There are many ways of 'upping the boost' on a turbo car. 
From the 'popular bleed off system' to fancy electronic solutions 
The follow is one way I have found to increase the boost that not 
many people seem to know about or do. But after testing compared 
the bleed off method I prefer the following method..... 

The test vehicle is a starion turbo...now before you all complain about 
how it isn't a Dat...well I have just fitted a turbo of a nissan 300ZX 
(not much consolation i know, but it will have to do.) The nissan turbo fitment has made the car a WHOLE lot more driveable with boost coming in around 1000 rpm earlier.....but the nissan wastegate was only running about 5 pounds of boost after the conversion to the starion (the original mitsubishi turbo had previously been 'upped' to around 13 pound), hence the reason for this little boosting  project.... 

The wastegate is integral, and is mounted on the side of the turbo. 

The principal of the wastegate is to open an exhaust bypass of the turbo in the turbo/exhaust housing at a preset boost level to stop the boost rising any further (In this case it was opening at around 5 pounds). 
The wastegate is activated by a wastegate activator attached by a rod mounted on the side of the turbo (as seen in the following images) 

Inside this activator is a spring and a diaphragm. The spring preloads the rod that operates the wastegate keeping it closed. the diaphragm sits on top of the spring. A Boost line is feed into the top of the activator on top of the diaphragm, and when the boost is greater than the spring pressure the wastegate opens and the boost pressure stops increasing. 
Ok...so the spring (preloaded) in the nissan wastegate we have just fitted must be around a 5 pound spring. 

Now the bleed of method works by bleeding off a bit of the boost from the line to the wastegate activator. thereby fooling the wastegate into seeing a lower boost pressure than the motor is actually making....a very popular way of 'upping the boost'....But I found with the amount of bleed off needed to increase the boost to the targeted 14 pound there was a noticeable movement of the power band back up to where it was with the standard mitsubishi turbo....another 1000 rpm back UP the rev range 
with full boost not until around 3700 rpm...Definatly a big step backwards. 
The problem is boost (precious boost) is escaping...being sacrificed for a bit more power...not a good sacrifice if you ask me. 

So back to my solution, the way I ended up doing it was with some inexpensive springs....that's right ordinary springs from the hardware store...stretched across the wastegate increasing the spring preload tension on the wastegate.

By adding the extra springs to the outside of the wastegate you increase the preload on the wastegate....thereby needing a higher boost pressure level to overcome the extra spring preload, thereby increasing your boost! 
Simple and cheap.  No boost wastage being bleed off into the atmosphere!

WARNING....Try this at your own risk...we take no responsibility for your actions. START SMALL and LISTEN to the motor under boost for pinging (a sign of detonation)...SEEK ADVICE as to how much of a boost increase your motor can handle. Different factory motors can handle different increases in boost before leaning out (starving of fuel) 
CHECK IT OUT BEFORE YOU START. 
Start with small springs and watch your boost gauge! 

I ended up having to use heaver springs than the ones in the pictures above. The following is a few pictures of the finished job in the car...

I cannot over stress the above warning...so I will risk repeating myself...
WARNING....Try this at your own risk...we take no responsibility for your actions. START SMALL and LISTEN to the motor under boost for pinging (a sign of detonation)...SEEK ADVICE as to how much of a boost increase your motor can handle. Different factory motors can handle different increases in boost before leaning out (starving of fuel) 
CHECK IT OUT BEFORE YOU START. 
Start with small springs and _watch_ your boost guage! 

The above are just my/our views and we welcome your feedback. 
If you have anything to add or have other informaton that may be of use, then please email us....ozdat@ozdat.com.au

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