Zatem

I wholeheartedly agree with your last statement.

Regarding stable steering technique...

While roll-yaw coupling is a common problem in many airplanes, the highway driving effect I was talking about is a pitch-yaw coupling, where taking a dip or bump (pitch) at high speed can induce dangerous swerving oscillations (yaw) if driving with one hand.

The problem in detail:

When you hit a dip or bump, the car experiences a pitch transient that moves the vehicle in the up/down direction. With two hands on the wheel at the 10 and 2 o'clock positions, the wheel stays mass-balanced. However, with one handed driving, a pitching motion causes the weight of your hand on the wheel to have the dynamic response of "bobbing" up and down with the vehicle motion. This motion couples into a yaw transient because of your inadvertent steering input. This results in swerving oscillations. The lack of stability that initially caused the problem will continue to act against efforts to regain control.

Solution:

There are probably several techniques out there. The one I worked out for myself is to move my left foot back in order to raise my knee. Then all I do is rest my wrist on top of my knee while holding the wheel with my left hand. This bracing prevents my hand from bobbing up and down and enables a very stable steering control. I have enough range of motion in my wrist for left and right steering adjustments.

For situations where I need to react with a larger steering input than my wrist can do, right turns are simple since upward hand motion is unrestricted, and I can easily make left turn inputs by moving my elbow inward while moving my knee out to free the bracing. Such larger inputs are really more of an issue only at lower speed. It would take a serious emergency to require a reaction of that magnitude while driving at extreme speed because steering sensitivity increases with speed.


During my road trip, I tested the stability of the RX-8 using various steering techniques. Here's what I found:

- The RX-8 is very stable at extreme speed.

- At 120mph with little crosswind, I was able to let go of the steering wheel for significantly long stretches and observe how straight the car drove. (I kept my hand very close to the wheel during this test, prepared for the worst case of a blowout.)

- At 130, it was easy to drive the car with my knees, no hands. Another tribute to the RX-8's stability.

- At 140, one-handed driving was very stable (using the technique described above).

- Pressing to 150 and above, I felt the need to keep two hands solidly on the wheel. The smoothness of the ride at this speed can be evidenced by the first speedo pic posted in this thread. I suspect that my tight grip on the wheel was a result of my personal limits (/adrenaline level) and less so indicative of the RX-8's handling limit. The blur in the second pic (240km/h) is not an accurate representation of the level of smoothness I would feel at that speed. It was probably due more to me fat-fingering the camera shutter than anything else.

rx8spiritR

have anyone gone anywhere close to 170? or i should ask, can a stock 8 (6sp) able to reach more than 160. i don't have a chance to test it, i have no where to test in where i live, but i've ALWAYS want to know, i've tried 158mph @ 6th around 8K rpm on bay bridge @ 3:00am, my other friend with a Evo MR was shock cuz he can only do 150 max. i know i could gas it a little bit more.

Zatem

SpiritR, I'm guessing that you're familiar with this Bay Bridge factoid:

Yerba Buena means "Good Herb".

8_is_enuf

You won't think it is so funny when you wife and babies are out on that highway..

khtm

I thought the 8 was limited to 152mph? Are you stock?

AQA101

Do you have any evidence for the limitation? 152 mph is 244.6 km/h. I've seen more (the equivalent of 157 mp/h to be precise).

Edit: Also, why would not being stock help unless the ecu is modified if there's a limiter? I don't think that the RX-8 has an extra overspeed protection, so if it's limited, it would be limited by the ecu.

rx8spiritR

yes i am stock, everything is stock, my rear view mirror was the only mod i have back then.

khtm

I don't have any evidence...I've just just heard from numerous people that they couldn't get it past 152mph. Including a couple people who tested it on a FLAT airstrip. Several people said it was electronically limited to 152mph.

Now I've been up to about 148 mph on a flat stretch of highway and it definitely wasn't going to go much (if any) faster unless I went downhill.

And the starter of this thread even said he was in 5th going 152 which I find really hard to believe considering I redlined 5th at about 230kph = 142mph. Now maybe I just have an 8 with some sort of manufacturing defect? I don't know...

Maybe you have different cars in Germany but unless i see proof of a stock N.A. car going over 152, I'm calling BS.

(And my stock question was referring to the ECU)

AQA101

I agree that 152 in 5th sounds unlikely, the rev limiter kicks in somewhere near 235 km/h, that's 146 mph.

I see no reason why Mazda would limit the car at 152 mph or 244 km/h. Both numbers don't apply to any known (to me) regulations and car isn't even near redline at whatever known top speed. 6th gear redline would be somewhere around 270 km/h.

First I thought myself that 242 km/h is the magical number, because I didn't get beyond that. But later I had several occurences of speeds beyond 245 km/h and others when I didn't manage to go beyond 235. I guess wind is quite a factor.

A limiter probably would reduce fuel supply though and slow you down whenever you hit the limit. Besides that, other people from Europe have reported speeds beyond 250 as well.

