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Unread 07-30-2006, 01:54 AM   #1
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Default Performance through efficiency

Beware: Very long post ahead.

With gas prices on the rise, and average incomes dropping lower and lower, I'm sure pretty much everyone is concerned with saving fuel. Even if you're not doing it for the environment, you're doing it for your pocket. Most people say fuel economy and horsepower can't coexist. This is not true. The reason they haven't cooperated with eachoter has been due to the auto manufacturers approach to "efficiency."

The biggest problem is this word efficiency. The easiest way I can describe it, is there are two separate views of efficiency when it comes to motor vehicles. The first (and most common) is vehicle efficiency. This is simple to figure out, just find your gas mileage. The other way to look at it is engine efficiency. This aspect is most often overlooked when shopping for an "efficient" car. Most people would say that your average Honda Civic getting 30mpg is more efficient than a big rig getting 10. This, however, is a falacy. In fact, that big bad diesel is much more efficient. The truck is getting a much larger "boom" per unit of fuel than the little gas engine is.

How, you may ask, can you get that little 4-cyllinder to get as big of a boom out of that fuel as the diesel? Well, technically it's impossible. Since diesel fuel stores more chemical energy than gasoline, the perfect diesel engine will always be more efficient (per unit volume of fuel) than the perfect gasoline engine. But let's first skip the technicalities for the moment and look at the fundamental differences between the diesel engine and gasoline engine.

There are a few key differences between the diesel and the gas engine. First is fuel delivery. Most diesels incorporate some type of direct chamber injection, where the fuel is squirted straight into the combustion chamber just when the time is right for the fuel to burn. This gives the engine a definate advantage, since the timing of combustion can be precisely controlled.

On a gasoline engine, you have a few options. You can have carbuerator, throttle body injection, direct port injection, or chamber injection. Chamber injection is just like the diesel (from above) and is generally the most efficient but is also the least common (and most expensive). I think some VW's and maybe a Honda or two incorporate direct injection.

In a carbuerator, the air that is injested by the engine is sucked past what's called a "jet" that, by means of a difference in air pressure, draws fuel droplets into the air stream. This air fuel mixure (will be reffered to as A/F mixture) is drawn into the intake manifold where it is distributed to each respective cyllinder. The intake stroke of each cyllinder is what causes the difference in air pressure.

Port injection (DPI) utilizes a pump that pressurizes the fuel through lines to "injectors" that, when stimulated by an electrical pulse, allow some of the fuel to be released. The speed and duration of the pulses determines how much fuel is squirted into the port.

Throttle body injection (TBI) is a hybrid between the carb and the port injection. Instead of having an injector for each cyllinder, the injector replaces the jet in the carbuerator and the fuel is electronically metered on top of the engine, where it is drawn through the intake manifold and fed to the cyllinders.

Historically the carb has been known as the least efficient, followed by throttle body injection and then port injection. The key difference between these systems that causes differences in efficiency is the metering accuracy. Since TBI and DPI are electronically metered, the onboard computer can accurately controll the amount of fuel that enters the engine at any given moment. A carbuerator is metered by the physical aspects of the carb itself, which cannot automatically adapt to differences in RPM, temperature (other than a "choke") or quality of fuel, in the way that the comupter controlled systems can.

Last edited by Pinhead; 07-30-2006 at 09:11 PM.

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Unread 07-30-2006, 01:54 AM   #2
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Getting back to the efficiency aspect of these engines... The other main difference between a diesel engine and a gasoline engine is the compression ratio, CR. The compression ratio is the ratio of the volume of the cyllinder when the piston is at bottom dead center (BDC) to the volume of the cyllinder when the piston is at top dead center (TDC). [If you don't know what I'm talking about when referring to cyllinder, piston, TDC, BDC, etc that will have to be another topic because I could write an entire book describing it lol.] Typical CR's on a gasoline engine range from 9:1 to 11:1. Race engines push that further into the 12:1 or even 13:1. Diesels, on the other hand, are running CR's in the 25:1 range.

There are two aspects that increase efficiency with a higher CR. The first is the compression. When the air and fuel are compressed they get hot. This is due to Boyle's law that says that when you compress a gas its temperature goes up. With the increased heat, the more quickly and completely they will combust. The second aspect is the Expansion Ratio, ER. This is the exact opposite of the compression ratio. It deals with how far the now burned [read HOT] gasses can expand. There are limits, but basically the more time the hot gasses can push on the piston, the more the heat will be converted to physical energy. The expanding gasses is what does all of the work inside an engine.

Since nothing is instant, this burning has to take place slightly before the piston reaches TDC. This is referred to as ignition advance (or spark advance). It takes a little time for the actual combustion to start, it takes a little more time for the heat to be transfered from the burning fuel to the nitrogen in the air (the nitrogen gas is what is expanding) and it takes even more time for that pressure to "push" against the piston. This is why the spark plug (ignites the fuel) is fired before TDC.

