An idea I had at work

[YellowMaranello]

Here's an idea I had while I was working the other day:

Ok, first off, a car accelerates hardest when its making its peak power at a certain RPM. Lets say that we have a car that makes its peak power at 5000 RPM. What if someone designed a transmition that when the car was at WOT, it automatically took it down to the lowest possible gear ratio for the speed they are going, while keeping the engine at 5000. Then as the car accelerates, the tranny constantly changed the gear ratios to keep the car at 5000 RPM while it accelerates. Which would mean that you never notice it actually "shifting." This would have to be done with some sort of continuously variable transmition. I'm really horrible at explaning things, so feel free to ask if sometimes isnt clear. My first question is, would it be possible? If it is, would it be beneficial? What is everyones thoughts on this?

[ivymike1031]

yes, it's possible, it's called a continuously variable transmission (CVT), and there are several mass-produced vehicles on the road today that have CVTs available. Usually the controls on these CVTs aim to keep the engine operating near peak torque, but it's the same idee-er.

[YellowMaranello]

But what I'm saying is that the tranny would never actually "shift" but instead would gradually change the ratios while still delivering power and keeping the engine at whatever it makes it peak power at. So, you would be able to floor it, and have it keep it at 5000 all the way from 10 mph to 100 mph without ever stopping the delivery of power. I thought that CVTs were just like other transmitions, but just never shifted into a specific gear ratio.

[97stratus]

they make cars liek that. The new audi A4 has a transmission that doesnt' shift in the traditional sense. Toyota also has something similar on there mr2

[454Casull]

I talk out of my ass too much.

1) Not check if it already exists.
2) If it doesn't exist, post it on the internet.

This isn't a flame, just a suggestion that if you had thought up some kind of new gearbox, your best bet is to keep it secret until you've actually invented it

[ivymike1031]

454: While I haven't driven a car equipped with a CVT, I feel confident saying that they're anything but "just like autos and manuals."

Yellow: CVTs are always using one gear ratio or another... they just have an (almost) infinite spread to choose from. It's like having a 1,000,000 speed transmission instead of a 5-speed. Here are some quotes from articles about CVTs:

"Going WOT in any mode (E, D, or S) will cause Multimatic to use the highest possible engine rpm (>7000rpm for S) which delivers the optimum gear ratio for the highest possible acceleration from then onwards. This feature offers superior pick-up from 4AT and superior flexibility over 5MT during driving." http://asia.vtec.net/article/mmt/

"The "stepless" nature of its design is CVT's biggest draw for automotive engineers. Because of this, a CVT can work to keep the engine in its optimum power range, thereby increasing efficiency and gas mileage. " http://www.edmunds.com/ownership/tec...4/article.html

"Obviously, a CVT feels smooth in operation because no actual shifts occur, but the real advantage comes from its ability to vary gear ratios instead of engine rpm for a given driving situation. For example, if an engine's peak horsepower and torque occur at 3,200 rpm, a CVT would allow the engine to remain at this rpm even when climbing moderate hills or accelerating. While a traditional transmission must shift between multiple gears to try and keep an engine in its prime operating zone, a CVT just slides its belt between the narrow and wide ends of the pulleys to create a much more efficient drivetrain" http://www.edmunds.com/news/innovati...6/article.html

"during full throttle acceleration runs when engine revs are held almost constant while road speed increases rapidly" http://www.autobytel.com.au/consumer...s/Civiccvt.htm


Does that sound a bit like what you were referring to?

[BeEfCaKe]

Constantly keeping gears running at 5000rpm.. wouldn't this cause overheating eventually? An extra cooling system will be required if this concept really is used.

CVTs currently in mass-produced cars, that I know of are the hybrid cars, such as the Toyota Prius, which features the "Electronically controlled continuously variable transmission (ECVT)"... I forgot if the Honda Insight has the same system, but I would guess it would have something similar to increase efficiency.

[R34GTRVspec2]

OMG that is the coolest picture i have ever seen

[YellowMaranello]

Originally posted by ivymike1031

"during full throttle acceleration runs when engine revs are held almost constant while road speed increases rapidly" http://www.autobytel.com.au/consumer...s/Civiccvt.htm

That is what I was talking about. Seems it can and already has been done. Thanks Mike!

[YellowMaranello]

and R34GTRVspec2, that pic sure is an awesome red x.:silly2:

[454Casull]

Now they just need to figure out how to strengthen the setup so that you can slap it onto a 1Khp+ car.

[R34GTRVspec2]

Originally posted by YellowMaranello
and R34GTRVspec2, that pic sure is an awesome red x.:silly2:

:jump: ya, my bad LOL

[pimpin4profits]

If a CVT tranny never really shifts, and keeps it at the optimum rpms, then it must sound REALLY goofy to hear a car that has a cvt with aftermarket exhaust....

The impression I get is that it would produce a flat, "BBBBAAAAAHHHHHHHHHHHHHHHHHHHHHHHH"

True??

[ivymike1031]

yes and no... if you put a "standard" aftermarket exhaust on, it would probably not sound the way you wanted it to. I'm sure you could design an aftermarket exhaust for the CVT application that would give you a more desireable sound.