ST205 fuel pump relay mod

The standard ST205 runs around 9V on the fuel pump most of the time and then at higher boost and revs the ECU switches the relay so that it is the full battery voltage - around 13.5V.

I have a Blitz ECU fitted to my car and I have noticed that it is very lean (i.e. a flat spot) at mid revs and medium throttle just as the boost comes in. It did the same with the stock ECU though it wasn't as pronounced.

I have now modified my car so that the fuel pump gets 13.5V all the time while the engine is running. This has got to be the easiest mod ever! I'm hoping that this will help my problem. I have read that others have experienced richer mixtures with this mod, which is what I want!

There is a small relay box just behind the radiator. Remove the two bolts and turn the relay box over. Pry the two clips with a small screwdriver to remove the panel and also the top cover. Take note of which relay is for the fuel pump. Under the fuel pump relay, you will see a thin green and red wire. Cut this wire and seal the cut ends with electrical tape. Put it all back together and you are done. Easy!

I haven't tested my car yet though I will report back on how it feels once I have. If this fails to fix the problem, I may need to put the car on a chassis dyno and fit an adjustable fuel pressure regulator to see if I can get the AFRs closer to what they should be.