# fuel surge tank split?



## mattysupra (Oct 31, 2008)

how many people have suffered a fuel surge tank split? 

I think 'pupsi' had his split ? 


Mine has gone also! has anyone else suffered this?


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## AlexH (Aug 17, 2008)

thats one of the reasons i dont have one mate, i hope it hasnt caused too much damage mate.
how about a new rips item, they seem to have never had a split


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## mattysupra (Oct 31, 2008)

AlexH said:


> thats one of the reasons i dont have one mate, i hope it hasnt caused too much damage mate.
> how about a new rips item, they seem to have never had a split




Its was a rips system that split! (pupsi's i think) 

However this was down to other reasons and nothing to do with the quality of the product. 

I dont think the quality of my system is at fault either but there must be a issue that i presume is down to not a big enough feed back to the tank. 

im suprised tho as i only have one pump so surely its supply and return that are both the same size pipe should cope? I think the rips issue was down to pupsi using 2 times feed to 1 return? 


Or si there something else causing issues here? Maybe heat? as mine is creating alot of heat


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## GT-R Glenn (Nov 9, 2002)

You need the hell big overflow / return to the main tank
Otherwise it can try to blow up like a ballooon (ok not really) but they do pressurise and get hot from friction


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## SafT (May 20, 2004)

To give you an idea on return sizes. I have a -6 line fed by an 044 pump. I still get a little bit of pressure in the surge tank with a -10 return.


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## mattysupra (Oct 31, 2008)

so how come i cant use a -6 in and a -6 out? 

All we are doing is creating a loop with a pump that flows the fuel around? 

Surely if it can get enough fuel through -6 then it can flow the same (actually less as the engine has drank it bit) back out the -6? 


How about the valve on the tank? should the pressure releases valve on the tank not release the pressure? As the tank/fuel gets hotter then the pressure will increase on the tank? 

I opened my fuel cap the other day and the pressure was so high that it spat fuel out and blow air at me for a good 30 secounds! Surely the tank cant / should not be allowed to get to this much pressure?


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## chico (Aug 24, 2002)

If You have the same size inlet and oulet, then you turn your tank into a pressure vessel.


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## mattysupra (Oct 31, 2008)

chico said:


> If You have the same size inlet and oulet, then you turn your tank into a pressure vessel.




How come? so if i have a bigger return then dont this turn the tank into a pressure vessel in stead? 


End of the day we have a sealed loop here? The only way to increase overal pressure on a 'sealed' loop is to add fluid/air or heat and expand whats inside! 

So where has this extra pressure come from?


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## gtr-loz (Feb 10, 2006)

fuel gets hot = expands, especially on the return


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## mattysupra (Oct 31, 2008)

gtr-loz said:


> fuel gets hot = expands, especially on the return



Is it me or is the forum full of one word answers tonight! Im sure your all trying to wind me up tonight LOL

I know the fuel expands! 


Whats with the pressure tho? surely the tank should have a valve on it to regulate pressure? 

For instance my fuel when it left the garge tonight was at 20c, i returned it was at 27c! (yes i have fuel temp sensor and a heated garage) 

but it had enough pressure to burst the tank! The system is a loop so the only way to increase tank pressure is to add air/fuel or expand. 

So with a 7c increase its burst the tank. 

If the car was in japan or NZ maybe it would have to cope with maybe 10c night temp to 40c day time temp so a 30c increase! 


How come there tanks dont burst while sat there doing nothing ? 

Pressure releaf valve?


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## gtr-loz (Feb 10, 2006)

im sorry but it was the only thing i could think of!!!

im not sure how a surge tank works if its full of fuel at all times then an increase in pressure could well split the tank the only way this can happen is by expansion of the fuel


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## mattysupra (Oct 31, 2008)

gtr-loz said:


> im sorry but it was the only thing i could think of!!!
> 
> im not sure how a surge tank works if its full of fuel at all times then an increase in pressure could well split the tank the only way this can happen is by expansion of the fuel


Sorry mate, wasn't a dig at you! More a pee take, ye your right on expansion of fuel. 

