Fuel economy of flat six

[knuckleharley]

6 minutes ago, Tom Skinner said:

I really don't want to hijack this thread, but here goes,

Chrysler owners know Chrysler products like gas. Gas is Cheap by today's standards. Gas is small potatoes. Don't sweat small potatoes.

There now. Drive your big Chrysler's and enjoy them. I really don't give a fat babies behind what my gas mileage is. I hope and pray for you, that you really don't either.

With the inflated prices of everything else in parts for our cars, insurance, etc. does $2.10 a gallon gas scare you? I thought not.

Tom

You big meanie,you!

[Jeff Balazs]

Knuckleharley you are right about how driving conditions affect the outcome. I brought up this tuning technique though to highlight how one might be able to really achieve optimum ....whatever that happens to be. If one were to do this type of tuning at least you would know for certain when you were at optimum for the equipment you have to work with. You could only take it so far with a device like the Carter B & B but if you had something like a Weber then you might be very surprised by the difference a few jetting adjustments makes. Of course there are many parts to the puzzle but it would be fun to see what could be gained. I went through this many years ago with another car I had and just by swapping to Webers I managed to go from 25 mpg to 43 mpg with a heck of a lot more grunt. So it is doable......and potentially a win-win. None of us win any prizes for dumping raw gas out the tailpipe.

Jeff

[knuckleharley]

2 minutes ago, Jeff Balazs said:

Knuckleharley you are right about how driving conditions affect the outcome. I brought up this tuning technique though to highlight how one might be able to really achieve optimum ....whatever that happens to be. If one were to do this type of tuning at least you would know for certain when you were at optimum for the equipment you have to work with. You could only take it so far with a device like the Carter B & B but if you had something like a Weber then you might be very surprised by the difference a few jetting adjustments makes. Of course there are many parts to the puzzle but it would be fun to see what could be gained. I went through this many years ago with another car I had and just by swapping to Webers I managed to go from 25 mpg to 43 mpg with a heck of a lot more grunt. So it is doable......and potentially a win-win. None of us win any prizes for dumping raw gas out the tailpipe.

Jeff

Jeff,I agree. What you wrote above only verifies my opinion that a device like an exhaust gas analyzer has a prime purpose of rating EFFICIENCY. Obviously if you make some sort of tweek to your vehicle and suddenly you gain 1 MPG while driving at the same speed on the same road under the same climate conditions,you have done something right. If all else is equal and you suddenly get less MPG,you have done something wrong and need to go back and change it. Something like that would be a huge help if you were modifying an engine with the intent to make it more efficient in whatever RPM range it is expected to operate under.

While I am uncertain it is even appropriate to associate "fuel mileage" with something like a AA/BF dragster,IF you could rig one to Gartlitz's "Swamp Rat"  it would be a useful tool to tell you how many gallons per second of nitro methane are required to operate a 3000+ hp engine operating at astounding RPM's.  When you are turning the quickest times while burning the least amount of fuel at the same time,you are dialed in.

Still,the basics haven't changed and they will never change. No matter what type of engine it is or what it is doing,efficiency for purpose is everything.

BTW,am I the only one that thinks it would be a real hoot to see a couple of those things rolling down the road with radiators in them,seeing who could go the furthest on a gallon of nitro?

Can ANYONE picture Wild Willie Borsch in the Winged Express trying to feather the throttle to coast an extra few feet? I doubt you could have got him to ease off on a throttle if you held a shotgun to his head. I used to have a poster of him on my wall locker in VN ,in the Winged Express crossing the finish line at Lions or Pomona running in the high 190's,with one hand on the wheel and the only tire touching the ground was one of the front ones.

[Don Coatney]

What is amazing is top fuel dragster engines only turn 940 revolutions under load  before they must be rebuilt and that includes the initial burnout.

[knuckleharley]

15 minutes ago, Don Coatney said:

What is amazing is top fuel dragster engines only turn 940 revolutions under load  before they must be rebuilt and that includes the initial burnout.

Yeah,but consider the loads they are operating under.

