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dwightlooi

Return of the 2-Stroke Engine

  

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  1. 1. Returning to a 2-Stroke Engine is

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When you make 300 hp without having to run high boost + low compression, and when you move the same amount of air needed to make that 300hp by turning over at half the speed, your fuel economy is better. 300hp is from a air pump that moves at at roughly the same rate as the engine ingests it -- ie. very little boost just enough to overcome the residual pressure of the exhaust gases. Basically you are getting 3.6 liter NA V6 class output from a 2.0L with high compression and near atmospheric aspiration. If you feed it with 22~23 psi of boost like the 272hp 2.0T (LTG) does, you are looking at about 500 hp.

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This one below at the link is a two stroke engine:

http://www.stuntbase.com/forum/kb.php?mode=article&k=30

People need only to eliminate the polution but

WITHOUT ADDING COMPLEX EXTRA PARTS. In this case is better to use a 4 stroke counterpart...

How can we achieve this goal?

I have some ideas..there´s a bit of them at www.motor2t.net

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Very cool sites Ingama, thanks for sharing.

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Guest Charlie

Theres a Problem with the design pictured that would cause failures if built, the Ignition source needs to be central as the pressure during ignition will cause blowby and piston scoring, You could use a crescent shaped port opening instead. 

 

 

Also the heat generated in 2 strokes is a problem as they are firing twice as often as 4 strokes, when heat is built up it causes pre-ignition, this would be aggravated by the use of forced induction but could be managed as your only doing half the RPMs of a 4 stroke and you have large exhaust ports to vent the hot gas faster than a 4stroke. 

 

Build it!

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Actually this is a modern rendition of an old idea. 2-stroke engines with overhead valves and sleeve ports have existed before and had worked very well -- albeit mostly in diesel applications.

 

Remember the M113 Armored Personel carrier and the AMX13 light tank? They are powered by the Detriot Diesel Allison 6V53 engine in blown or turbocharged form. This engine had overhead intake valves, side exhaust ports and operates on an externally pressurized 2-stroke cycle. It did not have an overhead cam however, relying instead on an in-block cam, pushrods and rockers to operate the overhead valves. It is one of the most reliable and long lived tank engines. The Japanese Type 90 Main Battle Tank is another example of a heavy vehicle powered by an overhead valve, side port 2-stroke engine. In this case it is the Mitsubishi 10ZG32WT 10-cylinder 1,500 hp 2-stroke engine and this engine does employ overhead cams.

 

BTW, the spark plug does not have to be central. In fact in most 2-valve designs it is not. A centrally located spark is a  favorable design choice for combating detonation and knocks. Basically, you can think of knocking as a race between the spark initiated flame front and the flame front generated by hot spots in in the cylinder (usually near the rim of the piston). A centrally located spark offers the shortest distance from the spark to the furthest point in the combustion chamber. An offset placement is less desirable, but it is no worse than... say... using a larger cylinder bore which has the same effect.

 

TM-38-301-40083im.jpg

detroit_diesel_inframe_kits_rebuilding_k

engine.png

Edited by dwightlooi

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BTW, the 6V53 displaced 5.2liters 318 cu-in (6 x 53 cu-in/cylinder). It made 275hp. This may not sound like much, but it is actually quite impressive given that this was the 1960s before electronic anything and this is a diesel engine. For comparison, the M60's AVDS1790 engine displaces  29.3 liters (1790 cu-in)  and made 750 hp -- that is 5.6x the displacement for 2.7x the output. Why? Because it is a 4-stroke engine and it fires each of its cylinders half as often.

Edited by dwightlooi
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i miss dwight's topics like this.

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1 hour ago, loki said:

i miss dwight's topics like this.

Totally agree, I wish he would come back and continue cool discussions like this.

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A little update...

There has been considerable interest in 2-stroke diesels lately. Companies like Achates are design new 2-stroke engines -- in the case of the Achates an Opposed Piston Diesel design with no cylinder heads, no valves, no spark plugs. Their first production engine is a 3-cylinder design which displaces 2.7 liters. It produces 270 bhp and 480 lb-ft.

Now, to be fair, the engine has six piston, two crankshafts and is closer in size to a 5.4 liter H6 than a 2.7L I3. But it has three advantages. Firstly, there is no camshafts, no cylinder heads and 40% as many parts. Secondly, because there are two pistons for each cylinder, the expansion ratio of each cylinder is twice that of a conventional engine of the same bore and stroke length which allows for insane effective stroke lengths (hence energy extraction) without high piston speeds. Finally, the thermal efficiency of the engine is above 40% (between 40.2 to 43%) across it's entire rev range which is about 15% better than 4-stroke diesels of the same output. A Silverado light truck so powered will deliver 37 mpg on the highway -- not bad at all.

