Ok, I've only explained this a thousand times, but here goes..

The by-pass valve is open during periods of vacuum, which is about 90% of the time you spend driving. The only time you don't have vacuum, is under boost. When you have vacuum, the by-pass is OPEN, allowing air to pass around the blower. This keeps the intake charge cool and does not let pressure build up in the intake.

When you are under boost, the by pass valve closes. All the incoming air now goes through the blower, and gets compressed by the rotors. This increases heat, but that's a normal by product of making power.

The by-pass is operated by a vacuum source off the motor. It's just a vacuum operated mechanical valve. However, on the Lightning, there is an electrical solenoid that ties into the vacuum source going to the by pass valve. This allows the PCM to shut down the blower being able to make boost, if the PCM sees something that triggers a failsafe.

There are two ways to stop the PCM from cutting boost. One way is to modify the vacuum source, such as with one of those "by pass kits". This method takes the vacuum off the by pass and it is closed all the time. The down side of this is that you never by pass the blower. You are always building pressure and creating heat. When you are at idle or crusing, the by pass is closed when it should be open. This is BAD.

The other way to stop the boost dump, is to simply unplug the electrical solenoid. This takes away the PCMs ability to kill boost. It does set a P0234 code in the PCM, but that is easily cleared with a battery disconnect. It does NOT set the light.

Whichever method you choose, keep in mind that either way stops the PCM from killing boost. The chances of engine damage are slim, but if you do run into a case where the PCM needs to shut down the boost to save the drivetrain, it can't do it. Just a little disclaimer for the info .

And by the way, I am not bashing JDMs by pass kit, I have been explaining this by pass info way before JDM was even selling Lightning stuff.

Hope this helps!!

 

Sal thanks for explaining it. I couldn't think of another way to explain it other than going all out like you did.

Though I believe on the JDM by pass kit, it takes the dump silinoid out of the vacume loop and closes the loop. I dont think it takes the waste gate out of the loop, thus not keeping waste gate closed all the time.

But my original point was why pay $10 for the parts your self, or $25 for a tuner kit, when you can unplug the silinoid for free and have the same effect?

 

Thanks Sal now lets make some horsepower...