Power Junkies! 2-stroke Chambers (Domes) for Real Power on Pump Gas.. What if?

[gtfoxy]

If you are looking for Maximum Compression ratio and Power, on pump Gas, then this thread is for YOU!

I'm not trying to sell anything...

Overview
Everyone pretty much knows the current state of what compression ratios can be run, within certain detonation thresholds, on given fuel at a given altitude. While certain applications and parts and tunes may vary among certain combinations and brands, there is still a predominant state of being that is the limitation for Pump gasoline, that is, with current "conventional", Dome design.

So many think that residual heat generation from the combustion process is a prerequisite in 2-stroke engine operation and can not be avoided. That is FALSE!

It is my perspective that there is a fundamental flaw in the design and operation of this "Conventional" mind set. This flaw, as I see it has traversed itself in a way of approaching detontaion thresholds and thus power productions on a given octane fuel.

The Problem
As it stands right now, with current Dome design, people are having to turn to, in alarming quantities, High octane racing fuels in some form or another. This being in the form of Pump/Race gas mixes to out & out straight racing fuels, or even worse Av-Gas.

Take one glance through these forums especialy, as well as others, and a popular trend becomes quite aparent. That is, in order to run elevated cylinder pressures a more detonation resistant fuel is needed.

We all undertsand WHY it is done. This is simply because nobody wants their junk to blow up, but we don't see the real reason behind this "Why". Atleast not yet fully as an industry and consumers. We see the detonation or pre-ignition aspect of it, and while the cause is apparently clear, the solution doesn't appear to be so. That is, atleast, not yet.

Current State of Technology
The current design of domes have some very interesting traits that lend themselves to being very pooor in Flame propogation, Quench area Detonation, Directional pessure wave control, and energy transfer. No matter whos "better" design you choose from you undoubtedly end up with a final point of increased compression ratio before detonation, from one of the above mentioned sources, rears its ugly head. Then begins the travel down the path to more detonation resistant fuels.

Many decades have been spent trying to refine this basic architecture of a rased dome chamber. If there was a way to make this design perform better, it would undoubtedly have been found by now, right?

There is currently a multitude of maufacturers each with there own take on this old concept. Each being only marginaly better than the least able one on up. They are purchased in droves every year by hopefull enthusiasts such as ourselves looking for that extra performance to be found in a bolt-in part. Yet in the end, we feel somewhat duped as our expectations have led us astary to real world gains.

We are left eventualy resorting to the tried and true engine savior that is high-Octane racing fuel.

Race Gas sucks!

Before I get a bunch of hate mail on bashing race fuel, hear me out...

For so many the avenue of more power and higher octane requirements is a slow and resistant path. It starts off as mixing pump fuels and race gas to save money and to add just that extra bit of protection to keep from junking your engine. Then as your desire for power increases you begin to go in transistion from 50/50 mixes to 60/40 to 70/30 and so on. Then the next thing you know you are carrying 50Gal drums to your outings so you don't run out of the go juice that keeps your beast alive and breathing.

The cost of race fuel vs Pump gasoline is irrefutable. The availability is much more of a pain than many like to realize or admit. There is the storage, the transporting, the known environmental and health risks involved with handling and using it. It is stuff that just doesn't belong in engines if they don't need it.

Furthermore, many do not know HOW race fuel is able to have the burn resistance that it does. Not to mention how this impacts actual power production. Race fuel uses much heavier Hydrocarbon chains that are much more difficult to break up. They do not vaporize as well and therefore their detonation cielings are elevated. The propblem is that most engines run better on fuels with a higher ratio of easier vaporizing components, or light hydrocarbons. The light hydrocarbons are easier to evaporate and combust and actualy lend to increased energy conversion when used in the proper application.

Fact is an engine, that doesn't require the octane, will make more power on pump gas fuels. So we need to make the engines not require the octane. Sounds simple enough, right?

