a top speed run.. - LotusTalk - The Lotus Cars Community
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post #1 of 38 (permalink) Old 01-03-2005, 07:10 AM Thread Starter
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a top speed run..

first off, so we dont get into a bitch fest about safety, this was done on a deserted airstrip. there were no planes landing or taking off.

anyway, fifth gear run....the car only pulled to 7600rpms and would pull no more. indicated speed was 142mph. held it there for a good 7 seconds to confirm....cannot pull fifth gear beyond where it was at.
after that i shifted to 6th, but didnt have enough room by then to determine if i could squeeze a few more mph....
next time i wont waste time in 5th....ill bring it to 7500rpm and go to sixth and see what happens.
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post #2 of 38 (permalink) Old 01-03-2005, 07:38 AM
 
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Not that I would know anything about this since I never break the speed limit but I have a.....friend....who had his near the 150 mark in 6th.
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post #3 of 38 (permalink) Old 01-03-2005, 07:41 AM
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post #4 of 38 (permalink) Old 01-03-2005, 08:26 AM
 
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I saw an indicated 152 or so while using our local demo car! That was in 6th gear!

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post #5 of 38 (permalink) Old 01-03-2005, 08:31 AM
 
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Something to ponder though. At 120mph my gps indicated 107 mph. The speedo is really generous.
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post #6 of 38 (permalink) Old 01-03-2005, 08:51 AM
 
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Quote:
Originally posted by plesset
Something to ponder though. At 120mph my gps indicated 107 mph. The speedo is really generous.
true, but I have read some things online that suggest the some gps units not being real acurate them selves...

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post #7 of 38 (permalink) Old 01-03-2005, 09:24 AM Thread Starter
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when i had my first service done, the reading showed my top wheel speed at 191kph......my top indicated speed that i saw was 140. (in sixth gear)
so i think there is some speedo error at play.
i looked at a lambo speedo cause it has both kph and mph and i remember it was lower than 140, but dont recall exactly...130ish?
what i dont understand is why the speedo doesent read what the ecu reads for speed?
maybe lotus wants us to think were going faster than we are?
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post #8 of 38 (permalink) Old 01-03-2005, 09:29 AM
 
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It must be for marketing reasons that the speedo's lie. Almost all performance cars have this same issue. As you said, it makes no sense that the ecu would read differently than the speedo.
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post #9 of 38 (permalink) Old 01-03-2005, 09:57 AM
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Quote:
Originally posted by plesset
Something to ponder though. At 120mph my gps indicated 107 mph. The speedo is really generous.
Or as others have mentioned the GPS lean. Perhaps the uplink update time could not keep with sudden shifts in velocity and averaged them previous read and current read.


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post #10 of 38 (permalink) Old 01-03-2005, 10:08 AM
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I've got some friends that did some top speed runs on their bikes with multiple GPS's on board at the same time. I don't remember what they said the difference was but there was a definate difference between each GPS unit.

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post #11 of 38 (permalink) Old 01-03-2005, 10:16 AM
 
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But....

Where the GPS may be 3 to 4 mph off, the Elise speedo is 10 to 15 mph off at high speed. I can confirm that even at 55mph when passing one of those this is your speed signs the gps was accurate while the speedo was a bit off. I wonder if the GPS's used in the past were WAAS enabled or not. I am going to try a run with my airplane gps (Garmin 296) which is pretty accurate with WAAS.
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post #12 of 38 (permalink) Old 01-03-2005, 11:15 AM Thread Starter
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how about something like a g-tech....will that record speeds?
ha, i know i have one, but not sure if it will record top speed like that....
if it does, those are supposed to be very accurate. even when u do a quarter mile, they dont average the way track does...it measures actual. the track averages ur last 60'.
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post #13 of 38 (permalink) Old 01-03-2005, 11:24 AM
 
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Most road map oriented GPS units are not that bad for speed accuracy.

FWIW my GPS datalogger is pretty accurate speed wise:

"With average GPS reception, speed accuracy is about 0.1mph (or 0.1% if greater) when you are just driving along at fairly constant speed, and about 0.2mph (or 0.1% if greater) during fast accelerations or braking. The only exception is at very low speeds (under 10mph) where the error increases to about 1mph. Do not be fooled by exaggerated claims from other manufacturers… this is as good as it gets!"

The unit takes a GPS reading 5 times a second and reconciles that with accelerometer data logged 100 times per second. And yes out speedo reads high!!

Last edited by Stan; 01-03-2005 at 12:02 PM.
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post #14 of 38 (permalink) Old 01-03-2005, 11:38 AM
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If memory serves me right, in the UK, speedos have to read high in the UK, but this does seem a little bit much !!
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post #15 of 38 (permalink) Old 01-03-2005, 11:50 AM
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I am just disgusted by this thread of reckless speed.

When i get my elise it will never go above 55 even in a 70 mph speed limit zone.

(in the fast lane of course)

just kidding
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post #16 of 38 (permalink) Old 01-03-2005, 12:23 PM Thread Starter
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more to come.....
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post #17 of 38 (permalink) Old 01-03-2005, 12:24 PM
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would the speedo calibration error of almost 10% also cause the odometer to overestimate miles driven, or is the calibration totally separate????
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post #18 of 38 (permalink) Old 01-03-2005, 12:27 PM
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Quote:
Originally posted by ivan1
would the speedo calibration error of almost 10% also cause the odometer to overestimate miles driven, or is the calibration totally separate????
In many/most other European cars, the speedo is optimistic but the odo is usually dead on. The speedo error is designed in by law.
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post #19 of 38 (permalink) Old 01-03-2005, 12:33 PM
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Quote:
Originally posted by plesset
Something to ponder though. At 120mph my gps indicated 107 mph. The speedo is really generous.
Hmm...interesting. So maybe the 122mph I was hitting on the front straight at Willow Springs was actually much slower! BTW: that has been my top speed so far...and yes, Willow is a racetrack.

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post #20 of 38 (permalink) Old 01-03-2005, 12:35 PM
 
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>>>Hmm...interesting. So maybe the 122mph I was hitting on the front straight at Willow Springs was actually much slower! BTW: that has been my top speed so far...and yes, Willow is a racetrack.<<<

Yeah...but any other car you've driven there also had an optimistic speedo, most likely! The speedo on my M3 is similarly "happy", for example.
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