Re: Performance meters.

[Ext User(The Raven)]

"a9x5l" <a9x5l@hotmail.com> wrote in message
news:pan.2005.12.21.10.42.06.868151@hotmail.com...
> Hi all, has anyone here had any experience with either the g-tech SS,
> passport GT or maybe even another brand? I'm mainly curious about the
> reliability and build quality of the units.
>
> G-TECH...
> http://www.gtechpro.com/

I've used the bigger older version of one of these and found it to be a few
tenths off, enough to make it rather useless for any drag racing
application. In my case, the worst figure was 7tenths off actual drag strip
figures and the best was about 3tenths off.

I'll be honest and admit that comparing "street" readings with the G-Tech
against genuine drag strip times isn't always fair given the differences in
surface. However, the accuracy is poor as the car was in identical spec
"street" and strip.

> Passport...
> http://www.escortradar.com/gtimer.htm
>

If you want a reliable reading head off to the drag strip for an "off road
legal drag racing" night.


--
The Raven
http://www.80scartoons.co.uk/batfinkquote.mp3
** Now I will bring chaos to the world!

[Ext User(Brenden Will)]

That's half the problem. No two launches will ever been the same. Especially
on street tyres. It's hard enoough to do on slicks off a transbrake like I
do.

I had a bloke who had one tell me his car runs 12sec 1/4's. I got a laugh
when it went no better than 14.9@93mph.

I personally think they are a wank factory gauge. I guess they could be
accurate if it was used in a drag car or a 4wd due to traction efficiency?

"a9x5l" <a9x5l@hotmail.com> wrote in message
news:pan.2005.12.21.11.12.49.37923@hotmail.com...
> On Wed, 21 Dec 2005 21:56:33 +1100, The Raven wrote:
>
>> "a9x5l" <a9x5l@hotmail.com> wrote in message
>> news:pan.2005.12.21.10.42.06.868151@hotmail.com...
>>> Hi all, has anyone here had any experience with either the g-tech SS,
>>> passport GT or maybe even another brand? I'm mainly curious about the
>>> reliability and build quality of the units.
>>>
>>> G-TECH...
>>> http://www.gtechpro.com/
>>
>> I've used the bigger older version of one of these and found it to be a
>> few
>> tenths off, enough to make it rather useless for any drag racing
>> application. In my case, the worst figure was 7tenths off actual drag
>> strip
>> figures and the best was about 3tenths off.
>>
>> I'll be honest and admit that comparing "street" readings with the G-Tech
>> against genuine drag strip times isn't always fair given the differences
>> in
>> surface. However, the accuracy is poor as the car was in identical spec
>> "street" and strip.
>
> Were you able to launch the car in exactly the same manner on the road as
> you did at the track? I know I certainly can't get the stall speed up
> as high on the street nor am I able to use 100% throttle as early.
>
>>
>>> Passport...
>>> http://www.escortradar.com/gtimer.htm
>>>
>>>
>> If you want a reliable reading head off to the drag strip for an "off
>> road legal drag racing" night.
>
> I already go to Heathcote fairly regularly but I'm just looking for
> something to measure any tuning changes that I might make at home, do
> you think it's accurate enough for that purpose?
>
>
>
> --
> a9x5l
>

[Ext User(Arnie)]

"a9x5l" <a9x5l@hotmail.com> wrote in message
news:pan.2005.12.21.11.12.49.37923@hotmail.com...
> On Wed, 21 Dec 2005 21:56:33 +1100, The Raven wrote:
>
> > "a9x5l" <a9x5l@hotmail.com> wrote in message
> > news:pan.2005.12.21.10.42.06.868151@hotmail.com...
> >> Hi all, has anyone here had any experience with either the g-tech SS,
> >> passport GT or maybe even another brand? I'm mainly curious about the
> >> reliability and build quality of the units.
> >>
> >> G-TECH...
> >> http://www.gtechpro.com/
> >
> > I've used the bigger older version of one of these and found it to be a
few
> > tenths off, enough to make it rather useless for any drag racing
> > application. In my case, the worst figure was 7tenths off actual drag
strip
> > figures and the best was about 3tenths off.
> >
> > I'll be honest and admit that comparing "street" readings with the
G-Tech
> > against genuine drag strip times isn't always fair given the differences
in
> > surface. However, the accuracy is poor as the car was in identical spec
> > "street" and strip.
>
> Were you able to launch the car in exactly the same manner on the road as
> you did at the track? I know I certainly can't get the stall speed up
> as high on the street nor am I able to use 100% throttle as early.

I ran a GTech on the drag strip run and it gave times consistently 0.3-0.5s
faster than actual drag strip time.

