Toyota Celica GT4 ST205 turbo modifications

Under construction - not yet accurate...

Turbo

Mod Benefit Drawback Is it a problem? Notes
 
Increase boost pressure
What is and How to fit an RV
  • More power
  • More fun
  • Increased air intake temps
  • Detonation much more likely
  • Likelihood of engine failure increased
  • Stock turbo limited in pressure/flow

ish, depends on prior modifications

An SBC is far superior than the RV method, but an RV is much cheaper!
Dump Valve
How to fit a DV
What is a DV
  • Get a 'tish' sound like a boy racer on gear changes
  • Improve driveability
  • Helps to keep turbo spinning between gear changes
  • Helps to prolong turbo life
  • £
  • Noise

No

Atmospheric type will foul up fuelling when changing gears as metered is vented to atmos. Recirculating type will help to correctly meter fuel

Try not get a diaphragm DV - these fail more often and wear quicker than the piston type

Select the correct spring or idling may be a problem - 5psi

Fuel Cut Defencer
What is an FCD?
Make & fit an FCD
  • To generate more boost than the stock ECU will allow
  • £ if bought, cheap to make
  • Require ECU wiring diagram and a soldering iron - ECU pin out article here

ish - depends if you are any good at soldering!

Allows more boost pressure by overcoming the fuel cut level set by the ECU ~12psi (exact level varies from car to car)
Uprate/hybridise stock turbo
Pictures
  • More power, more fun
  • More efficient at a higher boost pressure
  • As it is more efficient, the likelihood of detonation at higher boost pressures reduced
  • Will flow better
  • Will help cure the wastegate crack you probably have
  • May cure the smoking at idle!
  • £ dependant upon choice of size
  • Upgrading stock turbo good for oil & water pipes and support brackets etc but not nearly as good as a GT30 or GT25 etc for power and efficiency
  • Watch the size of the compressor as the stock wastegate may not be able to flow out enough exhaust gases

No

Popular sizes for CT26 inducer:

42mm - 12psi (ST165)
44mm - 15psi (ST185)
48mm - 18psi (ST185 CS/RC)
48mm - 18psi (ST205)
52mm - 18psi
54mm - 24psi
56mm - 24psi
(based on Garret T04 wheel)

Note - this is only a very sketchy rough guide

You might also want to ask about:

  • Gas flowing the wastegate
  • Inconel wastegate seat, for 165
  • Polishing the compressor housing
  • Gas flowing the exhaust housing
  • 360 degree thrust bearing
Fit larger aftermarket turbo
  • Much more power, more fun
  • You'll probably want go for a Ball Bearing turbo...
  • Less lag
  • More efficient
  • Able to produce more pressure and more importantly increased flow
  • ££
  • May require a custom exhaust manifold or adaptor
  • May need a custom down pipe
  • May require custom oil feed and drain, water cooling to/from the turbo
  • Dependant upon turbo type may require an external wastegate...£
  • Some way of controlling this lot - an aftermarket ECU
  • Shortening the life of the stock engine, maybe not your daily driver car?

Yes

By now you are into some serious power - you'll definitely need an aftermarket ECU or addon/piggyback, go for a complete ECU...

Reliability shortened. Fuelling needs to be addressed, maybe larger injectors fitted, replacement/addon ECU, forged pistons may also be required etc

External wastegate
  • Better exhaust gas flow
  • Improved turbo control
  • Improved power output
  • £
  • Specialist external dump valve required
  • Need to fabricate a custom downpipe to accommodate the output from the external wastegate and the turbo
  • You'll obviously need an external wastegate turbo. NOT the stock CT26!

Yes

Expensive!
Disable TVSV
How to article
  • Better control of boost pressure
  • Run same pressure in all gears
  • Will run the same LOWER pressure in all gears

No

This is normally carried out when fitting some sort of boost controller.

Doing this mod without fitting a boost controller is pointless and will make the car slower!