2 Stroke Turbos - they can't be done. Period. 

As an owner of a supercharged 2 stroke Detroit I have a feeling this video will be entertaining.

R.I.P the RU-vidr called 2stroketurbo!

You can turbo everything but if it makes sense is written on a different sheet.

You should tell this to the hillclimbers around me who turbocharge their snowmobiles. Turbos create backpressure too, so both the valves being open doesnt matter when you design the exhaust to work with the turbocharging. I have seen it. These engines dont just blow themselves up either they run and idle and do it over and over. Is it as simple as turbocharging a 4 stroke? No. Not simple does not mean not possible

Can't be done? someone will have to go back to the 30's and tell DKW

Snowmobiles have been turboed forever skidoo is the first to make it factory

There is back pressure from the turbo to keep the air from "just running out". Basically you are raising the pressure across the whole motor. It's like running your motor 500' below sea level.

You're forgetting that the air going out of the piston and into the exhaust is much hotter that the cooler air going in and there's the back pressure wave from the previous combustion cycle. Skidoo might be the first manufacturer to put a turbo on a two stroke from the factory but boondocker and silber have been making aftermarket kits for years.

Pretty sure Ski-doo hired the narrator from Death Race for that advert for the extra 'cool'

But, but, but... he pointed to line drawings in a book, it must be undeniable fact. That proves it! IT IS WRITTEN!

this kid sounds about 11yrs old. lol

That snowmobile is nuts I wanna go 😂

Matt I know you're telling the truth, but i cant let you shatter my dreams of building a >100 whp trabant which still has a 2 stroke.

The pressurized air will exit through the exhaust port ONLY if the exhaust/turbine inlet is at significantly lower pressure. If the compressor and turbine are appropriately sized, the exhaust will be at similar pressure levels as the crankcase when the turbo generates boost. Thereby, there will be trapped and boosted charge present in the cylinder and hence more power.

You can 100% turbo a 2stroke I’ve ridden many turbo two stroke snowmobiles and the stock counterparts, huge difference in power. Turbo kits for snowmobiles wouldn’t be nearly as popular as they are if they didn’t work.

2 stroke turbos in this sense are used to maintain the density of air, not to add horsepower. And If you think about it, if you add more than enough dense air, some will air escape, but a portion of that denser air will stay inside the engine leading to more stable horsepower at higher elevations. so as elevation increases the turbo lets more air into the engine even if some escapes. Plus I am pretty sure gasoline operated 2 strokes have specially designed exhaust pipes to create back pressure so less fuel and air escapes.

yes.. I understand the "pressurized air is going to go out the exhaust ports"... but, it IS still a denser mixture. Obviously, there's NO way in hell would it ever be nearly as much of a power/efficiency gain on a 2 stroke vs 4 stroke, but the turbo is still packing the crankcase with more air/fuel. So, again. YES, you will lose most of it, but you will still have at least a slightly denser charge vs N/A. edit: just wanted to add, there is an event of "valve overlap" in nearly all 4 stroke engines (meaning there is a point in it's 'cycle of events' where the intake valve opens BEFORE the exhaust valve closes.) Why doesn't "all of the boost" flow right through both open valves? The answer is: SOME of it actually does...depending on lobe sep angle/duration/lift @ overlap event/etc.. Now think about how the 2 stroke works again... It basically has a ton of overlap (exhaust port is open for a LOT longer) so we're gonna lose most of the pressure as compared to the 4 stroke, but, remember, it's already way more of a dense mixture coming in from the bottom end due to the forced induction.

With a properly tuned expansion chamber it will function as intended, if you consider the entire assembly from intake to tailpipe it is all one system. The chamber pressure of the crankcase, cylinder and expansion chamber will equalize to the input pressure of 4 psi above ambient pressure. At altitude that means an internal pressure of approximately 14.5psi or the same pressure at sea level on a standard day, which the point of the skidoo turbo setup.

If the correctly tuned expansion cha.ber is fitted would refill the cylinder ?