With a high CR, some of the fuel is turned into large droplets of liquid (due to Boyle's Law). The fuel vapor that is left burns much more quickly than it normally would in under lower compression conditions, due to the added heat resulting from the high CR. This quick burn manifests as preignition, or ping. If left unchanged, pinging will knock holes in pistons, burn valves, "throw rods" and do all sorts of other nasty things to your engine. It also reduces power. Since it is firing too far before TDC, the piston that is trying to compress the air is simultaniously being pushed back down by the expanding air. The engine is basically fighting itself.

The most common way to deter ping is buying high-octane fuel (Premium fuel). Premium burns a little slower so it is able to withstand the level of ignition advance required to make power. While it is a simple fix, it has one major flaw: Premium fuel is more expensive than regular fuel. On to the next fix...

The next major "fix" to ping is retarding ignition (spark) advance. There is a compromise made between "advanced enough" to burn all of the fuel" and "advanced enough to eliminate ping." Retarding the timing makes the vaporised fuel burn when it is needed in the compression to make power power stroke, transfering the power to the engine. However, since there is still liquid fuel in the combustion chamber after the piston starts its trip toward BDC, the liquid is either slowly evaporated and burned later in the power stroke, pushed past the rings, or simply pushed out the exhaust and wasted. The "Old School" technique was to advance the timing to be just on the verge of ping. This is why you lose power and efficiency on an engine when retarding the ignition (less fuel is turned to power). It is also why engines with a lot of cam overlap tend to idle poorly. That unused fuel burns during the exhaust stroke and that added pressure transfers through the combustion chamber during overlap into the intake manifold. To eliminate these problems, we need to eliminate the liquid fuel droplets that are trapped between the squish pad and the piston, and ensure all of the fuel is in a gaseous state upon ignition.

There have been discoveries pushing combustion efficiency to the next level. Their key goal is to keep the fuel vaporized. Here are a few links to websites that have been pushing this technology foreward.

www.somender-singh.com
www.mpgresearch.com
www.fueleconomytips.com

The first link (Somender Sing's website) is one of the most interesting, yet very simple way to increase combustion efficiency within an engine. This simple modification increases the rate at which the fuel burns inside the engine, thus greatly increasing thermal and mechancal efficiency.

Think of it this way... You've got a crossbow and a compound bow. Both have the same draw weight. The crossbow will be much harder to pull than the compound bow, but the compound bow will out-shoot the crossbow every time. That is because all of the pressure is exerted by the bow is in a very small area (at the very end of the pull). This concept is the same for your engine. If you can get all of the pressure from combustion to push on the piston as soon as it goes over TDC you will get much more torque, power, and efficiency.

Gasoline vapor out in the air (very little turbulence) burns very slowly, in the low meter per second range. Obviously this wouldn't work well within an engine, because the piston would already be through a complete cycle before the A/F mixture is burned. The grooves achieve a quicker burn by inducing turbulence into the A/F mixture.

As stated in the high CR engine above, on a normal engine without the grooves, as the piston reaches TDC liquid droplets begin to form. Much of this liquid fuel is trapped between the piston and the "squish" pad of the head. Under normal conditions, this liquid fuel won't burn until the piston moves down in the power stroke and allows the fuel to come into contact with oxygen in the A/F mixture. Since most of the fuel in the open chamber has already been burned and used up a most of the oxygen, the fuel that is left doesn't burn efficiently. This leads to carbon deposits and unwanted exhaust "emissions."

On a grooved engine, as the piston approaches TDC, a strong jet of air and liquified fuel is forced out of the groove and into the [large open] combustion chamber. What liquid fuel that has formed in the chamber due to the process of compression is broken up into much smaller droplets and is much more evenly mixed throughout the open combustion chamber. Now the fuel that would have to wait to burn later in the power stroke is mixed throughout the chamber during the power stroke. Due to this thorough mix, the fuel can much more readily be vaporized and burned much more quickly when it needs to be. Also, since these tiny droplets have so much more surface area, there is more fuel in contact with the hot air charge and the hot engine components. The liquid fuel absorbs the heat from the air charge and piston/head to evaporate even more completely and stays in a vapor state for much longer during compression. This raises the thermal efficiency, since the heat that would normally be emitted through the radiator and exhaust is doing work inside the engine, vaporizing the fuel droplets. This also equates to a very quick burn. Remember the compound bow? We're getting closer...

If it hasen't become clear by now, the biggest "breakthrough" has been inferred: Liquid fuel doesn't burn. Only the vapors (fuel that is evaporated and greatly mixed with the oxygen in the air) will burn and create power. The Singh grooves help mix the fuel into the hot air charge which helps the fuel to evaporate.

