I Agree with the "caution" statement to let people know the unitrax gear/speed calculator does not agree with other gear calculators out there. As much as I like Unitrax, I cannot find any way to support the accuracy of their gear calculator. I addressed this before
http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=UBB14&Number=259060 but will further expand.
CAUTION:
The Chuckware viperspeed calculator is in conflict with the speed calculator on the the Unitrax website. A couple of interesting points;
1. The chuckware calculator math seems to checkout, however, the calculated speed does not seem to correlate to actual.
2. The Unitrax calculator does not publish its math, however, it seems to correlate better to actual. <font color="blue"> I must disagree and ask what you base this statement on </font>
I have emailed or talked to both, they are cordial and helpful, but, someone is wrong.
The Assumptions: 6,000 rpm ; 25.4" diameter tire; 4th 1:1 gear, 3.07 rear gear.
[*]So According to the
http://www.gounitrax.com/UNITRAX/pages/calculator/mph.html
6,000 rpm in 4th gear is <font color="red"> 156.98 </font> so we'll just call it <font color="red"> 157 mph </font> to keep it simple.
[*]According to the
http://chuckware.net/viper/gears.asp 6,000 rpm in 4th gear is <font color="red"> 148 mph </font>
But which is correct? Well let's take a few different approaches:
First Approach- The "Magazine" approach listing the speed in 4th at 6,000 rpm supports Chuckware:
[*]148 mph Road/Track 3-1992
[*]147 mph Car & Driver 3-1992
[*]144 mph Road/Track 11-1995 (showed estimated in 5th & 6th)
[*]144 mph Road/Track Specials 1998
[*]146 mph Road/Track GT-2 9-1998
[*]146 mph Road/Track Specials 1999
[*]144 mph Road/Track Specials 2000
[*]146 mph Road/Track Specials ACR 2001
Aslo Then M/T tests show 1,200 rpm and 1,220rpm in 6th gear at 60 mph. That would math out to 148 & 150 Mph in 6th gear at 3,000 rpm. The ChuckWare gear Calculator calcs out to 148. That's pretty close.
Second approach - the long hand math supports Chuckware. I'll walk you through the math and use 25.4" as the tire size:
25.4" tire diameter * pi = 79.7964368" covered each time the tire rotates
79.7964368"/ 3.07 gears = 25.99232469" covered each rotation of the driveshaft
6,000(rpm) * 60(min) * 25.99232469" = 9,357,236 inches per hour
9,357,236 / 12 = 779,770 feet per hour
779,770 / 5280 = 148 miles per hour
Third Approach - another gear calculator site aligns& agrees with Chuckware:
There is another site with a very nice gear calculator you can work with a bit. It gets the same results as the one at chuckware.net. Check it out at:
http://www.f-body.org/gears/
Fourth Approach - Personal observation lines up w/ Chuckware:
2 months ago I had several runs in 4th at 6000 rpm and I was not over 150 mph on the spedo, let alone the 157 mph the Unitrax calculator says I should have been going.
Summary: I can't find any evidence in the 4 approaches above that supports the Viper going anywhere near the 157 that the unitrax site calcs to but I can find lots to support that the chuckware calculator is pretty close.