Zatem

In all of my excursions above 150mph, I never hit the rev limiter. They all topped out at the drag limit. In 5th gear, this required going well into the red zone with the buzzer complaining the whole time even though the engine kept singing. In 5th gear, there is not much room above 152mph before the rev limiter will spank you.

I am certain that the stock RX-8 can reach significantly above 152, although this would require some combination of downhill and tailwind after shifting to 6th gear.

How fast can it go across the SF Bay Bridge? Well, there is a bit of a downhill stretch going into Oakland, but that is the lower level so any tailwind would be significantly obstructed. And anyone who has pushed the RX-8 above 140mph knows how much patience (read: distance) it takes.

A term used for jet aircraft is called Specific Excess Power. The same concept applies to sports cars. Drag forces increase with the velocity squared. Thrust/Horsepower is a limited quantity. The difference between drag forces and thrust forces define how much excess power you have available for acceleration. When you are approaching the limit of maximum speed, you have very little excess power. Each increment of acceleration occurs very slowly. Again, this requires significant patience and distance. The Bay Bridge has definite limits on its straight line distance. And the bend it takes east of the Yerba Buena tunnel is not trivial.

So is 150+ possible for a stock 8 across that bridge? We have one person who said "i've tried 158mph". As I've hinted at previously, whether you see the story as credible or not, we might all be able to agree that it's a smoking Yerba Buena run.

gusmahler

Actually, I once read an article in C&D where the author was describing a drive he had with Jackie Stewart. On the track, Stewart was amazing, able to drive near the limit seemingly effortlessly. Then able to drift the car at will when he wanted to "show off." On the road? Cruise control at 55.

Zatem

Interesting story. It leaves me with some questions, though. Assuming the story is accurate, I wonder how many times Jackie got busted for speeding (license revoked?) before settling in on such a habit. Also it is extremely difficult for me to imagine Jackie maintaining a solid 55 if traffic were to be flowing by him.

And then I'm wondering about how the C&D audience would be affected by such a testimony... "I want to be like Jackie Stewart. (cruise55)"

alnielsen

iTrader: (4)

Now that there are boosted 8's running around, I wonder how fast they can go and what the driving experiance is at 160 & above.

dmp

Gearing....

AQA101

... plus rev limiter would stop it slightly above 270 km/h (170 mph).

The driving experience is probably not far from 250 km/h. Glued to the ground by downforce.

Zatem

I'll side with AQA's guess. With as solid as the 8 is at 150mph, I would expect it to remain quite stable at 160 or even 170. Perhaps I'll get up there myself. I don't have any major mods planned any time soon, so it's going to take just the right conditions with a stiff tailwind.

By the way, I hope the non-USians on the forum are ok with me posting in non-metric nums.

Here's my random thought of the day...

Europe is big on metric, but when it comes to designing a flag they decide to put 12 stars on it. The official explanation belongs in the I'm-not-making-this-up file:

"There are twelve stars because the number twelve is traditionally the symbol of perfection, completeness and unity."
"It is also, of course, the number of months in a year and the number of hours shown on a clock face."
http://europa.eu.int/abc/symbols/emblem/index_en.htm


(On the flip side, one might also find irony in the US holding the hard line against metric while having a fixation on the number 13.)

AQA101

Off topic: Metric is OK because most of us have 10 fingers and can figure out things rather easy in a metric system. 10 Stars in the flag would look a little unbalanced (make that 2 crossed RX-8 rims and imagine the effect) though, so 12 stars is OK with me.

But the best numbering system would be hex (based on 6) all the way IMHO. Geometrically perfectly balanced and you could divide 10 by 2 and 3.

slllygrl10

LOL got that right

silverx8

I got to 255 mi and put in 15.01 gal.

silverx8

I once hit the rev limit in an RX4, 135MPH. This thing has got to be safer.

Zatem

All this time I forgot about the effect from DSC...

- That 326.1 mi stretch was all done with DSC fully active.

I don't know how much my range might have improved with DSC fully off, although I'm sure that others here have a feel for that. Being off would also have a slight affect on acceleration to top speed, although that's not something I see myself messing wth. I look at DSC as life insurance (which is why I bought the Sport Package). The only times I've turned it off are when I deliberately want to slide.

Zatem

In the 8, I've never hit the rev limiter in anything above 2nd gear. Early on I did a few experiments pushing 1st and 2nd gear well into the red to see how the limiter reacts. Hitting the limiter in the taller gears must be squirrelly.

...and at 135 in the RX-4... YIKES!

Zatem

I'm still curious about DSC On-vs-Off mileage, if anyone would like to share info they've gathered. I've searched the archives but didn't find anything quantified.

Zatem

I noticed that there has been some recent discussion on high speed driving. Maybe there is something from this old thread that certain members will find useful.

Yesterday, by the way, I pushed my 8 to 120mph into a school zone, followed by a quick brake to a full stop at a red light in front of the school. (Time was 10am. Obviously it is a rare school zone where it is safe to do something like this. This one is perfectly straight with excellent sight distance and nothing else around.)

LiveBlues

I rarely pass judgement on anyone, but if you slowed down from 120 into a school zone, then you sir are a dumbass.