Fuel Tank for Injection Engines
 

Hello everyone, I have a few questions regarding fuel tank manufacture...

I'm using a 2.0 Silvertop Zetec running my own Megasquirt EFI / ECU.

What fuel pipe should I use for my feed and return lines? Should it be rigid or flexible?

I'm using a standard Mondeo fuel rail, what fittings will I need to push onto this?

Which fuel filler caps would people recommend? I'm still undecided as to whether to leave the filler on top of the tank or route it to the rear bodypanel. If I was to route it, how have others done it?

Can anyone suggest a suitable swirl pot and pump to operate at ~180bhp @ 4bar? And will I have to incorporate a sump into my tank design?

What have people been using for a fuel level sender for the gauge?

Sorry for all the questions, thanks in advance for any replies!

Josh

Most of the fuel lines can be rigid, but you will need flexible tubing where movement or vibration can be a problem e.g. into the inlet manifold and fuel pump. This has to be marked as suitable for carrying fuel.

My 2¢.

I ran an 8 mm copper pipe inside the transmission tunnel, 8 mm fuel hose elsewhere. I used a brake flaring kit to make beads on the ends of copper pipe. Fuel hose comes in low-pressure (carb) and high-pressure (efi) varieties.

There were pieces of rubber hose on my Mondeo fuel rail. In the middle there were some smart metal-plastic joints that require a special tool to open. I just obliterated the plastic part and was left with a nice 8 mm steel tube to connect my hoses.

I have the "budget" (60 quid, yeah, right, "budget") aero fuel cap from the group buy (like this: http://www.cbsonline.co.uk/product/B...minium_AERO694). I have it mounted on the rear panel and joined to the tank with a 90 degree silicone hose bend. Filling in is fiddly, I have to drip fuel in at very low rate, otherwise it's splashing out and the pistol cut-off is kicking in.
My cap is positioned like this:


I just integrated a ~13x13x7 cm rectangular swirlpot to my tank. That's 1 litre of fuel, should be good for 10 km or so ;-) The hole from the tank to the swirlpot is about 1-2" in diameter and is central to the pot. The intake is also in the swirlpot's bottom center, and the return comes to the swirlpot rather than tank. I had no fuelling interruptions with this setup even with the tank near-empty.

Since I use the Sierra cluster for now, I used the Sierra's sender, too. In the carbed Sierra, The sender sits on the fuel pickup pipe. I cut out a part of that pipe and made an adapter for the 6 x ø60.7 (or what's that standard fuel sender PCD) fiment. The length of the float arm fit the book tank almost perfectly.


I hope this makes sense.

Thanks for the info Albert, plenty for me to digest!

What thickness and grade aluminium did you use to build your tank? I have enough 2mm ali left over from my floor sections to fold the main section of the tank, but I'll need to source more to make the end plates/baffle/swirlpot.

In your build photos I see you've placed a gasoline filter in the fuel feed line (I think?) Would you suggest I use one too? And what is the the item mounted next to it?

Thanks
Josh

An inline fuel filter of some sort is absolutely essential do not leave it out unless you want never ending trouble with either carb or injection

I used the leftover 2 mm half-hard. People commented that it's overkill. And, yes, 2 filters: the tin can one after the pump and the cheap plastic one before the pump!

Dont forget a large fuel filter also adds a smal amount of capacity to the system as well as filtering !

Flyerncle raises a damn good point, it also provides similar function to a small swirl pot. When I took my Jag to bits I was very surprised to note that there were no swirl pots in the tanks - they were exactly the same as the carburetor version tanks. Then I realised there is a very large fuel filter and a non return valve - the filter is at the engine end, the valve ensures it is always full. Voila - one swirl pot. Took me a good while to understand why my FI system did not suffer from fuel surge. If it works for something as thirsty as an ancient V12 it should work for most other vehicles too.

I'm not sure the filter volume is much help -- as soon as the pump sucks in air, fuel pressure drops.

