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Old 19th March 2010, 10:38   #1
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Lightbulb Can we add another pair of strokes to the 4 stroke?

I was studying a bit more detail, about the Combustion engines and their cycles.
The Valve openings being relative to TDC and BDC again wrt to speed (in Vtec and VVTec).
Now, If we happen to add, another stroke to the engine, which will "purge" the air out of the cylinder after the Stroke #4, what will be the net impact on the engine?

As in a 4-Stroke engine, four stroke:
1-Intake
2-Compression
3-Power


4-Exhaust.
If we add
+
5-Purge Air intake (Air Intake) **Spark close to mid of Suction stroke
6-Purge Air out(Air Out)



Probable pros:
  1. Reduced heat produced in the engine : Primarily, low heat production rate ie, 1:6 rather than 1:4 (conventional 4S Engine), Also, that would enable the cooling system to be more effecient, perhaps translating into longer running of the engine at much healthier temperatures!
  2. Better FE (offcourse) again due to longer intervals between Fuel going in the cylinder > Also considering Cons #2, to find which would be the conclusion!
  3. Better emission control if we further give a spark at mid of the "purge air intake" stroke, any remainder fuel (if any) will burn too, I am thinking this might as well give a mini power stroke (Experts, please comment on the percentage of unburnt fuel after the combustion cycle in todays 4S engines)
If the unburnt fuel is way too less, the spark at mid of suction stroke would do,
If the unburnt fuel is considerable, then, well, havent thought about that yet!
Probable Cons:
  1. will need to check if the same flywheel, can help charging the 2 extra "purge" strokes! (which I doubt myself, as it might be just enough to power through the 3 non-power strokes in current 4S-cycle!), So that might need some tuning
  2. Perhaps will result in considerable power loss too! (this will, IMO, govern the feasibility of the implementation anyway!)
I was thinking about solenoid operated valves (As the valve sequence is difficult to match with cams)

Would the change be justifiable?
As we are talking about modifications through solenoids, the changes are to be done to the chip itself, I am gauging no other modifications to go with the same!

Experts & Critics, please pour in your views!
Required modifications!?, other problems that may crop up, stalling/knocking!?, some improvisation with the same?

Care.

Ace.
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Old 19th March 2010, 10:47   #2
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Are you talking about one of these?
1. Five stroke internal combustion engine - Patent 6776144
2. Six-stroke engine - Wikipedia, the free encyclopedia
3. Rotary engine - Wikipedia, the free encyclopedia

Using solenoids, sounds like a good option; I'm under the impression that with desmo valves the engine does not have to produce any additional work to open/close the valves. Here's a demo on desmo valves - Ducatidesmo.com
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Old 19th March 2010, 11:04   #3
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Post Close but not exactly, rather different

Quote:
Originally Posted by aargee View Post
Are you talking about one of these?
1. Five stroke internal combustion engine - Patent 6776144
2. Six-stroke engine - Wikipedia, the free encyclopedia
3. Rotary engine - Wikipedia, the free encyclopedia

Using solenoids, sounds like a good option; I'm under the impression that with desmo valves the engine does not have to produce any additional work to open/close the valves. Here's a demo on desmo valves - Ducatidesmo.com
Boy, That was real prompt!

Well, I am not talking about that patent design (link #01)
neither close to link#03.

Well, I saw link#02, in that

Quote:
Velozeta six-stroke engine
In a Velozeta engine, during the exhaust stroke, fresh air is injected into the cylinder, which expands by heat and therefore forces the piston down for an additional stroke. The valve overlaps have been removed and the two additional strokes using air injection provide for better gas The engine seems to show 40% reduction in fuel consumption and dramatic reduction in air pollution. Its is not much less than that of a four-stroke petrol engine. The engine can run on a variety of fuels, ranging from and to.
An altered engine shows a 65% reduction in carbon monoxide pollution when compared with the four stroke engine from which it was developed.
The Velozeta engine features are:
  • Reduction in fuel consumption
  • Dramatic reduction in pollution
  • Better scavenging and more extraction of work per cycle
  • Lower working temperature makes it easy to maintain optimum engine temperature level for better performance
  • The six-stroke engine does not require significant modification to existing engines.
  • Better cooling due to additional air strokes, which mostly removes the need for a cooling system
  • Lighter engine
This six-stroke engine was developed by and awarded the 'Indian Society for Technical Education - National awarded' for Best B. Tech project of 2006. (ISTE/BBSBEC-B.Tech./Award/2006) The technology is being developed by Velozeta, a Technopark (Trivandrum) supported by the National Institute of Technology based in Calicut. Velozeta has been awarded a Phase-I research grant from the Department of Scientific & Industrial Research (Govt. of India) under the Technopreneur Promotion Programme (TePP).
  • Now this is exactly to what I am thinking now!!
  • (I am late by 4 years, I guess!, or Velozeta engine would have been Driverace engine!!)

