- Location
- USA
True, makes sense.
SX/SXi/SXi Pro 1100 triple in my sxi advice
- Thread starter dow
- Start date
- Location
- Winter Park, FL
i have a stock impeller in mine and went just over 60 mph
- Location
- USA
Would the 900 be easier to convert into an SX?
- Location
- Winter Park, FL
900 is physically the same as an 1100
- Location
- USA
Friend was telling me the exhaust on a 900 is a bit narower, so it would fit without any mods. Anyways, might be idea for a winter build...
- Location
- Winter Park, FL
im not 100% sure but i believe the expansion chamber on the zxi models are shorter than an stx
The 900 pipe is a bit smaller but it still doesn't fit in the sxi hull. I know cause that's what I'm working with. I just cut down my driveshaft to fit the 900 so now I'm gonna be milling off material off the exhaust manifold and maybe some off the exhaust side of the cylinders to hopefully make it all fit without a hull chop. Ill keep you informed with how much I take off.
- Location
- Winter Park, FL
i had to cut a lil of the side of the chamber and welded a new chamber plate then a jacket plate. that was with out milling the exhaust flange side. i know milling will reduce how much you have to take off the chamber. i would much rather do that than mod the hull
- Location
- Winter Park, FL
also if you are using the stock 750 engine plate to mount the 900/1100 i have an extra modded drive shaft that will fit if you want it, it just needs the coupler
- Location
- Winter Park, FL
- Location
- Bay City, Texas
Can anybody follow up on how they accomplished milling of the flange on the exhaust manifold? I just don't see where there is material to be removed here....
You can see where the face of the manifold comes pretty much flush with that bulge where the bolts need to thread into... If you take off even 1/4 you'd be cutting into that bolt hole plus even if you are milling underneath the bottom of that bolt hole it still wouldn't fit flat against the exhaust ports because that bulged out area would hit the outside of the cylinder...
Likewise, if you tried to trim some off of the exhaust port side of the connection, you can see the problem you'd have... Those exhaust "ramps" coming down out of the cylinder are angled in such a way that the ramp ends right at the ports on the face of the exhaust manifold. Milling the exhaust ports back towards the cylinders would mean you'd be milling backwards up the "ramp" and therefore the recessed ports would not mate evenly with the face of the exhaust manifold. This kind of misalignment would drastically effect volumetric efficiency and engine function.
So I'm kind of at a loss here... Where am I supposed to mill this extra space off?
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Nuclear you reading everything correctly. Nothing about this is fitment is perfect. You can lose your volumetric efficiency by milling off material or you can lose your exhaust chamber volume by cutting up your pipe to make it fit. The only way to do it without messing with the motor is to blister out the hull. So I'm going with the milling process. I think I can get 3-3.5mm off both the manifold and cylinder. It will be close to the headpipe bolt on the manifold (real close) but it should be just enough for me to fit the pipe in the hull without any cutting on the hull itself.
AND ID SAY DEFINETLY JUST CUT A HOLE IN THE HULL TO MAKE SPACE FOR THE EXHAUST MANI, FIBERGLASSING ISNT TOO DIFFICULT. take a block of foam, make a mold to fit into the hull, cut the hole out of the hole in the appropriate shape for the space needed, then just mix some resin and throw the fiberglass on. big deal, lol, id rather do that than loose engine performance ya know, not to mention u need a machine to mill the mani. fiberglass work maybe take u a day.
- Location
- Bay City, Texas
I'm definitely not going to blister the hull for this motor. Not because I don't want to do glass work or don't know how, but because I think blistered hulls look like $hit in my opinion unless you hide it under sponsons, which, as heynagel noted would have to be cut up too. I'd rather the hull remain a multi-purpose, multi-engine vessel. I have this triple, a big pin, a small pin, and a hyperkickass small pin that's currently in it, and this is my only SX hull so I'm not gonna make it a "dedicated" triple hull.
Also, DO NOT mill the exhaust ports on the cylinders!!!!! NOOOOO NO NO
@heynagel I hope you haven't pulled the trigger on doing that yet... I do NOT recommend doing that at all... milling back on the port ramps, like I said, will have a TERRIBLE effect on volumetric efficiency. Think about the amount of turbulence it creates when you put a shelf right there for the exhaust gasses to jump over while decreasing the diameter that it can flow through. And more importantly, think about WHERE that turbulence will occur.... IMEDIATELY upon exit of the cylinder. A 2-stroke engine would be crippled by this. It would still run, but it will NOT be just a small loss of power, it would be dramatic. You'd literally be better off leaving the 750 in there.
