Efficiency Questions

[theDyls3]

So this is my first post on this site, so I should probably introduce myself.

I have a 1953 B4B that I've been working on for a little over a year. Currently I am gearing up to start her for the first time. Then to finish up the interior and I'll be ready to drive her for the first time.

Anyway, since I'm spending all the time to fix her, I was wondering if there are ways to increase the efficiency of the engine and/or reduce the emissions, beyond just rebuilding everything which I have been doing?

Is it possible to add a catalytic converter? Would that even be beneficial? Am I being crazy to even think about this?

(I guess I should mention that this is my first time working on a truck, so I'm learning as I go).

Oh, and here's a pic of my truck as she looked when I got her, now she's in a few more pieces.

[greg g]

neat truck. I don't think the catalytic converter is something to consider. Low compression engines probably put out to much stuff for them to handle. If you search the forums (check the car board also) you will find some threads about adding a positive crankcase valve. Some folks claim these are benificial. You might want to consider having the cylinder head milled to increase compression. This seems to be the biggest bang for the buck as far as a bit more power is cincerned. You can also swap the rear end if towing and hauling arent a concern. Trucks usually had a high numeric ratio giving good hauling results but limiting speed on the highway, and causing fuel economy to be not as is could be. If you don't work your truck hard, a 3.55 or even 3.23 rear end would lower your highway rpms, and make your truck easier to cruise around in. Taller tires help i this regard also. Lots of folks front disc brakes are worth doing.

Welcome aboard, enjoy your truck.

[theDyls3]

Thanks for the info, I'll have to look into swapping the rear end. I have been worrying about the top speed since I read somewhere that I should expect it to be around 45mph.

I'd look into having the piston heads milled, but I already had my engine rebuilt.

[TodFitch]

Thanks for the info, I'll have to look into swapping the rear end. I have been worrying about the top speed since I read somewhere that I should expect it to be around 45mph.

I'd look into having the piston heads milled, but I already had my engine rebuilt.

The efficiency of the engine is largely related to the compression ratio, the higher the better. Until, of course, you get pre-detonation (ping or worse). So shaving the head is probably the quickest most effective thing you could do. Getting a high compression aluminum head would be better (aluminum conducts heat away better so you can usually run higher compression before pre-detonation occurs).

And then you have pumping losses you want to minimize. In the old days they talked a lot about "porting and polishing", that is grinding the block and manifolds so the openings matched perfectly and smoothing out the rough cast surface so they would flow better. But another way to reduce pumping losses is putting on either headers or split manifolds.

Also in the nature of working on pumping losses, you can change out the cam to one that is cut more for high end performance.

One thing you can't do much about is the L-head design: It just doesn't breath as well as an overhead valve design. Which is the reason why all engines nowadays are overhead valve.

[MBF]

I can speak personally about the advantages of adding a PCV system to my truck. I built it myself, but they are available through Vintage Power Wagons. Keeps the oil noticably cleaner and has reduced the sludging I was experiencing on the low use vehicle. It's probably doing something for admissions as the road draft tube is no longer dripping oil and vapor on the ground, its sending the crankcase fumes (at least a portion of them) back through the combustion process for a 2nd pass. Although I haven't done it myself, I believe going to a higher ration rear and increasing your mpg is probably one of the most efficient things you can do with a well tuned engine. More mpg means less pollutants per mile! Mike

[grey beard]

You are getting some pretty good advice here, on this thread. The plain facts are that when one considers our old flathead L-type combustion chambers, while they were very robust and dependable, from an efficiency point - which was your original question - they were abysmally INefficient. By this I mean that less than 30 percent of the btu heat value in a gallon of gasoline actually wound up doing useful work at the back wheels. The balance of all that energy was wasted on heat, which we all know had to be lost in order to keep thngs running happily. When you think about your engine's cooling system dispersing 70 percent of all the energy produced by the fuel we burn, it is small wonder that our flatheads give poor fuel mileage and are true culprits in terms of emissions pollution.

