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nodg
National Driver
1667 Posts
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 Posted - 22 Nov 2008 : 6:49:37 PM
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As the title says who does gtech runs aand what have you learnt about performance from using one?
Ive been using a gtech pro for about 6months now and have a few things i wouldnt mind talking about with members on this forum in regards to performance, how weather and weight can drastically impair normal times and the like. You can also post your times (either track or gtech) for comparison : )
My main question i want to talk about that im a noob with is weather, mainly humidity. I have been doing runs in both hot & cold situations although its been dry, the times in these circumstances range from 6.01-6.5 seconds 0-100KM/H, Now last night i was doing some runs, it wasnt cool but it wasnt hot either and in brisbane there has been wicked sotrm causing high level of humidity, after a dozen or so runs i found the absolute fastest time i could run was a 6.7 0-100 and quarter mile in 15.2 seconds flat. Why is this? how can humidity affect standstill performance when on hotter days with next to no humidity i can do faster runs? i would of though humidity in the air (making it dense) would have a better affect on engine performance not making it worse? - Thats the biggest one that has stumped me because this morning (still humid but not the best) i could manage an average recording of up to .3 of a second quicker?
Of i could have an explanation to why this happens than it would be great, im no weather or scientific junkie.
Now in regards to weight ive been doing comparisons, (will have to make this quick i have to go to tea) if i put my tool box (80 kilos) in the boot the average time i get slowed down is .1-.3 of a second, i read somewhere that removing 100kilos off you car ?CAN? speed your car up to a second quicker than it was before. What i have worked out is the figures are much lower, actually it didnt make much of a difference at all.
Ill continue this after i get back from tea but would like to hear other member responses t the above question related to humidity, wind, and general weather conditions.
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Cheers,
Nodg. |
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 23 Nov 2008 : 12:44:05 AM
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| With bikes and drag racing a common rule is 10kg less equals 1/10th less but cannot comment on cars |
What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
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nodg
National Driver
1667 Posts
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Posted - 23 Nov 2008 : 01:33:36 AM
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| can you comment as to why humidity has a downhill effect? |
Cheers,
Nodg. |
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crazybiker
Fully Licenced
141 Posts
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Posted - 23 Nov 2008 : 09:13:28 AM
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I'm not sure.
But I'm curious, is the G-Tech worth it?
Does it give pretty accurate readings on the run times and power outputs?
I'm considering getting myself one, but not 100% sure yet. |
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nodg
National Driver
1667 Posts
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Posted - 23 Nov 2008 : 3:51:01 PM
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They are the next best thing to going to a drag strip and they are fairly accurate depending on if you level the gtech inside the car correctly, dont get wheelspin at the start/middle of your run and your on dead flat ground, there are a few people ive been sus on looking at there gtech charts (the latest version comes with a digital screen and features such as a realtime dyno graph) and you can see where they have wheelspin at the beginning of the run, but there time doesnt start to be reordered until they actually finished the skid midway through there run and start accelerating, thats why on justcommodores theres alot of guys in v6's and v8's that claim they can do a 5 second flat run, but its not entirely true as they have massive wheelspin at the beginning of their runs, in the older gtech pro's like mine which simply starts counting as soon as the gtech 'feels' you car lunge forward but you still have to be careful of wheel spin, i noted on some of my runs the other night with skinny tyres that even though i did a massive skid through first off the mark it still counted from when i launched and i ended up with an 8.5 second pass & a 15.9 sec quarter mile.
I wont say that there 100% accurate but its farly close (gtech claims within .5 of a second accuracy) but i have shown people on the internet a video of me doing a run showing the dash and if you use the counter u-tube provides at the bottom of the page it was most definately in the 6 second bracket, so for the 50 bucks i spent on it im happy.
Copy & paste job on how they work-
Acceleration:
At the heart of G-TECH/Pro is a precision 3-axis accelerometer, a sensor that measures acceleration also known as G-Force. G-Force is what's keeping you in your seat and if it wasn't for that seat you would be accelerating to the ground at 1 G (32 feet per second per second).
Acceleration is measured in Gs and is one of the key things the G-TECH/Pro COMPETITION is measuring. You can see this when you position the unit horizontally, it will show 0.00G's on the X acceleration bar. If you position it vertically it will show 1.00G's.
Speed:
The G-Tech measures your speed and distance traveled by integrating forward (the forward direction is chosen automatically) acceleration over time. Basically, if you know how fast you are accelerating for a certain time period you'll know how much your speed changed after that time period. So if you start off from zero speed then you'll know what your speed is after every time period. These time periods are very small (a few thousandths of a second) and that's how G-Tech maintains its accuracy. However, if you don't start from zero speed your measurement won't be correct because you won't have a good reference point. Consequently, it's very important to start all of your measurements from an absolute standstill.
Distance:
Distance is measured in the same fashion, if you know how fast you are going for a certain time period you will know what is the distance traveled during that time period.
Horsepower:
The G-Tech measures horsepower though the formula: speed times acceleration times the weight of the vehicle. The more accurate the vehicle weight you enter, the better your measurement. The G-Tech measures delivered horsepower, sometimes also called Rear Wheel Horsepower. This horsepower includes the loss of power through the drive train which is usually 10-15%. Rear Wheel Horsepower is what most people are interested in because that is what they experience when driving. The use of Flywheel Horsepower measurement is often used in advertising, but not very realistic when it comes to accelerating your vehicle.
