Supercharged 2-stroke, who tried it?

[Bjorge1]

I would like to know who has tried it, I wrote a subject two days ago and all I got was don't try it, it don't work. I seem to always make things work, with enough time. If you have tried it, please let me know, I would like to find out how you went about it, I have some good ideas but you might have had the same. I info would be appreciated.

 

[roughrider99]

u can't supercharge a 2 stroke, its been tried and just does not work.

 

[winter brew]

I know of someone playing with this right now.......I hear he is getting some good results. Maybe he'll chime in???

 

[Reeb]

Portgrinder did this on a 600 custom billet motor. Was for the SAE Challenge. Had some hiccups that they couldn't/didn't get figured out by the time the competition was ran but after seeing a few short clips of it, and rider reviews.....it worked pretty good. Cost effective.......no.

 

[Bjorge1]

Thank you

Finally, some replys worth hearing, not just IT DON'T WORK. I guess I should give up since people who haven't tried it say that it is a waste of my time. That is why I said in the beginning, that if you have tried it I would like to talk to you. and if not, don't bother responding. I love a challenge.

 

[gus bohne]

Finally, some replys worth hearing, not just IT DON'T WORK. I guess I should give up since people who haven't tried it say that it is a waste of my time. That is why I said in the beginning, that if you have tried it I would like to talk to you. and if not, don't bother responding. I love a challenge.

You will not get the answer you want to hear, please..
PROVE us wrong, accept your own challenge and spend your money to make it work.

OR

search the S.A.E archives , all the equations are there as well as the countless souls who have wasted their time trying to make it work above the 5 psi threshold.
Gorgon Jennings should NOT have used that as an example in that book.

All the statements made are correct, waste out the pipes and other overlap issues that ARE corrected by the turbos balance of flow to pressure.
I'm sure YOU can overcome this with all your talents. prove us wrong then you can type all the stuff you want..


Gus

 

[allblowdup]

Ok it does not work and here is why. The exhaust port is still open after the transfers close. You can restric the exhaust and you will make the power but it is way to difficult to have th eright restriction. A turbo is a an infanetaly variable exhaust restictor that is directly correlated to boost so that is why it works. These days with computer controls it could works but would be alot of work and never make the power a turbo does.

 

[Backcountry]

http://www.mtukrc.org/download/alberta/alberta_design_paper_2005.pdf#search=%22%22CLEAN%20SNOWMOBILE%22%20ALBERTA%20SUPERCHARGER%22

Check out the Rolls Royce Crecy and the Napier Nomad. Check out Saber Racing's attempt to SC a custom ATV powerplant www.saberracing.com (not sure how much stuff he has on the public domain). Same for GP Engineering in Kansas.

May the force be with you...

 

[Drifter]

Put a super charger on and a turbo.

 

[lostNthesauce]

boysen is working on a mechanicaly timed exhaust valve cylinders, so you could in theory get around the exhaust pressure issue{turbos make there own back pressure}. with no back pressure it blows alot of the fuel out the pipe.you need to adress the heavy crank load issue, supers put alot of stress on the end of the crank that drives the belt. Dual spark plugs in each head and a programable ignition would be a place to start {super charger tends to blow out spark under boost and drop that cylinder}. we were runnin a vortech centrifugal supercharger, i would think that or a paxton would be a way to go. we wasted a lot of time and money on one, it worked but not well enough to justife the cost. turbos and big bores with nitrous much more cost effective. you probably could make one work, but probably wouldnt be very cost effective or competitive. but give it a try.

 

[Bjorge1]

boysen is working on a mechanicaly timed exhaust valve cylinders, so you could in theory get around the exhaust pressure issue{turbos make there own back pressure}. with no back pressure it blows alot of the fuel out the pipe.you need to adress the heavy crank load issue, supers put alot of stress on the end of the crank that drives the belt. Dual spark plugs in each head and a programable ignition would be a place to start {super charger tends to blow out spark under boost and drop that cylinder}. we were runnin a vortech centrifugal supercharger, i would think that or a paxton would be a way to go. we wasted a lot of time and money on one, it worked but not well enough to justife the cost. turbos and big bores with nitrous much more cost effective. you probably could make one work, but probably wouldnt be very cost effective or competitive. but give it a try.