A more interesting application for opposed piston designs is as a micro generator. A 400cc one cylinder O-P engine will generate about 30~35 KWe (40~47 hp). The supercharger (a necessity for 2-stroke O-Ps) can be a tiny and simple centrifugal impeller since this generator only needs to operate at its optimal rpm or not at all. It'll be spun up to its self-operating speed by the generator it drives before any fuel is ever injected. That is perfect as a range extender for electric vehicles. This is enough to completely recharge a 30KWh battery pack in an hous or maintain high way cruise at 60~80 mph while recharging the battery in about two. Effectively this means you CAN drive from San Francisco to LA on a full charge and about 6 gallons of diesel fuel. Not bad at all. Or, if you don't ever want to plug in that electric car you can drive around as a diesel powered hyrbid vehicle with about ~50 mpg and a ~300 mile range on that 6 gallon tank. Again not bad. The performance of the vehicle is quite independent of the generator or the battery capacity. It is governed largely by the size of the drive motor. Unlike the ICE , a big electric motor is not significantly less efficient than a smaller one (low load efficiency is about 70~75% vs about 90~95% at optimal). The single cylinder engine, its generator and the diminutive diesel tank will fit under the trunk floor in the same space currently occupied by a pair of mufflers and their exhaust pipes. Unlike a gasoline tank, rear placement is not a collision hazard because diesel spills are NOT flammable.

 

 

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1 hour ago, Drew Dowdell said:

What about diesel warm-up time @dwightlooi, or do these generators run all the time instead of start-stop like the Volt?

The way I will do it is for the vehicle to be a mid-range plug in electric with say a 20kWe battery. The car has no eCVT planetary transmission, just a direct drive motor like a pure electric. A 20KWe battery is good for about a 60~80 mile range (assuming regenerative braking) and direct drive. Unlike a Volt, this is actually enough for anyone with up to a 1 hour commute each way and a habit of driving to lunch or going shopping after work. But it is not so big that it has electric range which is not used on a daily basis. This is important because the battery is the single most expensive component of the EV. Saving $8000 in battery costs allow you to add a $4000 generator and still sell the vehicle for $4000 less.

If the driver does nothing, the Diesel Generator will automatically come on automatically when the battery drops to 20% charge and will cut off when it gets to 40% charge. That means it'll run for about 15 minutes at a time if you are cruising on the freeway or about 8 minutes if you are parked or sitting in stop-n-go traffic (give or take). More intrepid drivers can set the Generator on and off thresholds anywhere he pleases between 10 and 90%. Any time the driver pleases, he can depress the GEN switch which will turn the Generator On. When manually triggered, the generator runs until it is turned off with another tripping of the GEN switch or until the battery reaches 90% Charge (saving 10% to absorb regenerative braking energy recovery).

If you plug it in every night, the car behaves like mid-range electric such as the Leaf or an i3. The generator simply means that the car will never leave you stranded. If you never plug it in, the car generator will come on in 8 to 15 minute intervals, but drives just like a pure electric. If you are low of charge but can't plug it in for a while or if you never plug it in but want a full battery for some spirited driving, you can trip the GEN switch to keep your battery topped off. At full throttle a 200hp motor will drain that 20KWh battery from 90% to 20% in about 5 minutes (almost like in a RC Car).

The difference between this and a Volt or a Prius is that the single cylinder generator is nowhere near the cost, weight and size of an 4-cylinder ICE coupled to the drive line. The car has very simple powerplant consisting of a battery, a motor and an inverter (power converter) like a pure electric except it does not depend on a huge battery for practicality. The 400cc Generator installs like a pair of mufflers and is simply a mobile charger. The cheapest version of the car can have no generator. It can also be added later on with as much effort as replacing mufflers and plugging in a cable harness.

Because of the deep duty cycle, I'll very much prefer if the vehicle uses a Lithium-Iron-Phosphate battery rather than a Lithium-Cobalt-Oxide battery. Two reasons... LiFePO4 is much longer lived in deep discharge applications and LiFePO4 is inherently safe from thermal runaways and gasification (aka blowing up).

Edited by dwightlooi

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