I guess, from first glance, a stock sled/ecu fueling goes braaap and takes of WOT from idle no issues. has a HUGE airbox and nothing plugging the pipe. Also, on many NA sleds i have seen that went to small wire gauze metal topped pods, SUPRISE, they developed a low end rich bog... interesting. The two stroke motor CANNOT pull much vaccum. its a really low efficiency pump. a 4stroke can pull a lot more vaccum thus fight a lot harder to try and fill itself while a 2 stroke will just pull with its measly few inches of vaccum and if it cant, then you get minimal cylinder fill and terrible volumetric efficiency.
SOOO now we want a turbo, cool, kick as top end is fun, keeping the bottom is a different story we all fight with. so looking at order of operations, the motor needs to burn air/fuel to make exhaust heat/pressure to spool the turbo. For the motor to burn air/fuel mixture, it needs a steady supply of both. fuel is no issue, we have more then we need at the push of a button on a controller or a keystroke on a standalone. most people DO NOT have enough air. You stab the throttle, the motor in 2-4 revolutions (damn near instantly) has completely exhausted the air cavity known as charge tube/airbox, now it has to draw air in across the compressor wheel with almost no vacuum. best way i can describe this is a person with asthma(poor pump) trying to run breathing thru a coffee straw(restrictive intake). now your motor cant pump enough air so adds to much fuel making for a poor, undersized burn creating minimal exhaust heat and pressure, which results in a slow spool, and until the threshold is met where this small fire drives the turbo to a point where it is no longer restricting the intake, couple this with a restriction on the tuned pipe molesting the pumping efficiency even more, we have lag, bog, goating, etc. no fun
Now lets look at ways to combat this. the motor needs unrestricted air flow to rev freely when asked for instant and quick response, or at least until the turbo is lit up and can force it through. SO, we have a couple of options, BIG airbox, BIG charge tube, large blow off valves open at idle, vaccum operated doors, bigger compressor wheel turbos, etc. more resivour of air, and less restriction, we need to work from the intake to the exhaust side for tuning as that is how the air is working.
as for the exhaust/turbine side. we cannot restrict the exhaust unnecessarily, again this pump(2stroke) sucks, so if you restrict the outlet, you get less flow, slower response, etc. ideally, if we can run a relatively large turbine wheel with a tight AR housing, this way we get good flow levels, but we direct the exhaust at high speeds at the tips of the exhaust wheel(read leverage). This way we are utilizing the low rpm exhaust energy to its fullest in converting heat to mechanical energy, aka spool.
If we get this all rocking together, we have a motor that revs like a stocker, and pulls like a turbo. and makes big torque all the way across resutling in a super fun sled to ride.
any more questions??? lol/
