Here's a web site that has some nice illustrations to show what I am talking about:

http://www.datsuns.com/Tech/whentoshift.htm

Notice that at the speed he chooses for his shift, the torque at the wheels of 330 lb-ft is greater than even the peak torque at the wheels in the next gear.

 

Here's yet another good article:

http://www.allpar.com/eek/hp-vs-torque.html

This one even has a spot concerning the idea behind the CVT:

"Applying the maximum power rule, we'd like to race down the 1/4 mile with the engine always as close to 6500 RPM as possible. If we had a continuously variable transmission, the lowest E.T. would be achieved by keeping the engine dead on 6500 RPM. 5500 is not the best; at any vehicle speed, the engine would put out more torque but the transmission will have a less advantageous gear ratio, so you get a net loss of force to the tires. Apply P = F * V or P = T * RPM to prove this."

I added the bold. I think "E.T." is referring to "elapsed time" but I couldn't find his definition of the abbreviation.

 

I appreciate your view point, but like you stated yourself, you haven't driven the CVT, and its not exactly the same thing, not at all in fact. The CVT has unlimited ratios between two given points. So when we accelerate, it holds that gear until desired MPH is reached. It doesn't shift unless you keep it up to 6k rpms, but its pointless since the power dies off. That is why we talk about holding it from 3.5k to 5.5k. It doesn't get any faster past that, because it doesn't shift like a gear, since it has no gears. When it shifts, its very subtle.

 

We may be arguing the same point, but the peak torque is still at the same spot. When you shift to a lower gear it doesn't move the peak torque to a different RPM range. Peak torque is still in the same RPM range that it was in before. The only difference is when you down shift it makes it easier for that torque to change the rate of spin of the wheels.

Peak torque is only developed at WOT (wide open throttle). So, if you're cruising at 50 @ 4250 RPM the engine is NOT developing "peak torque". When you down shift to a lower gear the engine has to spin at a higher RPM, but to maintain the given speed it does not need WOT so it will not be developing "peak torque", it only needs the same amount of torque (at the wheels) that was being used before to maintain the speed. Granted the engine speed will be higher, but that is only due to the gear reduction of the lower gear.

So, in the end, the "peak torque" of the engine still occurs in the same RPM band, but the amount of torque that reaches the ground will vary from gear to gear. For the gears under 4th gear, it will be greater than what the engine develops. In a perfect world, 4th gear will have the exact amount of torque the engine makes going to the wheels. Finally, in 5th you will have less torque than what the engine makes going to the ground. The engine's 'peak torque' is still @ 4250RPM no matter what gear you select. While the amount of toque will vary with the selected gear, the at the wheel torque curve will still follow the engine's torque curve. So, for a given gear the torque at the wheel will always be greatest @4250RPM.

. . .

I just realized that maybe we have a discrepancy of 'peak torque' definitions. I'm defining "peak torque" as the maximum amount of torque the engine can develop relative to the rest of the "torque curve".

In rereading your explanations, it sounds like you're using the physics description of 'peak torque'. Which would be, the maximum amount of torque that can be developed for a given engine speed. When you apply a multi-gear ratio transmission to the mix then, yes, your explanation is 100% correct. You do have more torque available at the wheel in a lower gear than you do in a higher gear for a given engine speed or vehicle velocity. So, even though the engine torque is lower at 6k than it is at 4.5k, a lower gear will allow you to put more torque to the wheels at the higher RPM.

However, the engine is still only developing the same amount of torque and power for a given RPM, and the engine's WOT 'peak out put' (relative to the entire power curve) will always remain within a given RPM range. The engine's power is not increasing and decreasing with the selected gear, only the amount of power and toque that reaches the wheel. And the peak, relative to the entire power curve, is not moving up and down the RPM range, but the magnitude of the power curve will change with the gear selected.

There seems to be some intermixing of explanation there. Engine speed and vehicle velocity, though inter-related in real world application, should be kept separate as intermixing the two can have two people in agreement arguing the same point but from different angles...

