speed in 3rd gear
 

Just noticed that my 8 seems to top out at a higher speed than any of the others Iv'e seen in 3rd gear

most seem to be 148 km/hr - 92 mph
Mine is 165 km/hr- 103 mph

Mine is an 03 model imported from Japan - anyone know why this would be ?

You have 5 speeds. We have 6.

Nope - mine is a 6 speed too

o_0

Maybe you have the original 250 HP!

Doesn't your wheel speed = engine speed (rpm) dividided by 100 in 3rd gear? At least it is in the '06s. So...103mph = 10300 rpms...doesn't exactly work. Either you have different gearing or your speedometer is off.

2nd gear is the same as everyone else as far as I can tell . don't know about 4th as is speed limited to 180 km/hr .

Do you have stock tires/wheels? Different size tires? If so, that would give a different value as well.

That would be "Vehicle Speed (mph) = Engine speed (tachometer rpm) divided by 100"??

You are limited to 180 km/hr? That's only 110 mph! Man, are you being cheated. I rarely drive anywhere close to 110, but I enjoy knowing I can if I need to.

actually - maybe its 190km/hr - been a while since I checked .


Anyway - tyre size is 235/40/18 which is a tad smaller than stock but not enough to make that much difference .
Only thing I can think of is that Mazda changed 3rd gear very early on in production. I'll check a couple of other imports here when I can.

I always wondered why people talked about changing into 4th at 85mph & thought that maybe they weren't taking it right to the redline :shocking:

Uh, duh. You are kidding, right? That is nearly a +4% speedo error! (Which is significant - especially in light of the non-linear error built into the speedo from the factory.)

think about it MM- the speedo will read the same number at 9000 rpm no matter what tyre size I have .
Mine reads 165km/hr - everyone else seems to be around 145 km/hr
when I change from 2nd to third my revs drop from 9000 to 6500 - other shots of RPM guauges i've seen drop to 7000rpm .

No - your speedo will read the same for any given wheel speed - it is just that you will actually be going faster or slower depending on wheel size.

OK. So that means you will "top out" at a higher speedo reading that is actually a slower speed.
Same thing.
Are you drinking?

So - it seems you agree with me MM . Good , I thought you you must have been smoking something for a minute there.
why the drinking remark ?

if your wheel sizes are not the same as factory sizes your speedometer will be giving you an incorrect output. Thats why when people buy winters tires that are 17 inch they increase the side sidewall size to keep with the overall same circumference. If you had 1 inch wheels your speedometer may read 300mph but you would really be going that fast your speedometer would be wrong. This is why you think your going faster but your really not. The shifts from 1-2 maybe pretty close to stock but as you get faster the amount that this fault affects your readout gets bigger. Just basic physics.

Agreed (thought I was saying the same thing)
With 1" wheels at 9000 rpm in third gear my speedo will still read 165 km/hr & yours will read 145km/hr (91mph)

I am getting a 12% speedo reading difference in 3rd gear - basic physics does not explain that (unless my 3rd gear is a different ratio).

You are correct Brettus unless your RPMs are off compared to the others.

There is error in that also.

I know that most are off by at least 500 rpms

thanks SC - & yes my rpms do read 500 high .
So at 9000 rpm (which reads as 9500 rpm on my revcounter) I'm doing 165 km/hr in third gear .

There is only one logical reason for that - I have a different 3rd gear ratio than what you guys have .

today on my way to work i hit 110 in third gear on my AT 04? thats with stock wheels.

I wasn't "agreeing" with you - I was pointing out that you were trying to apply the converse math as a different explanation.
That is akin to trying to explain your movement down the road as the world moving past you while you remain stationary.
Relativism won't negate the argument.
Your speedo error is your tire size. The problem is your perception, not the vehicle.

I was suggesting that your altered perception might be the result of some imbibing, though I see that it is simply your natural state of perception.

I think you are just winding me up .

I'll try another explanation

Lets say we put the car on jack stands with the wheels off the ground . I rev mine up to 9000 rpm in 3rd . The speedo says 165 km/hr but im' stationary.

You do the same with yours & your speedo says 145 km/hr .

You see - tyre size is irrelevant - if my 3rd gear is a different ratio to yours I will get a different reading .

The only other possible explanation is the I have a higher diff. ratio but like I said earlier - 1st & 2nd seem the same .

I was not wanting an argument - originally I was just pointing out a noted difference between my car & others on the thread & wondering why it was so . Anyway , MM seems to be spoiling for one so "bring it on" as they say .

Here is a link to a vid of my car doing a 1/4 mile run . Note these things :
Speed at end of run is over 100 mph
The gtech does not know what tyre size i have
The third to fourth gear change takes place after the run is complete IE I'm doing over 100mph in third

http://www.youtube.com/watch?v=WF5axGDsCHs

This next clip is just of my revcounter going through the gears .
Note :
Speedo reading at 3-4th gear change = 163 km/hr
But the speedo does not know what size tyres I have so actual speed will be slower
gear change was at about 9100 & rev counter reads 500rpm too high so this would have been approx 8600rpm.

http://www.youtube.com/watch?v=NzlvSC_8N-Y



What do you say MM ?

ahhh,

but the tire size does give you and advantage in the run...

beers :beer:

True .
not sure if the fact that I don't need to change into 4th is an advantage or not though as acceleration in 3rd will be slower which is offset by no wasted time making the gearchange.

