MPG mileage

[NutmegCT]

Just read the August 2007 Hagerty Plus Members' Help page. A guy had asked how to increase gas mileage in his 1950 Chevy. I was surprised by one of the answers sent in from a Hagerty policy owner.

"If he removes the fan and replaces it with an electric fan, it will save 20-25% in gas. Keep all the old fittings and replace for concours etc.”

Does 20-25% fuel savings sound a tad unrealistic to you? Even for a 1950 Chevy with Powerglide?

As an aside, my own TR3A gets around 19-20mpg in two-lane blacktop (45-60mph) driving.

Any comments on the "remove the original fan" fuel savings idea?

Thanks.
Tom

 

[TR6oldtimer]

It takes power to move air, so no matter what type of fan is used it takes power. Electric fans are more efficient then the original engine mounted fan, and run only when needed, so I would expect to see a slight decrease in fuel consumption due to these factors. But not 20-25%. For fuel consumption to decrease as stated, it would mean the mechanical fan was using at least that much of the engine's power, an unlikely scenario.

 

[TR3driver]

Well, it would only have to be 20-25% of the actual power used under cruise conditions. I've read somewhere that it only takes about 10 bhp to move an average car at a constant 60 mph, so 25% of that is only 2.5 hp.

Obviously it will vary by car, but the Stag has a fluid coupling to the fan that limits torque applied to 3.8 ftlb (46 lbf-in according to an article published in Automobile Engineer) and 2500 rpm. So, at 3000 engine rpm (roughly 60 mph), that is 3.8 * 3000 / 5252 = 2.1 hp.

20-25% still sounds very optimistic to me, but not totally improbable. Those old American cars had great big fans with a lot of pitch.

 

[eejay56]

Physically turning a fan with the with the engine increases the load on the engine reducing mileage. However the energy to turn an electric fan is supplied by the alternator. The energy required to turn the alternator is not going to increase with increased current consumption I believe. So an electric fan places no load on the engine. That said I think I have read an increase of 2 to 5 horsepower can be expected. I don't know how that would translate to mpg. For me any slight savings would be negated because I could go faster. /bcforum/images/%%GRAEMLIN_URL%%/driving.gif

 

[tomshobby]

I had a '52 Chevy with a Powerglide. The Powerglide cars had a bigger six than came with the standard trans and it really sucked gas which did not seem to convert into power. I replaced it with a standard trans and not only did the mileage increase dramatically but it was very much faster.

Oh, I would not believe the electric fan mileage increase, that Powerglide was just too much of an anchor.

 

[TR3driver]

If memory serves, early Powerglides only had 2 forward gears, and a very slippy fixed fluid coupling (similar to a torque converter, but didn't actually magnify torque). Lots of power lost in that fluid drive, all the time. Later, I think they got a real torque converter, which helped performance a lot but still wasted fuel. Automatics always did cost fuel, up until the 90's or so when they started getting computer controls, and overdrive, and lockup torque converters.

Oh, and power required to turn the alternator very definitely goes up with output. I use a little 1/4 hp washing machine motor on my homebrew test stand, and it won't even notice an alternator that is just powering it's own field. But I can stall the motor by loading the alternator.

The advantage of the electric fan is that it can be turned off when not needed, which includes most cruising conditions (where you're concerned about fuel mileage).

 

[TR6oldtimer]

Randall
Here is an interesting article discussing gas mileage and having your headlights on. Under the NUMBERS section, it describes how to compute HP vs speed on a car. If you like numbers or not, I learned some things I did not know or lost from memory. Might just go out and measure the frontal area of my 6.

https://mb-soft.com/public/headlite.html

 

[eejay56]

Oh, and power required to turn the alternator very definitely goes up with output. I use a little 1/4 hp washing machine motor on my homebrew test stand, and it won't even notice an alternator that is just powering it's own field. But I can stall the motor by loading the alternator.

I stand corrected /bcforum/images/%%GRAEMLIN_URL%%/blush.gif however doesn't an alternator normally supply far more current than needed to run the electrics on a car so any additional load would just reduce current available for charging the battery?

 

[TR3driver]

It only supplies extra current when needed to charge the battery; not all the time. It's true, when the fan is running, there will be less extra capacity for charging the battery. But since the fan should run only when idling or stop-n-go traffic; normally that's not an issue even with the wimpy Lucas alternators.

Interesting article Ray. Not sure I agree with his numbers; for example he seems to assume that a 55 watt headlight actually consumes 75 watts in practice; and that alternators are less than 20% efficient; but I don't have time to go over the numbers right now. I think he also ignored driveline losses. The basic point is valid though, it will cost you something in fuel to run your headlights all the time.

And if he's right, my remembered 10hp is either way off, or for a much more efficient car than a Vette.

The next question of course is, how much is your life worth to you ? Personally, I run mine in the morning or evening, any time the sun isn't nearly overhead. Lots of people seem to fail to see my little TR3A (and I hate red), the lights seem to help a little bit. And there are lots of buildings, overpasses, etc. that cast shadows in the morning or evening.

The fellow that hit me admitted he wasn't even looking at the road at the time. Told the office on the scene he "Reached down to get a Coke." Not a whole lot I can do about someone driving blind !

 

[Harry_Ward]

Tom,

Have no thought about the fan in regard to fuel consumption other than to leave the original fan where it is for balance and turn the electric fan on at temps above 185 degrees F. lest you forget and bad things happen.

Your fuel consumption sounds a bit high. 24 to 30 MPG more the norm for fuel consumption. unless of course you're stompin' on it.

