The carbs work. With the current ski doo system it is hard to adapt a turbo fuel system. A lot has been done to try and replace the existing flat slide carbs with 38 mm round slide carbs to get more adjustment out of the them. This worked for turbo purposes but the round slides don't perform as well in the bumps and they are too sensitive to the higher fuel pressures required for turbo fueling. The only way to get the adjustability you need to a make a turbo system work in the bumps, in the air, and out of the hole is to add an external adjustment to the pilot circuit as well as the proper venting. You still have to make the adjustments by hand but now you have an option that before you didn't on the ski doo. It's not a matter of reinventing the wheel but simply having the right parts in the right combination that make this all come together. Many people have given up on these because they could get it to work in certain places but not others, but there are still a few out there who swear by carberators and keep what they do guarded. There's no doubt that it's not perfect but I haven't seen an efi system that works perfectly either. I am going to order a sled. When is arrives it will take me about a week to get the kit built and then I'll start working the bugs out. I'll post pictures and videos and try to keep things as open as possible at that point. There's no doubt that efi and especially direct injection is on the way for ski doo but not for a couple more years. Until then we've got carbs.
-Fack
You are worried about tuning off idle for good throttle response, here is my take on it. It is going to become worse with altitude you do loose a fair amount of static compression at 8000 feet. Ever notice you sled is easer to pull over at the top of a mountain as compared to the parking lot. When you crack your throttle from a idle you exhaust pressure is going to build to 3-5 psi before you make any boost. Now because of this you are letting a lot less fuel into the motor. To give you a idea of how much less fuel you need on a Dragon I did last year I had to drop the fuel pressure from 65 psi to 32psi, the fuel controller I used can’t pull fuel through the injectors.
Now here is the kicker, most folk are running +110 octane fuel, it burns slower and takes longer to light, the flame front is a lot pokier. Ideally your max cylinder pressure should occur around 15 degrees past top dead center, it is probably happening at around 25, I am not sure on the numbers but you get the idea. Because of this your tuning window for crisp response off idle has just become smaller and you have to go lean. It is over looked but timing control is needed, advance it at the low end and pull timing at boost.
“control is power” ( I think that statement comes from Burt at straightline 1320)
I am going to play with it next year, Dobeck has a gen 3.5 box that should do timing or Rapid Bike III is another choice. The biggest reason I like EFI is you’re A$$ has to be on the seat with the engine running to tune it.
I play with turbos till kill some spare time in the evening after the wife and kids are passed out, it keep from boozing it up to much. I still have a lot to learn and always will.
Fack I do not know where you are coming from, a few times you have been asked about the kits you have built, but no reply. Yet you are going to build a kit that will work better then the ones available, in one week……….. Ah ya sure ya are…………….. you got lots to learn yet buddy, give it 10 years.
Most but not all of the turbo builders I have talked to are pretty open to sharing ideas, just as long as they feel you are not going to steal a hunk of there market from them and not post what they are testing or trying. For the most part they are bright dynamic hard working people. I like Brycters light harted posts and if I was looking to buy a kit I would be calling him, I would like to find out more about the UFO that is running around with the 66 series hyper on it LOL.
