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  1. #1

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    Lightbulb Well, I thought I'd try something different, a 2-stroke Spark using an 800R E-Tec

    I started this thread over in the Spark section a while ago:

    http://www.greenhulk.net/forums/showthread.php?t=234284

    I thought it could be fun to try something else than a GPRRXP or GPRSVHO conversion that does a million MPH or so, but instead a very light and fun ski with lots of power and acceleration and maybe a top speed around 70-75. So the general idea, take a 60hp base Spark, pull the 3-cylinder Rotax 900ACE 4-stroke, replace it with a 160hp 2-cylinder Rotax 800R E-Tec 2-stroke from a late model Skidoo snowmobile.

    Sounds nice in theory and hopefully time will tell how it works in real life as well The 800R engine should be both lighter and smaller compared to the 900ACE but at the same time producing a lot more power. One question mark is the powerband and how much torque the new engine delivers at lower rpms, the rev range is very similar and both engines revs about 8k, the 800R has variable exhaus ports to increas torque at lower rpms. I just need to get a pair of dyno diagrams to compare. Idle rpms will most certainly have to be raised to cope with the constant load from the water.

    The particular engine I have in mind comes from a 2014 sled that has been wrecked, I will be able to gett all parts from that sled that I need to get the engine running. The plan is to completely remove all electronics/electrics from the Spark and replace them with the ones from the sled, including ECU and instruments. The sled doesn't have an electric starter now but a kit for that is available from Skidoo/Rotax.

    It would have been nice to get iBR, VTS etc. from a higher spec Spark but I think it will be very hard to get it working toghether with the ECU from the sled, I would probably have to keep both ECU's some how to even have a chance so I decided to just use the base model Spark for this project instead. A manual reverse and some kind of stand alone VTS might be a later part of this if I ever get that far.

    Major issues I've though about so far:

    Exhaust system routing
    My general idea is to keep everything about the new engine as stock as possible. In the sled the engine is mounted transverse and a 2->1 exhaust manifold is pointed straight forward, it then enters a single pipe that makes a 180 degree turn going back along side the engine and then enters the silencer. The engine routing in the Spark would obviously need to be longitudinal and thus the exhaust needs to be modified to a 90 degree turn manifold and a straight pipe along side the engine. The goal would be to keep the volume and combined length as close to the stock design as possible to keep the tuning specs of the stock pipe. Not sure if it will be possible to start with the stock exhaust parts and modify them or if I need to go custom from the start, it will probably depend on the next issue below as well.

    Exhaust system cooling
    This is what I think will be the single bigges issue to solve, normally you would like to have the pipe as hot as possible to gain power in a 2-stroke but as in any boat-like vehicle you would like to cool the exhaus as much as possible instead. I have two different ideas here, either I try to isolate the exhaus as much as possible using ceramic coating and/or exhaust wrapping and see if that is enough or I will have to start looking at some kind of water cooling using jackets or something. I would love some suggestions on this topic

    Jet pump
    Also a tricky one, getting a good impeller pitch that match the power band would obviously be crusial to get a decent ride. Of course it's not only the impeller that matters but the only idea I have here was to maybe copy the setup used when turbo charging a Spark. But not sure how that will work since they have a lot broader powerband even though peak power isn't that much off. Suggestions here would be nice as well

    I'm sure I will run into a ton of other problems if I decide to try this but you need something to lay your time and hard earned cash on, dont you?


  2. #2

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    Ok, a year and a half later, didnít get much response from the first post but here goes This is what happened, I bought a new 60hp 2015 Spark and a wrecked 2011 Lynx snowmobile with the 800R E-TEC engine. I then proceeded much like I described in the post above, stripping both the sled and the new Spark to get a clean start to work with:



    The main issues I stated above proved very true with one addition, power transfer. The sled engine obviously had a clutch system with a drive pulley for the belt drive and somehow I needed to connect the drive shaft from the jet pump to the engine. After much thought I decided to remove the outer part of the pulley and keep the inner part that also contains the ring gear for the future electric starter. Then I found a company that makes driveshaft and hubs for competition cars and they fabricated a custom adapter with internal splines that were crimped onto the axel of the drive pulley:

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  3. #3

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    Once that was done I started working on the engine mounts. Not as straight forward as one might think. The stock mounts on the sled was very specific, not one of them were in line in any direction with any of the others. But after a lot of measurements and trials I got a pair of adaptors made that fit the hull and the engine:



    Then I started with the exhaust manifold. The ACE900 is very narrow in that perspective and I had a hard time keeping within the available space between the engine and the top deck. I also had the same issue on the intake side but not really as bad and also I didnít have the heat issue to consider there.

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  4. #4

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    2-strokes are really picky about the exhaust system when it comes to design and temperature. I soon realized that water cooling would not work, the same goes for altering the length of the exhaust manifold before the tuned pipe. At the moment the theory is to insulate the whole exhaust using ceramic coating, exhaust wrap and ďjacketsĒ. And most of the inside of the rear part of the hull and deck needs to be covered with insulation and heat reflective materials. The final issue is to get the exhaust out through the hull, this part will however be water cooled to prevent the hull from melting. I will also use a high power high flow fan in the rear to ventilate hot air out of the hull.

    The tuned pipe is now cut up in pieces and I will try to put it together in the available space without altering the general design when it comes to volume and length. I had to replace the stock silencer since I just didnít have room for it. I got a decent aftermarket muffler that I will be using instead.



    I have also been working on modifying the fuel system by fitting the E-TEC fuel pump in the Spark fuel tank armature. The biggest issue here was that the Spark uses an internal pressure regulator fitted in the tank and a single fuel line to the engine. Compared to the E-TEC that has a more traditional layout with a regulator close to the engine and a return feed line back to the tank.



    This is about as far I have come now, a lot of work still remains but the goal is a first test ride this summer
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  6. #5
    Moderator beerdart's Avatar
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    Love it great progress..

  7. #6

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    Quote Originally Posted by beerdart View Post
    Love it great progress..
    Thanks

  8. #7
    madox-nola's Avatar
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    Nice... Look forward to see more...

  9. #8
    Kosh's Avatar
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    Some good work going on there, intersting conversion.

  10. #9

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    Thanks

  11. #10

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    man, beautiful work, looks great

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