Fuel economy of flat six

[Jeff Balazs]

I wonder why people who have no real interest in a topic feel it is necessary to demean it or drag it off topic? If you don't care about it why not just move on? There are plenty of other threads to read here.

We all know that this engine in the stock configuration is never going to set any amazing MPG records. And we have to accept that for whatever it is. But there are some of us who feel that with the right modifications we might gain quite a bit of efficiency and at the same time improve performance. Some of the old speed equipment based mods have been discussed and have some merit but they are all based on decades old thinking and equipment. These for the most part utilize the same old carbs and are limited by that same design. I have spoken with one member who ran dual Carter-Webbers that felt his car ran much better with them than it did with the dual B & B setup. I for one am not surprised by this as these carbs are light years ahead of the old B & B when it comes to ease and range of tuning characteristics. It would be interesting to hear from more people that have had actual experience with this setup. When I was looking for my truck I came across one that had a throttle body injection system installed on it. The owner claimed it ran very well but I never went to see it. Wonder what that was all about?

Some other engine related items that may be of interest in this topic are cam selection, free flow exhaust systems and ignition/timing. I think there is a fair amount to be gained from this discussion. I saw where one contributor mentioned having a cable controlled timing adjuster. There may be something there to consider? And I think there are other ways to gain a bit of efficiency in how well these vehicles drive and perform. I get it that most folks are happy just to have a decent runner.......but I can't help thinking there is room for improvement over this.

Jeff

 

[knuckleharley]

52 minutes ago, Jeff Balazs said:

I wonder why people who have no real interest in a topic feel it is necessary to demean it or drag it off topic? If you don't care about it why not just move on? There are plenty of other threads to read here.

We all know that this engine in the stock configuration is never going to set any amazing MPG records. And we have to accept that for whatever it is. But there are some of us who feel that with the right modifications we might gain quite a bit of efficiency and at the same time improve performance. Some of the old speed equipment based mods have been discussed and have some merit but they are all based on decades old thinking and equipment. These for the most part utilize the same old carbs and are limited by that same design. I have spoken with one member who ran dual Carter-Webbers that felt his car ran much better with them than it did with the dual B & B setup. I for one am not surprised by this as these carbs are light years ahead of the old B & B when it comes to ease and range of tuning characteristics. It would be interesting to hear from more people that have had actual experience with this setup. When I was looking for my truck I came across one that had a throttle body injection system installed on it. The owner claimed it ran very well but I never went to see it. Wonder what that was all about?

Some other engine related items that may be of interest in this topic are cam selection, free flow exhaust systems and ignition/timing. I think there is a fair amount to be gained from this discussion. I saw where one contributor mentioned having a cable controlled timing adjuster. There may be something there to consider? And I think there are other ways to gain a bit of efficiency in how well these vehicles drive and perform. I get it that most folks are happy just to have a decent runner.......but I can't help thinking there is room for improvement over this.

Jeff

 

Yeah,all that,plus it's fun to fool around with them just to see what you can do.  Has to be more to enjoying a old car than polishing it and rolling it off a trailer at shows.

[HellYeah]

On 13.1.2017 at 4:56 PM, knuckleharley said:

Well,the truth is that back when these 2x1 and 2x2 intakes were being made there WERE no such things as 4 brl carbs. I have a 54 Olds with a 324 and 4 brl carb from the factory,and that was the first year Olds put a 4 brl carb on any engine. I also have a 55 DeSoto 291 S engine that came from the factory with a 4 brl. 55 was the first year for Mopar 4bls,and they were optional.

It was the introduction of OHV V-8 engines that put both the flat 6 and 8 engines into scrap piles,as well as the old custom multiple 1 barrel carbs people used to hop them up.

55 was also the first year for a 4brl on FoMoCo stuff. My father bought a new 55 Victoria with a 272 and 4brl carb.

About the Olds and 4 brl: Oldsmobile introduced their first 4 brl carb on the 303 cui in 1952. It was stock in the Super 88 and I belive also in the 98.

[DrDoctor]

   I also think that 30mpg is an unrealistic goal. However, we routinely get in the low-20’s on the hiways around here, but one must keep in mind that the speed limits here where we are is only 50mph (and we have a 9mph “grace margin”), we unofficially drive 56-57mph (but I deny that officially…). Thx.

[55 Fargo]

18 minutes ago, The Dr's In said:

   I also think that 30mpg is an unrealistic goal. However, we routinely get in the low-20’s on the hiways around here, but one must keep in mind that the speed limits here where we are is only 50mph (and we have a 9mph “grace margin”), we unofficially drive 56-57mph (but I deny that officially…). Thx.

