SBT engines are de-tuned; Why would anyone want that? - Blogs - PWCToday

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SBT engines are de-tuned; Why would anyone want that?

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All the watercraft manufactures build their watercraft to withstand customer abuse.

Every year manufactures send riders out to ride their new watercraft nearly every day to
discover problems that may occur to a customer. Their constant testing allows them to
gain many more hours on the skis before the customer.Then manufactures send out service
bulletins, in advance of the problems occurring to the customer. Well run service departments
will fix those problems before they become a problem, or they can make a customer aware of
old service bulletins if they ask.

The manufactures use high quality parts based on testing to withstand everyday
use, EPA standards, they pay for the rights to use some engine parts, and patent
their parts to gain an edge on the competition.

Depending on the watercraft dealer, they may offer 3 months to a year on their service
department labor. Many watercraft manufactures have warranties on their new oem and
oem rebuilt parts.

When you deal with a reputable dealer, they are not taking used parts from a core engine
bin to use in your rebuilt engine.

Quote Originally Posted by The Great Defender View Post
SBT "de-tunes" their motors to less than stock efficiency and offers a no fault warranty which nobody else in the industry does.
The first question is why do they need to detune their engines? Are their parts inferior
to OEM parts.

This SBT customer bought his engine with an air leak in the crankcases, the wrong
main bearings on the SBT rebuilt crank, that main bearing caused a steel pin to fall
out of another main bearing and ruined the engine. No SBT Warranty.

Here is another PWCToday member considering replacing one of the engine's in his
Challenger 1800 with a De-tuned engine, or a rebuilt engine by a local shop.

Quote Originally Posted by I can't believe you are a mechanic! View Post
Since when does too much squish cause an engine to blow up, too little squish causing deto, yeah definatly ,
too much just makes an engine that is sluggish and doesn't produce a lot of power.
One of the ways SBT detune your engine is by cutting a large amount of material
out of the head to decrease compression. But this is not a safe way to reduce
compression or gain engine reliability.

When you build an engine for reliability, you machine the head and cylinder to run a tight
squish clearance around .040" or 1mm. If you are running loose piston to cylinder clearance,
.050" may be necessary. A tight squish prevents detonation by creating an area that is too
lean to burn, and the outer diameter of the piston crown stays cool. A tight squish also
promotes better combustion and increased power.

Detonation occurs when the fuel/air mixture along outer diameter of the piston crown can
increase in temperature until the fuel/air mixture will self ignite.

That is the basic difference, a tight squish prevents detonation because it prevents
the fuel/air mixture from burning, a loose or wide squish allows the fuel to burn and outer
diameter of the piston crown to heat up.

Quote Originally Posted by The Great Defender View Post
That being said, if you want a motor that is going to start and run and survive a high level of customer abuse SBT is a very good
Whether or not the engine starts or runs, is not related to the SBT engine. It is a
function of the carburation and ignition system.

If a SBT customer never found out why his engine failed in the first place, the SBT
de-tuned engine is not going to fix that.

If a customers ski has a large impeller, because he thought would give him more top speed,
and that impeller prevents the engine from producing the rpm where peak torque occurs,
that is a cause of detonation.

Because of how SBT detunes their engines, and it promotes detonation. Combine that with
old gas, and you have a recipe for a seizure that the customer would be unaware of.

Quote Originally Posted by The Great Defender View Post
It is also fairly easy to get some horse power back from your SBT motor by simply increasing the compression ratio and running fresh premium pump gas.
The problem with this is that SBT ruined the head when they de-tuned the engine. The only
fix the compression is to replace the head, and even that might not work if the cylinders were
decked too.

Cheap parts and engines can come with an unknown price. For example: I have seen Chinese
connecting rods just snap in half while running at wide open throttle on watercraft and other
engines. It is a bad way to save money.

Bill M.

Quote Originally Posted by I can't believe you are a mechanic! View Post
too little squish causing deto, yeah defiantly
OEM squish clearances are never tighter than .040" and will not cause detonation. But whether
or not a tight squish causes detonation is a point of contention between me and MCN6. My own
experience shows that the tighter the squish, the leaner the fuel/air mixture is around the squish
band, and that keeps the piston crown cool. Neither does high squish velocities. BM.
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