What is needed
Without a doubt what is needed is a chamber design that eliminates the problems of conventional design theory. That much is clear.

Challlenging Convention
If the conventional way of designing a chamber is fundamentaly flawed, why continue to use it? Something has to be better than something that works so apparently awefull.

It hasn't been discover yet, right? WRONG!

I have been blessed with being shown a design of chamber that challenges what convetional thinking tells us. Convention tells us that over certain compression ratios that running pump gasoline is not possible, that is FALSE!

Convention also tells us that residual exhaust heat enegry in the form of EGT is unavoidable. It isn't if energy conversion, by pressure wave to surface area interaction, is done properly.

I'm not stupid, Just crazy!
Don't think for a minute that I would come on a national site like this and drop a baited hook in the water without the test to haul in what I am fishing for.

The design I am talking about has been proven, now it needs to be validated.

What if...
I am not going to give specifics here but simply ask "what if?".

What if heat energy was being traded for compression energy?

What if 15-16:1 Compression could be ran on 87octane (91RON) whether at sea level or in the mountains?

What if this was with twin pipes or single pipes?

What if Cylinder temps were reduced because of drastic improvements in energy conversion eliminated piston siezing and exhaust side destruction of pistons?

Open Source
I know what I am saying is way beyond convention and that is why it works. I hope this thread will be filled with conversation and exchanges of ideas.

If anyone has questions on how these domes work I welcome the exchange. I will gladly share whatever knowledge can be divulged without giving it ll away. if someone figures it out on their own, then so be it, more power to them.

To prove that I am not just blowing smoke, I am going to be showing my findings in a semi-open source manner. I am not the originator of this design, just the person whos gets to refine it, for our market demographic, and realease it for all to share. As such...


Volunteers needed!
I am in need of 5 very specific test subjects to run these chambers, for FREE!. Before people get excited and I receive a bunch of requests I must be very clear on what I am looking for in test subjects.

The following are requirements for what I am looking for:

1) The sleds must be Carbureted only!

2) I am looking for the following manufacturers/ Mods

1 Polaris turbocharged sled, any engine size

2 AcrticCat sleds, any engine size, one N/A one turbocharged

2 Ski-doo sleds, any engine, one N/A one turbocharged

3) Sleds must be equiped with some form of EGT and Wideband monitoring, More data aquisition capabilities would be great

4) I must be supplied with a stock bridge for each vehicle that will be recieving chambers. You will get your bridges back, modified, to accept these chambers. I am doing this to save time and money. You will be free to test them at your leasure and simply provide me with your findings and data.

Closing
I know what I have stated will be hard for many to believe, and that's OK. I hardly believed it myslef. But what I am saying is True and Honest. Believe me, I wouldn't be going through all this trouble and give away my hard work for nothing.

I know there are a lot of people on here that are Dying for something like this for their sled. They are tired of wasting money on race gas and other high octane gasolines and are craving a real, honest design that performs as stated.

Again, I embrace input and question form anyone. I will do my best to answer questions anyone may have.

 

[MCIVER]

Why are you not interested in EFI sleds? It would seems those would make the most sense to be testing on since the fuel adjusts for the conditions and can remain a constant. Not to mention that EFI is what most sleds are now.

 

[Himark]

Clearly if your going to run boost on any motor you will have to drop compression, if you do it by raising head or "new dome" your still going to HAVE to lower it. You can do it that way or with piston re-design. I fail to see how any dome design can get you away from race gas and still have boost period. I could see a specific piston design that could stand the heat better letting you run a bit higher but that would have nothing to do with domes and pre-det is still pre-det you will just have more time to resolve it without failure.

**edit, on a side note if this was some remarkable discovery I would think the millions of dollars being spent on engineers at SVT, ROUSH, Dodge performance, GM performance groups would be all over being able to get rid of that sticker on the gas cap that says "High octane only"

 

[MCIVER]

Himark,

I'm sure it is possible to slow down burn time through head design, I think the question would be is there a power loss in doing so ? and a 4 stroke can't really be compared to a 2 stroke as for as head design goes, so that could be why some companys can't or haven't done it.

