Hey again all,
These questions relate to whether I have to plumb thicker fuel lines through the tunnel to feed an injection conversion on an early notch.
What if I mounted a largish, say 8 litre surge tank at the rear of the car (behind the back seat) and used the stock mechanical fuel pump to feed it?
Would the standard pump and fuel lines be able to keep up with the surge tank's fuel demand on a (one day) high boost turbo 1776?
Then I would use the VL turbo fuel pump and the magna regulator for the high pressure circuit and plumb excess fuel from the regulator back to the
surge tank? I do not know the flow rate of the stock VW pump but it seems to be able to feed a potent 1916cc engine just fine...
I have read other posts on the subject of surge tanks and the way to go seems to be to use a low pressure pump to feed a high pressure pump inside of
or external to the surge tank to the fuel rails and then through the fuel pressure regulator and back to the surge tank or fuel tank. I am not sure
whether the low pressure side needs a fuel return or not at least to help purge air from the system...maybe it depends on the type of pump used?
Maybe a race car would need the fuel returned to the main fuel tank to aid in cooling it but I don't plan to race it...rather enjoy it as a daily
driver.
Anyhow I am trying to avoid having to install 2 thicker fuel lines down the tunnel of my notch but part of me says it just has to be done...I am no
engineer but it makes sense that the fuel lines should all be the same diameter for low and high pressure sides of the system.
C'mon guys...tell me how it is....... 
The way you suggest to plumb your surge tank is almost exactly the way the I have done it on my Brothers Baja - and it works perfectly. I don't
think that you need to have the surge tank as big as 8 litres though, as this could potnetially suffer from surging due to its size....
My system (as fitted to my brothers Baja) is as follows:
Fuel is drawn from the fuel tank in the front of the car, through the stock fuel line (in the tunnel), by a low pressure fuel pump. This fuel is then
deposited into the surge tank (about 2 litres in size - which is waaay bigger than we need). Any air or excess fuel is returned from the top of the
surge tank to the main tank via another small diameter fuel line.
The high pressure pump draws fuel from the bottom of the surge tank, pumps the fuel through a fuel filter then through the fuel rail to the pressure
regulator. The unused fuel is returned from the pressure regulator to the surge tank.
You will definatly need a return line from the surge tank to the main tank, otherwise any air that makes its way into the surge tank will remain
trapped in the surge tank and will gradually build up.
The required size of a surge tank depends on who you talk to. I have been quoted sizes from about 600ml to 1.5 litres (for a NA engine) and twice
those figures for a Turbo/Supercharged set-up. I suppose the size required will depend on what you plan on doing with the car (ie: off roaders (like
my Brothers Baja) who will spend time on steeper angles than road cars will need a larger volume surge tank)
Did that make sense?
R 
...just thought of something - is the Magna EFI fuel pump an internal or external (mounting) pump? This would have an effect on the size of your
surge tank....
R
there's a whole post discussing surge tanks. Do a search and you'll find it easily enough.
for my 2c worth, mine is set up like ratty said. yes you definitely need a return line, otherwise the temp of the fuel can only rise too. a little bit
of bleed back into the fuel tank allows fresh cool fuel into the system.
http://forums.aussieveedubbers.com/viewtopic.php?tid=9938
...here it is at the top of the tech mods and FAQ forum.
[ Edited on 21-8-06 by pete wood ]
You can increase the volume of fuel the stock pump pumps, by making the bakelite base thinner...
the stroke gets longer...
more fuel....
the rest is way out of My league...
cheers
Lee
FORGET a stock fuel pump anywhere in your fuel system. It'll feed about 60hp + 50%. Maybe
[ Edited on 22-8-2006 by VWCOOL ]
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Guys I am stoked with all the productive replies made so far here...thankyou!
Here is my next proposal:
Fuel leaves tank via std fuel line through a normal LP fuel filter and is pumped by a LP facet or rotary electric pump mounted near but below the fuel
tank, and enters surge tank mounted at rear of vehicle. There is also a return from the top of the surge tank back to the main fuel tank which is
plumbed to the top of the fuel tank in the same ID as the supply line..
On the HP side there is a EFI fuel filter fitted before the HP fuel pump . The fuel rails are connected directly to the output of the HP pump. After
the last fuel rail there is a magna fuel pressure regulator (Has inbuilt vacuum reference and external solenoid to allow full fuel pressure for hot
starting I think). The outlet from the reg goes back to the surge tank. This reg will only be temporary just to get the system functional.
The surge tank will be no more than 2 litres in capacity and will be taller than it is wide to reduce surge under hard cornering etc. It will need 2
smaller sized outlets and 2 larger (EFI) sized outlets.
All the LP pipes are standard non-efi size, and the HP pipes are 8mm.
How does this sound?