Now I am going to have to go out and run my car up to redline in third tonight.

My tires are 225/50R17 and I have checked them against the GPS they are within 0.5-1 MPH lower than what it actually reads.

The stock tires are lower by 2 MPH of their true value. Of course that is not what we are really discussing here so I am merely saying that I will run my car up in third gear after I get out of work at 4am... :)

I see your point Brettus.

to funny x2.

i am in naples... not in my big racetrack home....... so i cant do a run.... waas enabled or not...

but i see brett is using cheater tires!!!!! and good for you..

beers :beer:

for the record Swoope - I did the 14.4 1/4 mile & the 5.85 0-60 on stock tyres . Have only had the new tyres a few weeks.

Is your car stock other than the tires?

ok.

you really really suck...:rollingla

i thought i had it figured out... i have not done the runs since the new motor and fly wheel....

the time will be soon...

you are doomed..

beers :beer:

ike.

dont read this stuff... it will just piss you off. :wallbash:

but we talk the same stuff...

brett. i think the stuff should just be 5 to 100 data logged..

beers :beer:

No - see sig

wow,
sig.

welcome to to 2k... :rollingla

btw, my other project might be doomed..

beers :beer:

ZOMG I better add my fluids and my shift knob to my sig.! :Freak_ani

you really get off on sarcasim don't you Ike .

nope,

just add one.. the people here might learn from you. or you could just make your well based comments and leave them in the dark about your past..

as to your sig... you are just a doushe... except to the ones that know you. :)

beers :beer:

Ehehehe... you crack me up.

I'm sorry, I don't speak ESL.

K

beers :beer:

sorry,

if not clear... you have more knowlege than most here.... that is getting more easy.
but you come from a different angle... not bad, and you know more about the 8 than most. and you can do the z vs evo vs wrx stuff without judgement..


a sig from you might give a hint as to the angle you are coming from.....


sorry if this is a complement.. but, i learned a lot from you before i ever posted here..


beers :beer:

I prefer being mysterious. It's how I roll.

so,

you only roll at the dragstrip... and have what .25 mile time? and your 0 to 60 is what.. and you may or not have a car...

so you are a like a noob, but with a lot of posts.. :cwm27:

beers :beer:

:rofl:

So did I, Ike. :kiss:

:bootyshak

:spank:

:mad:

:sad:

:cool:

:)

:D:

Hey Brettus,
I want to clarify something. Does the RX-8's speedo say 100mph at redline or is that your GTech? Does GTech require you to input your wheel size?

My guess is that the RX-8's speedo detects revolution pulses, so as you said, regardless of wheel size, the readings should be based on stock wheel diameter, UNLESS the RX-8 has some sort of advanced speedo setup that automatically detects wheel diameter.

I did some quick calculations. Your wheel setup is 25.402" in diameter. Stock is 25.972". So your circumference is 79.801" and stock is 81.593". Since a mile has roughly 63360", your wheels roughly spin 17.438 revolutions more than stock wheels per mile, which is roughly 1391" more per mile. I think it's a significant difference as MazdaManiac mentioned, but not enough to justify the 10 mph difference you're seeing on your GTech.

Now I'm curious just as you are, as long as your RX-8's native speedo says the same thing as the GTech in your video. If it's just an anomaly on your GTech, I'm not interested.

Yes Speedo reads over 100mph (160km/hr) at redline in 3rd.
& no - no input required on G-tech for wheel size - in fact no inputs at all . It works off the g forces created by acceleration and time .

And yes the Gtech and speedo are close in their readings

That's pretty strange, equivalent to almost 10,000RPMs in 3rd gear on our 6MTs.

So I guess, comparatively, your car pulls slower than stock throughout 3rd gear, but makes up for that in the quarter mile because you don't have to shift?

Have you taken it to a Mazda technician to figure it out?

Yes Exactly . I only picked up on it while watching a vid of an RX8 tach. while he was racing around a track . I noticed that when going from 9500(on the tach) in 2nd to 3rd his tach went down to 7000 . Mine is always gos back to around 6500 - that made me curious so I posted this to get some comments.
I should have known I would get roasted over it :)

This is just a crazy guess. Perhaps Aisin Seiki shipped a not-to-spec transmission to Mazda and it got put in your car. I read all sorts of crazy manufacturing errors in the VW forums, so it's not impossible for it to happen here, no?

I have just heard from another Jap origin 8 owner I know (Rotor - the guy with the Blitz supercharger)
His car goes to over 100 mph in 3rd also .

could be something with the early jap spec cars .............

Hmmm, getting interesting. I'll dig around some Japanese websites.

Mine 2 around 160km/h in 3 :) and has a top speed of 187km/h :( All JDM RX8s are still 250ps. It seems that in Japan they don't give a shit about emissions.