Top Gear Full Article
 

I only remembering hearing a summary of the Top Gear RX-8 article so I thought I would link the full article.

Sorry if this is just a rehash.

http://www.topgear.com/servlet/tg?DE...Number=01.html

From the way the article sounds, the euro version will have 500 rpm lower redline than the US version. I'm not real sure on this but I thought the buzzer came in at 9k and fuel cut was at 9.5k I could be wrong.

Also I don't believe anyone was really allowed to romp on the 8 at the testing grounds as this article states how they were told to slow down several times.

I looks like the cars they tested could have all been euro versions with the lower horsepower rating.

"Only the lightweight fully electrically-operated power-steering system can impinge on progress, at times feeling sluggish and numb to respond. " From article.

What does this mean? is it just this guys impression? is he driving the "crappy" car? i have no idea. of course these are just prototypes so i guess we can expect something different. what do u think?

Re: Top Gear Full Article
 

You can find the link here .

I hope we get the 250hp version in SA.

regards

I think that since this car has electric assist steering, that it loses some of the raw feedback that many sports cars have.

However I'll be quick to point out, that the new BMW Z4 has this system as well as their upcoming 5 series. Sometimes too much feedback gives you a pain in the arm :)

I think Honda's S2000 has this type of steering, as well, and I've heard of no complaints about its responsiveness.

Yes, the S200 does have electric steering. Personally, I love it. It is nicely weighted, and full of feedback. The benefit is that the engine does not have to spin a hydraulic pump.

S2000, darn typos............

you (as i often do) can use the "edit" feature to correct misstrokes, leaving no one the wiser... <<evil cackle>>

The MR2 Spyder also has electric-assisted power steering. It feels superb 99.5% of the time. I've only gotten "ahead" of it once or twice, doing some wacky drift maneuvers that most people will never try.

I do wish it had a little more detailed feel to it but that's the price to pay for a nice quick ratio and ease of turning.

"I think that since this car has electric assist steering, that it loses some of the raw feedback that many sports cars have. "

Pretty much every car sports car these days has power steering. There's no reason why a pump powered by an electric motor would inherently be less linear or have less feedback than one powered by a belt off of the engine. In fact, if you think about it, with all the changes in RPM that an engine makes when it goes through gears, you would think that it would probably be easier to make consistant power assist with an independant electric system. Its been around for quite a while, I think the first volume use was th '91 MR2.

There are speed-variable power assisted steering racks that are hydraulic, not electric. Some models of the FC RX-7 were fitted with this more expensive system.

The problem is that NO power assisted steering rack will completely mimic the razor sharp feeling and brilliant feedback of a manual steering rack, though I would bet that when automakers have gotten more experience with electric assist it will prove itself to be as close to manual steering as you can get.

There is one benefit to power steering - because it doesn't need to be geared as low for reasonable steering effort with grippy tires, the number of turns lock to lock is much smaller, allowing smaller inputs and a smaller steering wheel - all good things IMO.

You're confusing the power assist mechanism (the hydraulics) with the energy source that powers the hydraulic pump. All power steering systems are hydraulic and use hydraulic pressure from an oil pump to assist the rack. The issue is simply what mechanism powers the hyraulic pump to make that pressure. Traditionally that job has been done with a belt run off of the engine, versus the newer method of using an electric motor. Speed Variable assist has nothing to do with how the pump is powered and everything to do with valving the pressure that is made by the pump so that it tapers with road speed. That is all done after the pump and my point was that there is no inherent reason why one method of powering the hydraulic pump should inherently be superior or inferior to the other. AS you point out, its how well the pressure valving to the rack is controlled that has a big effect on feel. I agree the there is a great benefit if it is done well in having faster steering despite larger, stikier tires.

Most of us have read that the rx-8 has a "low polar moment of inertia". What the !@#$ is polar moment of inertia and what does it have to do with steering response?

Lets look at 2 cars with 50:50 front/rear weight ratios. One car has most of it's weight concentrated close to it's center of gravity and the other has most of it's weight further away from it's center of gravity.

The car with it's weight closer to it's center of gravity is said to have a lower polar moment of inertia. A low polar moment of inertia is important because you can rotate around the car's center of gravity much easier and with less force. This means faster and more responsive steering.

The electric power-assist steering that the rx-8 will have has been used to good effect on other cars as people here have attested. If anything, it is probably better suited to the rx-8 because the low polar moment of inertia means that less "assist" is needed.

Brian

Expanding on the low polar moment bit, think of an ice skater as you see in the Olympics. When they go into a spin with their arms out, the rotation is pretty slow, and when they pull their limbs in towards their body, they speed up their rate of rotation. Generally a car with more of its weight within the wheelbase will respond faster than a car with more weight outside of the wheelbase (ever wonder why wheelbases are getting longer and front/rear overhangs are getting shorter?).

I don't know about other cars, but the MK2 and MK3 MR2s (basically 1991 to the present) shut off their power assist to the steering at speeds above 40mph or so (I don't recall the exact number). I suppose it helps that they have <45% of their weight over the front wheels too.

My MKI MR2 has a completely manual rack-and-pinion steering rack. While it does have awesome feel and feedback, it does have its disadvantages. The steering ratio is on the slow side for one. And it can be a bit heavy in parking lots. Also, when you get sideways unexpectedly it can be difficult to get the car back under control neatly, as you spend more effort fighting the steering wheel than controlling it. I've injured my thumbs/fingers/arms on a few occasions from the wheel whipping around fairly violently and catching my hand in mid-flail. :p

Overall I prefer the lightly assisted steering of the current MR2.

Thanks Bryan... I am glad it will be easy to 'spin' my RX-8 :D

*practices 180s in his boaty Millenia*