Ok, I don't think anyone remembers, but I've posted here in the past about the scooter I used to own back when I was living in Italy.

If you don't remember, basically while I was living in Italy (my father was stationed, Air Force) you can't drive according to Italian law until you're 18. What did me and my friends do when we hit 16 and we had no ride? Well, scooters are the norm there before getting a car. Most of these scooters are just 50cc slow-mobiles. However, they are geared toward a very specific young audience, with sweet looking designs and, believe it or not, liquid cooled engines and dual caliper slotted disc brakes. Needless to say, these bikes had some serious potential.

Naturally, I began to mod the holy shit out of it. I replaced the engine with a 70cc Polini aluminum racing cylinder which was designed to rev up to 18,000 RPM! I swapped out the whole transmission for a "built" one (think: Shepard transmission for a scooter) and after all was said and done, I clocked mine at 92MPH from a Mercedes 190E. Dyno graphs of similar setups were showing close to 20HP at the wheels!! The power to displacement ratio is INCREDIBLE.

So, now that I am seriously considering going with a custom turbo setup and megasquirt on my 2GNT, I began to wonder what would keep me from building a custom MegaSquirt to modify one of those 70cc engines to fuel injection. Then, what if I could turbocharge it? Needless to say I would need to find a VERY small turbo and push very low boost, but in an engine of that size, it would most likely still make an enourmous difference.

I don't see why 40 or 50HP would be out of the question. According to a few 1/4 mile ET calculators, 50HP at the CRANK would be good for mid 10s in a scooter of the weight mine was (275 pounds).

So, why wouldn't this be possible? Any ideas on possible turbos to use? Any comments, flames, questions or anything? I think this would be an extremely cool project to pursue, and you may just set a few world records doing it :D

Think if it weren't liquid cooled you could tig weld the head on there and run 50 psi boost!


Star Stage II,Vecco SS heatshield,OBX intake,OBX fuelrail,MSD coil & wires,Epac voltage sys.,Hyperground sys.,Eagle rods,JE pistons,ARP studs,meling oil pump(Ceramic coated DP,wastegate tube,Manifold & turbo housing)

people have put megasquirts on their lawnmowers before. you could do this for a certainty, it'd be a really cool project actually :D

Potential problems associated with turbocharging a 2-stroke engine that my friend and I came up with after some discussion:

Problem: 2-stroke exhaust works by having fresh air and gas pulled in through the intake side and in effect "pushing" the old exhaust air out in the same cycle. The turbo may have a negative backpressure effect in which the exhaust gas is not able to escape properly.

Possible Solution: I suppose the only solution to this one is make the rest of the exhaust as restriction free as possible, and also choosing a turbo which is small enough so as to spool easily and not pose a problem.

Problem: These engines operate using "reed valves" that are actually just flexible metallic or carbon fiber flaps which are inverted so that air is allowed to enter but not escape. This is fine for an N/A application where the piston sucks in air (opening the valve) and then compresses it (closing the valve and not pressurizing the crankcase) but with forced induction, air would be pushed in through the reed valve all the time, even during combustion, causing pressure inside the crankcase.

Possible Solution: This would come down to trial and error, but perhaps with a sufficiently sensitive BOV, the boost present when the reed valves should be closed (ie, during combustion) could be expelled. This means the BOV would be venting at nearly the same rate as the engine speed. I don't think the BOV would last long operating like this, however.

Another option is to just ignore it and hope the existing pressure in the crankcase from the combustion process is enough to hold the valve closed.

As far as the conversion to fuel injection, that seems to open a whole new can of worms. As it is now, the carbeurator is responsible for mixing the oil with the gasoline at the right ratio. A fuel injection conversion would eliminate the process of mixing the fuel with the oil.

I suppose you could pre-mix the oil and gasoline yourself and ignore the seperate oil tank (which gets old). The carburetor used the natural vaccuum of the engine to draw the oil and gasoline into it, using adjustable jets to reach the desired ratio. There would be no such system with fuel injection. On the upside, pre-mixing the fuel would allow the stock oil tank to be used to lubricate the turbo. An electric pump could be responsible for keeping the turbo happy.

Also, you would have to build an entire pressurized fuel system. Including an intake manifold, fuel pump, injectors, fuel rail... oh man.

Input on these would be REALLY appreciated, if anyone out there knows 2 stroke engines and has some ideas...

Just some pics of the scooter I'm talking about so you guys can get a mental picture... mine was a nice metallic red.





They are restricted from the factory to 35mph. They only make about 3 horsepower :P

A little bit of cutting inside the exhaust and a removal of a limiter plate in the transmission bumps them up to about 50mph. After doing that and getting an aftermarket exhaust and intake is actually where most people stop modding. Hmm... sounds familiar, eh?? To be fair, an exhaust upgrade adds a much more noticable increase in power on a scooter than, say, a Honda however.

Not that this is advanced tuning related to 2gnt, but anyway:

I remember seeing those when I was in France. Some of them hauled ass, kids would ride wheelies around on them.