    Thank you for the feed!
anyway, but we can sure discuss this further!


Care.

Ace.

Last edited by driverace : 19th March 2010 at 11:05.
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Old 19th March 2010, 13:14   #4
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Hope I didn't disappoint you & helped you think more constructively
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Old 19th March 2010, 14:02   #5
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What about the fact that there is only one ignition cycle which is powering 4 or 5 non-ignition cycles.

Compared to only 3 in regular 4 stroke.

Which one would be more powerful/fuel efficient per bhp?
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Old 20th March 2010, 00:51   #6
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Quote:
Originally Posted by driverace View Post
Boy, That was real prompt!

Well, I am not talking about that patent design (link #01)
neither close to link#03.

Well, I saw link#02, in that
  • Now this is exactly to what I am thinking now!!
  • (I am late by 4 years, I guess!, or Velozeta engine would have been Driverace engine!!)

The velozeta engine was developed in The College of Engineering, Trivandrum.
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Old 20th March 2010, 01:09   #7
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But how does this work on a 4 cylinder engine?

A conventional engine with a 1-3-4-2 timing will have :

Cyl 1 - intake
Cyl 2 - compression
Cyl 3 - exhaust
Cyl 4 - combustion

Cyl 1 - compression
Cyl 2 - combustion
Cyl 3 - intake
Cyl 4 - exhaust

Cyl 1 - combustion
Cyl 2 - exhaust
Cyl 3 - compression
Cyl 4 - intake

Cyl 1 - exhaust
Cyl 2 - intake
Cyl 3 - combustion
Cyl 4 - compression

Whats the sequence for a 4 Cyl 6 stroke engine?

Maybe something like this?

Cyl 1 - intake
Cyl 2 - air in
Cyl 3 - air out
Cyl 4 - compression

Cyl 1 - compression
Cyl 2 - air out
Cyl 3 - intake
Cyl 4 - combustion

Cyl 1 - combustion
Cyl 2 - intake
Cyl 3 - compression
Cyl 4 - exhaust

Cyl 1 - exhaust
Cyl 2 - compression
Cyl 3 - combustion
Cyl 4 - air in

Cyl 1 - air in
Cyl 2 - combustion
Cyl 3 - exhaust
Cyl 4 - air out

Cyl 1 - air out
Cyl 2 - exhaust
Cyl 3 - air in
Cyl 4 - intake


Shan2nu

Last edited by Shan2nu : 20th March 2010 at 01:27.
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Old 20th March 2010, 01:25   #8
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Quote:
Originally Posted by aargee View Post
I'm under the impression that with desmo valves the engine does not have to produce any additional work to open/close the valves. Here's a demo on desmo valves - Ducatidesmo.com
It's a bit OT, but what advantage does a desmo valve have over a normal valve ? It's function appears the same to me, to open and close the valve. The only difference I found was that a conventional camshaft directly operates the valves, and the Desmo used a pair of arms to do the same. It might be a stupid question as I'm not what you'd call an expert.
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Old 20th March 2010, 03:04   #9
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Well,

Had heard about the Velozeta engine before as well, along with the Crower engine.

Your original idea also included firing the spark plug during the extra air stroke. That idea though I dont think will work.

The explanation of that is, whatever amount of unburnt fuel is left inside the cylinder will not be very large and will not be very well mixed with the air in the cylinder. This means you may not always get combustion. As the spark plug only ignites a small area around it. If there is no fuel in that area, you wont get combustion. Similarly even if combustion starts, the flame front will end up reaching pockets where there will be no fuel, thus the flame wont be able to move any further.

