How fast am I going?
10-16-2006, 04:20 PM
#1
Pro
Thread Starter
How fast am I going?
Doing almost 90 in my 06 C2 everyone is passing me. I'm beginning to wonder if my speedometer is off? Being out of town and not having access to a portable GPS I have a question to help me resolve this problem. How fast are you going in C2 in 5th gear with a Tiptronic at 3000 rpm?
10-16-2006, 04:50 PM
#4
Rennlist Member
80 mph would be 45 seconds per mile
90 mph would be ~40 seconds per mile
100 mph would be ~36 seconds per mile.
Do you have a tachymetre on your watch?
http://en.wikipedia.org/wiki/Tachymetre
90 mph would be ~40 seconds per mile
100 mph would be ~36 seconds per mile.
Do you have a tachymetre on your watch?
http://en.wikipedia.org/wiki/Tachymetre
10-16-2006, 05:10 PM
#6
Chainsaw
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Instead of timing your distance between mile markers. Reset your trip gauge at the start of a mile marker, drive interestate miles and compare the mileage to your trip gauge.
I did this a couple of months ago. I drove 79 interstate miles and my trip gauge showed 83 miles. My speedo is about 5% fast.
I did this a couple of months ago. I drove 79 interstate miles and my trip gauge showed 83 miles. My speedo is about 5% fast.
10-16-2006, 06:27 PM
#7
Drifting
according to my portable GPS my speedo shows 2mph slower than actual speed
CORRECTION: 2MPH Faster than actual
CORRECTION: 2MPH Faster than actual
Last edited by Bob in NY; 10-17-2006 at 08:20 AM.
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10-16-2006, 06:45 PM
#8
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Originally Posted by Bob in NY
according to my portable GPS my speedo shows 2mph slower than actual speed
19's on my car.
10-16-2006, 08:34 PM
#10
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Calculate as follows:
1. 3000 rpm divided by (.83 gear ratio x 3.56 final drive) =1015.3 axle turns per minute.
2. 265/40 x 18 tire. Sidewall height= 265 width x.4 aspect ratio divided by 25.4(mm to inch)=4.173".
18" + 2 x 4.173 = 26.35" tire diameter. 26.35 x pi x1/12 = 6.897 ft tire circumference.
3. 1015.3 X 6.987 divided by 88 = 79.57 mph.
Say 80 mph.
1. 3000 rpm divided by (.83 gear ratio x 3.56 final drive) =1015.3 axle turns per minute.
2. 265/40 x 18 tire. Sidewall height= 265 width x.4 aspect ratio divided by 25.4(mm to inch)=4.173".
18" + 2 x 4.173 = 26.35" tire diameter. 26.35 x pi x1/12 = 6.897 ft tire circumference.
3. 1015.3 X 6.987 divided by 88 = 79.57 mph.
Say 80 mph.
10-16-2006, 08:42 PM
#11
Originally Posted by ChipAZ
Doing almost 90 in my 06 C2 everyone is passing me. I'm beginning to wonder if my speedometer is off? Being out of town and not having access to a portable GPS I have a question to help me resolve this problem. How fast are you going in C2 in 5th gear with a Tiptronic at 3000 rpm?
10-16-2006, 09:04 PM
#12
Just returned from a weekend in Redwood City and the speed from north of SLO to south of Salinas is amazing! Hit 115 for a brief spell going and 125 for an equally brief period returning. Averaged about 90-95 in that area and I wasn't pulling away from that many cars! Car ran great.