Unless they have a lot of automitive industry training or experience, most people never realize how much more efficient gas engines have become in the last forty years - the time since the US has been concerned about hydrocarbon pollution from gasoline engines. Tremendous strides have been made in efficiency as a result of all the EPA mandated dynamometer testing, exhaust gas monitoring and the like. Just a quick comparison of carbureted engines with their EFI counterparts shows some amazing gains in efficiency. Air-fuel ratios are now monitored in all of our modern cars more than sixty times per second by the on-board computers, which get info from a string of sensors that monitor air temperature, manifold vacuum, road speed, exhaust oxygen content, throttle position, etc. It's hard to get a Carter B1B single barrel carburetor to do too many of those jobs.

Just in the area of combustion chamber design, our engines lack in every direction - as has already been mentioned in this thread. Technoloy has shown our flathead engine designs to be about as inefficient as possible, and still allow an engine to be dependable. My suggestion to you is to enjoy the old iron for its own intrinsic and historic value, and forget about even thinking of ever getting them efficient.

Herein lies a bit of romance, and it is this elusive stuff that most of us pursue - that and a good dose of fine old memories from the past.

Twenty-three skadoo . . . . . .

[Young Ed]

Dave how come my 48 plymouth only gets 2 MPG less on trips then my 94 dakota? And it would have been equal except I'm pretty sure the cat on the dakota is there in name only resulting in 2-3 extra mpg.

[TodFitch]

Dave how come my 48 plymouth only gets 2 MPG less on trips then my 94 dakota? And it would have been equal except I'm pretty sure the cat on the dakota is there in name only resulting in 2-3 extra mpg.

Engine efficiency is measured by how much power you get out of the gas you put in. In addition to the items mentioned below, the efficiency varies with RPM and is generally highest at wide open throttle (low pumping loss) at about 80% of the RPM for max HP.

Your 1940s engine, with stock gearing, is running about 3000 RPM at cruise (50 MPH or so) which is 83% of 3600 RPM (max BHP) so your old car is at its most efficient engine RPM.

Your 94 Dakota is loafing along at maybe 2000 RPM while its max BHP is, I'd guess, something above 4000 RPM. A long way off from its most efficient operating point.

Next your Dakota probably weighs more than your 48 and probably has worse aerodynamic properties. Those big rounded tail ends of the cars from the late 30s and 40s are actually fairly good shapes for wind resistance. Oh, and the power needed to overcome aerodynamic drag increases as the third power of speed: Double your speed and the power required goes up by a factor of 8.

So cruising your 94 Dakota at 65 or 70 MPH takes a lot more power than your 48 going 50 MPH. And for city driving your Dakota has more weight to start and stop and you are probably doing a lot faster acceleration in your 94 which takes a lot more power (gas).

Basically Detroit has found that 15 to 20 MPG is "good enough" to sell most of the time and so every increase in engine efficiency has been put toward acceleration or higher speed travel rather than toward economy. Remember back in the 1960s when it was a really big deal to get your hopped up car to do 0-60 in 10 seconds? The average SUV does that today straight off the showroom floor. That is where the increased engine efficiency has gone.

[theDyls3]

All right, so the take home message seems to be short of swapping to a more modern engine there's only so much you can do.

Also thanks for the information on efficiency Tod, I haven't really thought of it that way (in other words that there is more to gas mileage than just the efficiency of the engine).

It does remind me of another question: What kind of gas mileage should I expect with my mostly stock truck?

[greg g]

12 to 16.

[IanT_Qld]

Does anyone know if a small turbo would improve efficency? Only requires minor modification of air flow.

I read somewhere 8:1 compression was suited to 3lb boost?

I have a spare motor in the shed and I am dreaming of bolting a turbo to it.

