Pully Swap, Sizes and info

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Pully Swap, Sizes and info

Post by ßlåçk§mókè on 2010-01-12, 14:56

Recomended Max Continuous Blower Speed = 16,000 rpms

Stock = 3.35"

* 12 psi
* bypass mod pointless
* you need to upgrade
* Blower speed 14,000 rpms at 7,500+rpms

3" Pulley

* 14+ psi
* 10 hp and 15 ft/lb gains**
* Stock belt/idler pulley OK
* no engine management required
* bypass mod OK - good for additional 10 hp
* Blower speed 14,000 rpms at 6,700 rpms

2.8" Pulley

* 16+ psi
* 15 hp and 25 ft/lbs gains**
* belt or idler pulley modification required
* engine management recomended
* bypass mod OK with engine management, good for additional 10 hp
* Blower speed 14,000 rpms at 6,250 rpms

2.6" Pulley

* 18+ psi
* gains depend on tune**
* belt or idler pulley modification required
* engine management required
* fuel injectors required

Boost Bypass Mod
Originally Posted by ptparker
The boost bypass system on our superchargers has three parts: the solinoid, the actuator, and the butterfly valve (normally closed). The actuator is a diaphram/piston that has two chambers and a small metal shaft that connects to the buterfly valve. When the ECU triggers boost bypass, it opens a soliniod allowing charged air (in the range on 12+ psi stock to about 18+ with a very small pulley) to fill one of the chambers of the actuator. When this happens the piston in the actuator pulls on the shaft which opens the butterfly valve allowing charged air back into the inlet side of the supercharger instead of forcing that air into the engine.

The ECU uses boost bypass to bleed off some of the boost just before you hit the rev limiter to prevent damage from the engine getting fuel (or spark) cut off at maximum boost. The problem with this is that if you change the pulley, the computer detects that you are hitting the "maximum boost" (near 13 psi) and opens the bypass while you still have a lot of RPM's left to climb.

The idea of boost bypass is that if you allow the computer to open the solinoid, but do not allow the charged air to reach the piston chamber on the actuator, the butterfly (bypass) valve will never open. Many people on this board have this mod done, and it is considered a 'safe' mod, but remember that you are disabling an engine protection feature.

The following statement is true for a stock or near stock setup, but with signifantly smaller pulleys the boost bypass opens earlier:

The boost bypass valve opens up at 6,000rpm and bleeds boost off untill redline. The bypass mod disables it keeping it closed all the way up untill redline. You will see no difference in power under 6,000 rpms if you disable it. They only increase in power comes after 6000 rpms where you will see an additional 10hp gain in peak hp. See the attached dyno graph (courtesy of Sp00ner) The green line is with the bypass valve disabled.
Instructions on how to do this mod can be found here courtesy of AlphaJaguar5
How To: Boost Bypass Mod

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