I think i know what the issue is but i want someone else to come up with the same idea!


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## chico (Aug 24, 2002)

Have you still got the carbon canister connected?


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## gtr-loz (Feb 10, 2006)

if you run two fuel pumps etc and are driving hard then the fuel will heat up and expand alot, if you run the return back to the surge tank instead of the fuel tank then the expansion has to go somewhere this would be by splitting the tank/pipes, ideally you would either need a fuel cooler or run another return to the tank from the top of the surge tank to allow for expansion issues

but i am not really clued up on surge tanks etc so yours may already be like this


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## GT-R Glenn (Nov 9, 2002)

Actually....
The lift pump is lifting all the time to the surge tank, which will overflow to the main tank.
The main feed pump is sucking from the surge tank into the fuel rail, then returning to the surge tank ....
So its possible for more fuel to be going into the tank, than can get out, which is why you need a bigger return
The overflow, gets over used for want of a better term so it can form a restriction, friction bla bla read above...


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## SafT (May 20, 2004)

Free flow thru a pipe is less than the flow under pressure.

So if you dont want pressure in your surge tank your return needs to free flow as much as your feed can supply under pressure


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## mattysupra (Oct 31, 2008)

gtr-loz said:


> if you run two fuel pumps etc and are driving hard then the fuel will heat up and expand alot, if you run the return back to the surge tank instead of the fuel tank then the expansion has to go somewhere this would be by splitting the tank/pipes, ideally you would either need a fuel cooler or run another return to the tank from the top of the surge tank to allow for expansion issues
> 
> but i am not really clued up on surge tanks etc so yours may already be like this


Fuel at the moment returns to the surge tank from fuel rail, then it goes from surge tank to fuel tank and then back to surge tank to create a loop the same as a normal fuel system. 

I can understand the fuel heating up and like i say i have temp gauge so i can see just how hot my fuel is. 


My issue is that my fuel is taking on 7c heat difference from its cold to its hot. This can not be a issue as in other country's teh temps can be maybe 30 c from morning to evening. 


I think i have a issue with a releaf valve on my tank?


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## muzzer2002 (Oct 10, 2007)

have you got a pic of your setup 

i run a rips system and one thing i was told was the return to fuel tank should be bigger than return from fuel line 

also that the return to tank should be below the return from fuel line so that the swirl pot has time to leviate excess fuel


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## blue34 (Jul 28, 2005)

I have a T piece on the return to the swirl pot so some fuel can return to the tank as well as to the swirl pot, it's returned to the tank via a slightly smaller restrictor in the T piece. So it favours the swirl pot and keeps a small pressure in the swirl pot but allows some circulation of fuel via the main tank and so allows more heat to disperse. I guess it also stops excessive pressure building in the swirl pot. 

I don't get pressure build up in the tank, as the car is still fitted with the fuel tank breather to the charcoal canister in the engine bay. 

Does your car still have that conection or could it have been blocked off by mistake?


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## mattysupra (Oct 31, 2008)

The standard charcole canistor is still connected. 

I think my issue is with the pressure relief valve on the fuel tank as i have mnassive pressure when i take the fuel filler cap off. 


I get pressure blowing out the fuel filler cap for a good 20 + secounds! 

so much pressure that i had fuel spraying out the filler cap!


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## mattysupra (Oct 31, 2008)

right, i have just taken my surge tank out and connected the pipes together that used to go to it. 

I.E

Fuel supply from tank and tank pump now direct to 044 pump. (used to go to surge tank)

The return pipe from fuel rail connected to the fuel return from the surge tank. 

So basically the same piping but just missing out the surge tank. 


I have fitted a fuel pressure reg to the return pipe and i have 1/2 bar pressure if i turn the 044 pump off and 1 bar pressure on the return if i turn the 044 on! 

However the pump is now really noisy and pulsing the pressure up and down. I guess this is because all the fuel supplied by the intank pump is being forced into the 044 rather than being allowed to return to the tank if i t wanted to. (i can now see/hear what people say about the 044 being noisy) 

To me it seems that the 044 pump works alot better with a surge tank. 