I saw that mechanical timing valve at Hay Days, looks like a good idea but long gevity wise, we will see. I was planning on a vortech style myself. You say that there is no back pressure? I though the pipe in design was to always hold 3-5 psi of back pressure, no matter how hard you pushed exhaust into it. I thought it would be the way to go because it would eliminate alot of B.S. like the intercooler and so on. I was planning on putting a blow off valve on the intake side because I found out that excess pressure creates and engine brake under deacceleration and this way I could easily adjust the boost pressure. Do you still have pics of what you did? Any ideas would be great. This is one of those things that I need to try for myself, even if I feel it will fall on its face.

 

[lostNthesauce]

a standard two stroke pipe does provide some backpressure/scavaging effect, butnothing like you'll need. you will have to try several pipe lenghths, cone sizes, and diameters... i will see if i can dig up some old pics... what size motor r u running this on i might be able to make you a deal on a used vortech, after several discussions with vortech they had us run a super off of a big block chevy on our triple 1000. you'll need electric start.

 

[allblowdup]

I ran a root type supercharger back in 1992 and it worked great from a making boost point of view. It was not hard on the crank and I did not need twin plugs or electric start. It made 10lb's of boost instantly. The pipe will make a little back pressure but you need to always have that 4/5 psi above intake pressure so at 10psi you need like 14 or 15. I made a mechanical varialble exhaust restirctor that balanced pipe pressure to intake pressure and it seemed to work not to bad but I got real busy at work and haven't touched it since. The restriction is not the same at 7000 rpm as it is at 8000 rpm so it needs to be variable. It need to take into account temp, humidity, boost pressure, rpm, throttleposition in order to do it right. The turbo does that for you all in one. A computer controlled exhaust valve could work if it was set up properly.

 

[Bjorge1]

Thanks

appreciate the info, this is really what I was looking for on info. It is nice to talk to people who have actually tried and not just people who read other people threads and think they know what is going on.

 

[Boyko]

A right turbo does a primo job of controlling back pressure in the pipe, this is key in making power on a 2-stroke. There are 2 mechanical links between boost and pipe pressure on a turbo. The first is the shaft between the turbine and compressor wheel, at spool up energy that is needed to make boost is created by the turbine by building pipe pressure fist, the energy is transferred through a shaft to the compressor wheel which makes boost. Secondly the wastgate which is operated by boost relives exhaust pressure to control boost.

You are going to have a hard time simulating this level of back pressure control with a supercharger.

If your going to do it I wish ya luck, I sure a few guys on here can toss you some good ideas on how to control you pipe pressure. If your going to do it post some pics of what you got to work with and what you have done to this point. You got a long way to go with it and a lot to learn from it.

 

[SnoDmon]

What exactly is Boyessen doing with mechanical exhasut valves? It seems to me that if you could make an exhaust valve that only opens while the piston is traveling downwards and closes before it travels back upwards that there should be no problem boosting with a supercharger. Also seems to me that a tuned pipe wouldn't be neccasary in this scenario. The mixture would be trapped by the valve, wouldn't it? But also this adds weight and more moving parts. Weight isn't such a big deal I guess, but more moving parts would mean that it would be harder starting in cold weather, which is why traditionally snowmobiles have used 2 strokes. But I would like to know why you want to do it. As I've heard with car motors, superchargers build bottom end power and start to lack boost on the top end, where turbos lack bottom end and make better top end power. And top end power is desired on a snowmobile. I hope noone takes all that I have said too seriously. I haven't tinkered with anything at all similar and I am just brainstorming. This is something I find very interesting and would like to see what happens. So please post pics and let us hear some results. Oh, and I would also like to know what size and kind of motor you will be using. Best of luck.