Hi Alga, I assume that's where the one way valve comes in somehow. The pump lives in the boot, it is fed from one of 2 petrol tanks. The outlet from the pump goes to this valve, the outlet from the valve runs to the front of the car where this massive (about 1/4 litre) filter sits. There is no baffling in the tank and no swirl pot that I can see inside the tank. They do slope so maybe the fact that the pickup is right at the bottom of the lowest point is sufficient to ensure continuous feed unless the tank is really low. The only reason I can think of to have such a big filter is to provide a small anti surge reservoir. It can't be for flow rate as it's only about a 5mm bore for the inlet and outlet.

I built a roadster for someone to race and it used Ginetta G20 engine and box diff etc,all Quaife and brand new.
The fuel tank was from Rally design and foam filled(designed for nitro but no probs with petrol)it suffered fuel surge at half a tank for no earthly reason.

Low pressure pump through large FI filter to swirl pot and HP pump to FI filter to rail and now no problems,over capacity is better than being close to capacity.

sumped tank :D

Perzactically (mix up of perfect and exactly) :p

Update on my fuel tank progress (and questions!)

I have folded the main section of my tank from 2mm half-hard ali (left over sheet from my floor). It is exactly to the book specification; however it's a very (very!!!) tight squeeze to get it into position on the car. And I think the tank is deforming slightly as I push it in - it won't be able to do this once the tab has been welded in place and the sides/baffle welded in. Is there a trick to getting the tank in other than force in from the top?



I've brought myself a Mondeo in-tank fuel pump and level sensor which I plan to fit into the top face of my tank. It's just the right height to have the L-shaped fuel filter/pick-up sit just off the floor of the tank.

I'm thinking of constructing an internal swirlpot to prevent fuel starvation. This would probably be four 'walls' that sit around the 'L' with many small holes to prevent fuel rushing out. Will this work? I'm thinking the walls will have to be high enough to stop fuel rushing out over the top.

Thanks
Josh

Yes, the book tank is very, very tight. Mine is a bit bigger than the spec due to bend radiuses. When pushing in place, it contacts the rollbar rear stay bracket gusset plates and the rear vertical tubes. Massaging the relevant places with a heavy hammer helped. That said, I had removed and reinstalled the tank without too much bother last week.

Also, pay attention to the material thicknesses when making sides of the tank. I had to ditch the first attempt as they were too tight to fit on the main section with this thickness. Now the extra sides serve as trays for the nuts and bolts.

I cannot comment on the internal swirlpot, I have no experience whatsoever with them, but I have doubts about them theoretically. Cars like this corner on the skidpad at around 1 g, meaning the surface of the fuel will lean at 45°. If you have a third or a tank of fuel, how long will you be cornering until all fuel escapes from the swirlpot? Also, remember that a typical injection fuel pump circulates at least 2 litres per minute, high performace pumps up to 5 litres per minute.

Put sump on tank and junk in tank pump,it will cause problems with fuel surge as Albert suggests.

I had a look inside a Ford Granada fuel tank my dad had lying around today. This had an internal 'swirlpot' arrangement which sat in a very slight recess/sump (about 15-20mm deeper than the bottom of the tank). The internal pump and fuel level sender unit was very similar to the Mondeo one I have.



I am now planning on folding up a similar 'maze / spiral' that will allow for my 'L' fuel filter/pick-up to sit inside. I will cut a hole in the base of my tank and slide this in such that around 20mm sticks out below and a further ~50mm sticks up above. This will then be sealed on the outside with a small side blanking plate and a sump floor plate.

I will then make an insert with a sunken lip to allow my Mondeo pump/level sender unit to sit down lower than the top of the tank, such that the 'L' fuel pick-up sits on the floor of the sump.

I'm confident this will work; it seems to work for Ford! Your thoughts though, please? :)

Josh

When I read your previous post, that is exactly what I thought about. Same system in the fuel tanks of EFI Sierra, and I guess it really avoids fuel surge. If you build a similar "maze" in your fuel tank, I think you are safe. Just my modest opinion though...