Well it sounds like your speed limits are back in time, which is great for these old cars and trucks.

At least there sounds to be no issues with having to keep up to speed demons on multi lane freeways across the land...

30 MPG, can be attained, but 22-24 mpg is more like a reasonable and attainable goal...

[Los_Control]

I think smiles per gallon is a more worthy goal 

[DrDoctor]

   The only place with speed limits above 50 is on the interstates (65mph…), but we avoid them in the old Plymouth, as we don’t want to put any undue stress on the car by trying to maintain a reasonably safe/slower speed with those who’re also observing the 9mph “grace margin”. Also we don’t want to put any undue stress upon ourselves, either, for the same reasons. I’m not getting any younger, you know, so while I embrace the “elder statesman” status of our Plymouth, I also embrace that same status for myself. Thx.

[55 Fargo]

11 minutes ago, The Dr's In said:

   The only place with speed limits above 50 is on the interstates (65mph…), but we avoid them in the old Plymouth, as we don’t want to put any undue stress on the car by trying to maintain a reasonably safe/slower speed with those who’re also observing the 9mph “grace margin”. Also we don’t want to put any undue stress upon ourselves, either, for the same reasons. I’m not getting any younger, you know, so while I embrace the “elder statesman” status of our Plymouth, I also embrace that same status for myself. Thx.

Okay gotcha yah

[Tim Keith]

Flatheads have poor therrnal efficiency.  Too much surface area in the combustion chamber. The side near the valves gets very hot, the opposing side is relatively cool.  That is tough on the upper cylinder,, the compression rings and piston ring lands.   The uneven loss of heat can easily distort the head enough to blow the gasket.   Flatheads had problems fully utilizing the higher octane fuels that were developed after the war.   The first OHV motors had 7:1 CR, but it wasn't long before similar OHV designs were using 10:1 CR.  Flatheads couldn't match that.

A ceramic cylinder head - if such material existed might put some of the otherwise lost heat to better use.  I don't know of any suitable insulating material.  Direct injection probably could be implemented on a relatively low compression L-head without the complex engine controls necessary for 13:1 CR that is common today.  DI might help cool the exhaust valves and prevent spark knock. - provide very precise fuel distribution.  DI on 13:1 motors requires very precise controls and software because if the fuel is not introduced in a very tiny event there could be a hole blown into the piston or damaged rings/valves from the preignition.   In an L-head at 8:1  or maybe 10:1 that should not be a risk.

Ceramic engines have been talked about for decades, the thin coatings in common use today have some effect, a fully ceramic combustion chamber could assist combustion engineering, but would benefit overhead valve motors much more than L-heads, but could prevent overheating of a flathead that is being driven hard.

[Jeff Balazs]

I don't know as the design of our flathead engines is all that bad but they could definitely benefit from some help in the area of the induction system. The more I think about this the more I think a turbocharger and a throttle body injection system might just be the ticket. I have seen a few write ups on this but nothing really definitive.

Jeff

[Flatie46]

14 hours ago, Tim Keith said:

Flatheads have poor therrnal efficiency.  Too much surface area in the combustion chamber. The side near the valves gets very hot, the opposing side is relatively cool.  That is tough on the upper cylinder,, the compression rings and piston ring lands.   The uneven loss of heat can easily distort the head enough to blow the gasket.   Flatheads had problems fully utilizing the higher octane fuels that were developed after the war.   The first OHV motors had 7:1 CR, but it wasn't long before similar OHV designs were using 10:1 CR.  Flatheads couldn't match that.

A ceramic cylinder head - if such material existed might put some of the otherwise lost heat to better use.  I don't know of any suitable insulating material.  Direct injection probably could be implemented on a relatively low compression L-head without the complex engine controls necessary for 13:1 CR that is common today.  DI might help cool the exhaust valves and prevent spark knock. - provide very precise fuel distribution.  DI on 13:1 motors requires very precise controls and software because if the fuel is not introduced in a very tiny event there could be a hole blown into the piston or damaged rings/valves from the preignition.   In an L-head at 8:1  or maybe 10:1 that should not be a risk.

Ceramic engines have been talked about for decades, the thin coatings in common use today have some effect, a fully ceramic combustion chamber could assist combustion engineering, but would benefit overhead valve motors much more than L-heads, but could prevent overheating of a flathead that is being driven hard.