The horsepower that G-Tech measures also includes vehicle aerodynamic drag. This means that if you tape over your headlights and grill, remove rear view mirrors and windshield wipers to reduce your drag, you will measure a Horsepower increase even though you didn't make any changes to the engine. After adding an aftermarket spoiler you will likely find a decrease in measured horsepower, since you increased the drag losses on your vehicle.
RPM:
Engine RPMs are sensed directly from the cigarette lighter voltage. No installation required at all with this true plug and play feature. The unique RPM feature is used for anything from real-time torque measurements to shift lights. |
Cheers,
Nodg. |
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crazybiker
Fully Licenced
141 Posts
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Posted - 23 Nov 2008 : 5:57:19 PM
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Hmm, so do the have to be mounted on the windscreen? Or can you mount them somewhere else.
Personally, I hate having things on the windscreen.
Where'd you get yours, because I want one, but the only ones are on Ebay for like $300 AUD. |
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nodg
National Driver
1667 Posts
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Posted - 23 Nov 2008 : 6:20:41 PM
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thats for the latest version from the usa, mine is the first one they brought out & they go for 50-100 on ebay. look for autions as well as buy it now items
it says in the manual that it has to be placed on the windscreen, & to ve right under the rearview mirror for best results although i dont know why. i put mine centred in the windscreen just above the aircon vents. |
Cheers,
Nodg. |
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nodg
National Driver
1667 Posts
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nodg
National Driver
1667 Posts
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crazybiker
Fully Licenced
141 Posts
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Posted - 23 Nov 2008 : 6:41:22 PM
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Hmm, see, I'd rather not have it on the windscreen.
I may get one, I don't know, but right now, there's other things I'd like to spend my money on. |
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 23 Nov 2008 : 10:13:41 PM
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| To answer your earlier question nodg - humid air is lighter, or less dense, than dry air. |
What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
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nodg
National Driver
1667 Posts
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Posted - 23 Nov 2008 : 11:22:59 PM
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i thought humidity was moisture in the air which would make it heavier?
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Cheers,
Nodg. |
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 23 Nov 2008 : 11:30:21 PM
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Common misconception.
To see why humid air is less dense than dry air, we need to turn to one of the laws of nature the Italian physicist Amadeo Avogadro discovered in the early 1800s. In simple terms, he found that a fixed volume of gas, say one cubic meter, at the same temperature and pressure, would always have the same number of molecules no matter what gas is in the container.
Imagine a cubic foot of perfectly dry air. It contains about 78% nitrogen molecules, which each have a molecular weight of 28 (2 atoms with atomic weight 14) . Another 21% of the air is oxygen, with each molecule having a molecular weight of 32 (2 stoms with atomic weight 16). The final one percent is a mixture of other gases, which we won't worry about.
Molecules are free to move in and out of our cubic foot of air. What Avogadro discovered leads us to conclude that if we added water vapor molecules to our cubic foot of air, some of the nitrogen and oxygen molecules would leave — remember, the total number of molecules in our cubic foot of air stays the same.
The water molecules, which replace nitrogen or oxygen, have a molecular weight of 18. (One oxygen atom with atomic weight of 16, and two hudrogen atoms each with atomic weight of 1). This is lighter than both nitrogen and oxygen. In other words, replacing nitrogen and oxygen with water vapor decreases the weight of the air in the cubic foot; that is, it's density decreases.
Wait a minute, you might say, "I know water's heavier than air." True, liquid water is heavier, or more dense, than air. But, the water that makes the air humid isn't liquid. It's water vapor, which is a gas that is lighter than nitrogen or oxygen.
Compared to the differences made by temperature and air pressure, humidity has a small effect on the air's density. But, humid air is lighter than dry air at the same temperature and pressure. |
What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
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nodg
National Driver
1667 Posts
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Posted - 24 Nov 2008 : 12:38:12 AM
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that explains alot, i had to read it twice to get it all in, i now understand why you said lighter & less dense.
by what your saying is that with the humid temperature that we have at the moment in qld, the amount of combustable substance, air/nitrogen, is much less than when its simply dry & hot/cold. i didnt consider that & i simply thought that vapour in the air would make the car faster by decreasing the amount of physical space the air could be compressed by, otherwise known as increasing the compression in the combustion chamber. which by the sounds of things it does do this but the amount of air/nitrogen 'missing' is enough to make the advantages of humid air outweighed by its disadvantages in terms of making a car faster? |
Cheers,
Nodg. |
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nodg
National Driver
1667 Posts
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 26 Nov 2008 : 11:10:58 PM
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i am not sure i understand what you are asking
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What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
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nodg
National Driver
1667 Posts
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Posted - 26 Nov 2008 : 11:20:55 PM
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is what i said in my last reply what your talking about or am i way off?
So basically the lack of air in humid air is what was making my car slower? |
Cheers,
Nodg. |
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 27 Nov 2008 : 11:30:27 PM
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| pretty much yes. Less oxygen smaller bang. |
What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
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