Anyway, when the piston travels down toward BDC in a 2-stroke motor, it does create pressure and pressurises the crankcase. The reed valves work as a oneway valve that keeps that pressure in. That's what forces the air/fuel mixture up into the cylinder and the exhaust gases out.

If you were to turbo it, it would have constant pressure in the crankcase. Instead of sucking air in as the piston is traveling towards TDC, it'd be pushed up, helping in compressing the air/fuel mixture on top of the piston. However, I think it may build up too much pressure in the crank case and it'd be harder for the piston to travel back toward BDC after combustion. It may be minimal and run great. If you ran a max of say 2 psi, it'd probably fill that crank case up at TDC, then compress that even more on it's way down and close the reed valves.

Or, you could swap to a rotax motor with that rotary valve and not worry about the reeds closing or not.

All in all, I think it's possible. It's just a question of whether you want to deal with it or not. Is it fuel injected already?

You could probably put a 4 stroke in it with a little mount welding and slight rediesgn of the frame. not sure if you want to go that far though. MS would be a feasable project, tunig will be a little seat of the pants only though since an o2 would not be easy to work with considering the oil doesnt burn in a 2 stroke. There is a smaller version of MS for bikes that is smaller and easier to locate. The other issue may be the voltage output in the alternator of the motor. The MS needs 12v constant to operate, if the scooter doesnt have a battery and alternator system then you would have yet another little issue to work on.

What do those scooters go for? That would be a real nice birthday for my nephew in a couple years. Got a website?

Terry

Originally posted by Star Turbo Talon
You could probably put a 4 stroke in it with a little mount welding and slight rediesgn of the frame.

Eh, I want to stay away from that route... the reason I find the 2-stroke so appealing is that it makes double the power of a 4-stroke, all else being equal. Also, it would be incredibly difficult to find forged internals for any 4-stroke of that size... all of the racing 2-stroke cylinders are designed to withstand some serious abuse. It's not clear exactly how strong they are because they are all intended to be N/A...

Furthermore, since the oil and gas are mixed before it ever enters the crankcase, you'd need to develop a whole new lubrication system to accomodate the needs of the crankcase (which is still designed to operate on lubricated gasoline) and now the 4-stroke engine, that likes it's own oil reservoir to lubricate itself with. Just this problem in itself would require the fabrication of seperate systems of enourmous complexity.

Originally posted by Star Turbo Talon
The other issue may be the voltage output in the alternator of the motor. The MS needs 12v constant to operate, if the scooter doesnt have a battery and alternator system then you would have yet another little issue to work on.

Surprisingly, they have a fairly well-designed electrical system. It does indeed have a small 12v battery. I had a buddy (same guy who now owns a 1G TSi AWD) that was really into car audio. For shits and giggles he took a small no-name 50W x 2 amp (RMS was probably nearer to 10W), an old Pioneer tape deck with an LCD display and 2 pre-outs, and installed a semi-functioning sound system on his scooter.

There were some problems, mainly the voltage drops at idle and this would wreak havoc on the amp and head unit, turning them on and off. When he was moving, it seemed to work fine except for a faint ticking noise that I suspect was simply interference from the totally unshielded nature of the electrical system's design. I believe with some very minor tweaking you could create a continuous 12v power source (capacitor maybe?)

We both left Italy before he had a chance to work out all the bugs, unfortunately.

Originally posted by Star Turbo Talon
What do those scooters go for? That would be a real nice birthday for my nephew in a couple years. Got a website? Terry

I bought mine new at a dealer back in, oh, around '00 or so for $2,400 after taxes and such. They are going to be much more expensive in the US due to various import taxes and emmissions regulations. However, the body styles undergo much less frequent design overhauls than cars do, so you can most likely find a decent looking '95 model with the same body style for about $1,000 stateside.

Make sure the model you choose has a wide aftermarket if you're looking to mod. Not just any old 50cc scooter has racing parts available to it. If you want to find out more on the tuning options and parts available for these things, go to www.scooter-attack.com and browse around their English version site. I bought most of my performance parts from that company, and they take scooters very seriously (perhaps a little too seriously). According to them, the top of the line 70cc racing cylinders are breaking 20HP n/a!

Modifiying it will be cheap and easy. An entire new engine including the "head," block, piston, and all the extras, like gaskets, is around $250 to no more than $500. Bulletproof crankshafts usually come with the connecting rod and are no more than $400 or so for the absolute top of the line. All the mods I put on my scooter failed to exceed $1,000.

I've actually just recently thought about doing this to one of my quads, just for shits and giggles (like I don't have enough projects going :rolleyes) I thought of pretty much all of the same issues except for the boosting ones (i'm not concidering that route).

My issues are:

I have an air cooled 4 stroke (no coolant sensor possibilities). And a liquid cooled 2 stroke. Neither have an electric start (they are man quads :P) so that pretty much ends my progress right their. LOL But I still like to think...so I thought if I were to go ahead with this I would use a single TB from a GSXR, it's fuel injector and TPS. IAT and coolant temp sensor would still be the GM spec ones...easy enough. But IAC would own this project too with the GSX TB at idel.