And when they do fail,they fail in a spectacular way.

Fuel dragsters are perfect examples of function-built machines. They are built for one thing only,and that is squeezing out the maximum horsepower possible and putting it to the ground. If they ain't running at a eyeblink from destruction,they ain't doing what they were designed to do. They are all or nothing machines.

The same can pretty much be said for their drivers. Wild Willie was being interviewed once at the strip before making a run,and was asked what the front axle on the Winged Express was made from. He replied,"Exhaust tubing. It's all the car needs. The front wheels are always either in the air or in the wall anyhow,so what difference does it make?"

Ever meet Gartlitz? Soft-spoken nice guy. Seems to have no attitude at all. UNTILL he wraps a Swamp Rat around  him. Then he becomes a competitive monster. Last time I saw him was at a nostalgic drags in Petersburg,Va. He was in his 70's then and the doctors had told him to quit driving because the car was leaving the line so hard he had actually detached a retina in his eye. So,he was "retired",and I guess had a driver hired to run to the current number 1 Swamp Rat. Meanwhile,Don was having some fun and making some money hitting the nostalgic drags and making exhibition runs with one of the old Swamp Rats. That's what he was paid to do at Petersburg. Hit it kinda hard,run 100 feet or so,then shut it down. He nailed the throttle to the wall and made a pass in the high 5's. It's who he is and what he IS going to do as long as he is physically able to do it.

BTW,to anyone keeping score here,writing about Gartlitz and his Swamp Monsters IS keeping it Mopar. They were all based on the Chrysler hemi design

Edited January 11, 2017 by knuckleharley

[dale]

How much do you actually drive a car like an old Plymouth ?   Who drives it enough to really care whether your getting 20 mpg or 25 mpg...The old 46-48 Plymouths got 20 mpg highway.  When I was a teenager we increased mileage by 500% with a five gallon can and a hose.

Edited January 11, 2017 by dale
Added to it..

[55 Fargo]

9 minutes ago, dale said:

How much do you actually drive a car like an old Plymouth ?   Who drives it enough to really care whether your getting 20 mpg or 25 mpg...The old 46-48 Plymouths got 20 mpg highway.  When I was a teenager we increased mileage by 500% with a five gallon can and a hose.

Not to discount the OPs idea or interest, gotta agree, nobody is driving a Chrysler flathead thinking big fuel economy. There are vintage Vespas and Norco Bicycles for that...

[Jeff Balazs]

43 minutes ago, Rockwood said:

Not to discount the OPs idea or interest, gotta agree, nobody is driving a Chrysler flathead thinking big fuel economy. There are vintage Vespas and Norco Bicycles for that...

I drive my truck daily so I care about how efficiently it runs. That is I believe what the OP had in mind when he started this thread. May not be 30 mpg but whatever the best number you can get is better than just accepting a poor number because you are too lazy to give it some thought. I wonder what might happen if we put some new ideas to work here for a change?

Jeff

[55 Fargo]

Just now, Jeff Balazs said:

I drive my truck daily so I care about how efficiently it runs. That is I believe what the OP had in mind when he started this thread. May not be 30 mpg but whatever the best number you can get is better than just accepting a poor number because you are too lazy to give it some thought. I wonder what might happen if we put some new ideas to work here for a change?

Jeff

Jeff, thats great, and you should be happy if you get 20 MPG with your big truck, my little truck probably does better, its lighter probably by a 1000 lb darn near, and the dual carbs and intake have made a difference.

But to attain 25-30 mpg, bit lofty, but hey hook up an analyzer and see what more you can get.

I wish you the best of luck.

I would venture to guess you could increase your power and fuel efficiency with a bigger 265 engine and tri carb set-up, more power and better fuel economy. Thats my lazy thought on this...

[1950 Special Deluxe]

2 hours ago, Rockwood said:

Not to discount the OPs idea or interest, gotta agree, nobody is driving a Chrysler flathead thinking big fuel economy. There are vintage Vespas and Norco Bicycles for that...

Here are mine.