This may or may not help with thermal efficiency. Several years ago I built a Harley Shovelhead engine trying to up the performance a bit. I used Keith Black hyperutectic  pistons, they are made from a low expansion alloy that allows the piston to be fit at a closer tolerance therefore sealing the cylinder off better from the combustion process and sending the heat out the exhaust. I was skeptical of this claim until I took the bike on it's first long ride. I could tell a big difference in the amount of heat coming from the cylinders. Don't know how much or if it would help a Mopar flat 6, don't know if they make a hyperutectic piston for the Mopar flat 6 but I know pistons can sometimes be retrofitted from one application to the next. It's a thought anyway.

[sser2]

21 hours ago, Tim Keith said:

Flatheads have poor therrnal efficiency.  Too much surface area in the combustion chamber. The side near the valves gets very hot, the opposing side is relatively cool.  That is tough on the upper cylinder,, the compression rings and piston ring lands.   The uneven loss of heat can easily distort the head enough to blow the gasket.   Flatheads had problems fully utilizing the higher octane fuels that were developed after the war.   The first OHV motors had 7:1 CR, but it wasn't long before similar OHV designs were using 10:1 CR.  Flatheads couldn't match that.

A ceramic cylinder head - if such material existed might put some of the otherwise lost heat to better use.  I don't know of any suitable insulating material.  Direct injection probably could be implemented on a relatively low compression L-head without the complex engine controls necessary for 13:1 CR that is common today.  DI might help cool the exhaust valves and prevent spark knock. - provide very precise fuel distribution.  DI on 13:1 motors requires very precise controls and software because if the fuel is not introduced in a very tiny event there could be a hole blown into the piston or damaged rings/valves from the preignition.   In an L-head at 8:1  or maybe 10:1 that should not be a risk.

Ceramic engines have been talked about for decades, the thin coatings in common use today have some effect, a fully ceramic combustion chamber could assist combustion engineering, but would benefit overhead valve motors much more than L-heads, but could prevent overheating of a flathead that is being driven hard.

I was also thinking ceramic coating, but am not exactly sure whether it is a good thing or bad. The coating, which has lesser heat conductivity than aluminum, should supposedly increase thermal efficiency by keeping more heat in combustion chamber to do the useful work. But hotter combustion chamber is more prone to detonation. The effect of coating is thus similar to that of increased compression ratio. Aluminum head conducts heat better than cast iron, providing for more even temperatures in combustion chamber and  allowing for higher CR. By the same token, a piston without coating is more conductive for heat transfer from piston to cylinder walls, compared to a coated one.

"Ceramic coating" of aluminum is technologically very simple: anodizing. The anodizing process creates a very tough layer of aluminum oxide on the surface. The fact that anodized piston crowns are not used by engine manufacturers is telling in regard to the advantages of "ceramic coating". 

[Jeff Balazs]

Not sure what one could do component wise to increase the thermal efficiency of one of these engines. The piston treatment mentioned earlier is for an air cooled engine. Our engine behaves entirely different from those conditions. If fact I believe these engines take several minutes of run time until they are up to true running temperature. The one item in this equation that does come into play is sparkplug selection. They are definitely not all created equally and I feel that finding the "right one" does make a difference. The only other item that I can think of that has a profound effect on this thermal efficiency is the air/fuel ratio that is actually reaching the combustion chamber. Getting this "adjusted" properly is I believe what will make a difference across the board.

Jeff

[55 Fargo]

Give it up Guys and enjoy your engines as they were designed and meant to be. What came first the "chicken or the egg", the glass is "half full or half empty".....LOL

Better choice in rear diff gears, overdrive transmissions, optimal engine condition.

Dual or triple carbs, a more balanced more fuel efficiency ratio, optimal ignition condition, settings and design.

Once all is in harmony, and you are not revving 3000 + RPM down the highway, and getting 22-24 mpg is quite peak efficiency, you can get a bit more, but most sit in the range of 20-24 mpg with all going well.

here have a nice cup Of Tims or Starbucks and enjoy, don't worry be happy.....LOL

 

 

[RobertKB]

24 minutes ago, Rockwood said:

Give it up Guys and enjoy your engines as they were designed and meant to be. What came first the "chicken or the egg", the glass is "half full or half empty".....LOL

Better choice in rear diff gears, overdrive transmissions, optimal engine condition.

Dual or triple carbs, a more balanced more fuel efficiency ratio, optimal ignition condition, settings and design.

Once all is in harmony, and you are not revving 3000 + RPM down the highway, and getting 22-24 mpg is quite peak efficiency, you can get a bit more, but most sit in the range of 20-24 mpg with all going well.

here have a nice cup Of Tims or Starbucks and enjoy, don't worry be happy.....LOL

 

 

Here's my suggestion for better fuel efficiency............get rid of the flathead and buy a newer vehicle. If you are driving your flathead daily be prepared for crappy gas mileage. These engines were designed in the time before WWII and the flathead engine type goes back decades before that. As mentioned above, there are a few things you can easily do for improved mileage but overall, "You can't make a silk purse out of a pig's ear". Enjoy them for what they are, an anachronism.

