Results 111 to 120 of 120
05-11-2010, 10:58 AM #111
My 1982 with 4:31, W58, 225/65-R14 and standard 5M only made it to 128 MPH, at ~6,750 RPM. Stock weight + 250lbs (I'm a big dude). I was heading down hill at about 10% Grade. The chart just looks a little off. I may be wring though.
I was along side a 2008 Porsche... My speedo read past 85, that was as high as it went. But he signed "1...2...3-5." I took it as 100 + 20 + 3 + 5-Taylor Nielsen|Hidden Content
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06-05-2010, 05:47 AM #112
but my 5m is a late high comp engine, and it's on an 83 with 4:10 gears, all i have done to the car is suspension and exhaust.1978 datsun 280z 5speed, 1983 datsun 280zx n/a, 1983 toyota supra p-type, 1983 toyota corolla coupe
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06-07-2010, 09:57 PM #113
The pertinent inputs-
W58 gear ratios
5th gear = 0.783
Tire diameter: 205/60-15 = 24.7in
Rear Gear Ratio: 3.73
The formula: mph = (rpm * tire diameter in inches) / (gear * differential * 336)
mph = (3000 * 24.7) / (0.783 * 3.73 *336)
mph = 74100 / 981.3
mph = 75.5
IMO, if you feel the chart is off, it's more likely that some portion of the input is incorrect. My bet is that your RPM is inaccurate; next up is that your diff isn't really 3.73. Less likely is that the gps is wrong or, grasping at straws, you don't know how to read what's printed on your tire.
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07-16-2011, 08:44 PM #114
I hope that information is correct. 8750rpms, 17 inch rim/tire = 24.7 (same as 15 inch tire above?????)
(8750*24.7) / (1.00*4.10*336) = 156.88mph
The dyno said 158mph in 4th (R154).
I am just trying to calculate the speed because I have no speedometer.
Calculated 208.35mph in 5th.
Last edited by racerxj220; 08-12-2011 at 11:58 AM.
12-12-2012, 10:09 PM #115
hhmm interesting, think I'm going to print this into a sticker and slap it on my dash so I can figure out what speed I'm doing for once. My speedo's out 60+ kmh it fluctuates as you drive.
01-01-2014, 03:44 PM #116
precise speedo on the MK2!
With the 3.72diff, and its correct speed gear in the W57 and the speedo INTERNAL (all from the same Euro. spec MK2) behind the US standard MPH/kph dash, and 215/65R14 tires on the back, the speed is PRECISE! I clocked it on FEW roadside radars (used in Europe to show your speed so you can correct it) in different speeds, and I was stunned at the preciseness of my speedo!!! The reason I swapped the internal speedo mechanism, was because my original US Spec. one had over 330,000 miles on it and its gears were worn and the arrow would dance around, while the Euro spec. one I had only a bit over the equivalent of 111,000 miles.
So it is safe to say that the Euro spec. MK2s had pretty decent speedo (safe for the larger rear tires I run 215/65R14 vs. 225/60R14).
Last edited by punkara; 01-01-2014 at 03:45 PM. Reason: typo
01-01-2014, 05:36 PM #117
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My 85P has always been a bit optimistic and with 225/60/15's, it's very close. I can't recall the diameter difference compared to the 225/60/14's but I think it's a bit over 4%. Most vehicles tend to read a bit high though. It's not uncommon for some motorcycles to be read way over reality, some by between 10 and as much as 15%!
As far as top speed, my car has always been able to go faster in 4th gear and this is true of many vehicles. Upshifting to 5th and the engine just doesn't have enough power to sustain that speed. I've had mine verified by a friend with his police cruiser at 135 or so and might have had a few more in it but very few.
01-08-2014, 06:21 PM #118
Hate to continue to revive an old thread, but is there a way i can tell if i have an LSD without getting under the car? it sits relatively low to the point where its hard to get under plus its like 10 degrees out.Felix
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07-18-2014, 01:20 AM #119
This thread is funny, all you guys doing math when there's a calculator made to solve all these problems for you with just a few button clicks! Have you all not seen DeanFun's Tire Speed calculator? It was posted 2 years after this thread started. ANYWAYS, I just solved a huge mystery in the land of correcting Toyota speedometers and magical part numbers, see this post in the aforementioned thread...
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07-22-2014, 12:34 AM #120
Hidden Content "Who Needs A Radio, 5mge Is Music To My Ears."
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