/bcforum/images/%%GRAEMLIN_URL%%/driving.gif

 

[Andrew Mace]

Here's a related question. I realize that it does take some engine power to turn the typical crank- or water pump-mounted fans. But at some point and road speed, would the incoming air help to drive the fan at all, thereby lessening the "load" on the engine? Perhaps a silly thought.

I don't remember checking the mileage on my '51 Chevy when I was driving it (been stored since '88), but then gas was cheaper back then, and it was a typical three-on-the-tree connected to the old babbit-bearing 216.5 c.i. "Stovebolt" Six. I should see if I can find my gas records for that car....

 

[69tr]

You guys are driving me crazy. My favorite GM body style is the 1949 thru 1952 Chevys. I had 2 coupes when I was younger (a lot younger) They both succumbed to driver with more nerve than ability.

I hope my next project will be one of these models. A convertible or hard top would really be too much to ask for.

 

[Andrew Mace]

...My favorite GM body style is the 1949 thru 1952 Chevys...I hope my next project will be one of these models. A convertible or hard top would really be too much to ask for.

Egad, man, have you priced those lately? Bel Airs aren't too bad, but convertibles (and wagons, for that matter) are horrendously expensive! Guess I'll have to be content with my '51 Styline De Luxe Coupé, which is a family heirloom!

 

[Twosheds]

I had a '50 Olds Futuramic 88. It was done in a sort of Rocket Space Travel motif. Oldsmobile Rocket V-8 with 4-speed Hydromatic. It had a visor. Subject of what is thought to be the first rock-and-roll record. It was fast, but wouldn't go around curves very well.

 

[Brosky]

Doc,

That Olds dethroned the Hudson Hornet and changed stock car racing forever. And it didn't hurt the moon shine runners either!

 

[69tr]

yes, I have priced the hard tops and converts. Maybe I will hit the lottery or something. Meantime, I will keep looking. Right now I am worried more about the cost of the divorce if I drag in another car. hehehe

 

[kcbugeye1275]

My dad, a retired Chevy mechanic, loves to tell the story of an ambulance that came in with the complaint that it wouldn't run over 80 mph. It had a 454 for a motor, but dad said he new the clutch to the fan was broke and it had locked the fan in at all times. So, he replaced it and took it out on the highway and ran it up to 110 mph only to meet a highway patrol. Thankfully, the hp didn't pull him over, but when he came in to the shop, the owner came back and said the ambulance company was glad to know that the ambulance was fixed, but the next time just to turn on the lights and siren. I have removed the mechanical fan on my BE and replaced it with an electrical fan, but a buddy who has done the same thing drove his car up to visit had fan failure and overheating. I'm about ready to reinstall the origonal fan because of this.

 

[vettedog72]

When the fan clutch engages on any of the gas powered RV's it feels like the motor stalls or does good to maintain the speed. All the big blocks seem to have the same characteristics regardless if they are 440's, 460's, or 454's. Fan clutch engagement even made a significant difference to my old Suburban. It may take several horses to pull the old direct fans 2 or 3k RPM's; I suspect it takes 10hp+ to pull the big fans of today.

 

[Deleted member 451]

My TR3 with OD gets 19-20 mpg around town. I don't drive it on the highway enough to know what it gets there but it's about 25.I was born in 1954 and have this big button I got as a present that has prices and other info from that year, the price of gas was 29 cents a gallon. I think it was probably up to 30-31 when my TR was built.
A lot of people I talk to about the car think it must get good milage. I explain to them that during that time mpg was not an issue, gas was cheap and plentiful.
My 89 Porsche 944 gets the best milage of our cars, 30+ on the highway at 70 on cruse with a top speed of over 140.
Life is too short to drive boring cars.

 

[TR6oldtimer]

And there was thunder, thunder over Thunder Road

BALLAD OF THUNDER ROAD
Let me tell the story, I can tell it all
About the mountain boy who ran illegal alcohol
His daddy made the whiskey, son, he drove the load
When his engine roared, they called the highway Thunder Road.

Sometimes into Ashville, sometimes Memphis town
The revenoors chased him but they couldn’t run him down
Each time they thought they had him, his engine would explode
He'd go by like they were standin’ still on Thunder Road.

(CHORUS)
And there was thunder, thunder over Thunder Road
Thunder was his engine, and white lightning was his load
There was moonshine, moonshine to quench the Devil’s thirst
The law they swore they'd get him, but the Devil got him first.

On the first of April, nineteen fifty-four
A Federal man sent word he’d better make his run no more
He said two hundred agents were coverin’ the state
Whichever road he tried to take, they’d get him sure as fate.

Son, his Daddy told him, make this run your last
The tank is filled with hundred-proof, you’re all tuned up and gassed
Now, don’t take any chances, if you can’t get through
I’d rather have you back again than all that mountain dew.

(CHORUS)

Roarin’ out of Harlan, revvin’ up his mill
He shot the gap at Cumberland, and screamed by Maynordsville
With T-men on his taillights, roadblocks up ahead
The mountain boy took roads that even Angels feared to tred.

Blazing right through Knoxville, out on Kingston Pike,
Then right outside of Bearden, they made the fatal strike.
He left the road at 90; that’s all there is to say.
The devil got the moonshine and the mountain boy that day.



The complete song with Mitchum singing is found here

https://www.univie.ac.at/Anglistik/easyrider/data/ballad_of_thunder_road.htm

Oh, the car was a 1950 Ford coupe, not a Chevy...