Supercharged Two Stroke Engine – Explained in Detail

by Kannan on September 9, 2011

I am sure that most of you have already made so many thoughts in your mind by just reading the title; A Supercharged Two Stroke engine. It is one step ahead of two stroke engine. Let’s first discuss some common advantages and disadvantages of two stroke engine. Most of us know how the two stroke engine works. It uses only two strokes to produce power from air fuel mixture. We cannot distinguish between the suction, compression, power and exhaust strokes.

Two stroke engine uses ports instead of inlet and exhaust valves: Inlet port, Transfer port and Exhaust port. Opening of these ports are controlled by piston movement only. No separate mechanisms are provided to operate these ports.

At high speed of two stroke engine, these ports overlap with each other and increase the loss of fresh charge from the cylinder. Let’s have some pros and cons of two stroke engine over four stroke.

Advantages

  • Two stroke engine is very light in weight because of fewer parts
  • More mechanical power output because of better turbulence in cylinder
  • Easier to manufacture and assemble
  • Less unbalance forces due to few reciprocating parts

Disadvantages

  • Loss of fresh charge from the cylinder at the time of scavenging, resulting in poor fuel efficiency
  • More emissions because of incomplete combustion at high speed
  • Very noisy

Despite of many more drawbacks from the two stroke engines, they are very popular for getting more mechanical power. One of my students thought to bring out some modifications for the two stroke engine to have improved fuel efficiency with more power at the same time. The only solution we got in our minds was supercharger. Some big machine like marine engines uses superchargers in two stroke engines.

Supercharger works like a turbine to throw the air in to the cylinder. This provides more air in to the cylinder than the engine naturally does. Excess air helps to ignite more fuel particles which generally left the engine without having combustion. This helps the engine to improve the power output at same RPM. But still we also have to improve the fuel efficiency.

Carburettor supplies the fuel air mixture to the cylinder without measuring the amount needed. Engine has to burn the supplied amount of air fuel mixture and if fails, it throws this charge in to the exhaust port without any combustion. That’s why, for getting better fuel consumption, we are planning to incorporate fuel injection rather than carburettor.

No doubt, we will have to work more to have correct injection timing, otherwise it will again leads to more fuel consumption. Finally let me explain you hoe these all components going to work for our triumph. We are going to shut down the transfer port which is originally used to transfer the fresh air fuel mixture. At this place, we are planning to generate air vent for crank case ventilation.

The supercharger will be run by engine itself and will provide excess amount of air to the cylinder. This air will try to scavenge all exhaust gases from the cylinder to the exhaust port. Write now, this scavenging is done by fresh air fuel mixture coming from the transfer port, which also helps the fresh charge to escape from the cylinder. In our set up, only the air will be going to escape the cylinder.

After the proper scavenging and at the right time, we will inject the fuel in the inlet port of the engine. After the injection, air and fuel will get mix because of turbulence and will get combust with the help of spark plug. As we are going to supply sufficient air for the fuel for combustion, the efficiency will also improve and so as the emissions.

At present, we are doing literature survey on this type of combinations. This will help us to locate and operate the systems efficiently. We can also defend our work on the basis of this literature survey. We have planned to complete the fabrication and commissioning of this project till December 2011. I assure you all that we will definitely discuss the results of my project whatever and whenever it may be. Please share your ideas and experience to improve my success rate for this project.

Regards,
Dhruv Panchal

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{ 14 comments… read them below or add one }

Adwait September 9, 2011 at 11:21 pm

@Dhruv : How is the charge going to reach the combustion chamber if u are blocking the transfer port?

Reply

Dhruv September 10, 2011 at 10:28 pm

Adwait: As I shown in last diagram about fuel injection and supercharging, same things we are going to do with transfer port. we have planned to block the transfer port at crank case side and still it is open from cylinder side at which we will have our supercharged air and fuel injection.

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Adwait September 9, 2011 at 11:24 pm

Also, if u are supercharging a petrol engine, won’t it cause knocking resulting in power losses?