So this to me shows that there is not to much pressure in the system caused by the pump but must be down to pressure caused by the fuel heating up and the pressure valve on the tank not realising the pressure caused by expansion of the fuel, not presure created by the fuel pump as this is 1 bar. (also as im using the same return lines these must be big enough) ?


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## lightspeed (Jul 11, 2002)

I used to run an 044 direct from the tank without the lifter pump. Just had a rubber hose into the tank to the filter sock. 044 mounted on the boot floor.


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## pupsi (Aug 29, 2006)

I've P.M'd Rob (RIPs) to answer this. I had the same problem, the swirlpots welds were getting hairline cracks. He explained why they were happening and how to cure it, its cured now, his explanation is a lot easier to understand, than it would be if i was to explain it. I now have two returns from the swirlpot to the main tank, one of them being the same size as the fuel feed and one being larger.


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## blue34 (Jul 28, 2005)

matty you are now running two pumpps in series so pressure feeding the 044 which is very differen to supplying from a swirl pot. The regulator in the engine bay should open up when the 044 comes on so dont take too much notice of pressure in the return remember also if fuel pressure has changed then so has your engine fueling map. I would quit messing around. If your tank is pressurising it could also split. Run it off boost with the fuel cap loose and get it looked at by your tuner in my opinion.


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## mattysupra (Oct 31, 2008)

blue34 said:


> matty you are now running two pumpps in series so pressure feeding the 044 which is very differen to supplying from a swirl pot. The regulator in the engine bay should open up when the 044 comes on so dont take too much notice of pressure in the return remember also if fuel pressure has changed then so has your engine fueling map. I would quit messing around. If your tank is pressurising it could also split. Run it off boost with the fuel cap loose and get it looked at by your tuner in my opinion.




ye im not driving the car untill i fix the issue. Im trying to find out if the 044 pump is causing to much pressure but i think the pressure is being caused by the fuel expanding and the tank pressure valve not realising the pressure. 

My theroy around this is that is i remove the fuel cap it blows air out for a long time rather than a few secounds. 



Also im running a lifter pump in the tank (nismo) to fill the surge tank. Then the 044 takes its fuel from the surge tank. 

As i have removed the surge tank and connected the pipes together the car is now running the 044 as a 'inline' pump.


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## RB26 240Z (Dec 29, 2007)

What would happen if you returned the unused fuel back to the main tank than the surge tank would that not stop the presure build up ?.


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## mattysupra (Oct 31, 2008)

RB26 240Z said:


> What would happen if you returned the unused fuel back to the main tank than the surge tank would that not stop the presure build up ?.




The surge tank would run dry as the 044 pump will take more fuel than the nismo intank pump can supply.


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## AlexH (Aug 17, 2008)

matty, that is how i run my fuel system mate.
i have the in-tank lift pump feeding the 044 that sits under my boot floor this feeds the fuel rail and returns streight to the tank.
i have no issues with pulsing noise or pressure problems.
i will presume mark has set your car up the same as mine, im curiouse as to what is happening and i will keep a keen ear on mine incase i get the same problem

Alex


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## mattysupra (Oct 31, 2008)

AlexH said:


> matty, that is how i run my fuel system mate.
> i have the in-tank lift pump feeding the 044 that sits under my boot floor this feeds the fuel rail and returns streight to the tank.
> i have no issues with pulsing noise or pressure problems.
> i will presume mark has set your car up the same as mine, im curiouse as to what is happening and i will keep a keen ear on mine incase i get the same problem
> ...




Mark never set my fuel system up, i built it along with the surge tank etc. To be honest i dont think you would notice the pulsing of the pump, i only have as i have a pressure guage on the return + flow to monitor pressures and find out what my issue is. 

However mark did turn up at mine last night and checked over what i had changed. He also drank all my beers and then went on his way. 

personally i dont think he cared about the fuel issues but was more intrested in my beer and how cold the beer was!


