-Spec*

LOL hahaha yea i try not to speed jus got 18s on my baby and the roads in Montreal are terrible .....like pot wholes 6 feet long 2 feet deep :S that kinda stuff i gotta drive slow and look out for

wind'on'the'road

downshift + brake = emergency braking!! Tranny $2-4K - brake F&R $100 DIY = big saving.

o4Komodo

iTrader: (2)

lol. I know huh?! My 3G OEM 17" rims are damaged NOT from curbs.. but from potholes! There are so many that if you avoid one.. you end up falling into another one! Those freaking potholes are either HUGE or DEEP! lol
Also welcome to azine!

wind'on'the'road

Avoiding an accident - tranny's $2/4g's = priceless

acitydweller

yep... what he said

remikinz

iTrader: (4)

exactly what I though I dont like downshifting I get scared Im beating up the tranny I need that baby to last me lol

rob-2

In the 05 RL that has a live MPG rating, when I down shift, say going down a slight grade and take my foot of the gas - mpg spikes to 40-50mpg.

I have been told, that with fuel injection, the ECU will not put any fuel into the motor unless called for 1. by the gas pedal, 2. to stop the motor from stalling.

So if by down shifting you're keeping the revs higher, say about 1k then I suspect you're actually saving gas.

However, all that said there isn't really much point in doing this to save gas.

01tl4tl

rob2
you have made it very clear that you have no actual auto tech credentials and mostly have bad advice to offer
Why dont you go read how the system of the ECU_ EFI _FCU ~instant read~ works- is it vac operated or is there an actual fuel computer that moniters how much fuel is going thru the injectors???- how much fuel is being recirced to the gas tank??...
there are different ways things work, and instant is one of the least reliable guages known to mankind in general IMO
when you know something for sure fact- share it- bad info keep to yourself

TL2498

RPM has very little effect on gas mileage. Throttle angle and load is what will affect MPG the most.

Example:

Cruising in 4th gear @ 3000RPM vs. Climbing a hill in 5th gear @ 2000RPM.

The throttle tip-in and engine load are greater in the 5th gear example, thus requiring more fuel to maintain the RPMs. Whereas, in the 4th gear example given that there is very little load on the engine less tip-in and therefore less fuel are required to maintain engine RPMs.

I'm not saying that RPM has zero affect on MPG, only that there are other factors that play a much larger role.

rob-2

My comment was only to share my personal experience and what I've been told. Your comment however is rude and discouraging.

Please, don't find a reason to publicly insult or belittle me. If that's what you're about I'd rather you didn't respond directly to anything I post.

Thank you

myron

iTrader: (4)

sorry this isnt about gas milage but I was wondering, how long does it take for your tranny to shift when in SS mode. lets say I am in 1st gear and I shift up and there is like a 1sec pause before the the car shifts even tho the gear indicator says 2nd gear right away. and my tranny still shifts very smooth in d4.

rob-2

Sometimes I have that delay as well. Not always though, it's really strange.

01tl4tl

2498- read the owner manual - so should everyone
5th gear is overdrive- less than 1 to 1 ratio- meaning behind the power curve
On hills or in stop and go traffic- use D4 and it will be where you need it in the rpms

"I have been told, that with fuel injection, the ECU will not put any fuel into the motor unless called for 1. by the gas pedal, 2. to stop the motor from stalling."
Thats really funny- learn how smog controls and ECU work together to understand!!

"So if by down shifting you're keeping the revs higher, say about 1k then I suspect you're actually saving gas."
Thats just WRONG rob2. do your research and post FACTS- thats not even experience you relayed- just a story! and I will happily not reply in correction to your post.
This is not the first misinformation you have disbursed here~ thats what I am saying

ac08odl

im not down shifting no more...

MurdaZ

iTrader: (1)

if anything dont floor it and mash brakes, anticipate the stop i always leave a good distance infront of me, even in stop/go traffic, barely need to hit the pedal braking or giving gas...pace people pace!

mcflyguy24

I get it when downshifting and I'm always in the proper mpg and rpm range, when I first got the car I accidently pulled the lever twice cos it didn't shift right away and ended up double downshifting.

01tl4tl

thats allright- the computer will not allow the downshift into each gear above a certain speed-
if you would cause an overrev- it flashes the number of the gear you requested- then returns solid display of the current gear

guyenacurazine

just use a common sense.
Say for example for every 1 engine revolution, 4 sparks are detonated. And lets say fuel burned for each spark, therefore each revolution is constant or at least fairly constant. Let s say one spark will consume 1ml of fuel.

