<VV> Fuel mileage

[Ken Pepke]

Anyone wishing to get the best fuel milage possible should first, know what they have.  The first step would be a trip to a chassis dynamometer ... Find out the engine RPM at the point the torque curve crosses the HP curve.  It is in this area that the engine is operating at its maximum volumetric efficiency.  Do this at the level of 'tune' at which the vehicle is driven regularly but do adjust the timing between tests.  Gear the vehicle to run in that RPM range for most of the type driving done in the vehicle.  [City, highway, flat land, hills, mountains, etc.]  High gears / slow engine speed is not necessarily the best mileage builder.  A Corvair with the 3.27:1 axle gear and driven in the city might never shifted to a gear higher than second.

Even the best of the 'stock' Corvairs do not have a particularly good performance level ... The torque curve, instead of being high and flat, builds slowly with engine RPM and never gets all that high.  Sadly, long ago the Corvair was saddled with an 'affordable' reputation.  I say sadly because the Corvair engine has a whole world of potential that has not, and will never be, explored.  Had the aftermarket seen a potential for a performance market, we would be miles ahead in available equipment.  A respectable, by today's standards, torque curve is just not available.  While there is some possibility of increasing fuel milage in a daily driven Corvair, a respectable by today's standards, torque curve is just not available.  The car will probably not produce a feel / sound level to which we have become used to in vehicles of much more recent manufacture.  

A few years ago several of my co-workers decided to buy Suburbans.  While they were ordering, one of them came to me and asked about rear axle ratios.  I got the engine torque specs and vehicle weight information, plugged them into my 'handy dandy' calculator wheel and recommended he select the lowest available 3.90:1 axle ratio.  That vehicle got the best milage of the group and was the most pleasant to drive ... even on his trips to Florida although he did notice the engine speed on the expressways.
Ken P
Wyandotte, MI
Worry looks around; Sorry looks back, Faith looks up. 

**********************

> From: FrankCB at aol.com
> Date: April 16, 2011 12:32:01 PM EDT
> To: chartzel at comcast.net, virtualvairs at corvair.org
> Subject: Re: <VV> Fuel mileage
> 
> Right On, Clark!
> Further on the "overdrive transmission", the important thing is the OVERALL 
> ratio from engine to rear wheels which takes into account BOTH the 
> transmission  ratio in top gear and the axle ratio.  Most of the Corvairs have the 
> 3.55  to 1 axle ratio and 1 to 1 top gear transmission ratio giving 
> something like  3000 engine rpm at 60 mph.  In contrast, my 1995 "Dustbuster" Trans 
> Sport  Minivan has a 3.06 axle ratio and an overdrive ratio (less than 1 to 
> 1) in the  4th speed of the 4T60-E auto trans.  The result is only 1800 
> engine rpm at  60 mph.  This gives me 26 to 28 mpg on long highway trips with an 
> engine  (3.8 liter) that is 40% LARGER than the Corvair's 2.7 liter engine.
> GM did have a 3.08 axle ratio that they put out briefly to achieve better  
> mileage for the Economy Runs in the 1960s.  That would certainly help  
> improve highway mileage.
> In addition, a modern EFI engine has computer-controlled feedback from the  
> exhaust gas oxygen sensor that continually adjusts the EFI to maintain the  
> correct fuel to air ratio giving great mileage.
> But perhaps the GREATEST influence on highway mileage is due to the "nut  
> behind the wheel".  I'm continually amazed at the number of people who come  
> up behind me in traffic, pull out and pass me and then race to the next 
> traffic  light where they have to JAM on their brakes to stop at the light.  
> Many  times, by the time I coast up the to the light, it has turned green and I 
> can  get through it WITHOUT stopping.  Guess who's getting the better gas  
> mileage!!
> 
> Frank "tightwad" Burkhard
> 
> 
> In a message dated 4/16/2011 7:54:02 A.M. Eastern Daylight Time,  
> chartzel at comcast.net writes:
> 
> Harry  Smith wrote about using a Corvair as a daily driver.  I doubt  a
> Corvair is going to get 20 MPG in the city.  I have never gotten  more than
> 22 MPG in any Corvair I ever owned.  Corvairs have two major  drawbacks for
> good fuel economy:  carburetors and no overdrive.
> If  you are looking for good economy get a small fuel injected car with  an
> overdrive transmission.
> Clark  Hartzel





____________________________________________________________
Groupon&#8482 Official Site
1 ridiculously huge coupon a day. Get 50-90% off your city&#39;s best!
http://thirdpartyoffers.juno.com/TGL3141/4daaebada636754d83st04duc