This cutaway of the stock FD RX-7’s fuel pump shows the installation of the Radium Mazda RX7 FD Fuel Hanger Surge Tank and lift pump in the factory yellow plastic fuel baffle. The Radium Surge Tank and Top Hat/Hanger is a beautiful and really well-made product. The surge tank itself has a great capacity to it, but it does not solve the fuel pickup problem because the lift pump remains in the factory baffle. The ultimate solution would be to relocate the Radium lift pump remotely and/or use a HydraMat like we did.
Taking design inspiration from a 992 Porsche GT3 Cup Car, we found a surge tank with 3 flapper valves that allow the surge tank to fill up when cornering, in addition to the lift pumps that actively fill the tank.
We could not source the same GT3 Cup Car flapper valve, but were able to source 1” surge tank check valves (PN: CV100). We are using a Deatschwerks DWMicro (DW100) lift pump and a barb pump inlet fitting to convert the pump into an in-line fuel pump which will pull from the Holley HydraMat.
The Holley HydraMat is an outright incredible piece of technology that effectively combats fuel starvation. This is far from a large fuel filter. The HydraMat uses surface tension and fluid wicking to be able to suck solid streams of fuel, with no air, from any corner of the mat that is in contact with fuel, even when nearly the entire mat dry.
When any part of the HydraMat no longer touches fuel, tiny pores of the media seal off through surface tension, forcing fuel to be contained in the reservoir and drawn from any other area of that mat that is touching fuel. This makes the HydraMat an absolute must for any build.
Available in a wide variety of sizes and shapes, we used the 15” x 8” HydraMat, Cross (PN: 16-101) that has a center outlet pickup with -3/8” NPT fitting. This HydraMat works with Alcohol, Ethanol, Methanol, and E-85 fuels as well as 2-cycle oil blends as high as 20:1 (6.4oz per gallon), which makes it perfectly compatible for our rotary. It acts as a 15-micron pre-filter, eliminating the need for a separate filter before the fuel pump.
Our new fuel system design places the HydraMat in the right half of the fuel tank. Due to the HydraMat’s effective design, when fuel touches any corner of the mat, it will be sucked up by the lift pump and transferred into the factory plastic baffle (orange) that we are turning into a surge tank. Check valves (purple) work like the Porsche GT3 Cup car surge tank and allow for fuel to enter and fill the tank based off of longitudinal and lateral forces sloshing fuel around the tank when on track.
3 comments
Those Radium studs, where have you been all my life?! Damn I need to get those.
This build has included quite a few aspects I will be implementing in mine! Unfortunately the custom surge tank setup is more complex and I will be going with the Radium surge tank as a drop in solution.
It seems like E85 is the main fuel for the car, has Auxillary Injection with Methanol also been considered?
Curious to hear thoughts on the why or why not of AI in this use case.
Some awesome details and information in here, thanks for documenting everything so thoroughly Billy!