Archive for the ‘ Fuel System ’ Category

Header tanks mounted!

The header tanks have been mounted so that the plumbing system can be accurately measured and designed.

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FITTINGS!!!

It’s Christmas in March!!!

The beginnings of our Goodridge fittings have arrived!

… Let’s plumb.

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New stuff!!!

Our Fuel Lab pressure reg., Bosch fuel pump, in-line fuel filter and dry break fuel filler have all arrived!
Perfect timing, now they can be set in place to aid the planning of the engine bay plumbing process!

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Header tank sneak peek!

As we start to measure up and map out our fuel/ oil/ and coolant lines , the header tanks have been provisionally taped in place.

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Header tanks are in!

We have decided to go for a unique look and have our reservoir tanks all attached in one bracket. It will also allow for very nice, and very clean fuel/ coolant line runs.

Again another beautiful piece of artwork crafted by Mr. Bob Hall at Concept Racing.

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FIA Bag Tank

The standard Exige/Elise uses a 40L steel tank that uncomfortably resides within a much larger space behind the cabin.  For N2 to be FIA compliant as well as competitive in endurance races, a much larger capacity of fuel needs to be carried in an approved fuel cell.

Following the removal of the original tank, a new Lotus Sport bag tank to FIA standards was ordered (made by ATL).  The new fully homologated FT3 standard ‘Fuel cell’ neatly fits every available space that the Lotus chassis has to offer.  Construed from a flexible fuel resistant (of course!) ballistic membrane and filled with foam baffling, the cars endurance potential is stretched with an impressive new 70L capacity.  The installation process requires several sharp edges, notches, rivets and holes had to be smoothed and prepared ready to accept the bag tank.

In order to fill this impressive new capacity with fuel, N2 will need to employ a high-flow dry-break system.  The standard holes in the tank bulkhead must be increased in order to accept the large diameter fuelling hoses and associated roll-over valves and breathers.  Working with accurately drawn templates, the tank bulkhead has been cut and all the edges de-burred allowing up to 2.5L a second to be dumped into the cars now mammoth belly.

With the tank closely matching the chassis’ form; it’s no simple task to fit and requires the efforts of a team to squeeze it into its final position, saving just over 4KG on the standard steel tank.

Fuel System Design

One thing for sure is that 400hp is going to need a lot of fuel, so we knew we would have to change the stock in-tank fuel pump. 

On investigation, we found out that the 70 litre ATL Lotus bag tank comes ready to fit the standard Toyota in-tank pump housing.  It can even be used with the standard fuel level sender.  Inside the bag tank there is a compartment for the housing, with special trap doors to allow the fuel to flow into the chamber (on right hand turns) but not back again on left turns.  So we decided to stick with the Toyota system, which comprises a gauze mesh filter, a high pressure injection pump, a secondary finer filter, a collector pot, a pressure relief valve (to return excess fuel straight back into the tank), an outlet to the fuel rail and a breather that breathes both ways unless the fuel level rises or the car inverts.

For the Toyota fuel system to work as we need, we fitted the Walbro 255 litres per hour pump, which is tried and tested and is used by many of the high horsepower Mitsubishi Evos.  This is a longer pump and needs a special aluminium end cap to allow it to fit into the Toyota housing.  The Walbro pump wiring loom is sliced onto the Toyota loom, and this is all that needs to be done. 

 As we are using an open ended fuel rail, we have a return fuel line that needs to be fed into an external adjustable pressure regulator, and then back into the tank.  To do this, we are using the tank pressure sensor required by US Lotuses, and using this as a return port.  As we want to use screwed-on fuel pressure hoses (rather than push-fit plastic pipes as Lotus /Toyota use), we designed our own aluminium fittings that can be fitted to the housing from the outside.  We can now fit proper dash 6 racing fuel hose to the car and not worry about pipes coming off under high pressure!  As the fuel return now comes back into the housing, the internal pressure relief valve is no longer required, so we designed an exact copy of the original valve but machined from solid aluminium which will allow full pressure to be achieved.  The vent pipe continues to work as a vent pipe, and through the MoTec we will be able to use the fuel level gauge (as this is still technically a road-legal car!).

The fuel hose will go directly from the pump housing to the fuel rail, then from the other end of the fuel rail to an adjustable fuel pressure regulator (which will be connected to the induction system so that it takes account of the supercharger boost pressure to raise the fuel pressure), then it goes back to the tank.