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DIY Porsche 928 supercharger
system CLICK ON IMAGES
FOR LARGER VIEW |
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Looking down at the
supercharger, the boost pipe is clearly visible. The piping is standard 2.5”
exhaust tubing bought at the local muffler shop. For this build I needed 3 –
90 degree, 1 – 45 degree, 2’ of straight sections. The connecting rubber
hose were bought at NAPA. It’s a standard issue heavy duty truck radiator
hose with a 2.5” I.D. |
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This
is how the completed supercharger bracket looks when installed. At this
point the supercharger belt is fully installed, aligned, shimmed and
tightened. Both the belt and the tensioner were bought from NAPA. They are
both standard items and don’t require any special order to buy. The
tensioner pulley “arm” was reused from a previous supercharger kit, but it
can be easily fabricated at a machine shop. The bolt used was a grade 8
unit. This was necessary to prevent the tensioner form bending under full
boost. |
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A view of the complete
tubing system. It was essential for the 90 degree elbow at the back of the
engine to have a 3.5” dia. Anything less would create too much turbulence
and the MAF would get erratic reading, making the engine run poorly. This
3.5” pipe is readily available at any big rig dealership. I bought mine at
the local Mack Dealer. The left over piping from this elbow was used to
fabricate the oil vapor recovery tank (catch can). |
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To release some of the
excess air pressure during throttle closure a bypass valve was installed.
This unit was salvaged from a ‘90s Nissan 300ZX TT. After welding on the
adapter pipe for the bypass valve I used some 2 part epoxy to insure a
perfect seal. The two pipes material were barely compatible to weld and the
result was some leakage at the welding point, the epoxy fixed this problem.
The chrome ring attached to the bypass valve is only there to make the
bypass valve louder during operation and it’s not essential to a basic
build. |
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This is a close up view
of the “claws” I had to build to keep the MAF from popping out of the
throttle body housing during deceleration. The MAF already had tabs with
slotted holes at the top of the hosing. The claws were designed to hook into
the MAF at this location. The large hose clamp keeps the claws in place and
eliminates the possibility of the MAF to ever come off when the throttle
plate closes. |
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This is another view of
the MAF with the claws attached. |
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This is the MAF without
the claws. Notice the tabs with the slits at the top of the MAF. As
mentioned earlier, these were the points on housing that was used to connect
the claws to the MAF. |
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After painting all the
tubes and installing a temporary catch can, the car was ready for shake down
testing. A fuel pressure gage is was also installed to monitor fuel pressure
at idle. This gage isn’t necessary for a basic system. After a few full
boost runs it became apparent that the Nissan bypass valve’s capacity is not
enough to vent enough air during a closed throttle. The remaining air
pressure would force the boost pipes apart. At this point I decided to
install a secondary bypass valve. |
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