09-28-2006, 11:53 AM #1
Turbo charging an old 2-stroke Polaris.
I have a Polaris 650+ cc Triple (650 punched out a lil). I was curious if anyone on here had messed with supercharging the old two-strokes on a PWC? I know it's been done to sleds (I've seen some real nice ones).
I have an MRD fuel-injection system I'm going to use for the g-Pig craft. I'm not looking for large gains - just want to play with the idea. I already don't have to worry about carbs and such (pos fuel pump ran off the crank for the fuel-inj). Will run pre-mix, will "Push" thru the inj system - so it'll be a "Dry" turbo system. My main worries is the compression ratio (which can be cheated a little with creative means) and keeping water out of the inlet of the turbo system.
So, if anyone has been here and done that on one of these old dino's - chime in. I'm looking at using a very small turbo (don't know the trim size yet) - but it'll respond quick. I'm also going to run a pop-off and set it VERY low at first to pop off the extra PSI. I'll just keep dialing down until I get the dreaded Pings, then back off a little - then run it for a while.
Again, this is all done on paper - I've yet to throw it all together and run it - hence, why I posted this for any input or ? This is going to be more of a trash - backyard style of tinkering. Using "mostly" auto-intended-use items (cause that's what I have).
09-28-2006, 12:11 PM #2
- Join Date
- Sep 2006
I have not actually laid eyes on a turbocharged 2 stroke... but the idea IS intriguing.
Some random thoughts:
Would you be able to completely ditch the expansion chamber? If not you'll have to plumb the turbo into the exhaust stream after the expansion chamber.
Oiling and cooling the turbo may be a bit of a problem as well. most automotive turbo's use engine oil for lubrication, some use engine coolant for cooling too, but not all.
Will the water in the exhaust be a problem for the turbine wheel? It could possibly erode the blades...
I wonder how hot the turbo will actually get considering the exhaust is being cooled by water?
Intercooling is a no-brainer, find a water to air intercooler and give it some nice cool lakewater.
09-28-2006, 01:43 PM #3
Did you consider a little juice, might be easier and give some real good temp HP gains. I can't seem to leave that idea alone. LOL Anyway- WELCOME to the boards!!
09-28-2006, 01:50 PM #4
I have seen supercharges on the older kawi's. They work because it is driven off the crank, and is a constant boost, therefore making fuel delivery less of a headache. A turbo would be nearly imposible, IMHO. Remember that a 2 stroke has a wet exhaust. . .
Last edited by addicted; 09-28-2006 at 03:24 PM.
09-28-2006, 03:17 PM #5
I know this may sound negative, but with all the obstacles to overcome, it's just not worth it.
Some sled company's have tried this, but success was marginal at best. Too much to overcome.
Stuff like open exhaust ports while taking in a fresh charge. The turbo is effectively blowing much of what would be extra power right out the exhaust.
Placement is key. The turbo needs to be AFTER the expansion chamber part of the pipe and matched perfectly for the application.
The turbo screws with the pipes resonance.
Fried and trashed pistons are a common thing without knock sensors and such.
I think Bender is having some success, but they're using an SDI engine and knock sensor. I quote them:
The Mach Z equipped with SDI and engine knock sensor was the first two-stroke engine we ever considered turbocharging. Since two-strokes were notoriously fussy turbo partners, owning one used to be limited to those who accepted an occasional piston replacement or cylinder repair as part of the investment. With the addition of SDI and a knock sensor, 2-stroke turbocharging is now an extremely reliable modification for your Mach Z, Summit or Hymark.
The first two pics are Bender sleds. The last pic is a turbocharged Polaris two stroke motorcycle!!!
09-28-2006, 03:35 PM #6
Very nice! Thanks for the pics.
Sounds like too many obstacles to over-come, I too came to that conclusion. Keeping the wet pipe really puts a damper on it - IMHO. I also thought about running a paxton style (belt driven) s-charger off the PTO. But again, may be more time involved than I REALLY would want to dedicate to such a project. I was just messing with junk I have laying around in my shop - and thought how cool it would be to supercharge an old craft like this. More of being a conversation piece than anything else.
Thanks all for the input. Heck, I may just throw an old R100 rotary into an extra hull I have here and have just as much fun on the water .
Originally Posted by CrazyA
09-28-2006, 04:25 PM #7Originally Posted by Wankel
09-28-2006, 04:44 PM #8
hehe - would be cool. And on that note - it would take a-lot to cool it. The exhaust temp on my RPU runs right around 1800 Deg after a 2 min run at 5500 RPM. Wankels run a little hot on the exhaust side. AND, will die REAL quick if they don't get a good coolant flow. Sounds like fun .
Originally Posted by 800AMSOIL4U
09-28-2006, 04:55 PM #9Originally Posted by Wankel
09-28-2006, 04:58 PM #10
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