Building an engine.

Im looking into building an engine and making it very fuel efficient. Im not sure where to start though. Any input would be greatly appreciated. At first I thought about taking an engine from another vehicle and using that but then I decided to just build one myself. That way I can get a better understanding of how everything works together. What major parts would I need? How do I make it extremely fuel efficient? Is it difficult to build an electric/gasoline engine? Would it be more expensive to build a small engine or purchase an engine already assembled?

Like I said any input is appreciated. Thanks for your help. =]

First, determine your power/torque needs. From there I can help you select a displacement. Let's say you need 3.0L. With that displacement, typically a 4 cylinder would get better mileage than a 6 cylinder. This is because you A) have less frictional area per unit of displacement, and B) you have 4 rod bearings instead of 6. It also sometimes means less rotating weight which saves fuel on acceleration. It should also be noted that typically V-engines have less friction than inline engines due to the fact that in a V engine the crank is shorter, lighter, and often uses fewer main bearings. Most V8 engines have 5 main bearings. Inline 6 engines typically have 7 mains. It is also often easier to get a more equal distribution of intake air with a V-configuration as opposed to an inline engine.

From there, most economy is in the heads. Chamber and piston crown design is very important, as is how they meet each other. Do searches on quench for more information. You want the rising piston to cause as much turbulence as possible immediately before ignition. This increases flame front speed and also increases how much of the fuel gets burned. More of the fuel burned means more pressure on the piston and less unburned gas out the tailpipe.

Compression is another factor which is often misunderstood. More compression will tend to make the engine more thermally efficient; that is to say, a higher percentage of the BTUs in the fuel can be released as heat energy to push the piston. This is not to be confused as increased fuel efficiency, but since you're liberating more energy from the fuel with higher compression, theoretically you will need less fuel to produce the same acceleration. Provided your driving style doesn't change, better MPG can be a potential side-effect of increased compression. The one caveat to that is that increased compression requires more energy to compress the intake charge. The secret to increased overall MPG efficiency in that case is only realized if the additional released energy is greater than the additional input energy required to compress it.

The rest of MPG efficiency is realized by the rest of the vehicle; weight, drivetrain losses, tire friction, wind resistance, etc.

The other big factor is with the fuel you use. Alcohols have very low BTU contents compared to gasoline, so to provide the same acceleration it requires a lot more fuel to accomplish it. Diesel on the other hand has more BTUs than gasoline which is one of the reasons (along with very high compression) that make diesel engines so fuel efficient.

Excellent post curtis.

Imo the easiest way to get top efficiency is to simply buy a very fuel-efficient car. Building your own takes money and time, all of which can buy a lot of fuel. :)

Look at Smart Cars, especially the diesel. They have been sold in my hometown (Toronto) for some years. Owners really like them, and the diesel smart car is very efficient and reasonably pleasant to live with.
http://www.smartusa.com/

However, if we are talking efficiency theory, here are some more factors.
1. Engine material.
An aluminum engine is more fuel-efficient than a cast-iron unit. Aluminum is lighter, and takes less energy to move it down the road.
Internal combustion engines require heat to work most efficiently. A cold engine is less thermally efficient than a hot one. Aluminum holds less heat energy, so it can warm-up faster, with less fuel than iron.

2. Another word on heat. Fuel efficient engines need to be hot. Use the highest temp thermostat you can find, typically 195 deg. F. It may be possible to install a very accurate mechanical temperature gauge and manually-operated radiator shutters. With some practise, you could restrict air flow to maintain coolant temp at 230 deg. F or so for maximum efficiency.

3. Cylinder bore size. A larger bore, shorter stroke engine has less friction than a longer stroke engine.

4. Go small, low power output. Anytime a gasoline engine is operating at less than wide-open throttle, you achieve pumping losses, that is, energy is lost in generating intake manifold vacuum. Therefore, the most efficient gas engine is one that has just enough power to get you down the highway at 50 mph at or near wide open throttle. Given that a small car needs, at most 10 hp to achieve this, such efficient engines are tricky to drive in traffic because their acceleration is pretty slow.
*or go with a small diesel engine. They do not have these pumping losses AND have much higher compression for a more efficient thermodynamic cycle.