1978 Vespa P150X

1970 Honda PC5o moped 

[sser2]

Wow - a lot of insightful comments.

It looks like the consensus is emerging that 30 mpg is not a trivial task, and may be actually impossible.

To the point that it isn't worthwhile to do economy mods, instead driving our cars as they are - this is reasonable. Many folks keep old cars to take them to few shows and joy rides during a year, and, in this case, economy doesn't really matter. But if I want to drive it every day, or go on a journey across the country, 30 vs. 17 mpg is big difference money wise. Now gas is relatively cheap, but where I live, just a few years ago the price of regular topped $5. I am sure high gas prices are inevitable in the future. Even if money was not a consideration, I kind of feel guilty for participating in unnecessary waste of precious natural resources... 

Also, it is true that if fuel economy is the goal, one should drive a modern economical car. I do exactly that most of the time. But there is no excitement in modern cars. They are boring. The argument is the same as why should one drive a Ferrari if a Hyundai takes you from point A to point B in pretty much the same manner?

The comment about engine power matching the car weight is right on the mark. Actually, if power of flat six could be increased to 100+ hp, which is realistic, a '37 Plymouth will get into the same lb/hp league as many modern mid-size cars.  Weight doesn't considerably affect economy at steady speed, but is #1 factor of poor mileage in city driving, so reducing weight is yet another avenue for overall fuel savings. Shaving 100 lb or more off total weight might be possible. Things like aluminum head and radiator, alternator, lithium battery with supercapacitor, etc. 100 lb weight reduction is equivalent to 3 hp power gain.

Calibrating a carburettor for economy using exhaust gas analyzer is a great idea. It is akin to what I suggested for tuning the lean burn: output from an oxygen sensor. A broadband oxygen sensor, aka air/fuel ratio sensor, hooked to a laptop, should suffice, and, unlike bulky stationary gas analyzer, can be used during actual driving to record and collect real time data.

From what I've read, EGR somewhat decreases fuel consumption in addition to lowering combustion temperature. It reduces engine pumping losses by reducing manifold vacuum behind the throttle. It is like a little free turbo that uses the energy of pressurized exhaust gas to fill cylinders. EGR is equivalent to reducing engine displacement at steady speed and partial throttle, when only a fraction of engine power is used.

Multi-port injection is no doubt the most efficient, economical, and versatile fuel system. Technically it might be possible to transplant MPI from a modern 6 cylinder engine, but that will also require ECU with all the requisite sensors, which is challenging. I am not sure though that MPI would offer significant mileage improvement. Carburettor design much improved since 30s, and later model carbs were comparable to MPI fuel injection in economy. For example, Nissan's KA24 MPI engine in my truck has the same gas mileage as its carburetted predecessor Z24. ECU-controlled air/fuel ratio in today's cars is primarily to ensure certain amount of unburnt fuel for optimal function of the catalytic converter, rather than maximizing fuel economy.

Aerodynamics of late 30s to late 50s cars wasn't so bad as one might think. At least their bodies were designed with aerodynamics in mind. The Airflow strongly influenced that, not only for Chrysler, but for other makes as well. By contrast, even later model pickups are boxy and not aerodynamic. At 55 - 60 mph and higher, poor aerodynamics is the most important contributor to efficiency loss, and any improvement here will have noticeable effect. I can see at least two aero mods for our cars: rear fender skirts and underbody panels to smooth out the bottom. Chopped/lowered body are two more, although I am not a fan of those.

[Ricky Luke]

I should put this in the "Show us your tools" thread, but it's relevant here. When I was much younger I had an original shape Morris Mini Cooper with twin SU carburetors which were way out of tune. I was given a Colourtune (Colortune...) spark plug to help me get the SU's set up correctly. Basically it's a spark plug with a glass top so you can see the colour of the fuel burn at different points on the rev range. Orange rich - blue good, whitish lean. Obviously it's limited because the engine isn't really under load. There's a few videos on Youtube of it in action. If you can't get to a gas analyzer, it will help. It helped the Mini run better. 

