Legal at last

Discussion regarding Turbocharged and supercharged MX-5s

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johnnyreble
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Re: Legal at last

Postby johnnyreble » Fri Feb 28, 2014 11:59 am

I've timed it with a stopwatch and the best I can get is 4.9 sec.
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johnnyreble
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Re: Legal at last

Postby johnnyreble » Fri Feb 28, 2014 12:00 pm

I've timed it with a stopwatch and the best I can get is 4.9 sec.
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johnnyreble
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Re: Legal at last

Postby johnnyreble » Fri Feb 28, 2014 12:04 pm

also I should add; the rev limiter has been moved to 8000 rpm so that makes a difference, it will do 160kph flat out in 3rd gear.
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Magpie
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Re: Legal at last

Postby Magpie » Fri Feb 28, 2014 12:28 pm

Have you done the 160 in third? As 161 is the claculated speed for 8,000 RPM, 205/50/15 tire, 4.1 diff and 1.33 gear ratio and this excludes aerodynamic drag, losses through the transmission, and tire friction.

johnnyreble
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Re: Legal at last

Postby johnnyreble » Fri Feb 28, 2014 2:43 pm

Yes I have done it ..
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bruce
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Re: Legal at last

Postby bruce » Fri Feb 28, 2014 2:46 pm

You'd think all the smartphone apps would be able to give you more accurate figures?

Magpie
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Re: Legal at last

Postby Magpie » Fri Feb 28, 2014 2:57 pm

I'm impressed zero loss to aerodynamic drag/losses through the transmission/tire friction and I hope it was on a race track, drag strip or on a road in the NT that you did 160 kmh in third.

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Re: Legal at last

Postby rascal » Fri Feb 28, 2014 3:29 pm

Magpie wrote:I'm impressed zero loss to aerodynamic drag/losses through the transmission/tire friction and I hope it was on a race track, drag strip or on a road in the NT that you did 160 kmh in third.

If its geared to do 161 at 8000rpm then as long as it has the power to do so then aerodynamic drag/transmission losses/tyre friction is totally irrelevant.
Those three things only affect the power reqd to do 160, and the time taken to get to 160, not the actual speed itself..

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Re: Legal at last

Postby Magpie » Fri Feb 28, 2014 4:03 pm

I'm not arguing and yes those losses for aerodynamic drag/transmission losses/tyre friction are irrelevant as it only affects the time it takes to get there but it is very rare that a speedo will actually report the ACTUAL speed you are doing as they are design to have a safety margin, especially at higher speeds. If you have wheel speed sponsor as well as DGPS/Survey grade GPS both confirming the speedo reading then 1 kmh less than the calculated speed is a very good result. I'm lucky in that my speedo has been adjusted to match the wheel speed sensor and both are accurate however they never perfectly match the calculated speed. A further bonus is that at times the GPS reports the same speed.

GPS speed is not as accurate as people think and few of us can use DGPS or survey grade GPS to precisely measure speed.

Again it is still good result and a 8,000 rpm limit is not to be sneezed at, mine is set at 8,200 and therefore appreciate what needs to be done to an engine to allow this rev limit to be done consistently!

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greenMachine
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Re: Legal at last

Postby greenMachine » Fri Feb 28, 2014 5:27 pm

Magpie wrote:GPS speed is not as accurate as people think


This.

:mrgreen:
I never met a horsepower I didn't like (thanks bwob)

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johnnyreble
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Re: Legal at last

Postby johnnyreble » Fri Feb 28, 2014 5:40 pm

My speedo is very accurate as I had it calibrated recently for mod compliance, won't say where it happened.. :):):)
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