BRZ /F86 Direct Injection Fuel Pressure Issue

Car is a 2014 BRZ with an FA24, running the plug and play Motec M1 kit so the factroy DI control is still in the loop.

As shown in the attachment the fuel pressure drops by an order of magnitude during WOT operation, even though the M1 is still commanding the correct pressure. Note the low pressure fuel system has been checked throughly, although admittly it does fall a couple PSI but do not believe that is relavent and is solved (never falls below 50psi). Note the throttle closing slightly at WOT is correct (horse power limited class).

We have replaced the HPFP with no change. I am now going to replace the DI controller, and the pump again just to be sure. If it still fails I am down to:

Wiring issue between M1 and DI controller, or DI controller and spill valve. These I feel are unlikely since it doesn't look like "electrical noise" and it recovers.

or

Bad lobe/roller etc on the cam driven HPFP, but I also doubt this.

Any idea if there is anything the M1 could be sending the DI controller (injection timing?) that would cause the DI controller to want to crank back fuel pressure? cam timing looks ok, but wondering if that is drifiting causing the spill valve timing to be off?

Or any other input would be great. I didn't do the tune on this car (although it ran fine for a few races after it was tuned) and this is my first DI car. All 200hp of it.

Thanks.

[img="blob:https://www.hpacademy.com/62f85b57-e953-4681-8d5a-40652dbcc0db" alt="" alt="" ]

Is it a full FA24 long motor, or just the bottom end with FA20 heads?

The main reason I ask is that the FA24 has a 3 lobe DI pump and the FA20 has a 4 lobe pump.

You will have the direct pressure tank easily as if your number of lobes and delivery angle table are still from the FA20, but the pump and camshaft are from the FA24

Nathan,

FA24 long block, only FA20 stuff are the sensors and reluctor wheels. I think its resolved and almost spot on from what you are saying although I don't fully understand how it happened. The car was tuned (not be me) and was in theory OK. I got involved with the team last year and started improving the car, paying attention to logs and so on. That is when I noticed fuel pressure issues that quickly became major issues as noted in my post.

I started adding port fuel and the problem went away. That was when I knew it was a fuel volume issue on the DI side. Here is where things get a little odd based on what you just said. The Direct Pump A Offset was 47, and I noticed the original file from motec was 76. I changed it to 76 and the problem was instantly solved. I do have a second car with an FA24 in it also that was also not tuned by me that is at an offset of 155, but it has retained all of the FA24 sensors and reluctor.

Is this offset published? Or do you need to measure pump lobe TDC to pattern lock?

Either way when I moved from 47 to 76 I was able to put the DI contribution back in and the engine ran properly. But I do not like random dumb luck, but at least we are directionally headed teh right way.