RA28 Intank Idea (Carby to EFI fuel tank)

[The Witzl]

Mmm yes I think that idea Brett has merit. Would you have the main feed line to the hiflow pump coming out the bottom of the tank?

What if you made a surge tank with a removable lid, and fit the intank pump INSIDE the surge tank and fit that inside the fuel tank??

.... now that's just getting silly IMO.


Gravity feeding is how ALL high pressure EFI pumps work.
So why then would not a gravity fed "braffle-type" area inside the tank not work the same as a surge tank?

After all - a surge tank is gravity feeding an external EFI pump is it not?


... think about it.

[brett_celicacoupe]

What if you made a surge tank with a removable lid, and fit the intank pump INSIDE the surge tank and fit that inside the fuel tank??

.... now that's just getting silly IMO.

probly not as silly as having fuel fumes in the cabin (ra28/ae86), although that would send you silly

you wouldnt really bother on a car with a boot

[BabyZ]

So why then would not a gravity fed "braffle-type" area inside the tank not work the same as a surge tank?

Exactly!! Those of us with EFI tanks who just stick a high-flow pump in place of the stocker never seem to have surge problems. If you can copy whatever is done in the tank of an EFI car, then you should be set.

I just wish I'd taken more pics of the tank arrangement of the cressy when I had it apart - I seem to remember it was just a pot with baffles, but that doesn't really help you much does it?!?!

I'm all for keeping it entirely in-tank if you can too - less chance of leaks, fumes, hassles, etc in the long run. Not that surge tanks are a recipe for disaster (far from it if done properly), but simple is elegant ...

[Mr Ed]

I think you are missing the point of a surge tank entirely. It is a very narrow tank to keep fuel at the pump pick up under hard accelerating/braking/cornering.

If the fuel can just flow out the bottom under hard cornering it is no different to a normal tank. Any baffles will stop fuel getting to the pump just as effectively as they will stop fuel flowing away from it.

The only way to have a surge tank which doesnt require a lift pump is to attach it to the bottom of a normal fuel tank, like a small sump kinda thing. However this may cause issues with ground clearance on most cars.

[DoctorDubb]

Thanks for all the imput and ideas guys. Its not exactly a cost issue, but is one of the factors. I just think its more simple setup once its been fabricated and has too many advantages to ignore. I realise how import it is not to starve the engine of fuel (the same goes with having good brakes) which is why im checking my ideas with you guys

Sir_2jza70 i have no doubt in what you are saying about surge tanks, what we are curious is to how it is actually done in EFI cars then? As they dont seem to surge? I know some still run a lift pump and then EFI pump (VL turbo) but how/why are the baffles setup to stop the surging in only one pump setups?

Following some of the ideas, ive come up with a revised idea of the holes in the bottom as well as the connection on top.

As most of you thought that this was going to be the greatest problem. The idea was from bretts flow in/flow out problem and got me thinking simple. It consists of a few holes which have a metal or rubber flap that hinges at the top, to allow fuel in and would close when fuel tried to rush out. I think its the setup they use on some oil sumps in drag cars? The only question is wether a flap would work under a pressure system, id pretty sure it would as long as you worked out the opening and closing strength to be as minimal as possible. As its the pressure of the fuel wanting to get out that closes it, so you want to allow as much fuel in as possible.


The second idea came from BabyZ with the whole 'not having to weld anything'. This involves a ring which has two rows of holes. The inside set has nuts welded to the bottom, the outer you can reach in and bolt to the tank. Pictures say it better then words:



Ive also done some peliminary testing with water (as i dont want to blow myself up with fuel just yet). It is very simple in the mock and only took me 5 mins to make up. But shows that even though it does restrict flow in by about half (the plastic flaps were too hard and didnt give enough) it did extend the time the fuel took to run out by at least triple. The pictures are:

I also have some movies showing this, but need to make them smaller first as they are 20mb and 75mb each. Ill post them later hopefully.

Also another possbility would be to put inside the cylinder 'fuel cell foam' then im assuming u wouldnt use the flaps idea, but i have read on these forums that this foam even though made for fuel only lasts a few years? Can anyone confirm/deny this?

On a side note, i have heard that the baffling in the supras (mkII - but assuming most) is very good. And was reading on the supra forums that a lot of the guys drop in bigger intank fuel pumps without running into any surging issues. Does anyone know/have any pictures of what the baffle setup consists of in these supras? As it might be a good idea to replicate this setup.