 

[drmiller100]

I ran a root type supercharger back in 1992 and it worked great from a making boost point of view. It was not hard on the crank and I did not need twin plugs or electric start. It made 10lb's of boost instantly. The pipe will make a little back pressure but you need to always have that 4/5 psi above intake pressure so at 10psi you need like 14 or 15. I made a mechanical varialble exhaust restirctor that balanced pipe pressure to intake pressure and it seemed to work not to bad but I got real busy at work and haven't touched it since. The restriction is not the same at 7000 rpm as it is at 8000 rpm so it needs to be variable. It need to take into account temp, humidity, boost pressure, rpm, throttleposition in order to do it right. The turbo does that for you all in one. A computer controlled exhaust valve could work if it was set up properly.

this guy really did it, as my experiences were exactly the same as his.
you need to plug the stinger to build boost.

my theory was you only need big boost at WOT, so i used a centrifigal blower and aimed for boost at WOT.

 

[fantom]

Some other thoughts

My studies are leading me to think about the problem a little different. Yes by raising back pressure you are also changing the volume of the pipe. As we all know, larger two stroke engines typically need larger volume pipes. A boosted engine thinks it is a larger engine. Changing back pressure is alot easier, right now anyway, than changing to volume of the pipe as rpm increases. The whole idea of placing a restriction in the exhaust to make horsepower is counter intuitive. Experimenting is still continuing.

I am also leaning towards the centrifical instead of the screw type I am currently using. I think using a EMS (Motec, AEM) to electronically control the servo adjusting the backpressure might be my next step. Maybe using the servo to control a gate to additional pipe volume might be the answer. Maybe use a larger volume pipe or two single pipes to start with. And then fuel injection with the EMS. Maybe use a vented turbo to let the turbine control the backpressure and let the SC provide the boost as a way to study the problem. I have the complete setup mounted on my dyno so I can test each variable.

I would like to hear from those who have real data and experience with this issue to PM me and compare notes. I think once the phenomonem is understood some of the finding my open up or improve what we are doing today with SC and turbo engines both 2 and 4 stroke.

fantom

 

[portgrinder]

We spent a pile of time on it as reeb said. We were trying to make it clean too, so our efforts were divided a bit.

In the end we ran out of time and only had it working "ok".

As others have said, the key is in making the pressure in the pipe relative to your boost pressure.

Can it work, yes i have no doubts. Can't see how it would ever be as efficient as a turbo though. You need to put twice the load on the enigne. In a turbo sytem, the load on the exhaust is what spins the charger. In a supercharger arrangement you need to put that same load on the exhaust plus drive the supercharger off the crank.

To put it in perspective, the year before we fit a GSXR 600 engine in the same sled. Removed trans, dry sump, custom efi, exhaust, ran the primary off the crank. All under the stock hood. That was way easier.

 

[schooter]

Check out this prototype from LIM Technology

http://www.limtechnology.com/Pages/conventional_twostroke.htm

A supercharged two-stroke engine is a very real option. It has has been sucessfully configured for Diesel applications for years. Configuring it for a gas engine I'm sure will present some challenging issues which I believe can be conquered. I'm acutally working on plans to conquer these myself by starting an SAE Clean Snowmobile team at Iowa State.

As Gus mentioned, SAE has had this subject researched. Look at this link

http://www.sae.org/technical/papers/930982

Even Chrysler and Mercury Marine, from what I understand, provided over 10 years of funding for a group of engineers to research a two stroke engine that utilized "external breathing" (a similar concept). Which, I believe, lead to the development of the E-Tech series of engines that now dominate the two-stroke engine world. Look at this link

http://www.allpar.com/neon/stroke.html

Keep this thread going, excellent info