Fuel starvation almost never shows up on the dyno. It shows up on the third lap, in the fastest corner, with the tank half full and the wideband reading lean for half a second. The fix is not a bigger pump. It is making sure the pump always has fuel sitting on it.
The short answer
- If pressure drops in corners, under brakes or when the tank gets low, that is surge. A surge tank fixes it and a bigger pump does not.
- Keep the factory tank and add a surge tank for street and track cars. That is the cheaper and simpler route.
- Move to a fuel cell when the factory tank is gone, damaged or in the wrong place, or when the car is built as a race car.
- Budget for the bracket, the fittings, the level sender and the filler kit at the same time. They are not optional extras.
Why fuel surges and what a surge tank does
A factory tank is a wide, flat shape with a pickup in one spot. Corner hard with less than half a tank and the fuel climbs the far wall, the pickup uncovers, and the pump swallows air. Pressure falls and the engine goes lean at the worst possible moment.
A surge tank is a small holding tank plumbed between the factory tank and the engine. A lift pump keeps it full, the main pumps sit inside it, and the return comes back to the surge tank rather than the main tank. The fuel in the boot tank can slosh wherever it likes.
There is a cheaper trick worth knowing about for saddle tank cars, where fuel gets trapped on the wrong side of the tank. A venturi jet pump kit uses return flow to shift fuel across, which solves a specific problem without a full surge setup.
Picking a surge tank
Street and track cars keeping the factory tank
The single fuel surge tank is the standard answer, sold without a pump so you can choose one that suits your power target. If you already know the pump, the MPFST-R is sold to suit it directly: a version for Walbro GSS342, AEM 50-1200 and DW440 pumps, one for the Bosch BR540 and DW400, and one for the Walbro F90000 series.
If room is tight, the RA surge tank with an integrated regulator takes a couple of fittings and a length of hose out of the plumbing. Running external pumps already? There is a surge tank built for them.
Serious track, drag and high power
Once one pump is not enough, the FCST-X range combines the surge tank and the pump mounting into one unit. We stock it without pumps for the Walbro F90000 series, and as complete kits with two surge pumps and a lift pump using Walbro GSS342 or the F90000274 version. An extension kit adds capacity to the same unit if you need more reserve.
The Aeroflow dual EFI pump surge tank kit is the other option here, and the whole Aeroflow surge tank range sits alongside the Radium tanks.
Or start with a hanger
Before you commit to a boot full of plumbing, look at a fuel hanger with surge built in. The Radium hanger range covers the R32 GTR, FD RX7, Evo 7 to 9, early and late Subaru, the Chaser family, BRZ and GT86 and the R35. On a road car that sees the odd club day, that is often all it takes.
| If you want | Go for | Why |
|---|---|---|
| A street car that stops going lean in corners | Radium fuel hanger, or the single surge tank | Least plumbing, keeps the factory tank |
| One known pump feeding a built engine | MPFST-R in your pump size | Sized around the pump you already own |
| Multiple pumps for a race car | FCST-X with lift pump | Surge tank and pump mounting in one unit |
| A tidy install with less hose | RA tank with integrated regulator | Regulator built in, fewer fittings to leak |
When you need a fuel cell instead
A fuel cell replaces the factory tank. Radium Engineering, an American company out of Clackamas, Oregon, build theirs as a bladder inside an alloy can, which is what you want in a car that gets used hard.
The R10A 10 gallon cell is the common size, and replacement bladders are available for both the 14 gallon R14A and the 6 gallon R06A. For cars where the boot floor is the only space left, the spare tyre well can at 10.5 gallon is worth a look. There is also a saddle tank conversion kit for cars that came with a split tank.
Fitting one properly means more than dropping it in. The weld in cage supports the can, the 6 by 10 24 bolt weld flange gives you a mounting point for a hanger or a pump plate, and you need a filler: the 1.5 inch fill neck hose kit or the clear version. An 8 inch fuel level sender puts the gauge back on the dash, and an adapter from a 6 bolt to a 3 bolt filler sorts out mismatched parts.
One thing to sort early. Replacing the factory tank is a fuel system change, so it is a low volume vehicle certification conversation in NZ. Speak to your certifier about mounting, venting and separation from the cabin before you start cutting, not after.
What to buy with it
The wall or floor mounting bracket is the first thing people forget. After that it is fittings, and the Radium range covers rails, filters, dampers and gauges alongside the tanks. A stainless 10 micron filter kit protects the injectors, a pulse damper settles the rail on big injector setups, and a 0 to 100 psi fuel pressure gauge means you can see a problem instead of guessing at it.
If you are running a race car and refuelling between sessions, the dump can range covers quick fill cans and caps.
Where NZ Performance fits
We hold Radium fuel cells and surge tanks in Palmerston North, along with the hangers, senders and fittings that go with them, so the install does not stop halfway. The fuel surge tank hub and the fuel pump hanger page show the full range by fitment.
Sizing the pumps that go in the tank is the next job, so read our fuel pump sizing guide, then the fuel pressure regulator guide for the return side. If the car is heading for cert anyway, will it pass cert and WoF in NZ covers what the certifier is looking at.
FAQ
Do I need a surge tank or a bigger fuel pump?
If pressure only drops in corners, under brakes or when the tank is low, that is starvation and a bigger pump will not fix it. A surge tank keeps a small reserve full so the main pump always has fuel. If pressure falls away at the top of every run regardless of fuel level, that is a pump sizing problem.
What is the difference between a fuel cell and a surge tank?
A surge tank is a small holding tank that sits between the factory tank and the engine, fed by a lift pump. A fuel cell replaces the factory tank altogether, usually with a bladder inside an alloy can. Most street and track cars only need the surge tank.
Which Radium surge tank should I buy?
Pick by the pump you are running. The MPFST-R is sold in versions to suit Walbro GSS342, Walbro F90000 series and the Bosch or DeatschWerks pumps, and the standard single tank is sold without a pump so you can choose. The FCST-X is for cars needing more than one pump.
Does fitting a fuel cell need certification in NZ?
Replacing the factory tank is a fuel system change, so it is a low volume vehicle certification conversation. Talk to your certifier before you cut anything, because mounting, venting and how the tank is separated from the cabin all get looked at.
Can I use a fuel pump hanger instead of a surge tank?
On a lot of street cars, yes. A Radium fuel hanger surge tank keeps fuel around the pump inside the factory tank, which handles most road driving and the odd club day. Cars that see real cornering loads or run the tank low still want a separate surge tank.
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