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-   -   Sudden increase in top speed. (https://www.rx8club.com/series-i-tech-garage-22/sudden-increase-top-speed-116842/)

LainO 05-17-2007 10:23 AM

Sudden increase in top speed.
 
I have had my 8 for about 3 months now and although I've learned alot, I still dont know what its doing at all times. My car always beeped in second gear at 61 mph. Now for some reason it reaches 66. I recently changed gas stations for my fill-ups. Could gas quality really change that much?

fullsmoke 05-17-2007 10:32 AM

It's common sense, simply changing gas does not affect the gearing of the transmission, and thus will not affect the speed of each gear. More likely, you simply held the gas pedal longer or there is a certain tolerance where the beep will occur. Nothing to worry about.

FS

LainO 05-17-2007 01:35 PM

What happened? Dont just say its nothing to worry about. You sound like my dealership..... O it reaches 65 now at 9,000 rpms and it used to reach 61 hmmm o well everything sounds fine....

LainO 05-17-2007 01:39 PM

Sorry I blew up. Just tired of people saying everythings fine when stuff changes. I did everything the same 2 days ago as I do now and it reaches higher speeds before redline..... I dunno.

fullsmoke 05-17-2007 01:52 PM

No problem. I hate it when the dealer tells me things are "normal" too.

I think it might be maybe the tachometer has a certain tolerance and maybe the weather or something is causing the buzzer to go off at a higher RPM. I just hear the beep and shift :)

LainO 05-17-2007 03:03 PM

Ok. Thanx. Whatever it is Im glad it happened. Now I can get even farther ahead of people before going into 3rd.

Aseras 05-17-2007 04:16 PM

it's tire wear.. or low pressure, your speedo is reading faster as your tire diameter gets smaller.

2k4_8 05-17-2007 04:19 PM

The only thing that could explain that is an error or variance in the speedometer reading. (or rpms) Your car will ALWAYS be at the same rpm and any given speed....period, no exceptions. In a manual transmission speed and rpms for each gear are a constant ratio, and that ration never ever ever changes. The only way to go faster or slower in second gear at the same rpms (9k in this example) is to change the actual gear, and since this is a physical change that would have to be made, I think we can rule that out. :wink:

edit: Tire wear won't make a 5 mph difference at ~65MPH I would guess that from brand new, to fully worn tires you would be sitting at a <1mph difference. Tire pressure is fairly similar, and if they were low enough to make a big difference I would sure hope you would notice the crappy handling before the speed difference.:lol2:

LainO 05-17-2007 09:40 PM

The tires are all at 90%. And I just filled and checked the pressure last week.Not to shoot down your ideas or anything... Def changed 5 mph overnight tho, Any other ideas?

dillsrotary 05-17-2007 09:50 PM

magic?

cjkim 05-17-2007 10:40 PM

im sure 99% of the people will agree that you just held it longer

MazdaManiac 05-18-2007 12:30 AM

The beep is pseudo random and occurs way before redline.

MazdaManiac 05-18-2007 02:55 AM

No, because I think the pattern is actually deliberate.
I think the PCM fools around with the beeper depending on load and gearing.

MazdaManiac 05-18-2007 03:14 AM

It seems that the beeper uses time in gear/load rather than RPM to gauge the start point.

TeamRX8 05-18-2007 03:29 AM

the beep is irrelevent, let it slam and stay on the limiter and the speed will always be about the same; 68 - 69 mph indicated

MazdaManiac 05-18-2007 03:53 AM


Originally Posted by Charles R. Hill (Post 1883683)
So it assumes driver reaction times to the beeper? If that's the case wouldn't it have been nice for Mazda to just concentrate on installing an accurate tach and leave the predictive stuff alone?

I don't think its quite that well thought out.
I just think it follows a preset curve to where it thinks the fuel cut will be hit and warns preemptively.
American market-driven products are increasingly predictive.
Americans want cars that drive themselves so we can spend more time on the cell phone.

Nubo 05-18-2007 10:49 AM

LainO, please make it clear -- are you reporting the speed at exactly 9000 rpm as seen on the tachometer or are you just referring to the speed when the beep sounds?

LainO 05-18-2007 12:03 PM

When the beep sounds... I guess its nothing to worry about... I guess

jeffe19007 05-19-2007 01:18 PM

And I was going say you had tail wind....

Oh, well. I can now ignore the beep and try to figure out where fuel cut off is.

Razz1 05-19-2007 01:26 PM


Originally Posted by MazdaManiac (Post 1883712)
Americans want cars that drive themselves so we can spend more time on the cell phone.

Yea, that's what I like.

My brother was killed by a cell phone driver.

One of these days driving with a cell phone will be treated as drunken driving like it should be.

MazdaManiac 05-19-2007 02:28 PM


Originally Posted by jeffe19007 (Post 1885785)
And I was going say you had tail wind....

Oh, well. I can now ignore the beep and try to figure out where fuel cut off is.

Its waaaay up there. it will surprise you how far away from the beep the actual redline is.


Originally Posted by Razz1 (Post 1885797)
One of these days driving with a cell phone will be treated as drunken driving like it should be.

Its actually quite a bit worse than drunk driving.
Three studies, 2 British, one Canadian and the Mythbusters are all in agreement.
Of course, the American studies were funded by Verizon and Sprint....

VASasha 05-19-2007 02:50 PM

So if driving while talking on your cellphone is just as bad as drinking but the problem can be solved with a hands free unit like bluetooth then it should also apply to drinking as well.

Beer hats for everyone!

MazdaManiac 05-19-2007 03:31 PM


Originally Posted by VASasha (Post 1885861)
So if driving while talking on your cellphone is just as bad as drinking but the problem can be solved with a hands free unit like bluetooth then it should also apply to drinking as well.

Beer hats for everyone!

While the humor is appreciated, the problem with cell phone usage is not the hands, but the brain.

MazdaManiac 05-20-2007 01:28 AM

Yes and yes.
Test after test, drivers that were asked simple questions (repeat a number, describe simple tasks, recite the alphabet) and then were confronted with obstacles.
Reaction times were often 10 or 15 times longer and simple acts like maintaining a speed or stopping at an exact point were almost completely impaired.
They found that, when asked the same questions at the same rate, there was no statistical difference between the phone conversation and the one held with a passenger.

I think where the difference would lie is that the passenger, being aware of the driving situation, would cater their end of the conversation to the obstacles the driver was facing.
Its not likely your passenger would ask you to recite the alphabet as you mowed down an orange cone.


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