[nextsean]

As many of you know already, I am no expert. I am starting to get into cars with my purchase of Silver IS300.
I read people talk about downshifting when trying to pass someone. How does that work.
I never drove a stick before. So I don't really know about it.

Supposedly if you are going at 45mph and you are at 4th, you downshift to 3rd and it's supposed to accelerate faster? I don't understand why.

Sorry for the ignorance.

I am going to play around with the e-shift when I get mine. But I like to know how to use it.

Please input detailed explanation or a url link that will explain.

Sean

 

[DonCorleone]

same as you... i heard the lower gear you downshift to, the more horsepower is made available therefore allows you to accelerate faster...

 

[mrclam]

well the car is designed with differnet gears....as you come close to redline in first for instance you're pulling near the max amount of hp, but when you shift to second, you lose some hp/torque in most cases. now if you're cruising at 50mph in 5th gear, y ou're probably around 2k rpm or something..now, if you can get closer to redline, you will have a lot more power available to you, downshifting will do that for you

 

[nextsean]

Originally posted by mrclam:
well the car is designed with differnet gears....as you come close to redline in first for instance you're pulling near the max amount of hp, but when you shift to second, you lose some hp/torque in most cases. now if you're cruising at 50mph in 5th gear, y ou're probably around 2k rpm or something..now, if you can get closer to redline, you will have a lot more power available to you, downshifting will do that for you

Thanks for the info, but how does downshifting give you more power to you? I would imagine if you downshift from 5th to 4th while going at 50mph, the rpm would go up. Am I correct? But I don't understand how that gives you more power.

 

[JW]

Okay, let's take the IS300 for instance...

peak hp (215) is produced at 5800 rpm

Any time the engine is below 5800 rpm, there is less than 215 hp available, so power correlates to rpm. If you get a chance to see a dyno chart, you'll see how much power there is at a certain rpm.

Here is a dyno of a stock 2000 Celica and one w/ the butterfly valve removed:

The lower graph shows the hp produced (the upper graph shows the torque). At 5000 rpm, the Celica is producing 100 hp at the wheels, and at 7000 rpm there is 150 hp. Hope that helps.

On a side note, notice how the graph becomes steeper after 6000 rpm? That's when VVTL-i switches to the second cam.

[This message has been edited by JW (edited August 23, 2000).]

 

[wazzup]

Good Graphs JW.

NextSean, I basic jist is for everyday driving you'll be hovering around 2-4000rpm. All the power is at the higher revs. As JW's graphs show. So say you're on the highway cruising at 55mph in 5th gear. Then an ugly snot faced bimmer cuts you off. Quickest way to get the around the snot faced bimmer is to get you car into higher revs by down shifting to 4th. Watch you tach shoot up and hit on the gas pedal. It would take longer to hit the higher revs if you were to leave it in fifth and just hit on the gas pedal. Then to go back to cruising speeds upshift back to fifth. Now of coarse if you're red lining in 5th gear there's not much else you can do.

 

[TEG]

It sounds like the original question has been answered, but I will recap in case anyone didn't follow:

Car engines have different horsepower at different RPMs.

For a given speed range (say 50-70mph) there will likely be one gear that can accelerate quicker than the others because it is closest to the RPM where "peak" horsepower is made.

Typically one is "cruising" along the highway at a higher (numbered) gear than is optimal (for passing) because the lower RPMs give less noise, better fuel economy and less engine wear. *SO* it is common to do a "pre-emptive" downshift before passing.

For instance at 65MPH a typical car might do something like this :
(numbers are made up)

1st gear: exceeds redline - don't do it
2nd gear: exceeds redline - don't do it
3rd gear: 5000rpm - too close to redline - don't bother
4th gear: 4400rpms - good RPM for passing power
5th gear: 3800rpms - good RPM for quiet cruising

Now keep in mind that the current IS300 is _NOT_ a "stick" even though it has that stick-shift looking shift gnob, and the e-shift buttons. You can leave the car in "D" (drive) and let the transmission/ECU pick a good gear for your needs. In typical automatic fashion it should downshift (automatically) if you push the gas pedal to the floor for passing.

Also, the IS300 (with a decent sized displacement, and VVT-i) makes good torque across a wide power band, so downshifting is less of an issue than with some other cars (like for instance an Integra Type-R where you really have to "work the shifter" to get good acceleration). Torque vs HP is a whole other discussion, but let me just say that a car with a "flat torque curve" gives you decent passing power without the need to hunt for the "right" gear so much.