 

[gtfoxy]

Why are you not interested in EFI sleds? I would seems those would make the most sense to be testing on since the fuel adjusts for the conditions and can remain a constant. Not to mention that EFI is what most sleds are now.

Thanks for coming in an participating! You ask a very good question.

I am not completely against having people with EFI using the chambers I am working on.

In these begining stages of validation it is important, however, that a more consistant form of fuel homoginization is utylized.

We must first view every form of fuel delivery system as a system in which air and fuel are combined to create not only a mixture in proper mass ratio but also complete homoginazation of fuel to air in that mixture.

While it is true that EFI is fast becoming the prefered method for fuel delivery by sled manufacturers we must realize the main reasons for this. We must also then acknowledge it's inherent shortcomings.

You hit the nail on the head as to why EFI is on the track to being the only form of fuel delivery in sleds. EFI can compensate quickly for changing engine and atmospheric conditions to maintain a given state of tune. Unfortunately this state of tune may be far from what a properly set-up engine needs. What I mean by "properly set-up" is from the perspective of proper engine dynamics.

EFI also does a better job, for the time being, of vaporizing the fuel than Carbs traditionaly used on Sleds. Simply put carbs used on sleds even to this day do an awefull job at their job, and are being given the pink slip... In short, the carburetors used on sleds for so many years do a awefull job of vaporization and fuel metering. That is the main reason why EFI has become a prefered method of fuel delivery, for now that is.

Unfortunately when a chamber, as well as an engines operating dynamics, is incapable of proper distribution of the fuel/ air mixture in the chamber a properly homoginized mixture is prefered, necessarily, to a better vaporized fuel presence. This not not to say if a better vaporized mixture could be had, at the same time as properly homoginized, it wouldn't be better. It is simply at this juncture a variable that would possibly lend to more unknown issues in the case of properly staged pressure development within the chamber. A poorly homoginized mixture would not allow for proper pressure wave development because the fuel is not where it needs to be within the chamber as the flame propogation reaches certain regions in the chamber.



Ask yourself this: If we know that we have such a shortcoming in our chamber designs that they can not convert a given fuel/ air mixture into mechanical energy, with this being the most important aspect of combusting an fuel/ air mixture, without a profuse generation of heat energy, then what hope does the rest of the engines dynamic properties hope to accomplish?

We must also understand that the Sled manufacturers shot themselves in the foot by voluntarily adopting EPA standards without first addressing what engines realy need to become clean producers of power. Vaporization, homoginization and distribution of fuel/ air then followed by efficient energy conversion.

EFI is prefered because it can tailor an engines tune based on these EPA mandates. Mandates that provide emission outputs of various gas ratios in the exhaust. Ratios that quite honestly can be attained if the engines operating dynamics can create a situation where these gas ratio developments can occur at the proper sequence, and in the proper ratio.

We now, unfortunately, find ourselves at a crossroads in what is going to be available by manufacturers in the near future. It is for this reason that some very specific things need to happen if the proper solution to the problems are going to become known and presented to industry.

What I am saying is that if people, meaning consumers (US!!), can undertsand what needs to be done, then manufacturers, not wanting discention among their consumers, will have to build engines, and management systems, within these proper dynamics.

Simply to say an EFI vs a carb is better is a misnomer, a falsity, when viewed from a certain perspective. Carburetors are simply a mixing device and should be viewed as such. AS such any mixing device can be controled to deliver a proper, or desired, fuel/ air mixture at a given load/ RPM. If engine dynamics were then such that EFI's ability to vaporize fuel better were negated, then why must it be used?

 

[gtfoxy]

Awesome!!