Cheers,
Steve

[Grega]

steve. merit here mate good work
what you've drawn above mate looks EXACTLY like the hole that the sender/pickup on a VL-VS Commonwhore fuel tank bolts to
basically on the whore there is an assy which goes into the tank which has the internal in tank pump hanging off it and the sender
this then screws to the side of the tank (yes you read it right, the side) and using screws with little red washers (the type you use to insulate standoffs from a mobo in a PC case) - i think they are like a thin gasket paper material - the wholeshebang screws into place. also there is a cork gasket going between the flange of the sender/pump assy and the tank (almost forgot that bit)
if you put a flange in the top of your little "surge tank" with the holes drilled in the bottom and cut a hole in the tank you of a same commonwhore size you could readily adapt this kinda setup bending the fuel pipes ect to suit and getting rid of the sender.

the only thing i can think of is the pump lays flat in the commo, in this setup it would be standing up which it might not like (dunno)

Gravity feeding is how ALL high pressure EFI pumps work.

karl you absolutely sure about this? a submerged pump in a tank doesn't exactly need gravity push fuel out.....as its immersed in fuel it the pump uses suction to pull the fuel then pumps it up the fuel line. did i miss something dude in my peanut sized brain

[Mr Ed]

Sir_2jza70 i have no doubt in what you are saying about surge tanks, what we are curious is to how it is actually done in EFI cars then? As they dont seem to surge? I know some still run a lift pump and then EFI pump (VL turbo) but how/why are the baffles setup to stop the surging in only one pump setups?

I can assure you EFI cars still do surge, perhaps they are not as touchy though.

The general layout of the system is exactly the same, but you have the return line going into the top of the tank.


Still not sure about the whole baffles idea though.........Im no fuel system expert. Im sure there is some reason for having them, Im just not sure.

a submerged pump in a tank doesn't exactly need gravity push fuel out.....as its immersed in fuel it the pump uses suction to pull the fuel then pumps it up the fuel line. did i miss something dude in my peanut sized brain

A submerged pump still has gavity feeding fuel into it, as long as the fuel level is above the pick-up.

Besides, see how long a submerged pump stays submerged if gavity disappears!

[BabyZ]

I'd be pursuing the one-way-flap idea some more - I know some custom tank manufacturers use such devices in their internal collector tanks (which is what you are building). But I haven't seen up close just how they work ...

Oh, and I see your problem in finding a flat area on the tank to bolt anything to!!

[TA-022]

out of all the ideas on baffling i think the flap seems best.

also inlcude overflow holes at the top of the cylinder to let fuel flow back to the main tank.

i like the "tank in a tank" simple and no different to a normal external surge setup.
specially since i have a 3 piece surge tank that would lend itself to this nicely.

[TheToyman75]

Steve,

The concept of an intake pump set up for an RA28 has allot of merit and is really the best solution so hats off for looking into it and trying to reach an affordable solution that works.

To help your research see if you can get your hands on an intank pump assembly for a Ford XR6-T. They are an intricate but effective set up which if reproduced at the right height with a suitable mounting top would be great (And bloody expensive)

The downside to what your suggesting will actually be cost (Which is why I went the surge tank option) The cost to fabricate your intank fuel cell will greatly outweight the cost of a basic surge tank (Or even a tank and pump brakcet assembly like mine) Then you fuel tank mods with mounting ring and pump mount will well outweight the cost of a lift pump. Of course if you have the ability to make all these items yourself then the cost is not an issue.

I think what your doing is great but if its the result you want then at the end of the day it won't be much cheaper than a complete custom EFI surge tank (Especially if you can get one for $700).

[The Witzl]

Rod,

for as long as I have been thinking about this, and you know how long that is, I have been thinking about the costs of this exercise - and I dont think they are going to be as high as you think, if done with some good forethought.

if you made a relatively simple "baffle-box" that bolts into your tank from the top that also holds your pump, then that's not going to cost too much. I dont see a need for fancy welding and other expensive processes if it is going to be submerged in petrol, so that eliminates a lot of cost there. You could simply use some sheet aluminium and some aluminium angle to make your baffle box (unless aluminium dies in petrol?) and bolt it together, yes?

The difficulty/expense lies in chopping out the top of the tank and attaching your baffle box to the tank.

Using your $700 budget:
- $180 walbro pump
... leaves $420 for tank modifications and bafflebox fabricating
- $80 for bafflebox
= $360 for tank mods.

I rekon that's plenty, even if you do have to weld it.

[BabyZ]

There are of course pre-assembled pump/swirl pot units that may suit, like these from VDO:


The VDO catalogue (watch out, its a 155 page PDF!) lists various applications, up to 5.0 bar (~73 PSI) for a Porsche 911, but I am not sure what sort of flow rates they produce.

Nor do I know what the availability might be like in Australia - but they also do complete fuel supply units that have the pump, gauge sender and (for most) a swirl pot all in one. Maybe you'd be lucky enough to find one of the correct depth to swap out with your existing sender unit (no new holes needed). Probably a long shot, and maybe a PITA to find the right one ... but once you've found it, you would be a hero to RA28 owners the world over

[amon]

Hey fellas,i have used twin 4wd fuel filters(1.2 litre cap) and have no probs with surge or any other stuff.
Yes my EFI pump is external(attached to the plenum brace point)but this was uber cheap and contained 2 fuel filters and a glass fuel bowl.
The return from the rail goes back into the filters so no possible way of starving for fuel.
these things hang off the passenger firewall.
I got poo pooed for this idea(i dont think it was actually my idea) but with no real reasons why not.
i even went to our EFI specalist for flow and pressure checks(dyno)and all was good.

make of it what you may,but it does the job and some.

Cheers Guy

[TA-022]

pics pls amon