 

[nextsean]

Wow, I am impressed by all the good feedback from you guys.

Thanks!!

Sean

 

[Emerald]

It's called the "sweet spot" and any performance car has one. I think the final drive ratio on the IS300 is 3.90... that's like having 390 gears in the old days, 411 and 455 were used to drag... the higher the number the quicker the car would build speed off the line, but your gas mileage would suffer and your top end potential would go down the tubes also. I remember and incident on I-95 where I needed some power to get away from a jerk, I was new to the car, didn't realize I had it in manual shift, floored it and went nowhere fast. I usually drive with power setting off and in the full automatic drive position. I have since become profficient, when I want to apex a turn or get into the "powerband/sweet spot" by pushing power, slipping the drive to the left and getting my thumbs ready to do the work in conjunction with the engine. The breaking forces that are afforded with double downshifting can be exhilarating as can that swift shift into warp speed hp/torque.
Don't worry, the car will not let you downshift into meltdown mode, like has been happening with the GTS Celica, and it beeps you when it hits the rev limiter, tellng you to upshift.
You have to drive the car in the different modes and see how it responds to your specific needs at the time. I can get 23MPG driving with the egg under my foot, or I can carve up a nice on-ramp in sunny Florida or just cruise at 70 at just under 3000 RPM's and get great mileage. The car is simple but complex, like a good camera... it takes time to get the results you want, but all the necessary functions are there.
I was lucky and didn't realize it, my car came with LSD, and now I understand there is another mode I can try.... turn the traction control off and let the limited slip take me to places I might not really want to be. A truly marvelous, high-tech mode of transportation, fun and a human magnet. Enjoy.

E. Marshall, A.S., RPR

 

[ckolsen]

I think the original question was why does downshifting help acceleration. Ever ridden a bicycle? A higher (larger) gear (ratio) means the car's drive wheels turn more times per turn of the drive shaft. If an engine's drive shaft is turning at a certain rate, the gear ratio determines how many rpm the wheels will turn. By downshifting, the wheels don't have to turn as my times per rotation of the driveshaft, so there's more power per turn. Maybe someone else can explain this better.

 

[AltezzaRoku]

Em, ur posts are great.. keep em up.

 

[cardinal_creek]

Ditto. Emerald, Appreciate your input on my "tint %" post from yesterday.

------------------
cardinal

 

[Emerald]

Thanks for the compliments, guys. Just trying to give you the straight facts the way I learned them and still continue to learn. Have a lot of knowledge about a lot of things in life and I find the truth really matters.
There's no reason to brag,
be snooty or hold information to yourself.
If you ever want input that I can help you with, it's my pleasure to help out any way I can.
Respectfully, and with appreciation.
Elliott Marshall, A.S., RPR

 

[jiggafett]

Em,
It is a pleasure to read your posts I learn so much. Hey this is turning into an Emerald fan club

"Each One Teach One"

 

[Emerald]

Thanks again... just recently got the urge to come out and and talk to the world. Have been busy with family and my profession.... I appreciate your kind words and will do my best to keep up the good posts and information.
Sincerely,
E. Marshall

 

[ckolsen]

Emerald, what's A.S. and RPR?

Originally posted by Emerald:
Thanks again... just recently got the urge to come out and and talk to the world. Have been busy with family and my profession.... I appreciate your kind words and will do my best to keep up the good posts and information.
Sincerely,
E. Marshall

 

[Emerald]

The A.S. is Associate of science, majored in biology.... 30 credits shy of B.S. The RPR stands for Registered Professional Reporter given by the National Court Reporters Association. Sorry for my poor spelling lately, but I'm tired, it's the dog days of summer and I have been tracking Tropical storms and hurricanes and watching for the Perseid meteor shower, among other things. But thanks for asking.
EMC

 

[Sweetzzzz]

CAN DRIVING WITH THE E-SHIFT ALL THE TIME HURT YOUOR ENGINE? OR SHOULD IT ONLY BE USED TO DOWNSHIFT TO PASS PEOPLE? OR CAN I UPSHIFT AND DOWNSHIFT FROM 2-5 LIKE A MANUAL?

 

[92diamante]

why would u shift from 2-5...thought u can downshift more than one gear(in breaking or passing?) and not shift up more than one rite? im only learning manual..sorry..

 

[92diamante]

thanks again for all the good posts...answers MANY of my questions on driving manual.