Date:         Fri, 03 Mar 95 14:17:12 CST
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Joel Walker <JWALKER@ua1vm.ua.edu>
Subject:      Re: Travels

On Fri, 3 Mar 95 13:46:26 CST Matt said:
>My question is: What are the engine RPM compared to MPH, ie, 75 mph = ? RPM
>etc. ( I have a clock not a tach). I want to figure fuel, etc. during my
>trip as well as get the best RPM for cruising speed without undue engine
>wear. (the engine has about 94,200 miles on it.)
>'84 Vanagon GL

for my 2.1 liter, (and i think the 1.9 liter would be very close), it works
out this way:  (all 4th gear)

4000 rpm   =  67 mph    now, these are REAL speeds, not speedometer speeds.
3800 rpm   =  64 mph    my speedo is off by about 3 mph at these speeds, so
3600 rpm   =  60 mph    when it looks like i'm doing 70mph, it's really 67.
3400 rpm   =  57 mph    *** best torque speeds
3200 rpm   =  54 mph    ***
3000 rpm   =  51 mph

what with all the personality, road conditions, weather, traffic patterns,
and all that kind of nonsense taken into account, i normally run about
3600-3800 rpm or 60-63 mph. the engine sounds like it's happy; i can go up
hills without undue effort (yes, i slow down, but i do keep on keeping on);
and i get just over 20 mpg; and all the other idiots on the road are going
around me.

if i'm right about this, the max torque is at 3200 rpm, and the max horsepower
is at 3800 rpm. so i think somewhere in between here would be best.

below 3400, however, my engine sounds like it's lugging ... and above 3800 rpm,
it sounds like it's straining.

bentley says you are supposed to get 18 mph per 1000 rpm, but mine works out
to 16.75 (based on observed data with the trip computer ... ASSUMING i read
it right, and the tachometer is accurate). the above table numbers were from
the observations (from which i figured the conversion factor, not the other
way round).

so ... i think you ought to keep to 60 - 65 mph. if that sounds too 'busy'
back in the engine compartment, slow it down to 55-60.  a cruise control
will make your life a WHOLE lot easier on that trip. you want an address to
get one? about $100 or so. the same folks had trip computers that can help
you figure how much gas you've used up. :)
good luck.
joel