[48Dodger]

Grey Beard said it best I think. So much of the effective power is lost in heat. This is still true in todays engines. Mechanical Efficiency's biggest power stealer is friction (FHP), the difference between BHP and IHP. In a frictionless world you have IHP, which is the mythical 100% Mechanical Efficiency. BHP is the real world number. So after you start hanging every little pulley and pump and port on the engine, the losses add up. I think the real change comes from the gears and suspension. Torque is what makes you move and the suspension is what keeps it where it belongs, on the road. A 500 hp 360 will lose to a 500 hp 440 in the same set up because of the leveraging power of the big block. The fact you asked about a Catalytic Converter makes me think your question was more of a "green" question. In the US we measure HC's, where in europe they use MPG as the determining factor of pollution. Diesel engines are more efficient, but put out more HC's than gasoline engines. I think if you take care to build a well tuned motor and get the most out of the gearing, you'll have the best of both worlds.

48D

[theDyls3]

It's true 48D, I was thinking more in terms of energy efficiency than power efficiency, if that makes sense. I tend to be a pretty tame driver, not looking to win any drag races or what not. My concern was more ways of limiting the pollution of this old truck.

I do think I got my answer though. The engine is what it is, and if I want to increase the trucks efficiency I should look else where (gear ratios, etc). I did have my engine rebuilt and I have rebuilt all the peripheral parts, so it seems I should be thinking about bigger tires and lower gear ratios instead of trying to hobble on a catalytic converter.

[TodFitch]

It's true 48D, I was thinking more in terms of energy efficiency than power efficiency, if that makes sense. I tend to be a pretty tame driver, not looking to win any drag races or what not. My concern was more ways of limiting the pollution of this old truck.

I do think I got my answer though. The engine is what it is, and if I want to increase the trucks efficiency I should look else where (gear ratios, etc). I did have my engine rebuilt and I have rebuilt all the peripheral parts, so it seems I should be thinking about bigger tires and lower gear ratios instead of trying to hobble on a catalytic converter.

For better mileage you probably are better off looking at tires and rear end ratio.

If you want to do a little bit for the environment then put on a PCV system. Almost no down side to that. Cleaner oil in the crankcase it the big win for you. And, it turns out, the biggest source of unburned hydrocarbons (smog) from a totally "uncontrolled" engine is crank case blow by. So you are getting rid of the biggest source of air pollution in your vehicle. So it will do more than a catalytic converter for you on the pollution side and will help your engine last longer too.

[theDyls3]

That's good to know Tod. I will definitely look into doing that.

[48Dodger]

A PCV valve should be easy. But I dont think I've ever seen one on a flat six. Anyone have this set up?

Just to add a bit more info: Unburned gas is "the pollution". The Volumetric Efficiency of most engine cylinders are 80 percent. The trade off, to oil the piston in the hole, is "blow by". The "blow by" eventually makes oil acidic, keeping the oil from doing its job. A PCV valve using the vacum from the Carb or Intake manifold will suck the unburned gases out of the crankcase, keep the oil cleaner, and have a chance at burning up the unburned gas in the "blow by". EGR's allow unburned gas in the exhaust, back into the intake manifold. A.I.R. (air injector reactor) units force air into the exhaust so unburned gas will burn in the exhaust pipe. Catalytic Converters gets things hot, to burn up the last bit of gas in the exhaust. The Japanese Auto makers put spark plugs in the exhaust pipe or exhaust manifold to attack the unburned gas. Dodge went a big ol step further, putting 2 spark plugs per clyinder in its Hemi's. 1 for power, 1 for clean up. So again, I say, a well buildt, well tuned engine, along with well maintained running gear, is a fair offering to the enviroment.

48D

[TodFitch]

A PCV valve should be easy. But I dont think I've ever seen one on a flat six. Anyone have this set up?

48D

There have been a number of posts over the years on this and some photos of homebrew PCV systems for our L-6 engines.

And if you want something more "official", Vintage Power Wagon has the military PCV parts you can bolt right on. (Another reason for PCV is it seals the crankcase against water intrusion so you can ford deeper rivers so the military wanted it on their trucks way back when.)