It requires special crankshaft seals to do it right with case induction. VR Dichtungen has seals designed to increase sealing pressure as the differential increases. There's a metal casing on the outside of the seal that's only a few mm larger than the crank diameter. This let's the case pressure push the seal into the retaining case increasing sealing pressure. They can be designed for 150 bar. Using that on the outsides and dual back to back center seals,

What books you suggest for two stroke engines. I can't see in description.

I wonder where that person got the idea that 2-Strokes can not have forced induction? Cheers for the video bud :-)

There adding higher pressure to the crank case = more fuel and air goes into the cylinder if they weren't getting more chooch out of the 850s choch they wouldn't be doing it

Question: EGR is used to cool the combustion, to reduce harmful emissions. Why can´t EGR be omitted by using a cooler thermostat instead? Thanks.

Just me spitballing, if you can get the back pressure of spooling the turbo up and then make the pipe in accordance to that i bet you could get the scavenging back just like at atmospheric pressure, or close to it. i know it helps to have multiple cylinders (dont know the science behind it) but ive seen guys with drag snowmobiles do it, adjusted porting and port timing. not efficient at all but works for peak horsepower

Holy crap this is fascinating B-)

So the boost controller is variable ? Then it is redundant.

Not only is there expansion chamber design to create back pressure in order to support forced induction two strokes, there's also rotary exhaust valves like @2strokestuffing is messing with on his channel.

Excellent video lad

The lad mustn't be changing the compression ratio if he thinks 0.28 bar is going to cause a problem?

And this is what they call a booksmart!

Interesting how Detroit made hundreds of thousands of 2-stroke engines with turbochargers and superchargers and they made tons more power than with NA.

This video is funny as hell, i'm rolling on the floor.

Ski-Doo: hold my beer..

@twostrokestuffing is doing a supercharged two stroke

When you are riding at heights in the mountains the air is thinner, a turbo could increase the oxygen going into it? But then, the output of the turbo in this design is also connected to the input, so it would just be blowing air anyway and never generate pressure on any engine!

Just got back from a Sunday cross burn, guess who I saw arrive on his magnetic Busa powered scrap metal collector? 🧲

Any books on automotive/motorcycle engineering you'd recommend in general Matt? Or any that your other subscribers would recommend? I've read Hillier's fundamentals but would like some more good 'uns

I think because there's a little bit of back pressure in exhaust that doesn't change with elevation so low altitude equivalent intake charge can be maintained. Turbo... let's call it "blow through" is managed by exhaust pressure.

watching the title: is this guy a tool? watching the vid: why can't I like this vid twice?

I liked the bit where he says, "The pressurised air will go straight out the exhaust ports, that's physics!!", with the middle picture, in the book diagram, showing a Webb uniflow 2 stroke which has an exhaust valve and no exhaust ports. So many different types of 2 stroke engine out there. The earliest Victorian 2 stroke generator & pump engines ran on domestic coal gas from the household supply.

simple solution, massive crank case volume and low pressure boost , tuned chamber exhaust . I plan on testing this hypothesis.

Hey, is that a book? Can i know the book title? 😊 If not.. please If you have the link.. I want to learn more about 2 stroke 😊🙏

I hate to break it to you, but a fella in Michigan has a cartridge bearing turbocharger on a 40 Hp Mercury outboard on a 6 foot plywood hydroplane, it made 213 hp, had a Fast efi setup using GM coils. It almost killed him. He has the same turbo setup on a Skidoo Formula 3 from the 90's and it is a fucking animal. He also has a 427 Side oiler Ford in a 1976 Honda Civic that's rear wheel drive. Anything can be done with enough money and skills, my freind, and a wealthy genius machine shop wizard *can, and has already* done the things you said can't be done, more than 20 years ago.

I would like discover old snowmobile engines 2 stroke turned into a carburettor turbo to see how they work

There is one major, but simple, point that two stroke turbo naysayers are missing. They are wrongly assuming that as the piston is just about to close the exhaust port that there is zero pressure just outside of the exhaust port. The pressure between the exhaust port and the restriction just down stream of the port caused by the turbo, say twelve psi, continues everywhere from the turbo to the exhaust port and into the cylinder, so as the exhaust port is closed there is twelve pounds of boost in the cylinder. See how simple it is now? Funny how I missed this simple aspect myself for several decades until it hit me like a ton of bricks while driving home from an event that had a turbo charged drag snowmobile with a completely unmodified engine that made unreal power.