Himark,

I'm sure it is possible to slow down burn time through head design, I think the question would be is there a power loss in doing so ? and a 4 stroke can't really be compared to a 2 stroke as for as head design goes, so that could be why some companys can't or haven't done it.

This is truely an awesome statement! People take note...

Yes the burn rate in traditional designs is such that it is too fast for the shape of said design. That is not to say that it is not too slow for another... Let me explain...

If a given burn rate is achieved, by a given chambers design, that chamber must be able to present the acceleration of mass that is the combusting gases to where it needs to be presented, the piston face. Surface interaction that slows the burn rate will also lead to increase energy conversion.

Burn rate is not the be all to end all, it should simply be a function of given pressures and state of vaporization and homoginization within the chamber. If the mixture, as well as pressures, in the chamber is proper, flame propogation will occur at a rate befiting the energy conversion capabilities of a given chamber design with a given rod/ stroke ratio.

Chambers designed to achieve fast burn rates are not what is really important. A given burn rate is not usefull if the acceleration of mass is not converted into mechanical energy, leading to a reduction in residual temp.

Slowing the burn rate down with a increase of surface area leads to proper conversion of energy for a given application. The reduction in temp is not from a necessarily slower burn rate but is from this conversion of kinetic energy to mechanical energy. There is less energy left to become heat energy. That is not to say that you can not only slow the rate of heat development while increasing wave dispertion through the chamber, because you can, but the chamber must achieve this.

Yes you are exactly correct that doing this in the realm of a 4-stroke becomes much more a daunting task when ech engines basic architecture is taken into account.

2-strokes fortunately are not stradled with such shortcomings and their chambers can be better tailored to their particular dynamic properties.

 

[MCIVER]

do you have any cad drawing or pictures of this design.

 

[gtfoxy]

Clearly if your going to run boost on any motor you will have to drop compression, if you do it by raising head or "new dome" your still going to HAVE to lower it. You can do it that way or with piston re-design. I fail to see how any dome design can get you away from race gas and still have boost period. I could see a specific piston design that could stand the heat better letting you run a bit higher but that would have nothing to do with domes and pre-det is still pre-det you will just have more time to resolve it without failure.

**edit, on a side note if this was some remarkable discovery I would think the millions of dollars being spent on engineers at SVT, ROUSH, Dodge performance, GM performance groups would be all over being able to get rid of that sticker on the gas cap that says "High octane only"

High Compression ratios by itself does not lead to detonation... Detonation can be caused by too LOW of a compression ratio.... Try running an engine on a 2:1 compression ratio and tell me what happens...

An engines compressive capabilties are a determining factor for its possible energy conversion. It should be viewed simply as such. Thusly dynamic compression increases hold the same propensity for increased energy output. The engine only cares about the increase in mass density to volume ratios, not how it is attained.

What is important to consider when any form of forced induction is present is what is happening to the dynamic compression. More importantly, how that dynamic compression is utilzed...

If the increase in dynamic compression, ie cylinder pressures preceding combustion, is increased the burn rate in that chamber is increased. If the chamber can not distribute the kinetic energy created by the elevated temperature once the the combustion pressure wave is created, heat energy is created and then it will detonate. There are also other factors associated to heat and sound waves in the chamber that lead to non quench related detonation.

If the chamber, however, is such that, regardless of preceding pressures, fluid expansion of the flame front is achieved, with increased energy conversion leading to a reduction in temp dwel time, then detonation will not occur.

AS it sits now the actual cause of detonation in a forced induction, as well as any 2-stroke engine can be viewed as being caused by too much residual heat energy being introduced into the chamber because of the preceeding combustion events inability to convert kinetic energy. If EGTs are lowered and thusly the next combustion cycles preceeding temp in conjuction with it, cylinder pressures can be increased. This results in greater energy conversion.

That is why I previously asked what if heat energy is exchanged for compression energy...we need to exchange heat energy for compression energy! That is the pathway to greater power production with lower BSFC's.


