I have the Power Functions IR Speed Remote Control 8879 and it's great for, well, the train it came with and maybe other applications where you don't need precise control. 8885 looks like it would work for a car but does it speed up the motor the further you press up the joystick? Is the joystick spring loaded in that it returns to "stop" when you let go or it it more like the helicopter remotes of late where you press the joystick up and it keeps that current speed? Do the joysticks move left to right and up and down?
The two sticks on that remote are pure on/off switches (well, forward/off/backward) and come back in their central position if not maintained pushed, and don't move laterally either.
There are two classic ways to control a car with them:
Use each switch to control a motor and wheel (or set of wheels) - so you have to push both levers to advance, and only one to turn. That's how the first PF Motorized Bulldozer is built and it works great for that kind of model.
For a more realistic car, however, you'll need to use one motor to control the forward/backward movement of the car (that's the easy part), and the other for the direction. That's slightly less easy, but you can usually achieve it with some kind of spring-loaded mechanism that puts the direction to straight forward when you're not pushing the lever. Some people have used that part to do it, but I've never tried it myself:
Edit: as I said, using the 8879 remote by itself to control a vehicle directly may be difficult, but I forgot it's a Technic part by itself, which means you can build something else on top of it. See Sariel's modification for a good example with which you can easily control a one-motor-per-wheel model.
1Good answer but bad news. Seems like the train remote would work just as well. I think what I need is an IR transmitter for my phone or to program one of those universal remotes. But even then I'll have to press up up up up to get it to go faster and then down down to slow it down. Not great. Dec 16, 2011 at 18:41
The train remote should be OK for speed, but steering is probably not going to be easy. One thing you could do is combine one of each, but that may be extreme. Note there is also a specific PF car base, but frankly it's not that great. Or, a NXT brick with a IRLink, then you can do pretty much what you want programatically.– JoubarcDec 16, 2011 at 19:26
Somehow that car base is going for almost $300 on Amazon. Crazy. Dec 19, 2011 at 17:20
What speed is "on"? Can you set the speed for what "on" means for that remote? Jan 2, 2012 at 22:52
"on" means full power (apply whatever the battery delivers). I don't think it's changeable in that remote, or at least I've never heard anyone who did try.– JoubarcJan 3, 2012 at 9:33