turbo vs. supercharger
- Thread starter powder_rider
- Start date
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HANDSOME
Well-known member
Exactly, valves controlling the flow ... not expansion chambers.
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06MXZXRenegade800
New member
^^^
True enough. They are 2 strokes in the sence that they have a compression cycle every revolution of the crankshaft. But they still used the conventional cam and valves not piston port/reeds like the 2 stoke gassers that alot of us are acustomed to. So, just like any other 4 stroke, the detroits turbo/supercharger wouldnt be pushing all its boost out the exhaust. Not that it would really matter anyways, because the fuel isnt injected until a few degree before TDC when the exh valve is long closed!
True enough. They are 2 strokes in the sence that they have a compression cycle every revolution of the crankshaft. But they still used the conventional cam and valves not piston port/reeds like the 2 stoke gassers that alot of us are acustomed to. So, just like any other 4 stroke, the detroits turbo/supercharger wouldnt be pushing all its boost out the exhaust. Not that it would really matter anyways, because the fuel isnt injected until a few degree before TDC when the exh valve is long closed!
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drmiller100
Member
don kozel (sp????) a really smart man tried a blower on a big cat. he never got it to run as fast as a bone stock sled.
I put one on an 800 rmk. To my knowledge, I am the only guy to ever make a supercharged 2 stroke snowmobile faster then a bone stock one. I personally know of about 6 people who have tried it over the past 20 years.
I used ceramic bearings, a T3 compressor housing, and an 8 to 1 pulley system off the outer rim of the primary clutch to drive a 1 inch pulley on the blower.
It took a LOT of work, there were HUGE problems, the whole system was really flakey, and in total it lasted about 45 seconds before imploding. I've still got the blower in my scrap heap somewhere.
Interesting enough, ti was DEAD easy to jet to make it run. Leave the stock jets in, and she ran pig rich, but ran fine.
Like folks have said, the key is in the exhaust.
I learned a LOT about how exhaust really works during this whole exercise, and I will totally agree there is a LOT of magic in the stingers.
I put one on an 800 rmk. To my knowledge, I am the only guy to ever make a supercharged 2 stroke snowmobile faster then a bone stock one. I personally know of about 6 people who have tried it over the past 20 years.
I used ceramic bearings, a T3 compressor housing, and an 8 to 1 pulley system off the outer rim of the primary clutch to drive a 1 inch pulley on the blower.
It took a LOT of work, there were HUGE problems, the whole system was really flakey, and in total it lasted about 45 seconds before imploding. I've still got the blower in my scrap heap somewhere.
Interesting enough, ti was DEAD easy to jet to make it run. Leave the stock jets in, and she ran pig rich, but ran fine.
Like folks have said, the key is in the exhaust.
I learned a LOT about how exhaust really works during this whole exercise, and I will totally agree there is a LOT of magic in the stingers.
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triple7
Well-known member
Well the one underlying thing that everyone seems to have missed is that the concept of a supercharger and turbo is the same. Compress a larger volume of air/fuel mixture into the cylinder to create a larger fire to turn the crank harder. So how the he!! does a turbo do that differently than a supercharger?
A two stroke pipe works off of pressure waves being reflected up and down it creating a pressure charging effect on the engine in a given rpm range. Both a supercharger and a turbo are going to blow a certain amount of mixture directly through the cylinder and out the pipe. A properly worked out pipe will shove it back into the cylinder.
As for a turbo only using wasted energy, disconnect your charge tube, reset ur box numbers to stock and ride the sled. Tell me it doesnt cost any horse power then.
Dont get me wrong here I love turbo sleds. I am simply bringing the other side of the argument. I am an engineer and engine tuner; I happen to believe either system could work quite well
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portgrinder
Well-known member
You have alot to learn man.
I tried it. Custom billet jugs, Motec fuel injection we did up ourselves..yadda yadda.
It worked OK. Then we ran out of time and money. Wouldn't mind trying it again if I was independently wealthy and had another sled to ride for 3 years while I got the supercharger figured out.
You're sorta correct in the "free energy" thing though. Extra backpressure in a 4-stroke is NOT free energy but in a 2-stroke its alot closer because its also solving a problem you need to artificially create with a supercharger.
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triple7
Well-known member
And exactly what do you think is going to happen to the pipe pressure when you take an exhaust designed to have an 800cc naturally aspirated engine breathing through it and then pressurize that same engine to 15 pounds? If you think the motor needs more backpressure, which im not convinced of, its damn well gunna have it now.
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kennyblatz
New member
ok no im not an enginneer and i can barely keep my non turbo sled in tune but here it goes.
- yes a turbo and superchager work on the same principle get more air/fuel into the combustion chamber. but since exhaust air trying to turn a turbo is backed up or has more back pressure in minimizes the cold air from blowing through the exhaust port, befor the piston can pass the ports. i have no idea the ratio but lets call it kind of a equal pressure zone (but greater then atmosphere of corse). now a supercharger will have the back pressure from the pulsing of the pipe but no where near enough to hold back the Xpsi boost pressure from blowing past/through the exhaust ports.
- we said a turbo uses a WASTED energy we didn't say it doesn't take power to make it work.
cheers
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drmiller100
Member
i tried it. portgrinder tried it.
we actually each built one.
You guys can laugh at us, call us wrong, say we are full of crap, but independently, we arrived at the EXACT SAME CONCLUSIONS.
We are giving you huge hints for when you go build your own.
