<VV> Re: Fuel Economy

[Brent Covey]

Hi Bob,

The Corvair isnt really reknown for fuel economy, but is a pretty economical
car in round terms. One advantage of the relatively short gearing in a
Corvair is it sort of levels out the fuel economy- its never outstandingly
high, but its seldom terrible either. Rolling terrain, city traffic and
headwinds have a sharper effect on cars with tall axles. The 1980 GM X cars
are a similar size and displacement to the late Corvair and will get quite a
bit better economy at thier best on the highway but are not much different
in their economy on a long term basis, in all-around use as the gearing is
very tall (2.84 usually) and anything but favourable highway cruise
circumstances tends to more sharply effect them than the plucky Corvair
whirring away at higher rpm and able to take on headwinds, small grade
changes and speed adjustments in traffic with less drama. I'll happily trade
a little economy for the gutty responsiveness and snap of the shorter axle
ratio.

> I must however point out the other side of the Corvair's gas economy
picture.....

I agree with your general point of view that the Corvair is not ultra
economical, and is rather inefficient by light car standards. Corvair has a
lot of aspects that have a negative impact for fuel economy- its a fairly
large car by modern standards and probably has aerodynamic drag not much
different than say, a Camaro, it has wide tires relative to other cars of
similar size, and theres more things to go wrong that can impact economy
negatively, like twice as many carbs, two axles that can be misaligned etc.
Air cooled engines are already somewhat less economical than water cooled
engines although some of this aspect is mitigated by having a relatively
small amount of power required for cooling relative to the big fan and water
pump on an ordinary car, and the faster warmup from air cooling.

> But before I start listing some data, I want to address your following
statement……

> All the figures I mention have been converted from Imperial gallons to US
Gallons using the 6/5ths formula.
> There may be a problem here. And if so, maybe that could change
everything. As far as I know, there are
> 4 quarts to the US gallon and 5 qts to the Imperial gallon. Isn't this
correct?

Not precisely- there is 1.201 US Gallons in a Imperial Gallon. Gasoline is
sold in Canada by the litre (since 1977) but not many people bother
expressing consumption in metric, which is normally stated in Litres/100km.
People usually convert to miles per Imperial gallon here. 12MPG Imperial is
just about exactly 10MPG US. If you take a Imperial Gallon MPG figure,
divide by 6 and multiply the result by 5 you have a very close conversion to
the US Gallons result. I had converted my experiences into the lower US MPG
figures so they might be directly comparable with experiences of the
majority of VV members.

> And isn't it also correct that your Corvairs all had US
speedometers/odometers?

Yes, in Canada all Corvairs had US style speedos.

> OK, now for the data…………

I will comment on some of your figures from various sources-

> Consumer's Reports reported the following:
> 8/64 issue  1964 110/3.27  24.0 at 60 mph and 16.8 in traffic (city
driving?)
> 3/66 issue   1966 110/?    22.5 at 60 mph and 16.0 in traffic
> Popular Mechanics reported the following in their 5/65 issue:
> 21.43 mpg at 60 mph, 1966 110hp/?
> And I don't think breakin would be a factor either as the Corvairs came
ready to run from the factory.

These figures are pretty much exactly what I would expect on a new car.
Mileage does pick up quite significantly when the newness wears off and drag
from newly machined parts and fresh seals etc diminishes, and ring sealing
improves etc. Consider how much easier an alternator or fan bearing spins
after its been run in. It would be reasonable to expect a small increase in
economy once the car has 20,000 miles or more. Radial ply tires should net
about a 2-5% increase in highway driving fuel economy as well. Picking up
1-2 mpg wouldnt be too difficult on a showroom fresh Corvair by the time you
have 20,000-60,000 miles on it. The effect of breakin is evident in long
term road tests of cars some of the magazines conduct- acceleration figures
are especially improved as a rule after 20,000 miles or so.

If we take the middle 22.5 mpg figure as typical new 1966 car, a broken-in
car on radial ply or bias belted tires should be able to better that by
5-10% or so, which is ~24-25mpg. Perfect tuning, carb calibration and a
steady foot may improve that figure even farther. The 1964 car you cited on
185-80 radial ply tires would get 25 mpg with no other changes, presumably.
Driving 55ish rather than 60ish would enhance this even farther as well I
imagine. If you ran a new '66 on the weakest modern fuels and retained the
original tires and lacadaisical tuning you might be lucky to see 20 mpg of
course, less if you were pushing 70 mph.

It would be interesting to see what results a 1963 102/4/3.08 car gets- that
oughta be a miracle of efficiency but I wonder if it plays out that way.

> Remember that these were all cars fresh from the factory and all set to
factory specs.
> Corvairs in use today, may have many worn parts and mal adjusted component
which
> could lower mileage measurements made today.

Anyone who experienced a new GM car in the 1960's can assure you they seldom
were set up very well- look at the acceleration figures for most Powerglide
Corvairs ever tested, its apparent many did not have thier TV rod adjusted
well, and some appear to have been unable to actually open the carbs full
throttle. Factory wheel alignment is a horror, most stock Corvairs had
considerable carburetor issues from new (gas stink in the heater, hot start
issues, flooding, maladjusted chokes et al) and tuning was pretty erratic.
Taking a showroom fresh Corvair and sorting out all the little adjustments,
tuning and alignment kinda issues would make a large improvement in nearly
all cases.

Basically my intention is to demonstrate economy that can be acheived by a
regular Corvair under favourable conditions. Actual long term averages that
reflect all types of driving will give lower numbers but I think its
perfectly possible for a well set up Corvair to return figures similar to
mine on segments of long highway trips for example. 21-22 mpg is apparently
fairly easy to achieve at the very least, and a long (hundreds of miles)
trip at moderate speed (55-65) with few stops or obstacles should improve
considerably upon that. Knowing the best the car should be capable of allows
you a yardstick to judge if you have room for improvement.

Judging from some of the results people have posted the middle 20's isnt an
unrealizable target I'd say, if a person is interested in achieving it.

I enjoyed your thoughful post and especially the contemporary to new Corvair
data you posted, I think we're not so far apart on our expecations as might
have seemed the case. Thanks again,,

Brent Covey
Vancouver BC