5. Use a turbocharger. When used at wide-open throttle or when used in a diesel engine, turbos reclaim some of the thermal-expansion energy lost in the exhaust system and reintroduces it into the engine by compressing the intake charge. Ideally, turbos used on a diesel or low-power gas engine increase economy by approx 10% (if I recall correctly).

IMO the most fuel-efficient engines are tiny, turbocharged diesels. These are found in some vehicles built for foreign markets or in some types of construction equipment. Barring that, a small displacement, liquid-cooled 4 stroke motorcycle engine would be a good choice.


Isuzu builds some fine very small diesel engines. Take a look at the 7 hp to 53 hp range.
http://www.isuzuengines.com/products/products_i.asp

Curtis73,

Thanks for your advice. I apologize ahead of time as I might ask questions that might seem stupid. Just bare with me. lol.

I guess I should start my long journey by deciding whether I should build an engine or purchase one like MagicRat is suggesting. I dont have a problem doing either or. I actually would rather do what is cheaper. But, like I mentioned before I would like to get a better understanding of how things work together.

Also, I read that diesel engines are heavier than gasoline engines due to the higher compression ratio (http://auto.howstuffworks.com/question399.htm). The weight of my vehicle is very important to me. Is there a significant weight difference?

As far as my power and torque needs, I guess Im not looking for something very powerful. Im a very safe driver and I'm not all that concerned about acceleration and speed. Besides, this is my very first big project and I wanted to start with baby steps. Start small you know. The bigger the engine the more complicated it gets. And fuel efficiency is very important to me. So with all of that said Im going for nothing bigger than a 4 cylinder engine.

Im not totally convinced that V shaped engines are better than In line engines. I really dont know much to compare them but from what I've read there doesnt seem to be much of a difference other than the ability to put the V in tighter spaces. But I will do some more research on that. =]

So now Im totally convinced I want a turbocharged diesel engine. Now I just have to find out pricing to purchase one or how much it will cost me to construct one myself. Which will take alot more time and effort but when its all said and done I think it will be worth it.

MagicRat,

Thanks for your feedback! =]

After I read your post I did some research. Now I am dead set on getting a turbocharged diesel engine. I just have to decide whether to build one myself or buy one. Knowledge is very important to me. But I dont want to spend forever trying to finish this project. So if building one myself will take too long and be more expensive then I will most definitly just purchase one. What do you think about that? Approximately how long and how much would that cost me to do it myself? And how much does a small typical diesel engine cost?

MagicRat,

Thanks for your feedback! =]

After I read your post I did some research. Now I am dead set on getting a turbocharged diesel engine. I just have to decide whether to build one myself or buy one. Knowledge is very important to me. But I dont want to spend forever trying to finish this project. So if building one myself will take too long and be more expensive then I will most definitly just purchase one. What do you think about that? Approximately how long and how much would that cost me to do it myself? And how much does a small typical diesel engine cost?
Major auto manufacturers spend millions of dollars engineering their engines. To build one yourself is an expensive proposition.

It is possible to modify a production engine using aftermarket components, already engineered for the task. But most mods like this are for increasing power, not economy.

If you do buy a production diesel engine, you will be faced with the very real problem of installing it in a chassis of your choice and getting the engine to work with an existing transmission.

Now, if you do buy an engine, what kind of chassis will you place it in?

MagicRat,

Ahhh that is another real problem. lol. You've convinced me that building an engine is something that will take forever and cost me alot. When I thought about what you said it made perfect sense. Engineers do spend tons of money making them and the only way they get them so cheap is because they mass produce them. Since I am just making one for myself it will be very costly and time consuming.

You mentioned that the aftermarket components I could install typically increase power and not economy. What are some examples of these components?

And about the chassis...I'm thinking about ordering a nice chassis made out of aluminum. Im pretty sure aluminum is the lightest material I could find for a chassis. There is NOO way I could ever construct one myself because I have no idea how to weld and make it stable and safe. My ultimate goal is to have all brand new components on this car and I want it to be ultra light weight and fuel efficient. Oh and I'm looking for a street racer look. Even though I wont be doing any street racing. lol. So I will be doing some research on different chassis styles. I was thinking about posting another thread on the topic after I search for a related one.

