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Ubergeek
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Discussion Starter · #1 ·
performance meter.



My #1 reason was to analyze my autocross runs with the www.slip-angle.com software... but of course I had to do a few drag mode runs..

It's nice outside, probably about 60 degrees. ~75 ft above sea level. Pilot Sport PS2.

Did 3 runs. (I know this has been discussed as to which launching method is 'ideal', but I basically dumped the clutch at around 2500-3000RPM). Shifted at redline.

First run was closer to a 2500RPM launch. Absolutely perfect. A touch of wheelspin, no bogging at all.

0-60: 5.428
1/4 mile: 13.803 @ 104.12mph

All I can say is... wow!

Second run. Launched closer to 3000RPM. Way too much wheel spin.

0-60: 6.061
1/4 mile: 14.647s @ 94.50mph

Third run. Back down closer to 2500RPM. Bogged a bit.
0-60: 6.204s
1/4 mile: --- (unable to travel the entire 1/4 mile, approaching car)

I put in a vehicle weight of 3540 (Car weighed 3360 on truck scales + I'm about 180lbs) and the G-Tech recorded a RWHP rating of 212.5 HP @ 6042 RPM and torque at 208.9 ft-lbs @ 4998 RPM
 

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very nice..

Good numbers. You're doing far better with launching than me. Although i've been trying silverstreak's method as opposed to popping the clutch.

However, I would take those numbers with a grain of salt.

The performance meters like the G-tech are very precise, but they are not very accurate.
 

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Running around in circles
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Iniquity said:
Good numbers. You're doing far better with launching than me. Although i've been trying silverstreak's method as opposed to popping the clutch.

However, I would take those numbers with a grain of salt.

The performance meters like the G-tech are very precise, but they are not very accurate.
:confused:
 

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Very nice, may I ask where you did the runs?
 

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In my own cars again
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Iniquity said:
Good numbers. You're doing far better with launching than me. Although i've been trying silverstreak's method as opposed to popping the clutch.

However, I would take those numbers with a grain of salt.

The performance meters like the G-tech are very precise, but they are not very accurate.
Please expand/expound - if the thing is mounted level, and Kris puts in an accurate weight, and does not enter a time warp to alter the clock readings, then it's all up to the accelerometers. As you yourself note, the accelerometers are quite precise, precision breeds accuracy.

So what are we missing here?

Kris - Great numbers - the most impressive thing is nailing the launch. Outstanding!!

(Finally put the summers back on last night - and it's flooding outside. Maybe by Monday I can drive it..... :( )
 

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Ubergeek
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Discussion Starter · #9 ·
MicahO said:
Please expand/expound - if the thing is mounted level, and Kris puts in an accurate weight, and does not enter a time warp to alter the clock readings, then it's all up to the accelerometers. As you yourself note, the accelerometers are quite precise, precision breeds accuracy.
The RR doesn't even need to be mounted level. It has 3 accelerometers in it and auto-corrects. Weight also doesn't have anything to do with measuring 0-60/1/4 mile.... only horsepower.

I hear that car & driver did a test on performance meters this month and they liked the RR. I haven't received my copy yet..
 

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Where'd you buy it? And how much? :)
 

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OMGWTFBBQ
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KrisL said:
performance meter.



My #1 reason was to analyze my autocross runs with the www.slip-angle.com software...
Kris, FWIW I've been finding the gtech software to be far more useful than the MapMaker app. It's definitely helpful in conjunction with the gtech app (and it's worth the $20), but it's really difficult to get the maps close enough to right to be useful on their own (and even harder than that if you experience high yaw rates). Only been able to use it at one autocross so far (couldn't get the thing to stay stuck today in Houston :mad: ), but it's whet my appetite for something more advanced...if only the other options clost less. Sigh.
 

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They call 'em rigs here
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Iniquity said:
However, I would take those numbers with a grain of salt.

The performance meters like the G-tech are very precise, but they are not very accurate.
So the engineers who designed it must have been very smart but not very intelligent?:confused:
They post accuracy numbers on their website. Assuming we can believe their claims, they look very accurate to me. Not to mention very precise.
 

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Kris, did you quick shift into 2nd and drop the clutch or did you wait for the revs to drop before the shift into 2nd and then ease out on the clutch? Excuse the ignorance since I don't normally launch the car and I'm not sure if having the wheels chirp from dropping the clutch would help my acceleration.
 

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Ubergeek
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Discussion Starter · #15 ·
allaboutme said:
Kris, did you quick shift into 2nd and drop the clutch or did you wait for the revs to drop before the shift into 2nd and then ease out on the clutch? Excuse the ignorance since I don't normally launch the car and I'm not sure if having the wheels chirp from dropping the clutch would help my acceleration.
I shifted as quick as possible, wheels chirping. Rev-matching on the downshift would slow you down considerably.

Back in '97 when I was driving a Chevy Beretta, the Beretta.net mailing list used to call me 'Kris Quickshift' - at the drag strip, I had the fastest 1/4 mile time anyone could get out of the 3.1L, stock or modified (mine was stock). [email protected] Not too bad for 140hp. :)
 

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Why would I downshift when dragging? Or are you relating it to rev matching downshifts?

Anyway, your first run seems really good but it's an outlier with your last two runs. Nevertheless, you have some very impressive numbers. Maybe they need to hire you for car mags for dragging their cars.
 

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MysticBlue said:
So the engineers who designed it must have been very smart but not very intelligent?:confused:
They post accuracy numbers on their website. Assuming we can believe their claims, they look very accurate to me. Not to mention very precise.
The terms accuracy and precision are commonly misused. For one, accuracy does not equal precision and vice versa. A majority of times the terms are used interchangeably, which they cannot be. It's a very important difference to distinguish between the two in engineering, but for the average consumer, slapping some data about precision and accuracy is all about marketing, and frankly, the average consumer could care less about the differences. It's especially important to know the difference between the two when you are trying to characterize a DUT, which in this case, is the BMW.

I have no doubt that the accelerometers used in the gtech are very precise. Accuracy, however, is not determined by the gtech; it is determined by the user of the gtech and its environment.

EDIT: To make things more confusing, you can have precision without accuracy, but you cannot have accuracy without precision when characterizing a DUT.
 

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Ubergeek
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Discussion Starter · #19 ·
stephen05zhp said:
Damn! That's a half second better than my best time w/ my g-timer II (5.95 seconds).
Tires make a big difference, that's why I mentioned that I have Pilot Sport PS2s on.

Maybe I'll do a run wearing my Hoosier autocross rubber :)
 
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