Fuel


Mod Benefit Drawback Is it a problem? Notes
 
Fuel relay
Article
  • To run the fuel pump continuously
  • Eliminate the change over from low to high voltage/pressure/flow
  • More constant fuel pressure
  • Less chance of running lean
  • Increased wear on the fuel pump
  • Increased fuel consumption
  • Increased chance of over fuelling, especially during the mid rpm range
  • Fuel is heated up as it is cycled through the system more frequently
  • Over fuelling will loose you power

Yes

Even with a 48mm hybrid turbo running at 1 bar the car was over fuelling very badly <9:1. I would not do this mod again...and have now reversed this to help fuelling and fuel economy
Larger injectors
  • To increase fuelling due to increased demand for fuel, probably due to increased boost pressure and flow from your turbo
  • Not required for power increases up to 300hp
  • Car can run higher boost
  • Reduce injector duty cycle
  • Less chance of detonation
  • Increased fuel consumption
  • Need a rolling road or similar to set the Air Fuel Ratio
  • Need a replacement or add on ECU
  • The 185 can use the standard fuel rail and use the larger ST205 540cc injectors. The 165 cannot use either the 185 or the 205 fuel rail

Yes

Need to set the car up properly and fit an aftermarket ECU to correctly deliver the fuel

The 205 injectors are a direct replacement and will drop straight into a 185 fuel rail

Fuel pressure regulator
  • To increase the fuel pressure at the fuel rail
  • To increase the fuel delivered by the injectors
  • May be able to install an adjustable regulator to avoid buying and fitting larger injectors
  • A higher quality FPR may react faster than the stock FPR
  • Connecting to the existing fuel rail
  • Need a fuel pressure gauge to correctly set the pressure

ish

Fuel pressure gauge can be attached to the CSI fuel rail hole - M8 x 1 thread

Will need to get the car setup properly if you alter the pressure away from the standard specification

Larger fuel pump
  • To increase fuelling due to increased demand for fuel, probably due to increased boost pressure/flow from your turbo
  • Not required for power increases up to 300hp
  • Car can run higher boost
  • Reduce injector duty cycle
  • Less chance of detonation
  • Able to supply a greater volume of fuel
  • ~100
  • You will probably over fuel like mad if you don't get the car tuned
  The Walbro 255l/h is a popular choice

ish, need to get the car setup again

Upgrade fuel rail connections
  • Improve fuel flow
  • You might need the car tuned in order to cope with the increased delivery

ish

Improve the flow to the fuel rail by reducing the restriction from the existing connectors, fit AN style connections instead of banjo connectors

May need to get the car setup

You won't need this mod until >300hp

Upgrade fuel rail
  • Improve fuel flow
  • Expense

No

The 205 rail is the best flowing rail of all the GT4s.

The 205 rail will not fit either the 165 or 185 had

A Wolfkatz rail might be the best solution

Increase fuel RON rating
  • To improve power output
  • Reduce chances of detonation
  • More expensive

No

Shell Optimax is currently the highest RON fuel in the UK - 98

BP Ultimate - 97

Other methods to increase the RON rating are the addition of Methanol in the WI system or to use a "one shot" octane booster in with the fuel