speed in 3rd gear
07-27-2008, 05:29 AM
#102
Go get your indicated RPM vs. speed in as wide a range as you can in each gear then do the math.
Then, do the same in another RX-8.
Now what you have done is simply correlated the error in two cars.
You would still need independent speed and RPM readings from each to correlate the indicated readings to the actual.
07-27-2008, 05:53 AM
#104
But you don't even have any data like that and that hasn't been the thrust of your argument.
Go get your indicated RPM vs. speed in as wide a range as you can in each gear then do the math.
Then, do the same in another RX-8.
Now what you have done is simply correlated the error in two cars.
You would still need independent speed and RPM readings from each to correlate the indicated readings to the actual.
Go get your indicated RPM vs. speed in as wide a range as you can in each gear then do the math.
Then, do the same in another RX-8.
Now what you have done is simply correlated the error in two cars.
You would still need independent speed and RPM readings from each to correlate the indicated readings to the actual.
Say we do this test
I'll video the speedo/tach of my car in 2nd , 3rd,4th,5th&6th at 100km/kr (62mph)
You do the same in your car
we post the vids and tabulate the results and voila - argument settled
Are you up for it ?
07-27-2008, 01:24 PM
#109
You do realise that tyre size has no relevance to the information gained from a datalog don't you ..... ??????
In fact - we could do the datalog on jackstands because we are not interested in actual speed . We are only interested in what differences there are between gears .
That is what this argument is about ............................ isn't it ?
07-27-2008, 01:46 PM
#111
Destroying Threads
Bret, you car, and my car, goes exactly the same speed in all gears, well, not rly, if your tires are over stretched like mine, then the speedo is gonna read slower...............
07-27-2008, 02:29 PM
#113
Just do it. Please? Maybe, just maybe, you will understand the compounding error if the mixed question that this entire thread represents.
That is the crux of it. Your question goes like this:
A train leaves the station at 50 MPH to go on a 100 mile trip.
Another train leaves the station at 60 miles an hour to go on a 120 mile trip.
What color are the conductor's drawers?
07-27-2008, 02:52 PM
#114
neither ........ are ......... you
But i'll do it if it makes you happy .
Just so i'm clear - we are arguing that my car has a different 3rd gear ratio to US spec models .
We are not arguing about the effect tyre diameter has on actual speed
Yes or No ?
But i'll do it if it makes you happy .
Just so i'm clear - we are arguing that my car has a different 3rd gear ratio to US spec models .
We are not arguing about the effect tyre diameter has on actual speed
Yes or No ?
Last edited by Brettus; 07-27-2008 at 02:56 PM.
07-27-2008, 03:35 PM
#115
isn't rpm tied to the speedometer based on the OEM wheel?
we already know the speedometer is off for Brettus because of tire size, but it is still reading the same speed at the same rpm that it would with an OEM sized tire.
if there is error in the tach reading wouldn't comparing the speedo reading of different cars at the same rpm in multiple gears provide conclusion enough. such as 2nd, 3rd, and 4th gear readings at a mid-range rpm. if 2nd and 4th gear readings match, then 3rd has to match or it's a different gearing. if 2nd and 4th aren't similar at all, then there is error in the tachometer and the reading in 3rd gear probably as well.
we already know the speedometer is off for Brettus because of tire size, but it is still reading the same speed at the same rpm that it would with an OEM sized tire.
if there is error in the tach reading wouldn't comparing the speedo reading of different cars at the same rpm in multiple gears provide conclusion enough. such as 2nd, 3rd, and 4th gear readings at a mid-range rpm. if 2nd and 4th gear readings match, then 3rd has to match or it's a different gearing. if 2nd and 4th aren't similar at all, then there is error in the tachometer and the reading in 3rd gear probably as well.
07-27-2008, 03:43 PM
#117
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LOL @ an almost 2 year argument.
Who cares what mph you're in in whatever gear.
I can hit 101 in 3rd gear and only be in 8000rpm. So what?
You guys arent necessarily driving rocket ships so it doesnt matter. It will take a while to reach max mph in the higher gears anyway.
Who cares what mph you're in in whatever gear.
I can hit 101 in 3rd gear and only be in 8000rpm. So what?
You guys arent necessarily driving rocket ships so it doesnt matter. It will take a while to reach max mph in the higher gears anyway.
07-27-2008, 04:03 PM
#118
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Brettus.... the reason MM wanted you to test/datalog like this is to say: In X amount of time, your tires made Y number of rotations(based on logged pulses), and your tires have Z circumference. With that, you find your actual speed.
07-27-2008, 04:11 PM
#119
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no you cant. and i'm fairly confident that MM can reach 120mph in approx 15 seconds.
Brettus.... the reason MM wanted you to test/datalog like this is to say: In X amount of time, your tires made Y number of rotations(based on logged pulses), and your tires have Z circumference. With that, you find your actual speed.
Brettus.... the reason MM wanted you to test/datalog like this is to say: In X amount of time, your tires made Y number of rotations(based on logged pulses), and your tires have Z circumference. With that, you find your actual speed.
You're right.
I can hit a bit more if i shift at 8500rpm.
And a stock 8 wont hit 120 in 15 seconds. Never had, never will.
07-27-2008, 04:19 PM
#120
isn't rpm tied to the speedometer based on the OEM wheel?
we already know the speedometer is off for Brettus because of tire size, but it is still reading the same speed at the same rpm that it would with an OEM sized tire.
if there is error in the tach reading wouldn't comparing the speedo reading of different cars at the same rpm in multiple gears provide conclusion enough. such as 2nd, 3rd, and 4th gear readings at a mid-range rpm. if 2nd and 4th gear readings match, then 3rd has to match or it's a different gearing. if 2nd and 4th aren't similar at all, then there is error in the tachometer and the reading in 3rd gear probably as well.
we already know the speedometer is off for Brettus because of tire size, but it is still reading the same speed at the same rpm that it would with an OEM sized tire.
if there is error in the tach reading wouldn't comparing the speedo reading of different cars at the same rpm in multiple gears provide conclusion enough. such as 2nd, 3rd, and 4th gear readings at a mid-range rpm. if 2nd and 4th gear readings match, then 3rd has to match or it's a different gearing. if 2nd and 4th aren't similar at all, then there is error in the tachometer and the reading in 3rd gear probably as well.
I would have thought so too - but MM is not satisfied ........................
07-27-2008, 04:25 PM
#121
What you can datalog is speed vs rpm . The ECU has no idea what size tyres I have on ( it calculates speed from the known dimensions of the OEM tyre )so I'm not sure how knowing the circumference of the tyres helps with the datalog .
Last edited by Brettus; 07-27-2008 at 04:55 PM.
07-27-2008, 06:34 PM
#123
Rotary Powered Countryboy
any change in overall circumference of the wheel will change the speedo becase it is tuned for factory sized rims and tires so with 19" wheels per say the speedo will read faster than you are definately goin...anyway I dont think if mazda changed the gearing for 3rd gear they would change it 4 just ur car b sure ur calculation of km/h is right....