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Location:
The Eastwood MASSIVE !
Registered:
May 2003
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Gtech question.
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Mon, 19 January 2004 07:58
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With a gtech on a " estimated horsepower " run , wouldn't it make more sense to start the run , baby the car up to 4th gear and then hold it to the floor till you red lined 4th?
I was just thinking this because the manual says to run through all the gears , but on a dyno we use 4th gear to get close to a 1:1 ratio.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Gtech question.
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Tue, 20 January 2004 02:21
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i would guess that you have to start from standstill, otherwise it doens't know how fast you are going, since it calculates speed from time and acceleration.
Cya, Stewart
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Location:
The Eastwood MASSIVE !
Registered:
May 2003
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Re: Gtech question.
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Tue, 20 January 2004 03:47
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Thats not what I asked in my post.
Ofcourse the gtech needs to be started while stationary , I wanted to know that if starting the gtech , then going slowly through the gears till you got to 4th gear and then floored it to get a more accurate top reading then hammereing through all the gears.
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Location:
sunny coast, qld
Registered:
October 2002
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Re: Gtech question.
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Tue, 20 January 2004 03:58
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personally, i would do what the instructions say.
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Location:
NSW, East Coast
Registered:
July 2003
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Re: Gtech question.
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Tue, 20 January 2004 04:03
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Theres a website with all this info shit on it.
http://www.gtechpro.com/gtechprocomp_howitworks.ht ml
I believe it has something to do with the way it measures, using slices of silicon vs g-force or something like that.
Im not sure if it'll answer your question but maybe give an understanding of who it works.
Steve
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I supported Toymods
Location:
Australia
Registered:
November 2003
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Re: Gtech question.
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Tue, 20 January 2004 04:49
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It measures rwhp buy using a formula
For instance
A 1500kg car with a 1/4 mile of 14.2 sec and a terminal speed of 130mph, would need to have 195rwhp to make this possible
If you get what I am trying to say
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Gtech question.
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Tue, 20 January 2004 04:54
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my understanding is that the original one calculates the HP from the estimated 1/4 mile time.
i would not be confident that the G-tech is sensitive enough to measure the acceleration properly while you are babying it thru the gears... the calibration of the G-tech (original one) is such that when it is measuring 1G (ie tilted), it reads between 0.96 and 1.04G, os it aint that crash hot..
if you are really concerned, take the damn thing for a run, and check yourself...
do a standing start, and then do a 4th gear start..
also remember that it gives a HP that doesn't really mean anything... it doesn't give you a graph (maybe the comp one does)
so the actual number is mor elike a 'mean hp' figure, which is what is usually calculated from 1/4 mile runs....
or you could ask on the G-tech forum on their site.. surely that would have been a better place to ask than here?
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Gtech question.
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Tue, 20 January 2004 05:24
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ok...
i 'get the question'...
theoretically your engine should make 'x' amount of power at 'y' rpm point in whatever gear youre in.
this power (regardless of gearing) will produce 'z' acceleration of a car of a given weight (which you enter).
it doesnt matter what gear youre in as the gtech will calculate the change in accel in time (which will be high in low gears, and low in tall gears)... but its all very simple maths to work out.
(this is in contrast to rollers on a chasis dyno, that take a direct measurement off the wheels, and require a 1:1 ratio through the box to see what is happening at the engine)
HOWEVER: errors are what will distort you readings...
... in low gears you have a very small time scale in which to recard changes in accel. which can make the fidelity of data a bit rough
... in tall gears, the accuracy is improved as the time scale is lengthened, however, rate of accel decreases, and changes may be harder to quantify
... plus in taller gears, youre going faster, and losing more and more power to wind resistance
compromise, do a 2nd gear run to redline. that way you have about 10secs of recording, the rate of change of accel is decent, plus terminal speed wont go much over 100kmh, so drag wont kick you in the ass to much
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Location:
The Eastwood MASSIVE !
Registered:
May 2003
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