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## mattysupra (Oct 31, 2008)

pupsi said:


> I've P.M'd Rob (RIPs) to answer this. I had the same problem, the swirlpots welds were getting hairline cracks. He explained why they were happening and how to cure it, its cured now, his explanation is a lot easier to understand, than it would be if i was to explain it. I now have two returns from the swirlpot to the main tank, one of them being the same size as the fuel feed and one being larger.




has robby got back to you mate?


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## pupsi (Aug 29, 2006)

He'll probably post up on Monday, because of the time difference, Monday morning in NZ is Sunday night here IIRC, but he will get back with the answer.


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## Piggaz (Sep 5, 2002)

mattysupra said:


> The surge tank would run dry as the 044 pump will take more fuel than the nismo intank pump can supply.


I would argue that point. Yes the Nismo is rated at 276 L/Hr BUT that is at 3 bar of pressure. Seeing that the Nismo is the lift pump into the surge tank it is seeing almost no pressure.... so the flow rate would be ALOT higher. There is a thread on SAU which I started about this issue. After my tune which is Tuesday and have a spare moment I am going to measure what a Nismo and a 044 flow at no pressure.


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## comzilla87 (Jul 3, 2009)

Piggaz said:


> I would argue that point. Yes the Nismo is rated at 276 L/Hr BUT that is at 3 bar of pressure. Seeing that the Nismo is the lift pump into the surge tank it is seeing almost no pressure.... so the flow rate would be ALOT higher. There is a thread on SAU which I started about this issue. After my tune which is Tuesday and have a spare moment I am going to measure what a Nismo and a 044 flow at no pressure.



I have used a walbro as the lift and the 044 as the pressure and originally ran the fuel rail back to the tank and it was fine. 

Then when i put my new rb30 in it was running the surge tank dry on the track. It may be ok for the road but not for the track.

So i put the rail return to the surge tank and then a return from the surge to the tank.


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## R.I.P.S NZ (May 7, 2004)

I've been away racing for 3 days with the Borg and with the FED, just got back.

You MUST run a far bigger return from the surge tank to the main tank or your going to pressurise the whole system which is what happened to Pupsi.

Imagine you have a stock pump as a lifter and 2 x 044s after your surge tank and your engine is at idle.......you have about 6 liters per minute of fuel from the main tank just flowing through the surge tank keeping it flooded, with that pump alone there may be "very slight" pressure in the surge tank even if the return is the same size as the feed.

At idle your engine is consuming very little fuel so its not using much of the 6 liters per minute the lift pump is supplying and most of the fuel your 2 x 044s are flowing is comming straight back to the surge tank.

Your return from the surge to the main tank is already being used to capacity to keep up with the 6 liters per minute the lift pump is supplying so how is the extra 10 liters or so per minute from the engine suppose to get back from the surge tank to the main tank without creating pressure?


Robbie.


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## pupsi (Aug 29, 2006)

I did say Rob's explanation would be easier to understand.


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## SafT (May 20, 2004)

R.I.P.S NZ said:


> I've been away racing for 3 days with the Borg and with the FED, just got back.
> 
> You MUST run a far bigger return from the surge tank to the main tank or your going to pressurise the whole system which is what happened to Pupsi.
> 
> ...


The 10l/min is a closed system from the surge tank. His engine isn't producing 10l/min of fuel, it's simply not using it so it gets returned to the surge tank. (the same place it came from, with roughly the same volume of fuel departing to the engine bay as there is arriving back via the return)


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## SafT (May 20, 2004)

SafT said:


> Free flow thru a pipe is less than the flow under pressure.
> 
> So if you dont want pressure in your surge tank your return needs to free flow as much as your feed can supply under pressure


Just going to quote this again for people that don't understand it.

Imagine a bottle full of water with a 5mm hole in the bottom and a 5mm hole in the top

Pick the bottle up, and the water flows out the bottom.

Now imagine sealing your mouth around the top of the bottle and blowing into it to pressurise it. More water comes out the same size hole at the bottom

Your mouth is the fuel pump, the hole out the bottom the return.

