Brettus

iTrader: (2)

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 ?

AdRoCK3217

You have 5 speeds. We have 6.

Brettus

iTrader: (2)

Nope - mine is a 6 speed too

Raptor2k

o_0

Maybe you have the original 250 HP!

Vash137

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.

Brettus

iTrader: (2)

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 .

Paul_in_DC

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

RotrDoc

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.

Brettus

iTrader: (2)

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

MazdaManiac

iTrader: (3)

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.)

Brettus

iTrader: (2)

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 .

Brettus

iTrader: (2)

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.

MazdaManiac

iTrader: (3)

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

Brettus

iTrader: (2)

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 ?

bsteimel

iTrader: (5)

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.

Brettus

iTrader: (2)

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).

BoosTED

iTrader: (2)

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

Brettus

iTrader: (2)

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 .

Towlie

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

MazdaManiac

iTrader: (3)

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.

Brettus

iTrader: (2)

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 .

Brettus

iTrader: (2)

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 ?

swoope

iTrader: (5)

ahhh,

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

beers

Brettus

iTrader: (2)

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.

BoosTED

iTrader: (2)

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.