 

Yup, it can be very confusing. At times I've referred to torque at the crank and at other time torque at the wheels. I hope its clear which. Also, I've been assuming wide open throttle, although I didn't say it. Ultimately, what is important for acceleration is torque at the wheels. My main point is that based on Mitsu's torque curves, at a given speed there should be more torque at the wheels at 6000 RPM than at 4250 RPM, even though the motor's peak torque is at 4250.

Even though the CVT doesn't have "gears" it does have gear ratios. At some speed, say 50 MPH, the gear ratio to have the engine spinning at 4250 RPM must be lower than the gear ratio to have the engine spinning at 6000 RPM.

Torque at the wheels (TW) is a product of torque at the crank (TC) times the gear ratio (G). So, TW = TC x G
This ignores the final drive ratio, friction, etc. which I assume constant.

The math simply comes out that between 4250 and 6000 RPM, TC is greater at 4250, but TW is greater at 6000.

By the way, if you're driving a CVT at a constant 50 MPH and the RPM changes from 6000 to 4250, the transmission MUST be changing gear ratios. You can't have a constant vehicle speed and changing engine speed without a change in gearing.

I'll see if I can resist saying any more about it unless someone asks me :>)

I will, however, pose a question that someone might take a stab at answering: Why doesn't the CVT have the appropriate ooomph at the higher engine speeds? Is it a friction issue? Is it the computer? When you take the final drive into account, the range of gear ratios available with the CVT is very similar to those available with the MT. If the motors are the same, then what's up? With the same range of gear ratios and the same motor, there is the potential for similar performance. In theory (yes, I wish I had two Lancers to play with, but I don't) the CVT has the potential for better performance than the MT.

 

By the way, I do believe the latter part of Nunyas post is exactly what I was getting at.

 

Bottom line is that we need someone to hit a drag strip. 1/4-mile runs at WOT and at 4500rpm should pretty much settle the debate...

 

Again...release air pressure...make sure you're in a wind tunnel when you do it...

 

Hey guys,

Here is a very good explanation about the CVT, what it is exactly and how it works. This should shed more light on the subject than everyone's opinions, especially those who have never even driven a CVT before.

http://cars.about.com/od/thingsyouneedtoknow/a/CVT.htm

Youtube, Mitsubisi video of CVT

http://www.youtube.com/watch?v=4kNtF...eature=related

 

Right, I guess that's me. Well, a quote from the article posted above helps prove my point:

"This allows the CVT to provide quicker acceleration than a conventional automatic or manual transmission while delivering superior fuel economy."

Somebody should be asking the question, "Why doesn't the Lancer CVT live up to its potential?" I think everyone agrees that the MT Lancers provide faster acceleration than the CVT. So what's up?

I'm perfectly happy to believe what you are saying about the best performance coming by keeping the engine speed at 4500 RPM. You're the ones driving it, not me, and I am not contradicting you about what you are saying about the real world performance That is simply further evidence that the Lancer CVT is not living up to its potential.

I did a good bit of driving today, and I thought of this example (I'm trying to avoid grading papers, so here goes):

Suppose you are traveling at 50 MPH with the motor at 4250 RPM and you want to accelerate to 60 MPH. If you want to accelerate, then one of two things (or a combination of the two) MUST happen: an increase in the engine speed or a decrease in the gear ratio.

1. Increase the engine speed (with no change in gear ratio). A 20% increase in velocity means an increase in engine speed from 4250 RPM to 5100 RPM. As engine speed increases, you do move past the motors torque peak, but torque at the crank drops by less than 10 ft-lbs! If the gear ratio stays constant, then the loss in torque at the wheels is only about 7%.

