Turbo 2 stroke singles.

[System of a Clown]

Daft thought I know - well that's what I thought at first.

It has apparently been done according to a few YouTube vids.

Has anyone got any knowledge/experience of this sort of thing?

I've got a lot of forced induction experience but that's car stuff.

And no 'it can't be done' stuff!!

It has been done, I'd just like to know more and I love a challenge

[stevo as b4]

No answer's, only questions from me I'm afraid.

It's the two stroke tuned snowmobile racers that we need to ask apparently on how this strange phenomenon works, and how to plumb in the hard ware etc.

It's commonly excepted that you need to keep as much heat in the expansion chamber as possible for the best and strongest pressure waves to scavenge and force the fuel mix back into the cylinders for best cylinder charge filling.

But what do you do with a turbo, put it after the expansion chamber where the gases are cooler? Or do you forget having a spannie and use a short manifold straight into the turbo housing to keep exhaust volume as small as possible before the turbine?

[smegballs]

I reckon you want direct injection after the exhaust port has closed. That way you use the turbo intake to blow all the exhaust gases out during the period where exhaust and inlet ports are open.

That way you are getting rid of all the oxygen depleted gases, turbo boost is basically flooding chamber with an 'excess' of fresh air, and you are not throwing fuel down the pipe as you are direct injecting after then zorst port is closed and the charge is trapped.

Expansion chambers wouldn't come into it really as the turbo will doing the whole 'scavenge well and cram as much charge as possible in'.

[Pete.]

Draw-through would be the easy way. No fancy plumbing or pitot tube tuning just bolt the carb to the turbo inlet and go. You don't need exhaust scavenging because that's for using the exhaust design to fill the chamber. Now you're pressurising the cases with a big pump so the chamber will be getting filled quite well enough.

Also:
1. Buy a big pile of spare engines and parts before you start.
2. Keep buying spare engines and parts.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[-]

Even a "Ram-Air" style pressurised airbox is hard work on a 2 stroke. I tried feeding a hose from the front to the intake of the airbox on my old race TZR250. It was a nightmare trying to get the jetting right. It was either way too rich at low speed or way too lean at high speed.

I think they managed it on one of the TZ's but that had a reputation of blowing up.

Maybe fuel injection would be better for this sort of thing?
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[bikenut]

nsu?

ecu and direct fuel inj, electric "supercharger" to scavenge, triumph double piston, 2 t above piston ( blower to scavenge ) and 4 t design below piston, so crankcase not used, see Belfast uni work done on this, also brunnel uni.....
____________________
nuts about bikes

[stevo as b4]

[Iain.]

Could be done, personally i'd rear mount the turbo though.

Supercharger would be best bet - Asin AMR 300 or simmilar.

[jimspeed]

how do they lube the turbo?
I would think as others have said injection would be the way forward as jetting would be a nite mare, interesting project to play with tho.
____________________
Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[temeluchus]

Fair chuck of diesels are turbo/supercharged direct injection two strokes.

First thing to do would be to block the transfer ports and have the turbo blow directly into the intake port and into the cylinder.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[MarJay]

I have a fair amount of experience with performance two strokes, having owned two strokes basically non stop since about 2005, and my first bike back in '99 was an NS125R.

First off, exhaust design is critical. This means that the turbo, instead of taking wasted energy and using it for more power, actually will more than likely rob power from the bike, because I doubt putting a turbine in the way of the pressure waves (which need to move freely through the expansion chamber) will allow for the perfect exhaust design. Changing the exhaust design by a small percentage can make a bike unrideable, so adding a turbine in the way is probably not going to do any good.

Secondly turbos work best with a constant flow of gas. So the moving pressure waves within the expansion chamber could even cause compressor stall, or a kind of 'burp' which will stall the turbo. This is pretty much as good as blocking the inlet altogether. You might be able to manage it on a multi with no expansion chambers, but then you'll more than likely lose more power than you'll gain from adding the turbo.

Thirdly, turbos require a constant supply of quality oil, warm from the engine. This is impractical on a two stroke.

Lastly, most if not all two strokes use the crank cases to pre compress the charge before it enters the cylinder. The mixture is already pre compressed, it doesn't need more compression. If you add too much compression to this mixture before it enters the crank case, the crank will have trouble compressing it further robbing some power again.

