turbocharging 1000 twin two stroke snowmobile

allen avram · Newbie Joined: 28 Jul 2008 Posts: 3 197.80 points

Has anyone on this forum done this...Looking to get a ballpark idea on turbo sizing....max boost 30lbs, 8000rpm....any help would greatly be appreiciated...thanks, Allen.

clay · Posted: Mon Jul 28, 2008 11:53 pm Post subject:

Very interesting, but I don't know about adding boost to that style of two stroke. I guess it would pressurize the crankcase, but I can't get my head around what happens when it uncovers the transfer ports. If I'm correct, the volume of the expansion chamber kinda sorta acts like the exhaust valve - when it fills the expansion chamber and the pressure wave hits the stinger, it sort of stops any more charge from exiting the cylinder. I would guess the expansion chamber would really need resizing since the higher pressure intake charge would now want to push more fresh air / fuel out of the exhaust port. GMC diesels were supercharged 2 strokes, but the supercharger blew in a fixed volume of air to just evacuate and fill the cylinder with fresh air. Even in this case, if it happened to blow too much, all it was moving was air, not an air/ fuel mixture. That's the long answer, might not have helped, but maybe some food for thought. Clay

Big Dave · Posted: Tue Jul 29, 2008 9:38 am Post subject:

Jimmy two strokes had an X-71 (where X was the number of cylinders) Roots style supercharger. The super charger was mounted on the exhausts side to suck out the exhaust fumes. The negative pressue in the chamber allowed for more air to enter (there is always excess air in the chamber in the diesel cycle to acomplish the slow burn from top to bottom of the cylinder) the cylinder when the twin intake valves closed.

Instead of turbo charging which would require a great deal of engineering on a two stroke engine, follow GM's lead and run a vacuum on the exhaust side. You will still need a turbo charger, but you are going to apply power to the inlet side of the turbo to use the exhaust side to create negative pressure. Look for the biggest stock turbo (off of a Jap car) with a motor about twice the displacement of your Rotec, though it can be bigger as you will never get a true vacuum.

Big Dave

allen avram · Newbie Joined: 28 Jul 2008 Posts: 3 197.80 points

Thank you for all the replys gentlemen...Glen Hall, who is an avid snowmobile racer and builder is making 537hp with a 1200cc twin cyl two stroke snowmobile as of today...http://www.amsnow.com/SNO/CS/forums/238293/ShowPost.aspx Allen.

af2 · Posted: Tue Jul 29, 2008 5:46 pm Post subject:

clay · Posted: Tue Jul 29, 2008 11:50 pm Post subject:

Couldn't get there with the link - even pasting it. I'd love to read about it. I'm always open to learn. Clay

Paul P · Posted: Wed Jul 30, 2008 7:13 am Post subject:

Try this.

http://www.amsnow.com/SNO/CS/forums/238293/ShowPost.aspx

allen avram · Newbie Joined: 28 Jul 2008 Posts: 3 197.80 points

You can go to http://www.dynotechresearch.com/about.htm
to read about the dyno run but you have to subscribe and pay the 20.00 dollars to view the results...hope this helps, Allen....Sorry I don't know how to make this a clicky...