The velozeta engine just utilises the high amount of heat inside the cylinders to expand the air, and thus extracting more energy from the same amount of fuel. Though exactly what conditions they tested their modified engine in and what results they got, I have not been able to get any solid data. So no idea about the feasibility of any such engine.
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Old 20th March 2010, 11:27   #10
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Post re:

@julupani
Quote:
Well,
...
Your original idea also included firing the spark plug during the extra air stroke. That idea though I dont think will work.
the flame front will end up reaching pockets where there will be no fuel, thus the flame wont be able to move any further...
Ok, I agree about possible uneven combustion. My intention in providing spark for combustion, was to minimise the emission/unburnt fuel in exhaust.
But, then again I was of the view, that if there is considerable amount of unburnt fuel in the cylinder, we can try to burn it (or a part of it,perhaps) in the middle of the suction stroke of "purge cycle".
That way, it might even give a mini-power stroke (not sure about the magnitude, though)

But, I too think, that might cause a knock too!

@anku94
I think rather than relying on cams for valve openings, giving elec-pulses for opening the valves (decided by a MP), would be far better!

Analogy:
MPFI:Carbs:: Desmo:Cams

@Shan2nu

We can try to visualise the process, as
All the normal strokes finish like:
  1. Suction
  2. Compression
  3. Power
  4. Exhaust
then, as we know, some remainder burnt gases & unburnt fuel are there in the clearance volume of the cylinders>




now come two more strokes before we finish the complete cycle.
5. Air Intake (for purging) through Air intake valves
6. Air Out (taken in stroke#05) through exhaust valve.
and that would complete the cycle
then, again from Stroke#1 , cycle 2 begins.

We, need to pitch in these strokes in a 4S Engine

Cylinder I I C P E PI PO
Cylinder II C P E PI PO I
Cylinder III PO I C P E PI
Cylinder IV P E PI PO I C
I-Intake
C-Compression
P-Power
E-Exhaust
PI-Purge Air In
PO-Purge Air Out
We keep the firing sequence same, then, again last two strokes are without any power*
*not considering that the "PI" stroke might just "push" the piston a bit.!


I now think we should also change the firing sequence as we can have

1-3-rest-4-2-rest kind of firing to replace 1-3-4-2 !

@tharakan

Ya, I did notice that too!
wise kids !!

@aplha1
Yup!
1 power stroke powers the other 5 non-power strokes (for each cylinder) - that is being considered already.
whether it will prove more bhp/FE? yet to arrive at any solid result. - my gut says it will be more FE

@aargee
Not at all mate!
Quote:
aargee :Hope I didn't disappoint you & helped you think more constructively
I am really catching up, and I was glad I thought it by myself,(that is not reading it before!), so thats new and right direction for thinking (atleast!)
I will try to work up some more, perhaps may strike some idea of tomorrow !! :Bah: :tongue out:

Last edited by driverace : 20th March 2010 at 11:46.
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Old 20th March 2010, 13:58   #11
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Quote:
@Shan2nu

We can try to visualise the process, as
All the normal strokes finish like:
1.Suction
2.Compression
3.Power
4.Exhaust
then, as we know, some remainder burnt gases & unburnt fuel are there in the clearance volume of the cylinders>




now come two more strokes before we finish the complete cycle.
5. Air Intake (for purging) through Air intake valves
6. Air Out (taken in stroke#05) through exhaust valve.
and that would complete the cycle
then, again from Stroke#1 , cycle 2 begins.

We, need to pitch in these strokes in a 4S Engine


Cylinder I I C P E PI PO
Cylinder II C P E PI PO I
Cylinder III PO I C P E PI
Cylinder IV P E PI PO I C
I-Intake
C-Compression
P-Power
E-Exhaust
PI-Purge Air In
PO-Purge Air Out
We keep the firing sequence same, then, again last two strokes are without any power*
*not considering that the "PI" stroke might just "push" the piston a bit.!


I now think we should also change the firing sequence as we can have

1-3-rest-4-2-rest kind of firing to replace 1-3-4-2 !
Somehow i get the feeling this might work better on a 6 cylinder engine. Then you would have a (power/combustion) stroke at any given cycle. On a 4 pot engine, you might achieve good emissions and FE, but at the cost of engine performance/response.

Maybe if there is a way of making it a variable stroke engine where you could shift between 1-3-rest-4-2 (6 stroke for economy) and 1-3-4-2(4 stroke for performance), that would help a lot.

Shan2nu

Last edited by Shan2nu : 20th March 2010 at 14:00.
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Old 20th March 2010, 15:34   #12
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awesome take!
the 6 cyl idea is cool!
I was pondering abt variable firing sequence too :eek (spooky coincidences)
that's very much possible, provided we have solenoids. (seems real tough with cams, though)

care.