I would probably buy an older car. Prehaps an early 90's honda toyota or nissan or something. Something thats not expensive. You might decide to experiment and if something happened that hurt the engine or something, I'd hate to have bought something that cost alot. Junkyards have alot of cars that mechanically are really reliable. The only reason its there is cause it was wrecked. Prehaps if they have a car with the front end in good shape. Like I said, this would be for experimenting with so its not going to matter what it looks like. I had thought about doing this a while back and this is what I was told which made sense to me. I'd rather buy a cheaper like maybe 2000 rather than a newer car for like 5 or 6000. That way if I decide to try putting an additive in the engine like Cheetos and something for some reason goes wrong then I'm not out 6000$ on a newer car.

MagicRat,

Ahhh that is another real problem. lol. You've convinced me that building an engine is something that will take forever and cost me alot. When I thought about what you said it made perfect sense. Engineers do spend tons of money making them and the only way they get them so cheap is because they mass produce them. Since I am just making one for myself it will be very costly and time consuming.

You mentioned that the aftermarket components I could install typically increase power and not economy. What are some examples of these components?

And about the chassis...I'm thinking about ordering a nice chassis made out of aluminum. Im pretty sure aluminum is the lightest material I could find for a chassis. There is NOO way I could ever construct one myself because I have no idea how to weld and make it stable and safe. My ultimate goal is to have all brand new components on this car and I want it to be ultra light weight and fuel efficient. Oh and I'm looking for a street racer look. Even though I wont be doing any street racing. lol. So I will be doing some research on different chassis styles. I was thinking about posting another thread on the topic after I search for a related one.

Ah ha, now we're getting somewhere.
For a chassis, you want something like this, right?

http://www.arielatom.com/

There are a number of race car chassis companies in the US that already build small tubular chassis, complete with all suspension, steering etc. This would be much easier that custom-building one, since all the suspension and steering geometry is actually very technically involved to work out.

However, as mentioned before, working out the transmission and final drive arrangements will be difficult and will involve a lot of expensive fabrication.

The alternative is to use a motorcycle engine. This is actually a very good idea for several reasons. All bikes (except for the big Harleys) have integrated engines and transmissions..... that is, the transmission and clutch are built into the engine. Much easier to use!!!!

Also, many motorcycles are chain drive. It is easy to hook up a chain drive to one rear wheel...... a bit tougher to connect it to two of them.

You could use a 250 cc 4 stroke motorcycle engine.... it is efficient, cheap to buy used, and will produce enough power to get a streamlined little car up to highway speed... albeit slowly. But highway cruising would be efficient.

There is a company out there that will convert a motorcycle into a sleek little three wheeler sports car. (I forget the name though).
It uses the entire rear half of a bike, and builds a chassis around the front half. Most bikes they use are the 1000+ cc rockets, so gas mileage is not that great. But one could use a 250 cc bike with the same basic design for greater mileage.

As for mileage mods...... a small motorcycle engine is about as efficient as a gas engine gets. Perhaps shaving the cyliner head a bit to raise compression would help, as would experimenting with ignition timing and fuel mixture.

Unfortunately, there are no small, super-efficient diesel motorcycles that I know of. :(

I would probably buy an older car. Prehaps an early 90's honda toyota or nissan or something. Something thats not expensive. You might decide to experiment and if something happened that hurt the engine or something, I'd hate to have bought something that cost alot. Junkyards have alot of cars that mechanically are really reliable. The only reason its there is cause it was wrecked. Prehaps if they have a car with the front end in good shape. Like I said, this would be for experimenting with so its not going to matter what it looks like. I had thought about doing this a while back and this is what I was told which made sense to me. I'd rather buy a cheaper like maybe 2000 rather than a newer car for like 5 or 6000. That way if I decide to try putting an additive in the engine like Cheetos and something for some reason goes wrong then I'm not out 6000$ on a newer car.

Thats a great idea. Thanks for your input. Your right I would hate to put alot of money into something and then come to find out that it wont work for some reason or I might mess it up.

So you mentioned something about doing this awhile back, did you ever try it?