So I'm not going to say it's impossible but you can draw your own conclusions from that.

[edit] To add a caveat, you could probably do it if you designed the engine for forced induction from the outset, but bolting on a turbo to an existing bike will encounter the problems listed above. [edit]
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Major Doss]

Does a decent 2 stroke not rev up quick enough?
Bimota went bust trying 2TDI, so we'll suss it with turbo.. LOL.
How can you Force induction a cylinder that is designed to be open to 'breathe'?

[Major Doss]

Having said that, if a pulse system could be devised, so as to do away with disc induction timing limitation?
DI with turbo/wastegate fresh air? hmm..

[stevo as b4]

It can and has worked, but it's understanding how is the bit that's really hard to grasp.

For a long time my biggest question/are of concern was sealing the inlet into the engine under boost. I therefore assumed that only a piston ported or rotary valved two stroke would be able to be turbocharged, as with a reed valve motor the charge air would never let the reeds close?

I don't think this is as much of a problem as I first thought now, especially when you think how quickly reeds open and close at high speed, and the fact that there's little time in the two stroke cycle for air to escape anyway.

The snowmobile and quad bike turbo builds I've seen do generally tend to keep an individual expansion chamber per cylinder, and then join the stingers together before making a turbo flange to fit the turbo post expansion chamber.

I imagine turbocharging a two stroke is a bit like turbocharging a tuned Honda VTEC car engine, in that in the case of the cars, theres a lot of valve overlap on the high lift cams, and some of the boosted air will just blow straight out of the exhaust. But in these set up's it still works very well and gives a big power gain.

I'm thinking on a stroker you will be blowing away a lot of the charge air, but you'd still have some left to fill the cylinder with that is probably more than you would have otherwise, hence getting power gains. It's this effect which is why I think that keeping the expansion chamber is used? I would bet that there's not a lot of boost generated but it's enough to give greater cylinder filling than you could achieve otherwise?

[Pete.]

The engine parts don't know or care what pressure the incoming air is at, what matters is pressure differential. If the airbox is at 1 bar absolute (normal atmospheric pressure) then the mixture will enter the cases at 1 bar and when the piston starts to come down the case pressure will increase to more than 1 bar, meaning you have a delta-p across the reeds (1 bar one side, more than 1 bar the other) and the reeds will close. If you are running half a bar of boost exactly the same thing happens except now you have 1.5bar one side and more than 1.5 bar the other.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[System of a Clown]

Loads of info/hints here

Cheers all!

I'm still looking into this, it's going to be a slow burning project, but I'm still up for it

[stevo as b4]

Pete, so your saying if I understand correctly that if say pick a number 4psi? of charge air pressure is blowing in through the reeds from the boost generated by the turbo, that on the piston down stroke the pressure in the crank case will rise to a higher number say 4.5psi and then shut the reeds, and this how you'd still get your crankcase compression to occur and help to scavenge the cylinder when the piston falls to the point where the transfer ports start to open?

I'm still not sure on the ideal two stroke turbo exhaust and if it would be best to try and make the exhaust volume tiny before the turbine for fast response, or if a turbo after an expansion chamber can still produce a good effect, as the expansion chamber does increase exhaust pressure and bleed off gas through the small stinger pipe that must be several times smaller than the header pipe to work.

I'm thinking would the expansion chamber be a possible advantage on a single cylinder engine at least, as all that exhaust volume before the turbo would act as a reservoir, maybe a bit like a large plenum chamber before a set of carbs can, so that a balanced amount of air is available to draw on instead of pulses?

Or the ^ all horseshit?

[Pete.]

Yes you have it - the reed system works the same at any (sensible) pressure. Not sure how much boost the main seals will cope with but I bet you couldn't raise it far enough to pop them. Seal wear might become an issue.

Turbo after the expansion chamber does work. That's how the Buddfab setup was done.

https://i24.photobucket.com/albums/c5/pixelr0x/turbomotor.jpg
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[mentalboy]

[mysterious_rider]

Aren't those snowmobile engines like 200 horses? Wouldn't it be better to fettle one of those onto a bike?
____________________
KAWASAKIIIII

[System of a Clown]

[Vincent]