Ace.

Last edited by driverace : 20th March 2010 at 15:48.
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Old 20th March 2010, 20:53   #13
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Research on 6 stroke engine has been going on for long now.Some of my college mates have developed their 6 stroke cycle and the cycle can run on any fuel that is it is universal.Their paper has been selected by Imperial college of London.Unfortunately I dont have any details of their paper as of now.But this is one interesting topic.
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Old 21st March 2010, 17:43   #14
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Quote:
Originally Posted by driverace View Post
@julupani
Ok, I agree about possible uneven combustion. My intention in providing spark for combustion, was to minimise the emission/unburnt fuel in exhaust.
But, then again I was of the view, that if there is considerable amount of unburnt fuel in the cylinder, we can try to burn it (or a part of it,perhaps) in the middle of the suction stroke of "purge cycle".
That way, it might even give a mini-power stroke (not sure about the magnitude, though)

But, I too think, that might cause a knock too!

@anku94
I think rather than relying on cams for valve openings, giving elec-pulses for opening the valves (decided by a MP), would be far better!

Analogy:
MPFI:Carbs:: Desmo:Cams

@Shan2nu

We can try to visualise the process, as
All the normal strokes finish like:
  1. Suction
  2. Compression
  3. Power
  4. Exhaust
then, as we know, some remainder burnt gases & unburnt fuel are there in the clearance volume of the cylinders>




now come two more strokes before we finish the complete cycle.
5. Air Intake (for purging) through Air intake valves
6. Air Out (taken in stroke#05) through exhaust valve.
and that would complete the cycle
then, again from Stroke#1 , cycle 2 begins.

We, need to pitch in these strokes in a 4S Engine
Cylinder I I C P E PI PO
Cylinder II C P E PI PO I
Cylinder III PO I C P E PI
Cylinder IV P E PI PO I C
I-Intake
C-Compression
P-Power
E-Exhaust
PI-Purge Air In
PO-Purge Air Out
We keep the firing sequence same, then, again last two strokes are without any power*
*not considering that the "PI" stroke might just "push" the piston a bit.!


I now think we should also change the firing sequence as we can have

1-3-rest-4-2-rest kind of firing to replace 1-3-4-2 !

@tharakan

Ya, I did notice that too!
wise kids !!

@aplha1
Yup!
1 power stroke powers the other 5 non-power strokes (for each cylinder) - that is being considered already.
whether it will prove more bhp/FE? yet to arrive at any solid result. - my gut says it will be more FE

@aargee
Not at all mate!
I am really catching up, and I was glad I thought it by myself,(that is not reading it before!), so thats new and right direction for thinking (atleast!)
I will try to work up some more, perhaps may strike some idea of tomorrow !! :Bah: :tongue out:
Quote:
Originally Posted by Shan2nu View Post
Somehow i get the feeling this might work better on a 6 cylinder engine. Then you would have a (power/combustion) stroke at any given cycle. On a 4 pot engine, you might achieve good emissions and FE, but at the cost of engine performance/response.

Maybe if there is a way of making it a variable stroke engine where you could shift between 1-3-rest-4-2 (6 stroke for economy) and 1-3-4-2(4 stroke for performance), that would help a lot.

Shan2nu



I think this would work on smaller and lesser cylinder engines as for the bigger engines(4+ cylinders) there would be more work done than power produced unless the power produced by those extra strokes is good enuf...

Though good topic as it is making my mind work out endless possibilities....
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Old 24th March 2010, 09:18   #15
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Quote:
Originally Posted by anku94 View Post
It's a bit OT, but what advantage does a desmo valve have over a normal valve ? It's function appears the same to me, to open and close the valve. The only difference I found was that a conventional camshaft directly operates the valves, and the Desmo used a pair of arms to do the same. It might be a stupid question as I'm not what you'd call an expert.
Sorry to respond late, but from what I read & understand, the desmo valves saves the little energy to lift the valves with springs by adding additional cranks. I seriously wonder how much of saving this will add upto to the extra power, but Ducati's having been proving it on the race tracks, so I'm having hard time to believe this.

@driverace - Thanks for the positive spirit; also see how weird this sounds - when a multiple cylinder engine idles, how about keeping the engine alive only by firing a single cylinder & shutting off all other cylinders? Is this possible at all?

Last edited by aargee : 24th March 2010 at 09:23.
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