purple_people_eater
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Water Injection
ever wonder what the RAVE looking cap on the muffler is and what is does? well here you go:
from seadoo racing hand book:
WATER INJECTED EXHAUST SYSTEM
Several factors necessitate the use of a water cooled, water injected, tuned exhaust system. One
major concern is overall bilge temperature, which is kept low by keeping the part of the tuned pipe
closest to the engine jacketed with water and the remainder of the exhaust system cool by
injecting water directly into the exhaust stream. Injecting water into the exhaust system not only
helps keep the exhaust system cool, but also changes the characteristics of the sonic wave in the
tuned pipe. The water injected exhaust system reduces exhaust gas temperature, therefore
increasing exhaust gas density in the tuned pipe. The sonic wave moves slower in this cooled,
denser air so it takes longer to reflect back to the exhaust port. The net effect is that the tuned pipe
can be shorter yet achieving the same results as a longer “dry” tuned pipe.
By changing the amount of water injected into the exhaust stream, the characteristics of the
engine power band can be altered. It is important that enough water is injected into the exhaust
stream to keep the rubber hoses and muffler from damage due to excessive heat.
In Limited Class racing an aftermarket exhaust pipe and manifold are allowed. The water box or
muffler however must remain stock with no modifications. When purchasing an aftermarket pipe
consult the manufacturer of the pipe to determine if the pipe is race legal by your race sanctioning
body (IJSBA). Some pipes will fit your craft, but may not be race legal because of inadequate head
pipe cooling or mounting of the pipe requires relocation of the waterbox. Waterbox relocation is
illegal by several sanctioning bodies for Limited Class racing.
XP 800 EXHAUST WATER REGULATOR OPERATION AND REMOVAL
The XP 800 models utilize a water regulator located on top of the muffler to control the amount of
water injected into the exhaust system at the tuned pipe head and the muffler box. The purpose of
this is two fold:
1. It effectively controls the exhaust wave speed thereby creating a more usefull or broader
power curve.
2. It cools the exhaust system and hoses which prevents heat damage.
The water regulator is calibrated for use on XP 800’s which have no engine modifications. The
regulators works quite well on the stock watercraft and provides a noticeable increase in performance
over models not so equipped. If the watercraft is not being raced but modifications are
made to the engine such as increased compression, changes in port timing, etc. the water
regulator will not deliver the correct amount of water for optimum performance. Recalibrating the
regulator water flow will require most users to experiment with different size holes being drilled
into the regulator then threading and fitting the holes with jets. Various size jets will then be tried
until the best performance is found.
The water regulator has been disallowed for competition usage by the IJSBA. Furthermore any
valves used within the entire engine cooling system must be of the fixed type. This rule was placed
into affect during the mid 1995 racing season. Due to this ruling the water regulator must be
removed and the exhaust system must be “Hard Jetted” (fitted with jets of the fixed type).
ever wonder what the RAVE looking cap on the muffler is and what is does? well here you go:
from seadoo racing hand book:
WATER INJECTED EXHAUST SYSTEM
Several factors necessitate the use of a water cooled, water injected, tuned exhaust system. One
major concern is overall bilge temperature, which is kept low by keeping the part of the tuned pipe
closest to the engine jacketed with water and the remainder of the exhaust system cool by
injecting water directly into the exhaust stream. Injecting water into the exhaust system not only
helps keep the exhaust system cool, but also changes the characteristics of the sonic wave in the
tuned pipe. The water injected exhaust system reduces exhaust gas temperature, therefore
increasing exhaust gas density in the tuned pipe. The sonic wave moves slower in this cooled,
denser air so it takes longer to reflect back to the exhaust port. The net effect is that the tuned pipe
can be shorter yet achieving the same results as a longer “dry” tuned pipe.
By changing the amount of water injected into the exhaust stream, the characteristics of the
engine power band can be altered. It is important that enough water is injected into the exhaust
stream to keep the rubber hoses and muffler from damage due to excessive heat.
In Limited Class racing an aftermarket exhaust pipe and manifold are allowed. The water box or
muffler however must remain stock with no modifications. When purchasing an aftermarket pipe
consult the manufacturer of the pipe to determine if the pipe is race legal by your race sanctioning
body (IJSBA). Some pipes will fit your craft, but may not be race legal because of inadequate head
pipe cooling or mounting of the pipe requires relocation of the waterbox. Waterbox relocation is
illegal by several sanctioning bodies for Limited Class racing.
XP 800 EXHAUST WATER REGULATOR OPERATION AND REMOVAL
The XP 800 models utilize a water regulator located on top of the muffler to control the amount of
water injected into the exhaust system at the tuned pipe head and the muffler box. The purpose of
this is two fold:
1. It effectively controls the exhaust wave speed thereby creating a more usefull or broader
power curve.
2. It cools the exhaust system and hoses which prevents heat damage.
The water regulator is calibrated for use on XP 800’s which have no engine modifications. The
regulators works quite well on the stock watercraft and provides a noticeable increase in performance
over models not so equipped. If the watercraft is not being raced but modifications are
made to the engine such as increased compression, changes in port timing, etc. the water
regulator will not deliver the correct amount of water for optimum performance. Recalibrating the
regulator water flow will require most users to experiment with different size holes being drilled
into the regulator then threading and fitting the holes with jets. Various size jets will then be tried
until the best performance is found.
The water regulator has been disallowed for competition usage by the IJSBA. Furthermore any
valves used within the entire engine cooling system must be of the fixed type. This rule was placed
into affect during the mid 1995 racing season. Due to this ruling the water regulator must be
removed and the exhaust system must be “Hard Jetted” (fitted with jets of the fixed type).