Good point

In regards to the big auto manufacturers...

If manufacturers know a given design is better, and believe me they do, and how to achieve the things needed to run it, what does that tell us...?

 

[gtfoxy]

do you have any cad drawing or pictures of this design.

Yes

 

[MCIVER]

are you changing the placement of the plug in the cyl ?

 

[gtfoxy]

It is still centraly located, if that is what you are asking.

 

[MCIVER]

I was wondering if your changing the height of it in cyl. and what are your changes in the head. I'd love to see those pics

 

[gtfoxy]

I was wondering if your changing the height of it in cyl. and what are your changes in the head. I'd love to see those pics

I bet you would!

You have a PM sir.

 

[NINJIN]

I certainly would be really interested in seeing these pics as a engineering student that is very interested in snowmobiles. I took an automotive engineering class this semester with a teacher that worked in engine development for gm for 20 plus years and he really fueled my fire for snowmobile engines. I know many others are probably feeling the same as me that it goes against all convention to be able to run high compression ratios on pump gas. On 4 strokes you can use long intake durations to to make the effective compression low enough to run pump fuel while having high static compression ratios. This isn't really possible on two strokes. I am very interested in how you believe this can be done...

 

[rigrat]

Would you by any chance be using a deep dished or short piston with no combustion chamber in the head? The benefit of this is the combustion chamber is actually the cylinder. There will be no dome on the piston to restrict the flame travel. I have seen some competition engines built to run on regular fuel with high compression ratios that were built along this line of thinking. If you look at the combustion chambers of the highest performance, naturally aspirated race engines today you will find super small combustion chambers and no domes on the pistons. If a person follows the engine building contests in the POPULAR HOT RODDING MAG you will see high compression ratios using regular fuel. I realize i am comparing 2 strokes and 4 strokes but it is being done.

 

[gtfoxy]

I certainly would be really interested in seeing these pics as a engineering student that is very interested in snowmobiles. I took an automotive engineering class this semester with a teacher that worked in engine development for gm for 20 plus years and he really fueled my fire for snowmobile engines. I know many others are probably feeling the same as me that it goes against all convention to be able to run high compression ratios on pump gas. On 4 strokes you can use long intake durations to to make the effective compression low enough to run pump fuel while having high static compression ratios. This isn't really possible on two strokes. I am very interested in how you believe this can be done...

I will tell you right now, and you need to take this entirely to heart, FORGET CONVENTION!!! Challenge EVERYTHING you were taught! This is because it was from a perspective not looking at things as they actualy occur.

Conventional concepts are a dirivative on a skewed perception of many engineering assigned attributes such as effective compression ratio, volumetric efficiencies and the like. It's mostly all BS with a small place in what really matters.

They simply lead down the same dead end paths they have for years. Nowhere fast...

As for how this can be done, go back and re-read what I have written. It is mostly all there, except the very important shape of the chamber.

Here is is what may help, Close your eyes and begin viewing the whole process from the induction cycle on through to the combustion cycle and view how the combustion process comences, transitions and finishes. Then imagine the interaction of this process of the chamber shape and piston position, as it apporaches and passes TDC, in the process. Also visualize seperately what happens as the accelerated mass interacts with the piston and the pathways of enegry conversion that is created.

I am going to really blow your mind now...

Under proper engine dynamics this chamber design has already been run to 21:1 compression on pump gas! And I mean 91RON! That was not the limit mind you, simply where the R&D stoped.

Ponder that for a moment...

Still want to follow convention?

If ANY one wants to see what I am doing, I made it really clear, you need to simply volunteer. I am sure everyone has a sled that would simply need and EGT and Wideband in order to meet my criteria, it's that simple.