Also the violent nature and harsh enviorment would probably kill the poor Mega Squirt...LOL

But I think the GSX TB would be an excelent staring point for a project like this. my .02

you keep talking about boosting, but if you can't get around the valve being blown open, why don't you squeeze the bottle? (Yes, I just went there) Why not? Mount two 2lbs. tanks to the side of it, or hide them in the fairing, run a solenoid and smallest jets possible, you'll already have a high pressure fuel system for the MS, it's the easiest solution. Depending on how much bottle you have and how much you squirt it could probaly last for a long time.

Originally posted by Keith2172
you keep talking about boosting, but if you can't get around the valve being blown open, why don't you squeeze the bottle? (Yes, I just went there) Why not? Mount two 2lbs. tanks to the side of it, or hide them in the fairing, run a solenoid and smallest jets possible, you'll already have a high pressure fuel system for the MS, it's the easiest solution. Depending on how much bottle you have and how much you squirt it could probaly last for a long time.

Heh, quite simply because it has already been done. They actually sell a nitrous kit for scooters in performance shops where I used to live. They are THAT serious about this shit!

However, I've NEVER heard of turbocharging an engine that small... probably because as I'm starting to discover, it may just be impossible. Then again, they didn't have... MEGASQUIRT!

Originally posted by Keith2172
you keep talking about boosting, but if you can't get around the valve being blown open, why don't you squeeze the bottle?

I really don't think they'll be blown open. Once the pressure equalizes and reaches the max boost allowed, they'll be no more air being forced passed them. Then, when the piston starts it's downward motion, the pressure in the crank case will be greater than that in the intake, thus closing the reeds.

Originally posted by cougar694u

Originally posted by Keith2172 you keep talking about boosting, but if you can't get around the valve being blown open, why don't you squeeze the bottle?

I really don't think they'll be blown open. Once the pressure equalizes and reaches the max boost allowed, they'll be no more air being forced passed them. Then, when the piston starts it's downward motion, the pressure in the crank case will be greater than that in the intake, thus closing the reeds.

Didn't think about it like that but you're right, you would really only have to worry about the reed being open on intake and power strokes, and I don't think it'd open during the power stroke. What about a supercharger though, if you can't get the turbo to spool, cut-off the exhuast turbine housing and weld on a pulley. You'd get some boost, especially at 18,000 rpm! Then if you went real crazy you could do a twin charged, one supercharger, one turbocharger, that'd be a definate rarity. Ok, my bs DONE!

Originally posted by Keith2172

Originally posted by cougar694u

Originally posted by Keith2172 you keep talking about boosting, but if you can't get around the valve being blown open, why don't you squeeze the bottle?

I really don't think they'll be blown open. Once the pressure equalizes and reaches the max boost allowed, they'll be no more air being forced passed them. Then, when the piston starts it's downward motion, the pressure in the crank case will be greater than that in the intake, thus closing the reeds.

Didn't think about it like that but you're right, you would really only have to worry about the reed being open on intake and power strokes, and I don't think it'd open during the power stroke. What about a supercharger though, if you can't get the turbo to spool, cut-off the exhuast turbine housing and weld on a pulley. You'd get some boost, especially at 18,000 rpm! Then if you went real crazy you could do a twin charged, one supercharger, one turbocharger, that'd be a definate rarity. Ok, my bs DONE!

LOL, intriguing ideas!

Turbo Bar Stool with nitrous...
http://www.rmdsm.org/forums/showthread.php?t=3008

video of it running...
http://www.rmdsm.org/forums/showthread.php?t=3102

Nitrous would work, turbo might work. I think i would go with nitrous just for simplicity.

why not just use a basic stamp?

Originally posted by Chamuko
why not just use a basic stamp?

Eh? What's a stamp?

Originally posted by BRU_ce

Originally posted by Chamuko why not just use a basic stamp?

Eh? What's a stamp?

You know, the thing with Washingtons face on it, you stick it to letters when you mail them :P

(I don't really know either)

more and more I think that a twin charged scooter would be the proverbial shit, you could look at it and say things like 'This will decimate all!' and 'You're lucky you didn't blow the welds on the intake!' It's monday, Im trying :shrug . Go with the twin charged idea though it's never been done and you said thats what you're after.

Originally posted by Keith2172

Originally posted by BRU_ce

Originally posted by Chamuko why not just use a basic stamp?

Eh? What's a stamp?

You know, the thing with Washingtons face on it, you stick it to letters when you mail them :P (I don't really know either)

Search noo00bs! :P

http://forums.2gnt.com/dcboard.php?az=show_topic&forum=32&topic_id=1601&mode=full

Here's a bike that has a turbo'd polaris 2-stroke motor on it:

http://www.kawasakitriplesworldwide.com/triples/gallery/turbo_polarias_dragbike/turbocharged_twostroke_polaris_motorcycle.htm

With that, your idea of turbo'ing your 2-stroke should work.