I would hold that if a crank case scavenged gasoline 2 stroke had direct injection, it would benefit from forced induction. The port overlap could be timed to allow a bit of boost to build. It would have to be at least 2 cylinders or more with uneven firing I believe for the sake of exhaust manifold pressure Edit: The direct injection would be needed as there could be exhaustion of the gas mix out of the exhaust port before closing, as such an engine could not have the usual sonic back pressure type thing

So that comercial, that turbo just keeps the preasure on high altitudes as if you were on sea level?

You guys are forgetting that tuned 2 stroke exhaust has sound waves that bounce back from the prevous charge thru the exhaust port that helps pack the cylinder....like supercharging....add the turbo to the intake side and you are enhancing the compressed charge. At 70 l have a LOT of time racing 2 stroke sleds and boats ....we have played with tuned exhaust forever. BTW just add juice ( nitrous) when you really want some power! Haha

What if you could extend the crank case port higher then the exhaust port slightly and have an electric valve release for the turbo open right after the piston blocks the exhaust port?

Does this mean you won't be finishing the Derbi project? ☹️

Every large merchant ship is a turbo charged two stroke

I know I am gonna get crapped on but we have two Ski-Doo snow machines in Alaska with rotax e-tec 2 strokes and both have turbos. They have a lot more power than the ones we traded in with the same 850cc NA Rotax engines. I would love to know how they work?

They only work if the engine has valves or rotatory valve. Boost will open reed valves at wrong times and messes with the pulses of the power pipe negating it's purpose and engine/port timing. Also don't work on single cylinder engines without a "Boost tank" of the same volume or close to cylinder volume

Facepalm : you could push a few bar of boost - as long as your CFM is high enough. as the exhaust port is venting you must simply keep higher CFM flow (with the higher density) through intake vs exhaust port. This makes it hard if not impossible with turbo- but why not supercharged?

Okay so please explain this.....you take a 2014 skidoo freeride 800cc snowmobile and it makes 165 hp from factory and with forged internals and an aftermarket turbo kit making 9 lbs of boost it makes 312 hp....please explain how it almost doubles in horsepower if a turbo is counter productive lol

Detroit Diesel is going to be highly upset. Who wants to call and break the bad news?

it seems like a lot of complexity to only run up to 4psi for density compensation.

I'm currently running a bbr 100cc engine strapped to a kids bicycle frame..I have reversed the jug and piston..placing the intake up front and the exhaust in the rear.. specially in colder weather but not none the less..my bike runs beautiful.. had to richen up the carb jet..but does function great as air is being more forced into the engine..not saying that everyone will have great success at turbo..but regardless, a turbo can be done with a two stroke..

I'm confused. Is this video against or for two stroke turbos?

Ski-Doo unveils new 2-stroke turbo snowmobile...

There's actually a turbo banshee here on RU-vid 🤣🤣🤣🤣🤣

If it isn't possible how have all these people been doing it from the 90s till now

Considering the amount of videos I've seen and immediately recommended after this video I'm going to go ahead and say there's ways to get around it and I think it has to do with the exhaust pipe but idk

2 stroke snowmobiles have been done for years, polaris just made one

Achates engine is another one to look at if you're interested in weird engines. Be nice to see Matt cover it. I know it's not motorcycle related though

but i wanna turbo my puch maxi

4psi boost is like turning your 1000cc engine into a 1300cc

Laughs in Screaming Jimmy 2 stroke diesel. Watches 2 stroke diesel burn down from sucking oil into intake and over rev

most small engines dont want to have 4 egr pipes. thats why those engineers make less.

snowmobiles come stock turbocharged. Patriot Boost 850 for example.

If it goes out the exhaust port..... It's only further driving the turbo? It would then come back to "back pressure" from the filing the expansion chamber to the stingerpipe? Essentially it will waste a bit of fuel but the positive pressure just as the piston closes on up stroke will still be a lot higher than the stock compression ratio? So a net gain in HP. There are guys making this work....so the theory can't be that flawed?

turbocharging is just an artificial means of increasing atmospheric pressure. the more pressure you have, the more air you have, the more air you have, the more fuel you can burn!