Cheers, Toby 
Just another thought...it might be better to fit the HP pump from the magna inside the surge tank (it's an internal unit anyway). It would be neater
and less complex that way I imagine.
Fuel pressure according to the magna book is rated at 245-264kpa unregulated and 196kpa regulated. That's max 38.2psi and regulated 28.4psi - similar
to the VW system which should be regulated to 28psi but is adjusted manually.
This leads to another problem with turbo boost...if I was to run 20psi boost then I would need the fuel pressure to match the boost pressure
comparatively wouldn't I? Or is that just for carby systems?
Lots to learn and it's great fun too. And who doesn't want smooth idle and driveability when cold as well as precise fuel delivery throughout the
entire rev range? Show me a carby setup that does that...
You use a boost sensitive fuel pressure regulator.
touche!
Sounds like you have the basic idea - however there are a few more things you should consider:
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I am also considering fitting an EFI system to my girlfriends square type 3. I have a near complete original system which I may fit, but I am also
consideringa hybrid system like yourself and Ratty are building.
One thing I have been wondering about is where to run the return line. In the factory EFI cars, they have 2 pipes through the tunnel - 1 supply, 1
return - It would be easy enough to fit a second line to a car with the body off the pan, but I have not intentions of doing that. What did you do
Rosco? Attach it to the bottom?
My return line has been run down the inside edge of the passenger side of the tunnel (inside the car) - it is clamped into place so that there is
absolutly no movement. I have also seen return lines down the outside of the pan - the reason that we decided to run the line inside is that we use
the Baja for serious Off-Roading and a fuel line mounted on the underneath of the car would easily become damaged - this would not necessarily be a
problem with a 'road-only' car.
I am not certain about the legalities of running a fuel line through the cabin - I suspect that some people would consider that to be dangerous and
illegal, but we couldn't find anything written anywhere to agree with this (if someone can clarify this I would be greatful).
Idealy, the line should go down the centre of the tunnel and regardless of where you fit it, it should be mounted solidly so than it cannot rub
against anything.
R
"Fuel leaves tank via std fuel line through a normal LP fuel filter "
If you have any small lines anywhere on the supply side, you will kill your engine, even with a surge tank. Constant WOT will empty it quick. Boom.
All fuel system lines should be external to the cabin of the car
[ Edited on 25-8-2006 by VWCOOL ]
Both the kombi and type 3 factory EFI tanks have a small line on the suction side of the pump comming out of the tank (~5/16), before going to one of
those fuel filters with a 5/16 inlet and 1/2 inch outlet which goes to the HP pump.
The length of the 5/16 hose is not long ~200mm, and doesn't seem to hurt anything. I also have the factory EFI tank in my suby powered kombi, and
doent have any starvation issues.
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Thanks for the valuable input!
OK, here's something I hadn't thought of until now...
What if I just cut open the fuel tank and welded some baffling around the fuel outlet? It would not take much to set up and would remove the problem
of the LP pump not "keeping up" with the flow of the HP pump. I could then just run the HP pump up front (down low on the front beam) and keep it
simple. The important thing would be to keep the "spirited" driving for when there is more than 1/4 tank or so to be 100% safe.
Thanks also Ratty for pointing out that the filter goes AFTER the HP fuel pump. I think a screen similar to other OEM intank applications would be a
definite benefit though without cuasing any restriction to the gravity fed fuel supply.
As far as running the new thicker fuel lines I think that through the tunnel although tricky would be the best idea. Under the car would be easiest bu
leave the lines prone to stone damage not to mention if in an accident they are exposed to underside damage. I just didn't want to do that as there
is not much room especially for an amateur like me to engineer it!
Cheers,
T
[ Edited on 28-8-2006 by type3lover ]
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Originally
posted by ratty 63
If you have the returned fuel from your fuel rail (via pressure reg) going back into your surge tank, and the low pressure pump that you are using to pump the fuel from the main tank to the surge tank would be able to supply a carbied engine then using the stock (small lines) won't be a problem. We have done it this way with my Brothers car for over 12 months now (with a 2.1 Type IV engine) and have never had the surge tank become empty, even on steep slopes at WOT (like when climbing sand dunes or up long muddy hills). However, if the low pressure pump cannot supply fuel to the surge tank at the same rate as the engine is using the fuel then yes, the surge tank will empty and you risk doing damage to your engine and high pressure fuel pump. R |
A lazy 2.1 with 70hp they had more than that standard and it anit standard in specs and it has been driven at wot for last well since it has been put together and it has to turn 33inch treads. my last baja with a twin webbered type4 would sit on 5500 6000 all day and it never ran out of fuel even when i was racing a mate on the way to fraser flat out along the high way at about 160kph and if a twin webbered one didnt run out of fuel a more fuel efficient efi engine wouldnt maybe if it was a turboed crazy engine, but i doubt there would be to many na vw engines that could use more than the standard pipe could suppliy
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