speed in 3rd gear
#1
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 ?
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 ?
Last edited by Brettus; 11-17-2006 at 10:41 PM.
#5
Registered
Join Date: Jul 2006
Location: Pembroke, MA
Posts: 119
Likes: 0
Received 0 Likes
on
0 Posts
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.
#6
Originally Posted by 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.
#8
Registered User
Join Date: Jul 2004
Location: I've shaken off the sands of SouthWest Asia and returned to Houston and Gulfport, MS
Posts: 498
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 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.
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.
#9
Originally Posted by 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.
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.
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
#10
Banned
iTrader: (3)
Originally Posted by Brettus
Anyway - tyre size is 235/40/18 which is a tad smaller than stock but not enough to make that much difference .
#11
Originally Posted by MazdaManiac
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.)
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 .
#12
Originally Posted by abbid
^ how do you come up with that logic?
The speed sensor counts the pulses the wheels generate.
if you have smaller wheels, youll generate more pulses because you complete a revolution faster.. hence your speedo is faster..
The speed sensor counts the pulses the wheels generate.
if you have smaller wheels, youll generate more pulses because you complete a revolution faster.. hence your speedo is faster..
#13
Banned
iTrader: (3)
Originally Posted by Brettus
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.
Same thing.
Are you drinking?
#15
Nice !!!
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.
#16
Originally Posted by bsteimel
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.
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).
Last edited by Brettus; 11-18-2006 at 02:57 PM.
#18
Originally Posted by 4 years to Supercharge
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
There is error in that also.
I know that most are off by at least 500 rpms
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 .
#20
Banned
iTrader: (3)
Originally Posted by Brettus
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 ?
why the drinking remark ?
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.
#21
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'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 .
#22
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 ?
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 ?
Last edited by Brettus; 11-18-2006 at 11:11 PM.
#23
Zoom-Freakin'-Zoom
iTrader: (5)
Originally Posted by Brettus
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
change was at about 9300 & rev counter reads 500rpm too high so this would have been approx 8800rpm.
http://www.youtube.com/watch?v=NzlvSC_8N-Y
What do you say MM ?
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
change was at about 9300 & rev counter reads 500rpm too high so this would have been approx 8800rpm.
http://www.youtube.com/watch?v=NzlvSC_8N-Y
What do you say MM ?
but the tire size does give you and advantage in the run...
beers
#24
Originally Posted by swoope
ahhh,
but the tire size does give you and advantage in the run...
beers
but the tire size does give you and advantage in the run...
beers
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.
#25
Registered
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.
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.