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ski doo 800 2 stroke carb diy turbo

hey guys i started this build last year on a whim ,, and iv gotten pretty far but its my first turbo build so i'm a little lacking knowledge on some aspects of the build .. i just found this forum today on google and hope to learn a thing or two here, i am by no means a professional and by no means a righter so bare with me lol .. im going to try to upload a few progress pictures for you guys so you can see what iv done so far .. well last year .. havent touched it since the snow melted but i'm getting the itch to start working on it again .

ok where to start .. i built all the piping myself .. im running a mitsu td05 turbo that i had bored out to a 50mm compressor wheel .. i had a turbo head built for it with a 10.5;1 ratio .. i'm running an msd fuel pump and mallory fuel pressure regulator i had an hks bov on it but have since bought a 2 stroke specific one .. way less vacuum in a 2 stroke .. i have an inovative afr gauge that never works right ( any help on this would be great .. could be sensor placement or the leaded 100 av gas fuel ) also have duel egt gauges to keep an eye on me temps :) .. so long story short i got the thing together last year and got it tuned and running great .. goes like madd .. and then i ran the turbo out of oil .. my first assumption was my electric oil pump failed .. but i dont think that was the case .. it might have been where the pick up was on the tank causing it to starve for oil while i was doing a cat walk .. witch is basically the hole time it was on boost .. so since that day it has never ran on boost again .. i went and got a bigger and better oil pump and then i just blew oil past the seals and it would run like crap .. so what im hoping to start talking about is how to set up an oil system for the turbo on a 2 stroke

so first of all is my turbo scrap or can i just try to clean the bearing material off the turbine shaft and re use it. and rebuild the turbo and be ready to go again .. second .. im thinking of removing the oil system i have got installed in the pictures and possibly using the 2 stroke oil from the tank running it into the turbo and pumping it back to the tank .. what i don't know is how much oil, flow , pressure i need to keep this thing healthy and not blow past the oil seals and into my motor .. im likely going to have to run a supply and return oil pump if i do this because the oil tank is located higher than the turbo

How far has this gone? I have a soft spot for 2 strokes. for oil you will need min 10psi and 15 gallons per hour to keep the turbo happy. max I can't say but I'm running 60psi at wot and its not blowing past seals so its fine.

I'm running the innovate Wideband sensor and gauge and it works good for me. what BOV are you using that is designed to run on less vac? should be fun when its running!

I’ve thought about trying to boost my Ski-Doo 670 Summit. Think a Toyota CT12 would be perfect and spool super fast. I just hate the idea of making a box to pressurize the entire carbs, and somehow to pressurize the fuel equal to boost pressure... could a guy just run a large vacuum line to the gas tank vent? So the turbo would be pressurizing the carbs as well as the tank?

Quote:

Originally Posted by Daveyg (Post 1312997)

If you're pressurizing the carb, you're on the right track with increasing the fuel pressure, but that's not the method to do this. If you have an external pressure regulator, you should have a way of supplying it with a reference pressure (worst case if no other method comes to mind - stick it in the box with the carbs). If you have a mechanical pump, there's typically some form of pressure regulation built in, and you'd need to modify it so as to use boost pressure instead of atmospheric pressure for its reference, or switch to an electric pump and separate regulator.

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My sled though has just a vacuum fuel pump. Gravity feed from tank to the vacuum pump to the carbs. The pump I have currently probably wouldn’t work at all under boost. Here’s a pic of a typical snowmobile carb’d fuel pump. The small line on top goes to carb boot, close to one cylinder intake port, engine pulses make diaphragm inside pump move, which pumps the fuel from the lower medium sized nipple to the right lower medium nipple. The big nipple is from the oil tank. I know you’d be losing boost a ton by pressurizing the gas tank, but if you only wanted to run 8 psi to the engine, you could easily run like a 12psi wastegate spring, and that way the excess pressure lost isn’t really ‘lost’ just rerouted. I’m just thinking that would be a silly easy way to do it to get 100% equal fuel pressure to air pressure, without getting crazy complicated and adding extra parts, extra weight, etc. my gas tank is only about 8 gallons, and already has an extra nipple that is just plugged off. Would just need a check valve so that it’s not vacuuming the tank when off boost, and maybe would need a couple fuel check valves to bypass the vacuum fuel pump when under boost. Not like you stay on the throttle that long anyways on a snowmobile, my 670 will do 80mph in the blink of an eye without a turbo as it is, because I’ve geared it down a little, but after about 5-6 seconds at WOT you realize you’re completely exposed on a bumpy little sh*tbox dodging trees with the only thing between you and death is your guardian angel... but I just think it would be fun to get from 0-80 a bit sooner haha!

You're probably going to need an electric pump in that case - I can't see a vacuum pump working under positive manifold pressure.

That’s why I was thinking of running a few one way check valves as well, put a check valve in the vacuum line so it only sucks, as well as Teeing into the fuel line with the fuel circuit with boost before and after the pump with a check valve that bypasses the pump on the fuel side so as soon as turbo spools past 0psi (goes from vacuum to boost) the standard vacuum pump stops working and the pressurized tank becomes the ‘fuel pump’ and bypasses the ‘pump’ of course it would need to be tested a bit, once getting it to run I’d run it up to a reasonable rpm and then cut the power, pull the plugs, see if it’s leaning out a ton... but I still think it doesn’t need to be nearly as complicated as adding an electric fuel pump, a rising rate fuel pressure regulator, etc.

With mikuni round slide carbs, would the carbs really even need to be in a box or could I just add some nipples to the charge piping and run all the carb vent lines to the nipples? Maybe add a nipple to the carb tops above the slides too, so I’d be pressurizing the carb above the slide equal to the carb throat? I don’t see why that wouldn’t work.