😜 love it 🤣😂🤣😆😜 from R1 Greg

Hope that wasn't an electrical fire.

detroit diesels have superchargers and they make a turbocharged and supercharged one, ive worked on a bunch of the, 8v92TT 8v71TT... ect

Q. When is a workshop? A. When Allen Millyard Q. When not workshop? A. When sarcasm lectures! 🤣🤣😎😜

He is refuring to 2 strokes with the rotary valve system only

As someone who has built and tuned 2 stroke turbos I’m offended. Shoot my 70 year old neighbor has a 420hp sled.

Rotax engines are fuck amazing

Ski-Doo 🗿

Looks like the only benefit of the turbo would be it's better at getting rid of the exhaust gasses and have a cylinder full of fresh air. You'd lose all the boost the moment the exhaust port opens.

Gas turbines don't have valves between the compressor and turbine. I don't see why a turbocharged engine would be any different.

It does make sense to me.... The difference between motorcross engines and other 2 strokes is the expansion chamber, allowing the immediate back pressure reduction at high revs which allows specific porting and reeds to produce ridiculous power. I'm not sure 2stroke has any advantages for midrange torque unless it's diesel !!!

What if the crank wheels were machined to resemble turbines?

How old is the book that is being referenced? 1965? Look how yellow the pages are

I was laughing, they I read the comments and nearly got a hernia laughing so hard it's completely amazing the number people that don't understand the basic architectural differences between two strokes and four strokes. Not to mention throwing in diesel two strokes and four strokes I'll bet most of these people would completely freak out if they saw somebody building a fire under the cylinder head of their diesels before they started it up.

I wish i had a snow mobile.

Great video - Keep them coming Matt

We going to ignore two stroke turbo sleds?

What's so funny is the cheesiness of the marketing advertisement. With all those ads that have the super enthusiastic and overstated commentators, I actually wonder if the tech heads/engineering department within the company just cringe....because lets face it, all those ads are made by marketers who usually have zero interest or knowledge in the engines or machines they promote, but have an extreme penchant for CG, voiceover artists and distorted, jittery electronica "music" that gives it an industrial vibe.

really cause mazda just patented a supercharged 2 stroke and got amazing results.

Supercharged 2-stroke diesels have been used in boats for over 100 years. There's one on a pre-WWII motor yacht near my place and it's a beast.

LOL Not only can it be done...and well., but it works awesome. A 2 stroke mercury outboard goes from 39 HP to 90 HP and on a hydroplane goes from 70 MPH to 105 MPH. Works just as good on a snowmobile so well that my buddy's snowmobile can only race on a lake because the snowmobile race track does not have enough shutdown length.. I am presently building a 2 cylinder Mercury (20HP) and adding a turbo. This guy is supposing 0 PSI on the exhaust and didn't draw in the turbocharger in line with the exhaust and it's backpressure... NOT SO.

Have a look at 2 stroke stuffing he's supercharging one of the designs that you said don't work and it has had it's problems lol

The point is Crank case 2 stroke is a no go. Opposing piston is a maybe with little benefit lol Honestly if you look deeper into The 2 stroke and what they did to that snow mobile. It seems like they just made a compressor to gather air for higher elevations. When air is thinner its harder to gather enough in a area to run the motor. seems more like they created a pre air rich environment for the engine to breath more then a typical turbo charging system like a car would use. Old small 2 stroke helicopters used that idea. Listen very close! They even say higher elevation over and over which leads me to think there idea is what you would call a stored air feeding chamber design. Happens to be they used a turbo blower to gather air. When motor runs it wont do a damn thing but run in background, till you hit 11,000 feet above sea level.

You can turbo anything with a combustion chamber period.

yeah i guess the pressurized air goes straight out nowhere IF THERE'S NO VALVE ON THE OUTTAKE PORT

Two strokes sill make a come back… especially with advancements in direct injection and free valve tech. I can see two strokes as the superior choice over 4 strokes.

Then why do they put turbos on snowmobiles