[Ext User(Scotty)]

> I ran a GTech on the drag strip run and it gave times consistently
> 0.3-0.5s
> faster than actual drag strip time.
>
>

Would that be due to the fact that the strip registers when you get out of
the beam but the GTech registeres the initial movement?

[Ext User(Arnie)]

"Scotty" <scoter1@warmmail.com> wrote in message
news:43af5bb2$0$9289$afc38c87@news.optusnet.com.au ...
>
>
> > I ran a GTech on the drag strip run and it gave times consistently
> > 0.3-0.5s
> > faster than actual drag strip time.
> >
> >
>
> Would that be due to the fact that the strip registers when you get out of
> the beam but the GTech registeres the initial movement?
Firstly, the Gtech has no idea where the finish line is so if it starts
timing a few inches before the start line due to rollout, it'll
theoretically finish timing before the finish line by the same amount.
Rollout on the start beams is maybe 6 inches at best if you shallow stage. 6
inches out of 1440 feet means its significance is about 1/3000th of total
elapsed time. The rollout might affect ET by 0.005s (in say a 15sec run)
which doesn't explain the 0.3-0.5s difference.
Anyway, I've tried it with deep staging as well where I've rolled past the
1st light and staged with only the 2nd light so I'm on minimal rollout and
it was still out by more than 0.3s
The other thing I noticed is the terminal speed reported by my GTech is way
off. It is usually optimistic by more than 5kph, sometimes as much as 10kph
higher. I've heard explanations that the GTech calculates true finish line
speed whereas the drag strip measures terminal speed using 2 beams over the
last 60ft so it is essentially the average speed over that last 60ft.
However, there is no way my car would gain 5kph over the last 60ft, let
alone more than 5kph. So this explanation for the difference doesn't wash.
I've put the difference down to either inaccuracy in the hardware/software
and/or the fact that it's only using single axis g-sensor (I'm using the
older Gtech pro not the new wizbang model with the 3 axis sensor). When the
car launches and accelerates, it squats and thus the sensor is no longer
measuring the true acceleration of the car but also a component of gravity
as it is tilted by a small degree. This tilt is most pronounced at the start
when launching and any error at the start is magnified at the end due to the
cumulative maths involved in using force over time to derive speed and
distance.
I've tried calibrating it with a negative tilt to compensate with mixed
results. It's too much farting around especially when you use it in
different cars, so I just set it dead level and live with the fact it's
optimistic by a bit.
This kind of device does not measure distance or speed, it derives it thru
cumulative calculations, and that's where the danger lies in its accuracy.

[Ext User(Scotty)]

"Arnie" <arnienospam@nospamteamfob.com> wrote in message
news:43afdd07@dnews.tpgi.com.au...
> Firstly, the Gtech has no idea where the finish line is so if it starts
> timing a few inches before the start line due to rollout, it'll
> theoretically finish timing before the finish line by the same amount.
> Rollout on the start beams is maybe 6 inches at best if you shallow stage.
> 6
> inches out of 1440 feet means its significance is about 1/3000th of total
> elapsed time. The rollout might affect ET by 0.005s (in say a 15sec run)
> which doesn't explain the 0.3-0.5s difference.
> Anyway, I've tried it with deep staging as well where I've rolled past the
> 1st light and staged with only the 2nd light so I'm on minimal rollout and
> it was still out by more than 0.3s
> The other thing I noticed is the terminal speed reported by my GTech is
> way
> off. It is usually optimistic by more than 5kph, sometimes as much as
> 10kph
> higher. I've heard explanations that the GTech calculates true finish line
> speed whereas the drag strip measures terminal speed using 2 beams over
> the
> last 60ft so it is essentially the average speed over that last 60ft.
> However, there is no way my car would gain 5kph over the last 60ft, let
> alone more than 5kph. So this explanation for the difference doesn't wash.
> I've put the difference down to either inaccuracy in the hardware/software
> and/or the fact that it's only using single axis g-sensor (I'm using the
> older Gtech pro not the new wizbang model with the 3 axis sensor). When
> the
> car launches and accelerates, it squats and thus the sensor is no longer
> measuring the true acceleration of the car but also a component of gravity
> as it is tilted by a small degree. This tilt is most pronounced at the
> start
> when launching and any error at the start is magnified at the end due to
> the
> cumulative maths involved in using force over time to derive speed and
> distance.
> I've tried calibrating it with a negative tilt to compensate with mixed
> results. It's too much farting around especially when you use it in
> different cars, so I just set it dead level and live with the fact it's
> optimistic by a bit.
> This kind of device does not measure distance or speed, it derives it thru
> cumulative calculations, and that's where the danger lies in its accuracy.
>
>

Thanks Arnie, Ive learned a little more about drag racing, cheers.


(No it wasnt a sarcy comment, I love real information.)