 

[gtfoxy]

Would you by any chance be using a deep dished or short piston with no combustion chamber in the head? The benefit of this is the combustion chamber is actually the cylinder. There will be no dome on the piston to restrict the flame travel. I have seen some competition engines built to run on regular fuel with high compression ratios that were built along this line of thinking. If you look at the combustion chambers of the highest performance, naturally aspirated race engines today you will find super small combustion chambers and no domes on the pistons. If a person follows the engine building contests in the POPULAR HOT RODDING MAG you will see high compression ratios using regular fuel. I realize i am comparing 2 strokes and 4 strokes but it is being done.

Ok, some very interesting things here.

To answer your question frankly, no, there is no change in the domes on the pistons needed for this chamber design. It is all in the chamber itself.

The shape of the piston and chamber must react to the accelerating mass in a very specific manner. This must be done so as to spread the pressure wave in a much needed manner. Surface area must be balanced with volume and compresseion height to achieve the desired interaction. This interaction is important but it still in the end comes down to seal boundary and pressure retention in the chamber. Otherwise it is all for nothing.

2-stroke or 4-stroke matters not. It does matter, however, if the fuel is not vaporized, homoginozed and distributed properly. If the chamber is proper, the vaporization, homoginization and distrubution become somewhat secondary. Problem is in four strokes this is very hard to accomplish so the importance on a slide rule factor then goes the other direction, Understand?

I also follow this series and have to enduringly follow them as the same mistakes are made over and over again. Many times these builders chase volumetric efficiencies at the cost of energy conversion. Only recently has a focus been on chamber surface interaction.

 

[Bigblack]

This being in the form of Pump/Race gas mixes to out & out straight racing fuels, or even worse Av-Gas

Noooooo....not AV gas! Whatever.

 

[CBX]

this is a very interesting concept. I believe its do able too. It gets done every day on many cars like subaru's. Pump fuel and turbo's.

I think in the sled industry, everyone has opted for leaded fuels rather than the right intercooling setups and proper ratios with readily avalible head designs.

Intercooling I feel is a big part of this. Air to Air exchangers are the only real common place system in sleds. Or non at all. Only one consumer kit has Liquid to air intercooler.

There may be more costs from pumps, plumbing issues and an exchanger in snow contact, but to me it just makes too much sense. What better cooling medium than snow?

Air to airs just aren't really practical. Sure they do work with snow on them. But how effective is it then? The majority of the exchange medium isnt being cooled.

I've talked with a few individuals about head design in this. All three guys seem to agree that a larger squish, a ratio in the 10 to 11 range, retarded ignition timing and an effective intercooler will make a pump fuel turbo develop very good power.

If there was a head avalible that could keep high ratio's and still do pump fuel, turbo or non turbo at whatever elevation....... man you would sell a bazillion of them.

I would buy 3 right now. Its the one thing keeping 2 stroke turbos from being in every garage. Fuel cost and reliability. Everyone has nuked a motor on a trip some where and everyone can agree how un-fun it is.

Price of Race leaded fuels are crazy. Av is somewhat effective alternative price wise. In the mid 4 dollar range most places. Sunnoco 110 in bulk locally is in the $6.25 range. If you want 112 or other specialty fuel its even higher. Not hard to spend $70-90 in fuel on day for one machine. Not to mention if you put alot of miles on in a season. I had one day i used 14 gallons of fuel to ride 130 miles. Race fuel doesn't excite me much at all.

 

[gtfoxy]

Noooooo....not AV gas! Whatever.

I have no idea what your intentions were with this post but here it is so people can see the fault in AV-gas useage...

LL Av-Gas in only Low lead as it relates to aircraft fuel. Due to altitude operation, much greater than what sleds see, lead is a much needed element in the combustion process.

As altitude drops this requirement is much less needed.

Lead in fuel is a buffer to combustion, or it absorbs energy as the fuel is burned. Nitrogen in N2O does the same thing.

Anything present in the fuel that absorbs energy will result in a net loss in energy converison.

Just because it is cheaper than real race fuel does not make it better...