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Dhruv September 10, 2011 at 10:29 pm

may be….we will also check this probability.

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fas September 10, 2011 at 12:05 pm

I wonder when it will make it to Indian motorcycles!

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kusmaker September 10, 2011 at 8:03 pm

Hello this is kusmaker from delhi , i read ur article and iam quite excited about it is there any way by which i can be part of ur project, because i myself was thinking for some time that whether something like this can be done to improve to improve the efficency of the two stroke engine, i also own a yamaha rx-100 which is two stroke motorcycle so pls tell me that whether my bike engine can also be improved like this iam giving u my no do contact me if you think so 9953953413

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BHARAT September 13, 2011 at 11:20 am

Hi Dhruv,

I have worked on this project around 5 yrs back….. Let me know more….. Moreover there is already a patent for this design…..

http://www.freepatentsonline.com/7051824.html

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Dhruv September 13, 2011 at 9:08 pm

Oh….Can you send me your conclusions on dhruvautoengg@yahoo.com..???? and about patent, it for supercharged two stroke engine. there is also a patent for FI two stroke engine. but engine with supercharger and FI is yet untouched.

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RAJIV September 13, 2011 at 7:08 pm

hi dhruv.

As you said, blocking the transfer port will make the cylinder airtight for a certain amount of time in one particular stroke. So with a super charger , when you try to push more air in fixed time, will it do any good?

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nikhil shahane September 13, 2011 at 8:39 pm

I fell the theory part is good, may be a microprocessor based chip set will do the precise fuel controlling wat the fuel injector need. Also some other things related to 2- stroke such as detonation should be considered. Y not try the pulsar combustion chamber because its swirl type, twin spark more time for complete combustion of gases!!!

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Sendhil November 23, 2011 at 8:45 pm

The idea seems to be a good one. But have you given a thought to just using a modified head that can house an injector and a spark plug? You can include a feedback O2 sensor in the exhaust port. With a micro chip handling the fuel quantity per squirt, it should be far easier than working on the crankcase. Just a thought, but your approach seems good too. Please let me know if this works. I have been thinking on similar lines for my RX100 (1986) but have never found the time nor someone who shares my ideas

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Kennardy December 27, 2011 at 8:22 am

Hi all, I’m Kennardy from Indonesia. I’m very interested in this project.
the only 2 stroke that still peoduced in Indonesia is Kawasaki Ninja 150r and 150rr.
u can find the detail in motorkawasaki.com, the engine is the same tough.
the reason the bike is still produced is that the stock exhaust chamber has 2stage catalytic converter that makes he bike compliance with euro2 standard.
I’m enjoying the power 2 strokes, n hoping that a direct injection solution are coming for it, although still not receiving a positive step from the kawasaki principal in Indonesia.
i’m interested in “kokusan EFI battery-less which is used in new ossa 280i trial bike.
n i’m fully aggree that u will have the best of 2-stroke if you put the injector at the head with sparkplug. so the injector will sprite the fuel and oil which is premix in the system/pipe when the piston skirt close the exhaust port on upstroke.

i’m excited about Mr. Dhruv Panchal project, the supercharger will give 2 stroke a boost.
the 2 stroke bikes that produced nowadays has superb material in cylinder and pistons like nikasil or electrofusion, and will withstand the stress of being supercharged itself.
thank you n keep this project updated Mr. Dhruv Panchal.

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Kennardy December 27, 2011 at 8:46 am

ow, i’m forgetting something, i had seen from websites that reed-valving the exhaust port will make a decent progress in 2 stroke…

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rajat January 6, 2012 at 10:27 pm

hey dhruv..im working on the same project as im in final year btch (ME) student. there are some problem facin
1)when we connect the supercharger with flywheel the energy of flywheel decreases as a result the motion of the piston suffrd
2)as u said this project improve the efficiency but supercharger,fuel injector is costly overall cost is so high
3)the timing of fuel fuel injector is major prob

waiting for ur reply..

Reply

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