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Engine RPM and road speed
hpnotch - June 10th, 2015 at 06:16 PM

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 - June 10th, 2015 at 06:23 PM

Not sure if this would help?

Its a type 2 though...

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

1500S - June 10th, 2015 at 06:47 PM

Quote:
Originally posted by hpnotch
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 - June 10th, 2015 at 08:40 PM

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

grumble - June 10th, 2015 at 09:14 PM

Quote:
Originally posted by 1500S
Quote:
Originally posted by hpnotch
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 - June 10th, 2015 at 10:28 PM

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.

farkengruven - June 11th, 2015 at 02:15 PM

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

hpnotch - June 11th, 2015 at 07:14 PM

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?