1 rev = 4 sparks = 4ml fuel.

Now you floor it then you engine revs faster. Since that means more revolutions per
unit time and using a reasoning we are burning more gas per unit time.
Below is x that increases when you floor it or decreases when u let go of the pedal.
It has a direct relationship with the gas being burned after all. In another words when u increase x (faster rev) then more fuel per unit time is being consumed or vice versa.

x revolution / unit time = x * 4 sparks / unit time = x * 4ml gas / unit time.

So using higher rev at same speed is always wasteful. Got that?

A-Spec*

thank your for the math lecture i understand it ALOT more clearly now .....but when your drivin in SS and your in 5th and about to come to a stop you shouldnt down shift???....just let it go down on its own?????

01tl4tl

READ THE BOOK
Yes it auto SS downshifts itself into 1st below 15mph

As for the theory presented on 1000 rpm better than idle to a stop- rob2 version -

I watched the tach today- it keeps at about 1200 then 1000 as I coasted, then
750 at full stop. There are series of deceleration control valves and air injection and things going on far beyond what you can see- and the auto trans is doing its thing.

6MTUA5

iTrader: (2)

Yea why would you shift down? You don't need to get on the gas again until you are completely stopped and it will be in first by then.

A-Spec*

WELL SORRIE for wanting to know things the easy way by askin you guys ....thats what AZ is for is it not?????? instead of going through a book when you can jus jump straight to the answer:P

guyenacurazine

Well, at low speed you want to downshift to prevent your engine from turning off. I do not exactly what happens for auto tranny, but for manual when u decelerate you either need to disengage (tranny is disconnected from the engine) at which the engine will itself comes to lowest idle speed or shift to lower gear.
When u stop you must disengage the gear because the engine and tranny is mated together when in gear. When you stop by braking you telling the wheel to stop turning which in turn tells also tranny to stop. But your engine must be revving at idle when u stop at intersection. If you fail to disengage when you stop, then you 're effectively telling the engine to shut off.
I believe the auto tranny does this all things automatically so you dont have to worry about.

For SS I dont use that often i really dont know you have to downshift by yourself or it does it automatically. But when u stop i am pretty sure the tranny disengages for same reason I explained above although it looks like it is in first gear. Correct my if i am gear.

guyenacurazine

May be a better explanation than i posted above, I was not able to finish the above but 5 min expired and it automatically posted above!!!

Well, at low speed you want to downshift to prevent your engine from revving to slowly or die. I do not exactly what happens for auto tranny, but i think it is similar reason as manual tranny. With manual, when u decelerate you either need to disengage (tranny is disconnected from the engine) at which the engine will itself comes to lowest idle speed or shift to lower gear.

Reason is as follows:
Keeping the tire spin speed constant (you re travelling at constant speed), at higher gear means your engine revving slowly and at lower gear, your engine revving faster.

Now you decelerate, you tire turning slowly of course and this means you re causing your engine to rev even slowly. At some point, your engine is going to rev so slow it is below idle speed and in danger of shutting off, unless you put in lower gear. So when you put in lower gear, you re effectively preventing your engine from revving below idle by letting it to rev faster.

When u stop you must disengage the gear because the engine and tranny is mated (locked) together when in gear.

When you stop by braking you telling the wheel to stop turning which in turn tells all these tranny mechanism inside it to stop spinning which in turn telling the tranny part that interfaces with engine flywheel to stop and thus eventually telling the engine to stop revving. But you wanna keep the engine running at intersection even the tires are not spinning dont u? unless you wanna start your car at every red light . If you fail to disengage when you brake, then you 're effectively telling the engine to shut off.
I believe the auto tranny does disengaging the gear or downshifting at proper speed automatically so you dont have to worry about.

For SS, I dont use that often i really dont know you have to downshift by yourself or it does it automatically. But when u stop i am pretty sure the tranny disengages for same reason I explained above although it looks like it is in first gear. Correct my if i am mistaken,

guyenacurazine

Another reason for downshifting is to accelerate.
At higher gear, less of the engine power is delivered to your wheel but you need more power to accelerate right?
It is similar to ratchet theory.

Say your hand is enginer, your tire is stuck nut that you re trying to break loose.
Ratchet is your tranny. Shorter ratchet is similar to higher gear. Longer ratchet is lower gear. Let is say distance your hand travelling while you turning the ratchet is gas. (more hand travel more gas).

Now you have two long and short ratchet to break loose the nut. You wanna choose the longer one (lower gear) because your hand exert (engine) more power at the nut (tire) than if you were using shorter ratchet (higher gear). Now using longer ratchet you hand is moving at a greater radius (thus using more gas).

