Fuel - "Is 1.5km/litre bad?"

Where to start?

The fuel system in a stocker 1600 consists of a 55 litre fuel tank positioned between the rear shock towers, two fuel lines, a mechanical pump and a Nikki (?) carby. For a start the fuel lines are too small for the requirements of a rotary, the mechanical pump disappeared with the engine and the fuel tank would last about 80k's. That's about half the required distance, which means we'd be constantly refuelling every two laps of a long course. Time to change everything...

First to appear was the 48mm IDA Weber carb (re-sleaved to 51mm). This carb is stock apart from the grinding of the fuel bowl to enlarge the capacity. This is done so that on long right/left corners the main jets don't starve for fuel. Guys that race on bitumen also increase the volume by adding an extension to the side of the existing bowl. We haven't found the need to do this yet, as the car very rarely touches any black track.

We use a K&N paper filter that provides great service. The only problem with the existing filter setup is that dirt will (and does) collect around the base of the filter. When you change the filter you've got to be careful to clean all this stuff out. Unfortunately, even with the oversized jetting, the odd particle of sand does ruin the day. In view of this, we are planning to enclose the entire filter in a new cold air box and have a primary filter somewhere else. With any luck that'll stop the muck getting up to the carb.

As you can see the fuel inlet connection has a 1/2" pipe running back to the regulator.

The fuel regulator is part of the fuel delivery system.

This particular regulator is of the Holley variety and is set up to operate at 6psi. Note that the inlet valve on the carb is the largest available and setting the pressure any higher results in severe flooding at idle. Unfortunately the inlet valve cannot be down-sized (due to fuel demands at high RPMs) so we have installed a fuel pump switch to enable the pump to be turned off at idle.

This regulator is fed by a 1/2" copper line running the entire length of the car.

Note that it is not possible to set the pressure any lower than 6psi with this regulator.

The fuel tank is a custom design made of sheet aluminium and filled with anti-slop foam. It's also fitted with a lower reservoir that's designed to grab every last little drop and siphon it to the fuel pump.

Note that the tank is fitted with a custom sender unit that's matched to the VDO fuel gauge.

BTW, the plastic pipe velcro'd to the tank replaces the original springs used to hold the boot lid up. Unfortunately both the sender and filler neck were obstructing the operation of these springs, so out they came.

We need to put a bit more bracing on the near side of the tank as it's in the process of bending the mounts. Luckily the bracing (made from two strips of right angle ally) works well. Note that we had the tank professionally welded (nice job to).

The pump (Holley blue) is mounted under the tank (the pumps aren't good at self-priming when they have to suck air).

Next to the pump is mounted a truck fuel filter. This filter has disposable paper elements and was used because of the low differential pressure it creates and the volume it can handle.

All fuel lines are 1/2".