Here's why....
By introducing turbulence to the exhaust flow immediately, you interrupt the sonic pressure wave that a 2-stroke depends on. That sonic wave is what creates the vacuum pulling the exhaust gasses from the cylinder. If the exhaust gas encounters immediate turbulence, the sonic wave will be disturbed and broken apart as soon as it hits the sharp edge of that "shelf" (for the same reason sharp angles are used in sound-proof surfaces; they break up coherent sonic waves. and vice-versa, why a tuba in a marching band is shaped with the same smooth flowing curves as a 2-stroke pipe, to amplify a coherent sonic wave).
If you disturb that wave immediately after it is created, you essentially render the expansion chamber useless. The whole concept of an expansion chamber is based on that coherent sound wave traveling through it. It is designed to expand and amplify the wave (think tuba) before reducing the volume of the chamber down to normal pipe diameter. This amplifies the wave and then causes it to bottle-neck and resonate backwards towards the cylinder until it impacts a much more dense volume of gas (the fuel-air mixture) coming into the cylinder at the same time the exhaust gasses are leaving. When this backwards-moving wave impacts the dense cloud of fuel, it essentially "pushes" it back into the cylinder to ensure that the maximum volume of fuel remains in the chamber as the piston closes over the exhaust port to begin compression. ALL OF THIS IS LOST IF THE SONIC WAVE IS LOST!!!
That means you might as well just lose the expansion chamber completely and just run normal tubing out of the manifold because it wont even have an effect anymore. And of course by doing that, you have a much quicker and easier solution for how to fit the pipe into the engine compartment anyway!! lol
bottom line is... DO NOT mill your exhaust ports!!!
Also, DO NOT mill the exhaust ports on the cylinders!!!!! NOOOOO NO NO
@heynagel I hope you haven't pulled the trigger on doing that yet... I do NOT recommend doing that at all... milling back on the port ramps, like I said, will have a TERRIBLE effect on volumetric efficiency. Think about the amount of turbulence it creates when you put a shelf right there for the exhaust gasses to jump over while decreasing the diameter that it can flow through. And more importantly, think about WHERE that turbulence will occur.... IMEDIATELY upon exit of the cylinder. A 2-stroke engine would be crippled by this. It would still run, but it will NOT be just a small loss of power, it would be dramatic. You'd literally be better off leaving the 750 in there.
Here's why....
By introducing turbulence to the exhaust flow immediately, you interrupt the sonic pressure wave that a 2-stroke depends on. That sonic wave is what creates the vacuum pulling the exhaust gasses from the cylinder. If the exhaust gas encounters immediate turbulence, the sonic wave will be disturbed and broken apart as soon as it hits the sharp edge of that "shelf" (for the same reason sharp angles are used in sound-proof surfaces; they break up coherent sonic waves. and vice-versa, why a tuba in a marching band is shaped with the same smooth flowing curves as a 2-stroke pipe, to amplify a coherent sonic wave).
If you disturb that wave immediately after it is created, you essentially render the expansion chamber useless. The whole concept of an expansion chamber is based on that coherent sound wave traveling through it. It is designed to expand and amplify the wave (think tuba) before reducing the volume of the chamber down to normal pipe diameter. This amplifies the wave and then causes it to bottle-neck and resonate backwards towards the cylinder until it impacts a much more dense volume of gas (the fuel-air mixture) coming into the cylinder at the same time the exhaust gasses are leaving. When this backwards-moving wave impacts the dense cloud of fuel, it essentially "pushes" it back into the cylinder to ensure that the maximum volume of fuel remains in the chamber as the piston closes over the exhaust port to begin compression. ALL OF THIS IS LOST IF THE SONIC WAVE IS LOST!!!
That means you might as well just lose the expansion chamber completely and just run normal tubing out of the manifold because it wont even have an effect anymore. And of course by doing that, you have a much quicker and easier solution for how to fit the pipe into the engine compartment anyway!! lol
bottom line is... DO NOT mill your exhaust ports!!!
- Location
- Texas
yeah now im doing this conversion in an sx hull, i dont understand what to mill down, as of right now im going to mod the hull but if the other way is easier then hell..
- Location
- Texas
Yeah I dont see how it's possible my pipes off by like an inch and a half.. glass work... sigh.
you can only mill down about 1/2 inch before there isnt enough material left if that. but seriously, the 1100 motor barely fits in an sxr, the pipe touches the hull...soo good luck in any other hull. or try the 900 triple pipe.