Re: FOR CRYING OUT LOUD!! . . . .

ChrisCoaster wrote:

I can tell you how to do it on a Chrysler recirculating-ball PS unit from the muscle car era. I've never been into a rack-and-pinion unit, but control theory is control theory. There HAS to be a sense mechanism, there HAS to be a control valve that moves in response to the sense mechanism, and there HAS to be damping and reaction. What I don't know is whether or not any of that is realistically changeable on a Kia rack! Its not easy on the old Chrysler recirculating ball gear- it requires a complete disassembly and then re-setting-up of all the backlashes and tolerances. But it does produce EXACTLY the desired result, and there's even a company (FirmFeel inc., whom I think I've mentioned before in these discussions) that modifies those gears for restorers and customizers. If I were serious about trying this to a Kia rack, I would go out and buy the factory service manual that includes instructions on tearing down and rebuilding that rack. I'd study it and understand how it works and find out whether it uses reaction springs to determine how much steering wheel torque it takes to trigger power assist, whether I could replace them with stiffer springs, and if it doesn't use springs I'd try to figure out exactly how it DOES translate steering torque into assist. I would then try to find a junkyard rack, disassemble it, and see if I could modify it. And get it back together in working order.... And I'd be prepared to have a failure or two and spend some money that I really didn't want to spend. But that's just how things go in the hot-rod/custom/resto world ALL the time, and its how DIYers figure out how to innovate.

As I said before, my skepticism for anything external isn't just inherent negativism, its based on the fact that you're outside the closed-loop control system that exists inside the steering box (input, "gain" or steering assist, response, and feedback). Once outside that loop, changing anything like a line pressure may have a lot of unintended consequences. Its like trying to turn down the volume on your stereo by putting a dimmer on the electrical power cord.

____________________ Thank you for the well-thought-out reply. Bob Vila could not have done better with replacing windows, and it was just as good as any explanation from "Two Guys Garage"! :)

So basically, modern vehicles have everything pretty much engineered to work pretty much together. Am I right, pretty much? Actually, I never met Much so I don't know how pretty Much is, but I digress... :D

So back to point, it wouldn't be advisable to rip apart everything a major auto builder invested money in to engineer, build, test, rebuild, finalize, and get to market. Right?

The 2008 Kia Optima reminds me of something between my old '96 Contour GL(which I actually wish I still owned! Darnit!) and the car after that - a 2003 Impala LS. Both being reasonably nimble and just stiff enough at the wheel.

- No twitchiness or constant need for correction to stay on center.

- Quick enough return from turns.

- Very responsive to turns of the wheel - when called for.

- For a car with now 17,000+ miles on it(I bought it with 14,000), the alignment seems fine: Steering wheel is straight, excellent rolling, and only a slight pull, make that DRIFT to the right when I let go - obviously from road crown. It does not shoot left or right when I leggo the wheel, as did the 2005 Malibu, nor drift to the left as did the '03 Impala.

The car came with Kumho Solus H-rated tires which looked new when I got the car, and they packed a tenacious grip in turns on anything but very wet roads or snow. Beyond that, they were useless. I replaced them with T-rated(118mph) Mastercraft LSRs, which I find a far more balanced blend for anything from dry roads up to at least an inch of standing snow.

I'm beginnng to wonder if I should have gone for U-(124) or H(130mph)- rated tires with those Mastercrafts, for stiffer sidewalls. Hey at least I didn't really scrooge and put S-rated tires on it! :)

Would a set of H-rateds help the next time around? The H-rated Kumhos on the Kia rode a lot smoother than the H-rated Yokohamas I wrapped on the Malibu two years ago, so I know no two tires within a speedrating will lend the same ride.

-CC

You didn't read his post.

It COULD be advisable to do it, but if you do it, you need to understand how the system works in great detail before doing so, and sadly that means reverse-engineering the system because it is not documented in great detail.

Finding this out could be useful and it could be fun, and you will almost certainly learn something about feedback control systems in the process, but it is _not_ trivial. It could have been trivial if the engineers building the system had designed it to be adjustable, but they didn't.

--scott

Yeah, Scott summed up what I was saying pretty well. If you could score a rack from a junkyard Kia for relatively little money, and if you could lay hands on a service manual that included instructions on servicing the rack, then I think it would be a worthwhile experiment. That's

*probably* how FirmFeel steering got started... you might even wind up with a retirement career/hobby/company. :-p Except that hydraulic power steering is probably going the way of the velociraptor...

On May 27, 12:46 pm, Steve wrote: Except that hydraulic power

_______________ And that's a shame, Steve. We all know the reputation of electric PS from a handling perspective - despite what my environmental colleagues say about "going green." Good straight-ahead and handling feedback are more important than conserving energy when it comes to vehicle control and road safety. ;)

-CC