I'll give you another hint. Turbos work becuase they provide dynamic back pressure in the pipe, according to how much load the engine is seeing. You can recreate this with the supercharger if you want.
If you truly believe back pressure in a pipe is a really bad thing, open your stingers up 30 percent and enjoy all the free horsepower.
Or, another thought. Go look at how big EACH of the ports coming out of the cylinder is, and compare that to the size of the stinger.
Turns out the stinger is pretty small, and if you open the stinger up, the sled slows down.
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06MXZXRenegade800
New member
Of course you need the pressure in the pipe. Thats how a 2stroke works and why pipe design is so important.
With a 2stroke you have both the exhaust and intake ports open at the same time. Without proper pressure in the pipe (in the case of a turbo, its drive pressure built up in the pipe) all of your fresh air and fuel blows straight through the engine.
With a supercharger you need to artificially create pressure in the pipe relative to boost or you blow all your air and fuel straight through the engine.
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triple7
Well-known member
Im not saying its going to just bolt on and work. Im saying that it can work. Im saying that i am probably going to play with it. I appreciate anyone who has any information that they would like to add. Im riding ski doo's at the moment. If they were injected I would just turbo it and be done. To make a carburated sled work correctly you need more linear boost. It cant be so load related or the sled will run, then not run, then burn down. It seems to me that if a supercharger was WORKED OUT (not bolted on and expected to work perfect) it would provide linear boost and be possible to keep in tune.
Im probably wrong. Im sure that you guys will tell me im wrong, so thank you for your overwelming concern
Cheers
Im probably wrong. Im sure that you guys will tell me im wrong, so thank you for your overwelming concern
Cheers
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06MXZXRenegade800
New member
of course a supercharger 'could' work. boost is boost and the engine doesnt care where it comes from.
It just that all the BS like balancing the pipe pressure and driving the supercharger and the parasitic loss of a supercharger that really doesnt make it worthwhile, when you can damn near bolt on a turbo and go have fun.
It just that all the BS like balancing the pipe pressure and driving the supercharger and the parasitic loss of a supercharger that really doesnt make it worthwhile, when you can damn near bolt on a turbo and go have fun.
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Boyko
Well-known member
So ya want some info eh................
I got a small eaton blower I bought 7 years ago when I was wanting to have a blown 2-smoker I can sell ya, I did not spent to much time on the project.
Ok……..
What I would do………….. not that I would ever do this because a wack of people that are a lot smarter than me have put in some good time on this and walked away from putting a blower on a 2-cycle.
The fist thing is start collecting some data on pipe pressure and exhaust temps. So get some type of egt gauge and also have a gauge to monitor pressure in your pipe, collect and record the data from this.
Next you want to restrict the pipe big time and mount a external waste gate on the end of the expansion chamber before the restriction. See if you can source out a adjustable one with a 2 psi spring. Build some pressure in the pipe, see what you can get away with and how you can control it, this will give you more data you will need later. This is a start and it will not cost you much coin.
Anyone that has a good understanding of forced induction and turboed 2-strokes will tell you not to bother with this. The proper turbo on a 2-stroke controls pipe pressure in a quit sophisticated manner, It works F-in great, you will be hard pressed to come up with a better system.
As far as efi goes, at this point I would not build a turbo kit for any two stroke that was not fuel injected, I just works to well and takes so littel time to make tuning changes on.
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allblowdup
Well-known member
Seems a few of us have already tried it and all have had simular results. My experiences came in 1992 and after screwing with it for two months I know why it did not work and what it would take to make it work.
The simplist way that I can put it why it did not work is that the exhaust port is still open after the intake port closes so all your boost goes out the exhaust pipe. (proof 20 mile to a full tank of fuel)
You can restrict the exhaust to make the power but as the hp level increases the restiction need to decrease. This restriction need to be variable based on the intake pressure at all times.
I made a valve that mechanically opened and closed to vary the exhaust backpressure in the pipe. This did work but it also need to be changed based on air density.
I hade made a rotary exhaust vale after the exhaust ports that was water cooled and man that thing worked up about 5000 rpm(made close to 100 ftlb at 4500 rpm)but would not flow enough to make good hp.
The simplist way that I can put it why it did not work is that the exhaust port is still open after the intake port closes so all your boost goes out the exhaust pipe. (proof 20 mile to a full tank of fuel)
You can restrict the exhaust to make the power but as the hp level increases the restiction need to decrease. This restriction need to be variable based on the intake pressure at all times.
I made a valve that mechanically opened and closed to vary the exhaust backpressure in the pipe. This did work but it also need to be changed based on air density.
I hade made a rotary exhaust vale after the exhaust ports that was water cooled and man that thing worked up about 5000 rpm(made close to 100 ftlb at 4500 rpm)but would not flow enough to make good hp.
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06MXZXRenegade800
New member
Someone needs to try welding up the exhaust port and making an overhead valvetrain for the exhaust! 
Maybe a compression brake too, for those steep decents lol
Maybe a compression brake too, for those steep decents lol
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drmiller100
Member
here is another hint.
mean exhaust pressure needs to be 2.5 to 4 psi HIGHER then intake pressure.
mean exhaust pressure needs to be 2.5 to 4 psi HIGHER then intake pressure.
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allblowdup
Well-known member
This is why a turbo works. It is and infinatly variable exhaust restriction that happens to make boost while praportionally keeping the exhaust pressure higher.
A computer controlled exhaust restiction could do the same thing for a supercharger but has not been done yet.
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