Engine RPM and road speed

hpnotch Seriously Crusin Dubber

133 posts · joined Nov 2012 · 10 Jun 2015, 6:16 pm

#1014817

I've recently fitted an old Smiths tachometer in the Type 3.
Does anyone know of tables that exist to give an indication of engine RPM and corresponding speed?
Currently the tacho reads about 2700 rpm @ 50 mph in 4th gear, running on standard rims (15 in) and tyres. Does that rpm sound right?

adlbeetle66 Under the car.........again!

1,476 posts · joined Aug 2014 · 10 Jun 2015, 6:23 pm

#1014818

Not sure if this would help?

Its a type 2 though...

http://www.type2.com/library/misc/calcspd.htm

1500S Custom Title Time!

1,418 posts · joined Mar 2005 · 10 Jun 2015, 6:47 pm

#1014819

hpnotch wrote:I've recently fitted an old Smiths tachometer in the Type 3.
Does anyone know of tables that exist to give an indication of engine RPM and corresponding speed?
Currently the tacho reads about 2700 rpm @ 50 mph in 4th gear, running on standard rims (15 in) and tyres. Does that rpm sound right?

Somewhere in the distant past I seem to remember that a Type 3 with a diff ratio of 4.125 : 1 and the standard Type 3 gearbox the top gear road speed was around 19.8 mph/1000 rpm.

hpnotch Seriously Crusin Dubber

133 posts · joined Nov 2012 · 10 Jun 2015, 8:40 pm

#1014824

Thanks for the replies -based on that info 26/700 rpm @ 50 seems about right then

grumble Son of Jim - Creator of Good

2,672 posts · joined Jun 2008 · 10 Jun 2015, 9:14 pm

#1014829

1500S wrote:
hpnotch wrote:I've recently fitted an old Smiths tachometer in the Type 3.
Does anyone know of tables that exist to give an indication of engine RPM and corresponding speed?
Currently the tacho reads about 2700 rpm @ 50 mph in 4th gear, running on standard rims (15 in) and tyres. Does that rpm sound right?
Somewhere in the distant past I seem to remember that a Type 3 with a diff ratio of 4.125 : 1 and the standard Type 3 gearbox the top gear road speed was around 19.8 mph/1000 rpm.

My Ghia runs close to 20mph per thousand.

Craig S Wolfsburg Wizard

635 posts · joined May 2008 · 10 Jun 2015, 10:28 pm

#1014839

There's heaps of calculators on the interwebs. First one on Google:

http://www.osella.com.au/gear-ratios.htm

You just need to know some of the stats of your car (tyre size, gear ratios, etc)

For the mathematically inclinded you can create a spreadsheet yourself.

From memory Phil had an article in the ClubVW magazine that outlined the formula. Also, Daimo once shared a spreadsheet he had which graphed road speed at various rpm in each gear.

PM me and I'll send you the one I created.

1969 Beetle - June
1974 L Bug - Gwendolyn
2002 Bora V6 4Motion - Anita

farkengruven Seriously Crusin Dubber

167 posts · joined Jan 2006 · 11 Jun 2015, 2:15 pm

#1014867

What year Type 3?
3.875 or 4.125 ring and pinion?
What tyres radial or crossply?

3.875 running 165 80 r15 tyres - 2560 rpm
4.125 running 165 80 r15 tyres - 2730 rpm

3.875 running 560 15 tyres - 2527 rpm
4.125 running 560 15 tyres - 2690 rpm

2007 T5 TDI Crewvan
2003 Passat
NSU Ro80
1975 Passat TS
1973 L bug

hpnotch Seriously Crusin Dubber

133 posts · joined Nov 2012 · 11 Jun 2015, 7:14 pm

#1014888

Cheers - its a Jan'71 - 4.125 according to the manual.
I'll check the tyre size on the weekend.
I bought this tacho in a run down state through ebay and patched it up to look OK - but I wasn't sure of it's accuracy.
However the tacho is reading somewhere around the 2600/2700 mark @50 mph - so I'm happy to think its operating fine.
Thanks for all the replies.
Just as an aside - and not that I have any desire to get to it - what would be the redline mark on these motors?

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