Remote fuel pressure regulator

Hello all, I am in the process of planning out an almost completely new fuel system on my 2014 sti. I have run in to fuel surge, a common issue with this chassis, and was informed I should include a surge tank into my build. I am looking at using Radium Engineering parts, as they make everything I think I will need. My question comes down to their new regulated surge tank, fuel pressure regulator built into the surge tank.

https://www.radiumauto.com/FSTR-RA-Fuel-Surge-Tank-Regulated-P2768.aspx

After talking with their tech support, they have no issue with running a manifold reference line back to the surge tank, from the engine bay. Is there anything else I need to consider? If the regulator is on the surge tank it will turn the fuel rails into a return less style fuel system. Some downsides I can see are needing to make custom fuel lines to the rails, a custom fuel pump harness, and having an additional fuel pressure gauge in the engine bay to measure pressure at/near the fuel rails and one at the regulator?

Or should I run a regular surge tank and keep the regulator in the engine bay?

Is there anything else I am missing or need to consider?

yeah i looked at this recently for my WRX. Decided against it. Too many cons in regards to tuning.

On a NA engine, returnless works fine. Once you turbo charge, it becomes more difficult to ensure you have the correct fuel pressure in the rails to all the injectors.

So you may get into a situation where the last injector on the rail has slightly poorer fuel pressure due to the injector before it opening and dropping the pressure further down.

Think of it like a garden sprinkler hose, where it has holes punched in it. If you add a second hose, the amount of flow in the 2nd hose will be less than the first.

Fuel injectors work the same, and if the ECU doesn't know. It opens both injectors for a fixed amount of time based on the expected fuel pressure to ensure correct fuel delivery. If the 2nd injector has slightly lower fuel pressure, it can mean less fuel is delivered making that cylinder run slightly lean

Some ECU's allow you to correct for this, but its not as accurate as a return type fuel system where fuel pressure difference between injectors are basically negligible. Especially if you use a fuel pulse damper

From what i was told, to give you the safety net for a returnless system, its recommended to run a base higher fuel pressure. but this just puts your fuel system under more stress, inc your fuel pump and wiring.

This was why, for the sake of a external reg, it was just less of worry and also returnless on turbo cars is more abnormal, so if you need to troubleshoot or get somebody to do work or tune, more likely to create confusion.

Thank you. That was something that crossed my mind. I agree that a more stable/consistent fuel supply/pressure would be better. That being solved now i have more questions.

Would running a larger volume surge tank be a better idea? I am going to have one pump in the surge tank and the second in the OEM tank. I notice that most lager volume surge tanks are multi pump set ups. If I can find a larger volume single pump tank would that be better then a smaller volume surge tank? Is there any ratio of lift pump (in OEM tank) to supply pump (in surge tank)? I am planning on using that same pump in both, for convenience and simplicity.

Depends on your power goals and what you are using the car for as well as what pump\s you have in the tank.

If your doing street driving, then no. If you do circuit race maybe or drags.

Most the pumps that you can put into a single pump surge tank are capable of 460L\hour or more and can support upwards of 500HP on E85.

So long as you have a similarly sized pump in the tank, then it should be capable of keeping the surge tank brimmed so a large surge tank is not required.

If you are running a lot more than 500HP, then you might need to look at a multi-pump surge tank or a larger volume surge tank.

My own car has one walbro 460L pump in the tank, and another in the surge tank which is only 1L. As i take my car on circuits, i'm looking for protection against fuel surge from fuel sloshing in the tank and give me a buffer of a time while the pump in the tank hunts down some more fuel flying past. And worst case, my ECU has a fuel pressure sensor which if it sees low fuel pressure just limp modes it for safety and piece of mind if something was to go wrong

Using a calculator like this is handy as it can allow you to figure out how much time you have using a surge tank

https://raceworks.com.au/calculators/fuel-pump-calculator/

In my own car, using a 1L surge tank even at 500HP (which it isn't currently) id have 12-15 seconds of fuel in the surge tank

The car is used for road course track events, with the end goal being competing in time attack/time trial events.

Right now it makes 367WHP on pump gas, 93 octane. I'm not chasing power as this is still a factory engine and I know it has limits. I am planning on making it capable of running on ethanol while I'm redoing the whole fuel system. I'm currently using the factory ECM as that's what the rules call for in the classes I'm initially looking to run in.

I am aware that multi pump tanks are needed for higher fuel flow needs or redundancy in endurance situations. Both of which are not in my current plans. The smallest volume surge tank I've seen is 1.5 liters with the largest being 2.7 liters. With my current power level and future power levels it sound like a 1.5 liter surge tank will work.