renesisgenesis

Ok so, according to the tachometer, the stock RX8 redlines at 9000, and then rev limits at about 9300-9500 or so. I have heard plenty of sources saying the tach is off, by various amounts. So, does anyone actually know what a completely unmodded 8 actually is running at in terms of rpm when the tach is at redline, at rev limit?

JinDesu

iTrader: (2)

Supposedly 500 less at 9000? I think it's around there.

tmak26b

<5000RPM=100RPM
6000RPM=200RPM
7000RPM=300RPM
8000RPM=400RPM
9000RPM=almost 500RPM

CyberPitz

I wonder why the tach is off....and why isn't it accurate *like with some people's speedo, I guess.*

Brettus

iTrader: (2)

/\ Mazda may have done it on purpose to stop people actually reving that high ........ ????

RufusVonStorm

OR it's a human factors psychology thing:

Higher perceived revs = higher perceived fun

renesisgenesis

hmm...why would one bother to place a large, easy to read rev counter right in the center of the cluster, with the apparent intent on offering a reliable and easy way to determine rpm, and then intentionally make it inaccurate?

This is not a rhetorical question, but an actual one...



ahh sigh

xun4gvn4everx

iTrader: (2)

^ I would imagine for the same reason that the speedometer on most cars reads a couple mph more than the speed you are actually going. To most people, seeing is believing. They do not question the accuracy. So in turn, people drive slower than they think they are which results in fewer accidents (theoretically).

iwc3707

at least they didn't make the same mistake as Yamaha did with their 17.5 k redline tach.
In theory it looked really nice. At least till they dynoed it and found that it was widely reported that the 2006 YZF-R6's motor did not have this engine rpm redline level and was closer to around 16200 engine rpm, but because of a deliberate tachometer error of about 9%, it read 17,500 tachometer rpm. In February 2006, Yamaha admitted the bike's true engine redline was more than 1000 rpm lower than displayed on the tachometer than advertised,[2] and offered to buy back any R6 if the customer was unhappy.[3]

fyrstormer

My guess is they made the tach read high to make up for the fact that the ECU needs to collect several data points from the input speed sensor before it can calculate RPMs (an effect which you can clearly see in the speedometer lag), and also to make up for the inertia in the tach needle mechanism.

In first gear, that engine can rev stupid-quick -- I actually believed I could shift right at 9000rpm in first gear at WOT with two days' driving experience, and I hit the rev limiter before the tach needle even entered the solid part of the redzone. (not the alarm, but the actual fuel cutoff limiter.) It never happened in any other gear, which suggests the tach simply can't keep up with the engine in 1st gear at WOT, and that's the worst-case scenario the engineers have to design for.

renesisgenesis

So, is it correct then to say that the actual electronic rev limit for a completely stock rx8 is actually a little under 9000 rpm? Because the tach dial gets a little shy of 9500, and since it is apparently off by about 500 rpm by that point, the actual rpm is a little under 9000 then right? Good to know the stock rx8 doesn't actually let you get to 9000 rpm....



BTW so far no one has come even remotely close to a decent explanation for the intentionally inaccurate tach. The reasons still don't explain why it's better to make it wrong.

Brettus

iTrader: (2)

Simple

Mazda made an engine capable of 9000 rpm but they don't actually want people to rev it quite that high all the time due to warranty concerns so they made it read higher to make people believe they were at 9000 when they were only at 8500 , and change gear at that point.

xun4gvn4everx

iTrader: (2)

^

renesisgenesis

So do you guys support the decision to make a faulty gauge? ...despite the fact that it was made large and in the center, suggesting it's importance for giving useful, accurate info for the driver?

xun4gvn4everx

iTrader: (2)

Well, for incompetent drivers, I do support the decision because they would continually blow motors making our cars look bad and the value to go down. For competent drivers, I would rather have the gauge be accurate, but since we are competent, we at least know how to acquire the means to correct the "error".

renesisgenesis

That makes no sense because the electronic rev limit would still be there set at the same RPM anyway, so the motor wouldn't get hurt anymore than it would with a correct gauge.

xun4gvn4everx

iTrader: (2)

^ not if you deactivate the rev limiter

SleepeR1st

iTrader: (2)

Just bring the needle to the rev limiter, problem solved.

04RX8man

hook up a scan tool and get a reading off the ecc shaft sensor and see if scantool reads the same as tach...only way to b sure

renesisgenesis

Right, but then you are obviously planning on going past 9000 rpm anyway, so it doesn't matter if the tach is correct or not, you would be going into the Red. So, it still would benefit you, in fact benefit you even more, to have a correct tach so you can tell what the hell you are running at as you go past the manufacturers normal rev limiter.

Also, that is a mod, so it wouldn't be stock anymore. And why would someone who is into cars enough to deactivate the rev limit then need an inaccurate tach? again, makes no sense.

xun4gvn4everx

iTrader: (2)

You are not understanding what I was saying. Let me try and clarify. For individuals who "know what they are doing", an accurate RPM gauge would be beneficial. For individuals who "do not understand cars" an inaccurate tach theoretically helps to prevent them from f*&king up their engine and/or transmission. Me personally, hell yea I wish the gauge was accurate. But, I can see why a car manufacturer (especially ones with extensive engine and tranny warranties such as Mazda gives on the 8's) would make the gauge read inaccurately to reduce the possibility of individuals putting too much stress on the components and causing mechanical parts to fail thus leading to the manufacturer having to dish out money in warranty repairs.

renesisgenesis

It was probably for transmission health. All accounts seem to think that, as long as the motor is well cared for and is fully warmed up, then revving to 9 doesn't hurt it. I can imagine though that the transmission life might start to decrease pretty quickly the more time is spent in the 9000 rpm area. But then again mazda still could have just made the electronic redline somewhere around 8600-8700 or so and then actually make the damn tach show accurately.

Socket7

Because it was designed by the same ******* who gave us an oil pressure gauge that only measures in terms of on and off, and a temperature gauge that only reads "you'll flood it", normal, and "your engine has already cooked itself"

Jedi54

iTrader: (7)

Socket speaks the truth.

The Reverend

iTrader: (1)

A+++++++++ post