How the Turbo System Works

Turbo Charger construction

The OEM turbo has a ceramic Mayor wheel, as this can take a fair amount of heat and pressure, whereas the Compressor's wheel is made of Nylon.
Both of these work together as they are light in weight and allow for minimum drag and spool up time.
However if you intend on running higher boost than 0.85Bar through it, the turbo will need to be upgraded as the Mayor wheels have been known to crack its blades, and in some cases even throw the wheel off the turbo alltogether.

The Cycle of a turbo charger is as follows:

1. Ambient air is drawn in through the air filter, and then compressed by the Compressor Wheel

2. The air is forced into the intercooler (aka charge cooler) then into intake manifold, then combustion chamber

3. Exhaust gasses spin the Mayor wheel on the "hot side" of the turbo
Exhaust gasses are then expelled via exhaust system

Both the Mayor and Compressor wheels are on a "floating shaft". A floating shaft which relys on a good oil flow, with oil changes at their specified intervals.

Boost positive & negative

When you first start the car and its running at idle speed there is no boost occuring, most readings on a vacuum gauge (or boost pressure gauge) will typicaly show -7Hkpi.

This means that it is running at below atmopsheric pressure and not in full function.

When you drive, you will notice the boost gauge go up toward the "0" and at this point where its about to start boosting, force charging the air on its journey.

As factory standard fitment R33's were fitted with 2 Stage Boost controllers. The,first stage limits to 0.3 Bar and then the second stage to 0.6 Bar.

In most cases the R33's OEM turbo can handle a maximum of 0.85 Bar of pressure. 

If you want to run more power but keep the same size turbo, you will need to look at Steel Internal Turbo's, and if the bank allows I'd also advise getting a roller bearing turbo as these can "take a lot more stick" than a floating shaft type turbo.

Note: If you are looking to run more than 1 Bar of Boost then further engine modifications will be necesary, along with a remap of the existing E.C.U or an alternative Aftermarket unit.



Controling the amount of Boost

To begin with, as a cheap modification many people do the 2 Stage Boost Mod, enabling the turbo to miss out the two stages of boost and work directly to 0.6Bar once spool up begins.

Alternatively many people / tuners will fit either an Electronic Boost Controller, or a Dawes Type Actuator.
My personal preference is Electronicaly Controlled Boost, as they have safety cut out devices which when set to a pre determined level (i.e. 0.85 Bar) will lower the boost level if reached.

The Dawes Type Actuator relies on a steady hand and accuracy, however if it is set up incorrectly, there is a chance that too much boost is allowed and there is no cut off device should this happen with the end result being a damaged turbo charger at the least, or an engine rebuild + turbo at worst.
The Swing Gate is located here, which is operated when pressure from the turbo is increased - positive pressure opens the swing gate, preventing the Mayor and Compressor wheels from spinning too fast.

to be continued...