Rick

[sser2]

2 hours ago, Ricky Luke said:

I should put this in the "Show us your tools" thread, but it's relevant here. When I was much younger I had an original shape Morris Mini Cooper with twin SU carburetors which were way out of tune. I was given a Colourtune (Colortune...) spark plug to help me get the SU's set up correctly. Basically it's a spark plug with a glass top so you can see the colour of the fuel burn at different points on the rev range. Orange rich - blue good, whitish lean. Obviously it's limited because the engine isn't really under load. There's a few videos on Youtube of it in action. If you can't get to a gas analyzer, it will help. It helped the Mini run better. 

Rick

I used those too, they were not supposed to run for any extended time, or at higher than idle speed. Mixture screw was to be adjusted to the transition from yellow to blue. Very useful for setting idle mixture.

The beauty of AF sensor is that it can precisely measure stoichiometry at various regimes: idle, acceleration, steady driving at various speeds, climbing with full throttle.

[Jeff Balazs]

I will be working on this later this spring. I am certain that there is more than one way to get there. Just have to remain open minded. One thing is for certain there is all sorts of room for improvement.

And Fred my use of lazy was meant to be collective.......in that it is all to easy for all of us to settle for status quo or less than optimum.

Jeff

[BigDaddyO]

On 1/10/2017 at 3:28 PM, Ralph D25cpe said:

....Note to self, - Remember this quote.

Yeah, feel free to use it in lieu of getting a life.

[knuckleharley]

On 1/10/2017 at 7:41 PM, dale said:

How much do you actually drive a car like an old Plymouth ?   Who drives it enough to really care whether your getting 20 mpg or 25 mpg...The old 46-48 Plymouths got 20 mpg highway.  When I was a teenager we increased mileage by 500% with a five gallon can and a hose.

I don't currently have an old Plymouth on the road,but I do have another brand with a flat 6 on the road,and I drive it every day it's not raining or the road isn't wet. I live up a dirt road and don't drive any of my old stuff when the road is wet because I don't want mud caking and  causing rust under them. Don't give a damn if the 2015 GMC  rusts out or not. It just a tool I use because it is convenient,and it will be gone in a couple of years. The 51 won't be gone until I'm gone.

And I  honestly don't give a damn if the 51 gets 20 MPG or 10 MPG. I would drive it anyhow because I love the car and love driving the car.  Don't get me wrong,I would enjoy trying to figure out why the gas mileage was so lousy and work to improve it,but would just be doing that because I enjoy doing that,not because the actual gas mileage is important to me.

Once I get my 42 Dodge coupe on the road,that one will most likely be my prime nice weather car,and the 51 will only get driven occasionally. I smile every time I look at that car parked on my lift. I literally wouldn't trade it right now in a even trade for a new Dodge Callenger or Charger,and the front clip is already off of it.

The truth of the matter is I loved all this stuff when I was a kid growing up in the 1950's,and I still love it today. if I lived somewhere with no dirt roads,I wouldn't even own a car newer than 1971. I sure would love to have my 71 340 Duster back again,though.

[T120]

1 hour ago, BigDaddyO said:

Yeah, feel free to use it in lieu of getting a life.

Hey! A classic response and should I be inclined to use it in the future,(with discretion of course), I will include..."As BigDaddyO would say, ....."

[plyroadking]

On 1/10/2017 at 6:41 PM, dale said:

How much do you actually drive a car like an old Plymouth ?   Who drives it enough to really care whether your getting 20 mpg or 25 mpg...The old 46-48 Plymouths got 20 mpg highway.  When I was a teenager we increased mileage by 500% with a five gallon can and a hose.

I'd be driving mine now if they didn't salt the roads here in the winter! I've had it 10 years and I'm close to 75k miles on the odometer that I've driven. And that's not including the first year of driving before I got the odometer working, or the 20mph it read slow till I found a speedometer drive gear that makes it only read 10mph slow now. The fuel economy is nice and during the unsalted seasons I try to drive it as often as I can because it is my most fuel efficient vehicle that will do interstate speeds. 

