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Thu Dec 04, 2003 4:05 pm

:?:
Does anyone what the formula's or such to work out what RPM's/Revs my engine is at at certain speeds?
I am also interested in the following:
Max RPM,
Most Economical Speed/RPM

This is for a Stock 1974 SuperBeetle, with the 1600 mill and a stock(assumption on my part) transaxle.

If you have the formula's, I can build a spreadsheet for figuring it all out, I would be glad to share whatever I come up with.

Thanks,
matt

Thu Dec 04, 2003 7:43 pm

Here you might find this helpful. CB performance also has a link to it.

http://www.et-studios.com/motorsports/gears/gears.html

Mike
59 single, 69 bus, 73 super

Thu Dec 04, 2003 7:44 pm

74...

I can't help you with the rpms & such - I don't have a tach on my 71 Super.

What I've found with my Bug (all stock) is that it cruises along at 60 mph beautifully. That's about the best speed I've found. High enough rpms to keep the engine cool, but not too high.

That's my 2 cents...

JSH

Fri Dec 05, 2003 6:59 am

i believe the ratios changed arround from year to year.. and of course with the size of the engine that went along with it..

1st Gear: 3.78
2nd Gear: 2.06
3rd Gear: 1.26
4th Gear: 0.89

some figures for u to plug into that calculator.

Fri Dec 05, 2003 1:54 pm

You'll also need the ring and pinion ratio which I believe should be 3.88. But, I have found that a lot of trannies that have been rebuilt have the stronger 3.88 removed and replaced with a weaker 4.12 or 4.37. The only to be sure is to pull it and look.

As far as the most economical speed/rpm most of the vw's are set up to run at 3800-4200 in that range. Air cooled cars need to run with more rpm than a typical water cooled car to spin the fan fast enough to cool the engine.

Mike

Fri Dec 05, 2003 2:10 pm

I wrote a MS-Excel spreadsheet that does all the calcs. you supply the tire size and gear ratios and it gives you the speed in each gear at 1000rpm intervals.

You can download it at
http://www.glenn-ring.com/temp/tranny_calc.xls

Sat Dec 06, 2003 2:52 pm

Thanks for all the great input, I really appreciate it.

I am trying to figure out what redline rpm's/rev's is on my Stock 1974 1600DP engine. Is there a reference I should be looking at, or is it in my Chiltons? (which I hate, because of it's generic-ness)

What my purpose with all this is to get a better handle on how I should be driving this car. As well as having an Idea of the RPM's without having to buy a tach(Cannot afford to right now, that is far down the list, after brake hoses, brake shoes, and right side pan).

BTW, I mod'ed the spreadsheet I got a little, so that if you don't have a 5th gear, it does not show DIV/0 errors, do you want a copy back Glenn74?

Thanks,