Edited January 25, 2017 by RobertKB

[classiccarjack]

On 1/10/2017 at 2:39 PM, 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

$2.10 a gallon?  Must be nice, we get raped in California and have to pay 30% more.  But then we don't experience winter here, so it's a trade off....  I visited mom in Kansas for Christmas vacation in Kansas.  -7°F....  I don't miss it.  LOL

 

And you do have a valid point.  I love driving my old stuff more than when gas was $5.00 a gallon here a few years ago.

[classiccarjack]

I am curious about turbocharging one of these engines.  Is it a viable solution when it comes to gaining MPG?  I would think that the turbo would need to be somewhat small in size.  Or am I totally wrong?  

[Dartgame]

If you want to increase the operating temp put in a hotter thermostat - 195F. Most folks limit this to 180F. A hotter thermostat will help efficiency if i am not mistaken. Look at the current fuel injected cars they run at around 200F for better combustion efficiency and mileage etc.

[classiccarjack]

3 hours ago, Dartgame said:

If you want to increase the operating temp put in a hotter thermostat - 195F. Most folks limit this to 180F. A hotter thermostat will help efficiency if i am not mistaken. Look at the current fuel injected cars they run at around 200F for better combustion efficiency and mileage etc.

I do believe that this has some truth to it.  I have not applied this to older technologies, but it may be a fun topic to experiment with.

[DrDoctor]

   I’m going to throw in with Rockwood, and RobertKB – just enjoy the old car for what it is: an old car. If fuel economy is a major issue for you, then you should drive a newer car with more fuel efficiency engineered into it from the get-go.  We personally love driving our ’46 Plymouth Special DeLuxe Club Coupe. People wave at us as we go by. Most drivers recognize it for what it is, and old car, and give us some latitude. It evokes a kinder, gentler time for all. For us, it’s a time-travel trip to a simpler time. If we’re going a long distance, we take the Cadillac, which gets right at 30mpg on the hiway. We don’t baby the Plymouth, tho’, we just tend to stay within a 50 mile radius of home. Anyway, that’s my thot's on this. Thx.

[Niel Hoback]

My Dad used to call that kind of thinking, "Common sense". 

Edited February 3, 2017 by Niel Hoback
Leaking brain

[maok]

10 minutes ago, Niel Hoback said:

My Dad used to call that kind of thinking, "Common sense". 

But common sense is not that common...

 

I guess it all depends on how far you are willing to go.

1.  No modification - good tune, slightly lean carb setting, sensible driving technique, higher tyre pressures.  Lets say 20mpg

2. Minimum mods - electronic ignition, plus the above. around 25mpg

3. more mods - as above & higher compression ratio, better exhaust and induction systems. up to 30mpg

.

.

.

10. Maximum mods - engine swap to a modern 2L turbo diesel. up to 50mpg

How far do you want to go?

[Jeff Balazs]

13 hours ago, classiccarjack said:

I am curious about turbocharging one of these engines.  Is it a viable solution when it comes to gaining MPG?  I would think that the turbo would need to be somewhat small in size.  Or am I totally wrong?  

I may experiment with this later this spring. I have a buddy that is an amazing fabricator and likes a challenge as much as I do. What we have been discussing is indeed a small turbocharger with 4# to 5#s of boost. He has some very clever ideas about the manifolds and associated plumbing that I really like. Can't say what it will do to fuel economy yet but more grunt should make the taller gearing I already have work better.

We all have different reasons for having an old truck. I use mine daily and it has been extremely reliable. I see no reason why it would be any less fun to drive with a little boost from something simple like a turbocharger.

Jeff

[DJ194950]

Turbo on these motors probably would work much better with either a small sized (diesel ?) turbo or maybe better  a new style with the dual sized spools inside as these motors do not run high rpms and this newer type will spin up at the lower rpms and at higher also.

Love to follow any build you might do!

DJ

[Jeff Balazs]

I will do posting on this once we get started. Since I use the truck all the time this needs to be built up as something that will will go in as a quick swap. I feel fortunate to have someone as talented as my buddy Jon helping me out this way. He makes his living building race cars and off-roaders for many well known teams and privateers. He has indicated that he may be able to get quite a bit of the hardware for next to nothing...so we shall see. We are going to try and engineer this so it is a direct bolt-up system. Not necessarily a kit.....but as something that could be easily put back to stock should someone want to remove it in the future.

Jeff