As regular viewers may recall I had a fuel pressure issue. Basically Dave Walker raised my fuel pressure to 4 bar as he was having to run the injectors flat out at high RPM with the standard fuel pressure.
The problem wasn’t picked up until later when I fitted a fuel pressure gauge. As the revs rose over 6,500 rpm the fuel pressure started to drop off in a linear way reaching a low of 3.3 bar at 8,000 rpm
The map was correct as the extra .3 bar at 8k was enough to make the injectors safe.
But I don’t like stuff only just working, so I thought I would uprate the pump. A call to Demon Tweeks had an Elise Motorsport pump from Walbro on its way (ï¿½100). However that is where the fun and games started.
The standard fuel pump in our cars sits inside a swirl pot inside the tank. The pump has two inputs, one sucks from inside the swirl pot, the other from outside the swirl pot. The fuel return from the engine returns the fuel to the swirl pot.
The Mortsport Elise pump that I received only had one input and it was a different shape and size and everything. So when fitting a lot of modification to the standard swirl pot / fuel level sender assembly had to be made and I knew that what I was doing wasn’t going to be the final solution . The main reason for this being that as I only had one input to the pump I had to take fuel from outside the swirl pot (as under full load the swirl pot would empty) the problem with this is fuel surge, as when I took left hand bends at speed all the fuel moves away from the pump and cough and splutter city ensues.
The pump however is awesome, the pressure is now 4 Bar all the way to the rev limiter and it is also quieter than the standard pump.
My next plan is to install an external swirl pot. The in tank pump, will feed the swirl pot and then another pump will feed the engine from the swirl pot. The return from the engine will return to the swirl pot and the return to the tank will run from the top of the swirl pot.
I have drawn up an aprox 1 litre design as I reckon that will be more than enough to keep the fuel flowing even through the longest left handers!!
I’ll take a few pics and stuff when it is all installed.
Fingers crossed it will all be done for Croft. Otherwise it wil just be a case of keeping the tank full. I had to do this at Bruntingthorpe at the weekend and it wasn’t that much of a pain in the neck.