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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / February 2007Infinitely variable transmissions
I see one of the new Japanese models has this, and I think a model of Ford does. I am sure there are others. Anyway, how is the ratio programmed? Does the engine run at only a single speed? What is the basic program that selects the ratio? With the torque curve on most current engines, it seems you'd have to run a pretty high engine rpm to get good performance, but that would be very wasteful of fuel at light load. So I suspect the engine is NOT run at a constant speed, and that the actual commanded ratio is a fairly complex combination of road speed and throttle position. I think they use some sort of a mechanical ''belt'' arrangement and automatic variable speed ''pulleys''.For lack of how much I know about them anyway.Dutch company DAF in the Netherlands had something similar on the market back in the 1960's. cuhulin > I think they use some sort of a mechanical ''belt'' arrangement and > automatic variable speed ''pulleys''.For lack of how much I know about > them anyway.Dutch company DAF in the Netherlands had something similar > on the market back in the 1960's. > cuhulin Something like a snowmobile. I did a couple of googles for, DAF Automobiles and, Continuously Vairable Speed Transmissions A lot of information there.I own a real good Briggs & Stratton twin cylinder 12 horsepower air cooled horizontal shaft engine.I ought to buy a Comet torque convertor transmission and some wheels and other parts and build my own three wheel car.If it would haul me to the food store and back with my groceries,that would be good enough. cuhulin On Feb 24, 9:32 am, cuhu...@webtv.net wrote: > I think they use some sort of a mechanical ''belt'' arrangement and > automatic variable speed ''pulleys''.For lack of how much I know about > them anyway.Dutch company DAF in the Netherlands had something similar > on the market back in the 1960's. > cuhulin I understand how many of the mechanisms work. What I am interested in is the program- the map that commands the ratio. >I understand how many of the mechanisms work. What I am interested in >is the program- the map that commands the ratio. In the 60s, that map was in the driver's head. And my sneaking suspicion is that, just like with a conventional transmission, no two drivers have quite the same style of operating it. My suspicion also is that the manufacturer of the car using an automated system will use different maps for different vehicles... the algorithm you'd want in a sports car may be optimized for high torque at low speeds, while that for use in a family sedan is probably optimized for mileage and emissions. --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > I understand how many of the mechanisms work. What I am interested in > is the program- the map that commands the ratio. I don't know the whole algorithm, but basically the ratio is determined by a combination of power demand (basically throttle position) versus road speed). At a given road speed, the ratio will move to a higher numerical value (higher engine speed) if the driver steps down on the gas, or otherwise will migrate to the lowest numerical ratio that will sustain road speed for economy. > I see one of the new Japanese models has this, and I think a model of > Ford does. I am sure there are others. Anyway, how is the ratio [quoted text clipped - 5 lines] > and that the actual commanded ratio is a fairly complex combination of > road speed and throttle position. The engine does not run at a constant speed. It varies according to the torque demand from the drive. For example, for acceleration, the transmission will alter the drive ratio so that the engine quickly goes to the maximum power speed and then the trans will progressively sweep the drive ratio until the desired speed is reached. In cruise mode, the trans calibration will set a ratio so that the engine is running at its most efficient speed and load; usually low speed and high load (and still meet exhaust emission constraints). And yes it is a fairly complex map of pedal position (uses electronic throttle control), vehicle speed and acceleration demand. On Feb 24, 10:20 am, "Don Stauffer in Minnesota" <stauf...@usfamily.net> wrote: > I see one of the new Japanese models has this, and I think a model of > Ford does. Like another poster has said, snowmobiles, Cushman scooters and various other golf carts have a system similar (in principal) to what these cars have. Basically the drive pulley gets bigger and the driven pulley gets smaller. My mom has a Ford Five Hundred that has this tranny and so far it has been great. It's interesting that if the Ford tranny goes bad, the Ford shops pull the whole thing and have a rebuilt one shipped in. It is not yet rebuilt at the dealer. If this policy has changed in the past few months, I'm sure somebody will let me know....... >I see one of the new Japanese models has this, and I think a model of >Ford does. I am sure there are others. Anyway, how is the ratio [quoted text clipped - 5 lines] >and that the actual commanded ratio is a fairly complex combination of >road speed and throttle position. Some car manufacturer did this in the sixties, with two opposed cylindrical gears and a small follower gear that moved between them and changed ratio with position. The driver could select the ratio as well as adjust the throttle, so he could select a lower ratio when he wanted more torque and then crank it up for highway cruising. It would be interesting to see how it is handled automatically. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." http://www.vibratesoftware.com/html_help/html/Diagnosis/Reference/CVT_Transmissi ons.htm Bob > I see one of the new Japanese models has this, and I think a model of > Ford does. The Nissan has it, and I was curious about it too. I am not considering buying one now, but wondered who made this for Nissan, how it worked, and how it holds up. As to the last, the belt is steel and apparently Nissan did their homework on this one, from what I am told. Owners say it is very durable. It may have come out of Nissan research but I dont know who actually makes it for them. I finally found a website with some pictures, and its design is pretty much what you would intuit. As far as the control programming, I have no idea. |
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