2. Decrease the gear ratio (with no change in engine speed). In other words, to accelerate the car while keeping the engine speed constant at 4250 RPM, the transmission MUST "upshift." With the CVT, this means a constant reduction in the gear ratio by infinitely small increments. Can we all agree on this??? The engine speed stays the same, but the gear ratio doesn't. Decreased gear ratio means a decrease in torque at the wheels. Since the gear ratio must drop by 20% in order to increase velocity of the car by 20%, that means there is a 20% drop in torque at the wheels.

Situation #2 shows that while you may be able to keep the crankshaft torque at its peak while you accelerate, the torque at the wheels DOES NOT stay at its peak. It drops! In fact, torque at the wheels drops faster when you decrease the gear ratio than it does when you increase the engine speed! This is why the CVT Lancer should have more ***** at higher RPM.

So, those of you who actually drive the CVT say that its ***** are bigger at 4500. Well, I believe you, but it's not because I'm wrong about the principles. It means that there is something else going on, and this is what we should be looking for.

Blacksheep said, "Bottom line is that we need someone to hit a drag strip. 1/4-mile runs at WOT and at 4500rpm should pretty much settle the debate..."

Doesn't that immediately raise red flags? As Nunyas said, if you're not at WOT, then you're not getting peak torque anyway! If holding back on the throttle is giving you better performance than WOT, then something is not right!

I can only guess at why there is the discrepancy between theory and reality. Here are three guesses:

1. Mitsu has concerns about reliability of the CVT being run at high engine power. So, as the motor gets into the higher RPM, the computer cuts back on the fuel.

2. Mitsu wants the EPA and its customers to see good fuel economy numbers from the CVT. So, as the motor gets into the higher RPM, the computer cuts back on the fuel.

3. At high RPM something funny happens with the belts causing slippage or friction or something that I don't understand.

If it is something to do with the computer programming, then some enterprising person out there should be able to come up with a fix. How much would you CVT owners pay for a solution that would live up to the promise of the CVT out-accelerating the MT???

Anyway, I do enjoy a good debate, and I couldn't resist picking back up on it. However, it really isn't my point to debate the mechanics of the CVT. Rather, I've been hoping to open the doors on why the CVT doesn't live up to its promise. Back in 1989 I had a friend with a Subaru Justy with a CVT. It was novel at the time, but the engine had so little power there was nothing to be impressed about. My father was an engineer, and he thought CVT's were very interesting. If I wasn't addicted to having three pedals, I would likely prefer a CVT over a conventional automatic. But, I would want a CVT that holds power up to the red-line and performs as it should

 

In the video they do state that it provides the best mileage, and I really believe that is what they programmed it for. The sport mode is just a gimmick they made to give the "feel" of performance. HOWEVER, I do believe that the CVT can be reprogrammed for serious performance applications. Look, there is a major difference in acceleration from the manual and the CVT, which theoretically, shouldn't be the case. I would pay good money for a reprogrammed CVT, especially if it made it faster than the manual. But its probably worth as much as an ECU reflash.

 

By the way, Blue, if you are holding RPM in a narrow range as you accelerate (as I believe you are saying is best, like 3.5K to 5.5K), then the statement above is totally untrue. In order for the car to keep accelerating as RPM is kept in a somewhat narrow range, then the car absolutely DOES NOT hold that gear. As I described in my last post, the CVT will decrease the gear ratio and you will lose torque at the wheels.

The CVT can only "hold that gear" if you are letting the engine speed increase linearly with wheel speed. There is no way that you can accelerate from, say 30 MPH to 60 MPH, and keep the engine speed between 3.5K and 5.5K without a considerable reduction in gear ratio.

Perhaps I have misinterpreted what you were trying to say, but you weren't particularly clear.

 

Just read Blue's last post, and now I think we're on the same page.

 

true..i never owned a 4 cylinder before..and to tell u the truth its killing me..i cant wait for the turbo to come out so i can smack one of those in there...of course its a lot more to it..but hey ill have a lot more than 140 mph on a dyno

 

4 cyl, 29 mpg and 240hp, 0-6 in 5 sec = SWEEEET