Oh and I hope cheetos never get in your engine. haha

MagicRat,

w0w I love that chassis. I love the whole thing actually. lol. I like the design and the low center of gravity. Now Im faced with another decision though...should I go with a motorcycle engine like you suggested or with that small turbocharged diesel engine. Im going to do some more research. Thanks for presenting me with a bunch of different ideas. I really want to explore all the options before I start buying things and get started with this project.

Do you know how the two engines compare as far as power and fuel efficiency? I will be doing some research on that. Im all about a fuel efficient engine but I dont want to totally sacrifice power. Im a guy and every once and awhile I have to feed some speed to my ride. haha.

Oh and I will also be looking for some of those companies you mentioned that build the chassis with the steering and suspension.

Thats a great idea. Thanks for your input. Your right I would hate to put alot of money into something and then come to find out that it wont work for some reason or I might mess it up.

So you mentioned something about doing this awhile back, did you ever try it?

Oh and I hope cheetos never get in your engine. haha

No, I never got around to it. I had thought of trying it with a cheaper car and keep records of what exactly I do to the car. And if things work right and prehaps after driving the car for a year and seeing nothing damaging is happening to the engine, then go out and get something real and duplicate the proceedure. No, I don't think Cheetos will end up in my engine. Besides, my engine is in pieces right now anyways so it wouldn't matter. Sodium Silicate would be a nice additive if you really wanted to beef things up. Just kidding.

Which is better as far as power and fuel economy...

1. A turbocharged diesel engine with direct injection?

or

2. A turbocharged gasoline engine with direct injection?

The whole idea of turbocharging any engine in the first place is to increase fuel economy and power output. The diesel engine is more thermally
efficient than the gasoline engine, which in itself will result in less fuel consumption by the diesel; turbocharged or not. To answer your question; in this particular case I'd go with the diesel.

The wide array of cheap (or free) diesel alternative fuels that have very little net carbon emissions further solidifies the diesel in my opinion. Engineer it to run on recycled veggie oil and the net carbon output drops about 90%. Plus you can get it almost free.

Which is better as far as power and fuel economy...

1. A turbocharged diesel engine with direct injection?

or

2. A turbocharged gasoline engine with direct injection?

Just to expand on BlueD's answer.

As I stated earlier, a turbocharger reclaims some thermal energy (that is otherwise going to waste) and reintroduces that energy back into the engine by pressurizing the intake manifold. But this only works on a gasoline engine when the throttle blade is open far enough to allow for intake manifold pressurization..... so it only gets an efficiency boost under heavy acceleration.

Diesel engines get an efficiency boost from a turbo ALL the time, so a turbo diesel is far more efficient than a turbo gasoline engine.

Can I setup any transmission with any engine? I found the perfect engine but Im not sure if I can or how difficult it would be to setup a 6 speed manual transmission with it.

No. Every manufacturer has their own bellhousing pattern, input shaft length, number of clutch splines, etc. Some companies make adapter plates or bells to mate a transmission to an engine it wasn't designed for (like a Powerglide to a Ford engine), but you're better off picking something made for the engine in question.

No. Every manufacturer has their own bellhousing pattern, input shaft length, number of clutch splines, etc. Some companies make adapter plates or bells to mate a transmission to an engine it wasn't designed for (like a Powerglide to a Ford engine), but you're better off picking something made for the engine in question.

Thanks. That answers my question.

Depending on the engine you can mate it to several transmissions. For instance, within the major american manufacturers, someone makes adapters for nearly any combination; dodge tranny behind a ford, ford tranny behind a chevy, etc.

If you are going diesel, then a careful choice will yield super easy swaps. The SAE requires that all engines have an accompanying SAE bellhousing adapter. That doesn't mean they are readily available, but what it does mean is this: any engine that served duty in a generator, heavy machinery, or sometimes even air compressors uses a standardized bellhousing. This was done because companies often mix and match components with engines. They needed a standardized bellhousing pattern so you can put a Cummins where a Detroit used to be, or a Perkins where a Cat used to be.

I have a couple SAE projects in my head. I wanted to put a VW TDI in a compact pickup, and it was as simple as finding the SAE bellhousing for the tranny and the SAE adapter for the engine. Both were available, but the only place I could find an adapter for the TDI was in India and it killed the bargain.