Fuel Line Setup for Radium Surge Tank and 10 PSI + Ethanol (just FYI stuff)

[DarkJak]

Wanted to document this here for others in case they run into a similar issue.

I run the Topgunz Rotrex kit and flex fuel and Eugene was seeing the ECU having to overcomensate for fueling due to underdelivery from the injectors.
This boiled down to a flow restriction somewhere in the system.

On the tank side, I have the Radium fuel hanger surge tank and have it set to 52 PSI with a 1:1 rising rate line from the manifold.
On the engine side, I have OEM rails with 1050x injectors.

Previously, I had OEM lines from the Radium setup all the way to my flex fuel sensor. This caused a lot of restriction and maxed out compensation from the ECU. Eugene had said it was like I had 700-800 cc injectors, with how much extra duty the injectors had to run to get enough fuel delivered.
I found that the pressure gauge right after the fuel hanger (the one that comes with the Radium kit) was reading perfectly, 52 PSI +/- manifold pressure, meaning I had no issues within the hanger, pump, or the run of hose going from hanger top hat to OEM fuel line. I found that at the rails, this was 50 PSI at 1 bar absolute pressure and while it would rise with boost at first to 54 PSI, would drop from 54 to 50 PSI as I went from 4500 RPM to redline.

To resolve this, I first upgraded the smaller line in the engine bay to 8AN PTFE hose and ran a Radium ethanol sensor housing to ensure the ethanol sensor was not a restriction. This made very little difference.

I then replaced all the OEM line with 8AN hose, leaving my system with the 6AN hose that came with the Radium kit running from driver's side tank to passenger's side tank and 8AN all the way from there to the rails.

The result was negligible pressure drop when I monitored pressure at the rails. Verified to have fixed the ECU compensations needed when I checked data logs. PSI held steady at 52 + manifold pressure up to redline.

Reasons the OEM line setup was so bad (I didn't isolate each):
1. Long length of fairly small hose, ID smaller than 6AN.
2. OEM quick disconnect plastic piece that would typically connect to the top hat has a puny 4mm-or-so diameter opening.

Yes, a regulator setup at the rails would have worked around this. I wanted to see if I could make the hanger mounted regulator work just fine and it did. (I have the deadhead plate and a compact Radium regulator just sitting now. Might put that up for sale later for someone wanting to run a regulator in the engine bay)

[pkxu123]

Thanks for sharing, it sounds like similar issue I am having. I have 1050x injectors with radium surge tank too same as you. Stillen A2A SC

The mechanics working on my car installed 2 fuel pressure gauges, one at the line and one after the rail. Pressure is good at the line but falls after the fitting on the rail.

I have forwarded them this post so hopefully it'll help them out.

You are still using OEM rails? I was told these needed to be upgraded to fix the issue however upon researching, most other supercharged cars around 500hp are still running OEM rails perfectly fine.

[SeeThruHead]

when i asked cjmotorsports instagram (is that phunk?) about their fuel canister vs radium surge tank
they basically said, among other things, massive fuel line or regulate at the rails is the way to go to avoid pressure drop in the fuel line.

and then he linked me this article
https://www.fuelab.com/blog/fuel-lin...essure-drop/31

[DarkJak]

Yup, I'm running OEM rails. They do seem to have some restriction still, and there is still evidence some pressure drop looking to data logs but worlds better than before.

And yup phunk owns CJM! If I were doing everything clean slate, I'd just do his kits for everything. I just already have the Radium setup from when I was NA.

I ended up bumping the regulator pressure up 2 PSI to compensate what pressure drop is left.

If you're running into this issue, then at the bare minimum upgrade to as much 8AN line or 6AN as possible.