01tl4tl

will you people PLEASE read the owner manual- I have provided the free download link enough times for everyone to have it
A little research and initiative goes a long way to understanding and operating your TL in the manner it was designed!!!

guyen- good effort~ but read the book, or dont offer tech explanations on subjects you dont understand- thank you

MurdaZ

iTrader: (1)

just think of it...higher RPM (revolutions per minute)=more fuel being dumped since the engine is working fast....cmannnnnn

LukeaTron

If you get any higher on that horse you're going to need an oxygen mask.

Why not explain the facts instead of making vague references to things that you claim to understand and admonishing the curious to read the damn book. It seems to me you're more interested in appearing learned than actually being so.


FWIW, the relationship between RPM and fuel consumption is not a linear ratio. There are a lot of other factors involved as others have mentioned, engine load being one of the biggest. The ECU can safely lean out the mixture (I don't know if the TL will shut off fuel completely when coasting or not, the TSX does) if their is low enough resistance on the engine that predetonation will not occur.

That said, downshifting is best used to hold a particular speed when going down a long grade vs decelerating the car. In this case, you're doing it to avoid overheating the brakes. The best way to slow the car down is the brakes. Only use the engine to accelerate or prevent further acceleration, not to slow down.

01tl4tl

Luke- the view up here is nice- maybe if you werent directly under the horse's rear quarters you would see the simple logic of education yourself to the truth of automobiles!
I am not the one who said anything about linear ratios and camfibrillator modifications increasing fuel economy

If members would read the book instead of making ridiculous claims based on nothing but rumor and total guessing--- I would not see fit to offer FACTS on the matter
If I can go to the book and read it and understand the operating systems- why cant you or others?
These statements of how the trans works- or use the trans to save the brakes-- are those of young uneducated persons- especially ones who want someone else to do their homework and give them the answer.

I learned about my TL by reading the book- reading azine threads and asking questions, looking things up on wiki that I didnt understand etc.
If you want to use the trans in an abusive manner- you either have lots of warranty left or a wad of cash to replace the trans- thats $4000 for those that dont know~

LukeaTron

Firstly, the second part of my message wasn't directed at you but rather the thread in general. So you can calm down about that.

Secondly, you're attitude sucks. This is a forum expressly for asking questions and you're pitching a total hissy fit about people doing just that. I don't know, maybe it's indicative of your age that you seem to believe that only knowledge acquired in the most laborious process possible is of any value. The kid asked a question on this site instead of reading the voluminous manual because it's a shorter path to the information he wanted. He wants what's in your head and instead of being helpful you browbeat him with your bible.

You're going to either have to get past your hang ups or die soon. The amount of information in the world is growing exponentially and for people to be able to digest enough of it to grasp the bigger picture, they need to be able to consume the relentless flow rapidly. Reading the manual from cover to cover is commendable, sure. However, the vast majority of owners don't need or even want to know everything in there. There are specific bits they may want or need to know more about and quite simply, asking around here is a very quick way to get to those pieces of information.

If you don't want to be part of that paradigm that's fine. But coming in to thread just to shit all over it and offer nothing remotely useful breaks the system. Either get on board or just save us all the hassle and keep your mouth shut.

01tl4tl

Hey Luke- its not a huge book- read the section that applies to your questions

If you have time to come ask basic questions and make unfounded guesses as to systems- you have time to look them up too~
KNOWING about your car is not a luxury - its what they gave an owner book for!
I have been working on cars longer than you have been on earth-
I have to read, study, and commit to memory, the operational specs limits and emergency procedures of every type airplane that I am rated to fly.
If only cars were the same, and USA driving license test were like that used in Germany for the autobahn, a lot of the people on the road today would be on public transit instead

Your desire and expectation that OTHERS should do ALL your work and research- you being a generic term--- shows YOUR age and the generation of Give it to me- for no effort in life
Thats not real life!!! If it were not for people like fsttyms and me who know wtf we are talking about- you guys wouild be in deep stuff!!!!
Maybe its YOU who needs a week off and spend an HOUR reading the book cover to cover -its even online for ease of referance and page flipping.

As for my usefullness here- go read the trans failure stories and how many members I personally helped get a free warranty trans when they thought there was no hope or had already been denied
By my count- I save ziners over 40thousand dollars in the last year alone- by helping them with things NOT in the book
What did you do beside GUESS about stuff and blaber on....

MurdaZ

iTrader: (1)

easy girls...dont wanna see a cat fight brew..