Another thing, if the "L" shaped filter of the Mondeo takes too much room, you can have smaller ones ("I" shaped :D ), like the one from the EFI pump of the Sierra (you can see it on the last pictures at the very end of this post of my blog: http://vouchtroadster.blogspot.se/20...reservoir.html)

I bought a brand new one from FSE Glencoe. I've been working with this company for 15 years, and they are in the UK, you can order one from them, you have the choice. Just check the diameter of the fitting, but I'm sure you'll find something to replace yours if you need to.
http://www.glencoeltd.co.uk/walbro-f...in-tank-parts/

Good luck :)

Very smart!

One more consideration. The swirlpot below the bottom of the tank allows one to run the tank to nearly empty, not to mention the 1 l of extra capacity it adds. This design will require a couple of litres left in the tank for the pump not to suck air.

On my 2l Zetec with factory ECU the fuel usage is ~8.5 l/100 km, meaning the range is below 300 km.

I took a pic of my swirlpot when the tank was out:
http://imgur.com/4eZ7pIh

Here you can see it stick out at the back, as you see it's not in harm's way:

very like mine and mine works a treat
external pumps make life alot easier
put a baffle at the center like wit a hole under it so left/right slosh keeps it full in the corners

I've found a company that can weld my ali tank for me and I'm keen to get this done next week. However I have not decided which fuel filler cap I'm going to use yet - do I need one to know what diameter to make the neck on my tank that the filler hose will connect to? Or is there a standard diameter?

Also, what is a fuel nozzle insert, and why do I need one fitted to my unleaded vehicle for it to pass the IVA?

I'm thinking now that I might neglect to have an external fuel filler cap mounted on my rear panel and use a motorbike style fuel filler cap mounted directly on top of the tank.

More boot space this way as there is no filler hose in the way, but maybe a bit annoying to get to when the boot is full. Thoughts?

Some fuel filler caps (aero style) have dual size built in so pick you cap then get tank neck made to fit
If I remember sizes are 55mm and 50mm last being most common
As you can't buy leaded fuel any more I think the restrictor flap thingy is not needed
Car Builder solutions have filler caps and dimensions

Since my tank setup have rubber hoses in at the rear, changing to copper through the tunnel and back to plastic exiting at the front firewall, I decided on the following system to eliminate high pressure in the fuel line from the tank that can leak (fire risk) at the joints in the line.

At the tank I installed (any suitable place) an inline low pressure pump that move the petrol to the front and dump in a surge tank. At the surge tank I have four nipples fitted for;

1. return fuel line to tank when surge tank is full (on top)
2. Return fuel line from fuel injection rail (on top)
3. Supply from the low pressure pump at the tank (top side)
4. Supply to high pressure fuel pump (bottom) which result in the fuel pump always gravity primed in my setup

The beauty with this is that the fuel line to the surge tank is open ended so to speak and now pressure in it which is safe (just circulating and no pressure in the surge pot). The only high pressure pipe is the little distance from high pressure fuel pump to injection fuel rail. Another plus with this is the fact that the high pressure pump cannot surge cornering etc.
The con is you have to have two fuel pumps.

See this picture taken from my car's setup.

Thanks for the info. Interesting set-up Wynand. I've already gone and got an in-tank fuel pump from a Mondeo so I'm going to go with that, just make sure my connections are strong enough to take the pressure.

One last question - how have people done their tank vents? Will a one-way valve be enough to allow air to enter the tank as the fuel level lowers, or does it need to be two-way to allow for expansion of air on a hot day?

I'm pretty sure it must be a two-way affair. It must allow air in when the petrol is being used, and it must allow air out for thermal expansion. I just used a 1 m length of fuel hose, from the right rear corner, where the breather port is in the tank, it runs up to the chassis, then left towards the opposite corner and down. Previously it used to be just up and down, but that used to spill fuel on heavy cornering.