This weekend I added a second feed to the #4 end of the stock fuel rail to even out pressure and stop #4 running lean under boost.

Basically it involved removing the hose connecting the PCV valve to the Intake manifold, removing the idle valve on the side of the intake manifold above the fuel rail (watch out for the silly double D shaped O ring) and undoing the 2 bolts that hold the rail in place. Then you lift the rail upwards and tilt slightly to get it high enough to get a pair of pliers onto the fuel hose clips to get the supply and return clips off. To minimise fuel spilling out, remove the fuel filler cap to reduce pressure but you will spill some. The injectors are held in with O rings and should pop out.

Once you have the rail off you need to get it in a vice and remove the stock FPR with the 2 bolts. Then drill a 7mm hole in the #4 end trying to keep as much swarf out as possible. Tap the hole to 1/8th BSP or NPT (same but NPT is for tapered threads) and check your fitting screws in OK. The fitting I used was a 1/8 NPT pipe stub made of brass which allows about 20mm of stub to fit the new fuel hose onto. Once you have a tight fit, remove the fitting and take the rail into the kitchen to clean it thoroughly. Make sure you get every possible piece of dirt and metal out of the rail as the last thing you want is an injector to block. Dry it all off and take back to the vice. I fitted the pipe stub with some JB Weld on the threads to lock it in place overnight. The excess JB Weld pushed out by the threads as it tightened in was smeared around the fitting to make sure there would be no leaks. Re-fit the stock FPR.

Next day when it was all set I cleaned up all the injectors and the side of the head where they fit, and re-fitted the fuel rail. I swapped out all the spring clips for jubilee style ones as I intend to raise fuel pressure at a later date. Fitting is tricky as you need all injectors in the right place and pushed in properly (to seat the O rings) and you need the plastic spacers to keep the rail in the correct place whilst you tighten up.

To connect a supply of petrol to this new fitting you need to T into the existing fuel supply at the metal pipe on the drivers side. Make sure you don't use the return by accident. Refit all the stuff you removed to get at the rail and fire it up. Have a good check for leaks whilst idling then go for a run to get it all up to temp. Re-check for leaks again as you've now had the system up to operating pressures.

The car feels smoother now and all knock has gone from the monitor at all boost and rpm levels. Before that I had a little knock at 4500 rpm if I floored it whilst waiting for the auxiliary pressure regulator to catch up. The car also feels more willing to rev now but that may be my imagination. It feels like it wants to spool up at minimal throttle rather than havng to floor it to get boost. It's always been a little like that but now even more so. The AF Ratiometer I run still shows the same, so it hasn't richened the mixture significantly, just stopped #4 going lean before the rest when the system is stretched, as the amount of injector on time and the pressure in the rail hasn't changed.

Will anyone get a benefit whilst NA? Probably not but maybe. The car certainly is being fuelled better now as the pressure across the rail should be constant. Anyone who's upgraded their intakes to JR etc. may feel a small improvement as they are getting more air in now, though the ECU should comensate. Anyone who gets knock may be able to run a small amount more advance with a dual rail - needs testing though.

How much? Well it took about 2 hours of my time, about 2 quid for a fitting and 2 quids worth of jubilee clips as I swapped every one on the fuel system whilst I had it to pieces. (9/01)