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Build Part 6

Installation Time

I finally managed to find a local shop with the welding skills to secure the spline plate for the pulley. The pulley that SmoothFlow made for me was good, but not perfect. I can't blambe the guy for the weld though. I know next to nothing about tig welding, and assumed it would be easy. The expert welder I found pulled it off, but he told me it wasn't for the n00b welder. None the less, he did a bang up job! So... here we go! Time to put it all together and see what happens.

Everything installed, mounted and secured.


It took a few hours to get everything in and secured. Just had to make a couple tweaks in a few places. Plus, I installed an electric oil pressure gauge while I had the Alternator belt removed. It was easier to get in there with the alternator out. You can see the sending unit right next to the PS reservoir.

A view from the other side.


So.. here we go! The FIRST startup of my long awaited SC project.
First Start Video

Ok... lets try that first startup again shall wee. This time, with all 4 plug wires on.
2nd First Start Video

And, a short spin around the block
Around the block Video

A Fixed Displacement BlowThru setup?

Those of you in the Know of Superchargers are already scratching your head at my build. Why? Because what we have here, is a Fixed Displacement Supercharger blowing through the Throttle Body. Pretty much laid out just like a Turbo setup, or a Centrifugal Supercharger. This is NOT the normal way to plumb a Roots or a TwinScrew Supercharger. Yes, it's doable, and I drove my car this way for about a year before changing it (see Part 7). But it has it's drawbacks.

The order of bits in the above setup is like this:
Filter -> Supercharger -> Intercooler -> BOV -> Throttle Body -> Intake Manifold Exactly what you would find in a Turbo Setup. And for my car , the BOV is CRITICAL!!


  • Simple Install without having to move the TB


  • LOUD!!!
  • No ability to modulate boost, It's either <0psi or MAX Psi. This is due to the CBV slamming shut at 0inHg.

However, the typical/normal sequence for a Fixed Displacement Supercharger is: Filter -> Throttle Body -> Supercharger -> Intercooler -> Intake Manifold The use of a CBV is actually optional

Why does it matter? Because a Roots or TwinScrew Supercharger is a Fixed Displacement Air Pump. This means, that for every Revolution of it's rotors, it pumps a fixed volume of air. And also, this air can't find it's way back through the SC, not without causing damage. As apposed to a Turbo or Centrifugal Supercharger, that pumps air as a function of it's speed, and also can allow air to pass backwards if it's boost buildup is too high.

So, you can see that with the Throttle Body placed AFTER the Roots Blower, there is no way to regulate the amount of air being pumped by the SC. It is always trying to move the maximum volume of air. This is the reason for requiring a CBV (BOV really) with a Blow-Thru TB setup. All that extra air can't go past the closed Throttle Body plate, and thus must be diverted by the BOV. Think about High-Vacuum cruise situations. Your just humping down the Highway at 3500 rpms, but your vacuum gauge reads 12inHg of vac. Your SC is "trying" to pump enough air to actually create boost, but your TB is not allowing this extra volume of air to enter your motor. Thus, it spews out the BOV (this you can easily ear in the above videos). If the TB was placed in front of the SC, as in a typical roots applicaiton, it would be physically limiting the air in the system. As a result, the SC is boosting in vacuum! haha.. yeah, funny concept, but accurate. So, the TB is causing 20inHg before the SC, the SC is boosting to 15inHg, and the excess air... well, there isn't any!

There are really only 2 major issues with the idea of having the TB after the SC.

You can't really control how much/little boost is fed to the engine. This is due to the use of the CBV. It's held open as long as your motor is in vacuum (anything above 2inHg of vac). But, as soon as it sees just enough to close it (1-2inHg) it slams shut, and all of a sudden ALL of the air being pumped by the SC is crammed down your motors throat!! In other words full boost! There is no way at all to achieve, say... 50% boost pressure with the Throttle. It can't be done. For your typical street driven car, this really isn't a major issue. It never bothered my on the street. But for AutoX racing, it was an issue. I needed better control of power output.

Loud.. really really Loud!! Just listen to my various YouTube videos, and decide for your self.

So, after about a year of this, I decided to take the plunge and attempt to relocate my Throttle Body. Needless to say, it was a total success!!