On MPGResearch, other things have been developed as well. PowreLynz(tm) introduce another way to increase the evaporation of that fuel. They're basically 20-pitch threads screwed into the intake tract of the head. This both increases flow and evaporates the fuel. The flow increases because it eliminates "laminar flow" that slows air delivery. Also, since there are no layers of slow-moving air, the fuel droplets on the outside of the mixture slam against the threads and are broken into smaller droplets that can be more readily evaporated. Even the fuel that doesn't slam and break up is "wicked" into the threads and evaporated from the heat within the metal of the head itself.

These two mods greatly increase thermal and mechanical efficiency and therefore have huge horsepower potential. Don't forget the fuel economy side of things, too, which was originally why they were developed. Since you're getting the most power out of the amount of fuel delivered, you can greatly lower the total fuel used (how hard you push on the pedal) to get the same speed.

This post got a whole lot longer than I expected when I started typing, but for a recap, here are the websites again.

www.somender-singh.com
www.mpgresearch.com <-- BACK UP!!
www.fueleconomytips.com <-- Was hacked and is down

Apparantely the last two were a strong enough threat to someone that they were attacked and cracked. They should be back up shortly.

If there is anything I should change, let me know. Maybe I should break it up somehow into a few different posts. Let me know!

Thanks, Bindusar (from the OCN forum), for your input regarding compression, Boyle's law, and fuel condensation during compression.

Last edited by Pinhead; 03-28-2008 at 02:15 AM.

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Unread 07-30-2006, 02:05 AM   #3
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wow that was very long

too lazy to read it but rep for effort

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Unread 07-30-2006, 02:15 AM   #4
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Quote:
Originally Posted by Born2KillU
wow that was very long

too lazy to read it but rep for effort
I warned you!

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Unread 07-30-2006, 09:12 PM   #5
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Original post edited for new information and accuracy.

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Unread 07-31-2006, 03:07 PM   #6
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I think it's finally finished!

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Unread 03-18-2008, 01:27 PM   #7
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Wow... I agree with Born2KillU I am not going to read that but I will say good effort.
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Unread 03-18-2008, 02:16 PM   #8
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Those 2 sites that were hacked are still down, gee I wonder who would want those guys out of business?
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Unread 03-19-2008, 11:16 PM   #9
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Originally Posted by Dman View Post
Those 2 sites that were hacked are still down, gee I wonder who would want those guys out of business?
Yeah, I know... They've been up and down like crazy lately. Coincidentally, MPG Research went down at about the time info about the Hydro Assist Fuel Cell and Pre-Ignition Catalytic Converter came out. SOMEONE doesn't like the idea of cars getting double the mileage...

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Unread 03-25-2008, 12:57 PM   #10
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I agree with a bit but there are a few things I don't quite agree with.

octane isn't related to fuel burn speed. it is related to the ability of the fuel to resist spontanious uncontrolled combustion. this isn't directly related to fuel burn speed just how easily the fuel ignites. nitromethane is a good example of this as it packs less energy per pound of fuel, burns slower then normal gasoline and yet still has a lower octane rating then gasoline.

slower burn speeds can actually make it easier to detonate as it will allow more time for the heat and pressure to ignite random pockets of the a/f mixture creating multiple flame fronts or spontanious combustion

singhs webpage sounds too much like a sales gimick for me to want to trust it. but here is one thing for you to think about that relates to my two previous things. you want turbulance so you can have a more efficient burn. in making for more turbulance it makes the fuel burn faster. with the fuel burning faster though you are actually less prone to detonation.
As far as his design I'll be honest I didn't look at it too much though other then a few parts just being it's to gimicky. look I use big words and make it sound great so you will buy my product. with what little I did read though it seems as though it might cause some problems also. cutting these grooves can lower overall combustion ratio, depending on how the groove is cut this can also acuse issues with hot spots in combustion chamber. in a way this might actually lower the velocity of the turbulance also being that under max compression there is more area open for flow. think of a straw. if both are going to flow 1cf/m of air which will have a faster velocity a 1" straw or a 1/2" straw? you would have much better performance by reducing the squish to a minimum without getting into piston clearance issues. another problem with this setup as well though is volume to surface area ratio. this is part of the downfall of the rotary motor. fuel against the surface of the cylinder walls and heads doesn't really burn that well even in vapor form so if you increase the surface area you might also make it to where the fuel in that area will not burn. I also noticed he talked about multiple flame fronts and that is another no goodie. this is partly where detonation comes from as the fuel with multiple flame fronts will cause an uncrontollled burn

the other two sites I can't access at work so eh can't comment there. only thing I can say is one of the ideas with the screw in the heads reminds me of the smog heads of the 80's used by GM that had the hump that was designed to introduce turbulance inside the port. sure the idea kinda worked but for this day in age that idea isn't the most efficient

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