Jeffers_S13
|
| posted on 14/2/05 at 10:53 AM |
|
|
Swirl Pots (yes, that old chestnut...)
Right having read all previous posts about these mainly by Steve  and being at the stage where I need to think about it can anyone tell me how to
plumb in an out of tank one and where to get an intermediate pump that can suck fuel up out the tank and fill the swirl pot quicker than the gravity
fed cossie pump uses it up for the engine.
Few questions :
Is the swirl pot under pressure ? ie as the cossie pump is forcing fuel to the engine and the returned stuff comes back, it goes into the swirl pot,
if this is also fed by the other pump its gonna fill up quite quick and will need an overflow back to the tank I suppose if its big enough it wont
pressurise, but if it does is this gonna cause probs if there are two pumps pressurising the fuel in it and the cossie pump is not gravity fed but
force fed...err..by itself and a another ? ?
Im thinking of just doing what Steve did and put more of a fuel sump under the tank, but Im running out of height ! the cossie pump is at present only
just below the fuel tank as it is so Im gonna prolly gonna have to have a secondary swirl pot above the fuel tank.
Also are some swirl pots mounted in the engine bay ? does that mean the pump is there aswell ?
James
[Edited on 14/2/05 by Jeffers_S13]
[Edited on 14/2/05 by Jeffers_S13]
|
|
|
|
|
Jeffers_S13
|
| posted on 14/2/05 at 11:00 AM |
|
|
The tank, already installed, has what others would call an itegral swirl pot, the end of the tank has a baffle with a gap right at the top, then a
tube in the middle at the bottom from the main tank that extends horzontally into it (so be quite hard for fuel to get out) but Im not convinced its
gonna work properly, as Steve has described in lots of other threads, the feed hole is effectivley the exit hole and it will be 12mm deep in the swirl
pot if its 12mm deep in the tank bit, (except for the return from the engine) as soon as some corners are encountered or some hard acceleration then
the pump is gonna be sucking fresh air at low fuel levels. I know, this is when I fill up, but I think Id rather have the engine fed by fuel till the
very last drop is used up.
James
[Edited on 14/2/05 by Jeffers_S13]
|
|
|
ned
|
| posted on 14/2/05 at 11:08 AM |
|
|
sbd have a good diagram on their website, i believe it goes carb pump at low level by fuel tank pushes fuel upto swirl pot (in/near engine bay), swirl
pot then has high pressure pump to fuel rail, then return line from fuel rail to top of swirl pot. Only pressure will be from return line from fuel
rail. (all imho)
Ned.
sbd site
[Edited on 14/2/05 by ned]
beware, I've got yellow skin
|
|
|
Jeffers_S13
|
| posted on 14/2/05 at 11:19 AM |
|
|
So I have to mount the high pressure fuel pump in the bay along with the swirl pot ? bugger I already mounted it in the boot does the swirl pot have
to be in the engine bay ?
Also, what if the low pressure pump cant keep up with demand of the high pressure one draining the swirl pot ?
It looks like the swirl pot will be pressurised.
|
|
|
ned
|
| posted on 14/2/05 at 11:42 AM |
|
|
with the return from the fuel rail going into the swirlpot in addition to the low pressure pump i doubt it'd run dry. Also remember there is a
difference between flow rate and pressure of the respective pumps, this confused me a while back.
Ned.
beware, I've got yellow skin
|
|
|
ethomas
|
| posted on 14/2/05 at 09:53 PM |
|
|
There is a really good explanation of how (and why) these work in the Burton's catalogue (it is a really useful read). It may also be on their
website.
Check out the articles on www.burtonpower.com
|
|
|
zetec
|
| posted on 14/2/05 at 11:04 PM |
|
|
I don't see why you can't mount the swirl pot in the boot. The swirl pot is need mainly to make sure the high presure pump always gets a
good supply of fuel even when cornering hard. My injection pump is in the boot as are most and it works just fine, most newer cars just have a single
tank mounted pump, and therefore don't need an extra low presure one.
" I only registered to look at the pictures, now I'm stuck with this username for the rest of my life!"
|
|
|
stephen_gusterson
|
| posted on 15/2/05 at 10:19 PM |
|
|
cant you just do what I did and use a shallower pot/sump of larger diameter?
The guy I had the heavy discussion with posted pictures of what was a 'pot' in the (ford?) he used,...... however he never did answer the
question of if it was the lowest point in the tank. Many cars have weird shaped tanks, and with a low point / slope / indentation in them to help
pickup.
I worked on the simple theory that you needed fuel to slosh into summat, but not out. anything thats flat inside the tank surely will let fuel out as
fast as it lets it in.........?
Its a lot harder to defy gravity.
atb
steve
[Edited on 15/2/05 by stephen_gusterson]
|
|
|
NS Dev
|
| posted on 16/2/05 at 10:29 PM |
|
|
quote:
Originally posted by Jeffers_S13
So I have to mount the high pressure fuel pump in the bay along with the swirl pot ? bugger I already mounted it in the boot does the swirl pot have
to be in the engine bay ?
Also, what if the low pressure pump cant keep up with demand of the high pressure one draining the swirl pot ?
It looks like the swirl pot will be pressurised.
You can put the swirl pot wherever you like! I have always put them in the boot area/rear of the car on rally cars in the past!
The low pressure pump needs to be able to keep up with the maximum fuel demand of the engine, not the high pressure pump, as long as the return from
the fuel rail (high pressure return) is back to the swirl pot.
It really is VERY SIMPLE!!
This is how I have always done it in the past and never suffered a surge problem yet (on slicks!)
Low pressure pump (with integral filter basket, which the Facet red-top pump has) draws fuel from the tank and pumps to an outlet near the top of a
swirl pot mounted near to the tank. The high pressure pump draws fuel from an outlet near the bottom of the swirl pot and feeds the fuel rail on the
engine. The regulator at the end of the fuel rail returns the excess fuel (most of it in fact!) to another inlet near the top of the swirl pot (so the
pot is fed by the return and the lp pump). An overflow outlet vertically in the top of the swirl pot then returns excess fuel from the pot to the
tank.
Of course the pot isn't pressurised, the return to tank prevents any pressure! It doesn't need to be big, just use the std 5/16"
bore, these aren't dragster fuel pumps!!!
The design of the pot itself is basically just a capped cylinder. As long as it's at least twice it's diameter in height, and holds at
least 1/2 litre, but preferable 0.75-1.0 litres, then all is ok.
I have made them from 3" exhast tubing with squares of mild steel mig welded over each end before, at a cost of about 10p! A neater one I made
was from the casing off an old truck oil filter, with a square baseplate welded to it (obviously in both cases with appropriate inlets/outlets welded
on!!)
None of it is rocket science, you are just making sure you don't pump air to the fuel injectors!!
|
|
|
NS Dev
|
| posted on 16/2/05 at 10:36 PM |
|
|
The simplest surge preventer I have used (and I am quite proud of even though it's blindingly obvious!) was when making a mild steel fuel tank,
I made the whole tank, and then hole sawed a 25mm hole in the bottom of it, and welded concentrically over the hole a 4" length of 2"
exhaust tubing, which I then welded an and cap over. The feed and return to the high pressure pump were from this little pot! On a tank like that in a
seven you would need a bigger pot as the tank is wide and flat, this was in a tank that was quite vertical anyway but the principle is the same!
|
|
|
