Pontiac G8 Stock Fuel System

The stock G8 fuel tank is plastic, and uses two individual fuel tank canisters with a separate fuel level sending unit in each one. There is a pump in he passenger side canister only though. The fuel system is returnless, and maintains a static fuel pressure of ~ 59 psi under all conditions. The stock fuel injectors are high impedance and stubby, and seem to flow in the ~ 41.5 pounds/hour @ 43.5 psi range.

The completely stock fuel system is very stout, and in our opinion will work just fine - even for highly modified cars - as long as you stay naturally aspirated.

« Previous | Next »

Adding Boost Strains Stock Injectors

Once you install any sort of power adder, the entire situation changes. Just above 7 psi of boost (depending on your air/fuel ratio), the stock injectors will reach 100% duty cycle. You can still run them like this if you want, but we don't recommend it.

« Previous | Next »

Greater than 7 PSI Of Boost Requires Larger Injectors

Once you exceed ~ 7 psi of boost, it will be time to upgrade to the Siemens 60-pound fuel injectors. These pieces are top quality, and will take you as far as you want to go. You'll need some custom ECM programming for these, and some electrical adapters too. This will take you to somewhere around 9 psi of boost (depending on your air/fuel ratio), and then your stock fuel pump will no longer be able to keep up.

You'll see that your fuel pressure will start at ~ 59 psi and begin dropping if you stay at full throttle for more than a second or two. We've seen ours as low as 40 psi by 140 mph (on the dyno of course), but we don't recommend pushing it any farther until the fuel system is beefed up.

« Previous | Next »

9 PSI Of Boost Requires Fuel System Changes

Above 9 psi, the stock fuel pumps and fuel line are completely inadequate. Working in conjunction with APS and B & R Racing, we came up with the following solution.

1. Drill two additional 3/8" holes in the lower portion of the stock plastic pump unit, so that more fuel can enter it.
2. Fabricate a small custom surge tank to be located in the trunk and run at zero pressure.
3. Reroute the stock feed line from the fuel tank into the surge tank.

4. Feed two small Walbro GSS392 inline fuel pumps from the surge tank.
5. Give each fuel pump a separate -06 AN feed line to the engine bay.
6. Install aftermarket (LS7) fuel rails with modified mounting brackets.
7. Install an aftermarket fuel pressure regulator, set for 60 psi.
8. Route a new return line, running into the new surge tank.
9. Route a new return line from the surge tank to the stock plastic pump unit.
10. Add more boost until completely satisfied.

« Previous | Next »