Last year I stumbled upon a 1955 Dodge two barrel intake manifold and Stromberg carb. I didn't do any milage tests yet but it seems comparable to original single barrel Carter.

[baggieboy1965]

Hi Tom, wish we paid 2.10 a gallon in the UK, price is currently around 6.60 in dollars..and going up, nearly all of it is tax.

[1949 Wraith]

As many have stated we drive our old vehicles because they are fun to drive. When I'm driving my original and a bit tired, old smelling, ugly, 4 door Dodge sedan I usually a big stupid grin on my face. I drive it like an old fart mostly on secondary roads and can get around 22 mpg. If I want efficiency I can drive one of my motorcycles or modern cars.

I believe that there was an economy carb option (smaller diameter throat) offered in the Canadian market in 1949 and probably other years. So back in the day efficiency was achieved by restricting the amount of fuel that could enter the intake, not likely that anyone would want to go that route today. My 1949 Dodge (218) is not only Deluxe but it is also Special , so I have the big bore carb gas guzzler.

 

[sser2]

17 hours ago, plyroadking said:

Last year I stumbled upon a 1955 Dodge two barrel intake manifold and Stromberg carb. I didn't do any milage tests yet but it seems comparable to original single barrel Carter.

Twin barrel carbs are of two principally different designs. Early carbs had synchronous throttles. This design was basically two carbs in a single body. One hole fed cylinders 1,2,3 and the other 4,5,6. Later twin barrel carbs have throttles that open sequentially: the second throttle beginning to open only after the first has already fully opened. It is functionally same as adding a second carb, but only when the first begins to restrict engine's air intake. Usually, the second barrel opening starts transition from economy to power regime. Some of the designs even have a switch that turns on a light on dashboard when second barrel is opening, indicating that you are in the non-economical power regime.

[knuckleharley]

1 hour ago, sser2 said:

Twin barrel carbs are of two principally different designs. Early carbs had synchronous throttles. This design was basically two carbs in a single body. One hole fed cylinders 1,2,3 and the other 4,5,6. Later twin barrel carbs have throttles that open sequentially: the second throttle beginning to open only after the first has already fully opened. It is functionally same as adding a second carb, but only when the first begins to restrict engine's air intake. Usually, the second barrel opening starts transition from economy to power regime. Some of the designs even have a switch that turns on a light on dashboard when second barrel is opening, indicating that you are in the non-economical power regime.

I honestly had no idea there was such a thing. Did they work as advertised,or were they a pain in the butt?

[sser2]

7 hours ago, knuckleharley said:

I honestly had no idea there was such a thing. Did they work as advertised,or were they a pain in the butt?

The first carburettors with sequentially opening throttles appeared in late 50s. Advantages of this design were such that in 70s-80s essentially everything that you can call a gasoline-powered car was equipped with these carbs. There were no drawbacks. No pain in the butt. Simple and efficient. This design solved the previously intractable problem of how to improve high power high speed performance without compromising low speed performance and throttle response.  

[DonaldSmith]

Carbs worked fine until EPA regulations called for extreme tuning.  I had an 80-s Datsun that would not want to start and run.  And the idle screws on the carburetor were gummint-sealed to prevent intervention.  Fuel injection to the rescue - and computers.   Nowadays, a car will idle all day, which my son found out after work one day.  

[Robert Horne]

7 hours ago, sser2 said:

The first carburettors with sequentially opening throttles appeared in late 50s. Advantages of this design were such that in 70s-80s essentially everything that you can call a gasoline-powered car was equipped with these carbs. There were no drawbacks. No pain in the butt. Simple and efficient. This design solved the previously intractable problem of how to improve high power high speed performance without compromising low speed performance and throttle response.  

My new 1980 Chevy Van, with the 6, came with the 2 barrel, that ran on one barrel, then the second barrel kicked in later.

The Van did ok, if on level roads, and no extra weight, and got 10 mile to the gallon.

I pulled the engine, and installed a 400 small block, and got up to 17 mile to the gallon...

Edited January 13, 2017 by Robert Horne
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