You keep the 5mm hole at the top and have a 20mm hole at the bottom, and there won't be as much difference between free (gravity) flow and the pressurised flow


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## R.I.P.S NZ (May 7, 2004)

SafT said:


> The 10l/min is a closed system from the surge tank. His engine isn't producing 10l/min of fuel, it's simply not using it so it gets returned to the surge tank. (the same place it came from, with roughly the same volume of fuel departing to the engine bay as there is arriving back via the return)


So your saying the pressure produced in the surge tank has nothing to do with the 2 x 044s at all and that pressure is created by a -6 return into an open tank trying to flow the same amount of fuel the -6 feed from the intank pump creates?


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## SafT (May 20, 2004)

Apart from the heat (and associated expansion) added to the fuel on it's trip to the front and back again there won't be any more fuel arriving from the engine than there is being pumped up to it.
Ie. No change in net amount of fuel in surge tank.

If there is more fuel returning than being pumped out of the surge tank I want his engine, because its making it's own fuel!


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## Piggaz (Sep 5, 2002)

SafT said:


> Apart from the heat (and associated expansion) added to the fuel on it's trip to the front and back again there won't be any more fuel arriving from the engine than there is being pumped up to it.
> Ie. No change in net amount of fuel in surge tank.
> 
> If there is more fuel returning than being pumped out of the surge tank I want his engine, because its making it's own fuel!


No... but in the mean time you have the lift pump stuffing more fuel into the surge replacing the fuel that is being taken BY the feed (to engine) pumps.


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## mattysupra (Oct 31, 2008)

O.k! 

Thyanks for everyones ideas. 


Instead of me fitting a larger return to the tank can i fit a 2nd return to the tank instead? so i end up with 2x -6s ? 

O and i only have 1 x 044 not 2 of them. 


What about the pressure im getting in the main fuel tank? Surely this cant be solved by fitting a larger return as if any thing it will increase the pressure in the main tank. 

Like i say i have so much pressure in the main tank that it managed to blow fuel out the filler cap.


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## SafT (May 20, 2004)

Yeah, I think the pressure in the main tank is a separate issue.

I'm not sure how the factory tank in the 34 vents.


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## SafT (May 20, 2004)

Instead of fitting a second -6 is there any way to make the second one a -10 or something around that size?


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## mattysupra (Oct 31, 2008)

SafT said:


> Instead of fitting a second -6 is there any way to make the second one a -10 or something around that size?


The reason why im thinking of fitting a secound -6 is because i have the braided hose and fittings spare. Also i would have to drill out the top of the tank to fit a bigger return so i gues its just as easy to drill a new return hole and use this?


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## freakazoid3 (Jan 19, 2008)

I would just put a second -6 return from the swirlpot to the main tank, and check the breather of the main tank just above the rear diff.

And put a hose on the breather outlet off the tank to see if that solves the overpressurised tank issues when you disconnect the OEM breather system


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## R.I.P.S NZ (May 7, 2004)

Piggaz said:


> No... but in the mean time you have the lift pump stuffing more fuel into the surge replacing the fuel that is being taken BY the feed (to engine) pumps.


:clap::clap:Someone has their thinking cap on


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## mattysupra (Oct 31, 2008)

Robby, any ideas why i have lots of pressure in the main fuel tank? I.E spitting fuel out of the filler neck when opened?


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## R.I.P.S NZ (May 7, 2004)

The only way you can get pressure is if there is a restriction (like above, the fuel from the engine is trying to return into a flooded catch tank with the in tank pump continually keeping it flooded, when you have 2 x 044s, especially at idle, you actually have 3 pumps trying to get fuel out of the surge tank through a -6 line, hence the pressure build up)

Rob


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> The only was you can get pressure is if there is a restriction (like above, the fuel from the engine is trying to return into a flooded catch tank with the in tank pump continually keeping it flooded, when you have 2 x 044s, especially at idle, you actually have 3 pumps trying to get fuel out of the surge tank through a -6 line, hence the pressure build up)
> 
> Rob




I have 1 044 rob not 2 but obviously i can understand that there is pressure there. 


I have removed the surge tank now and joined the pipes up as a tempory fix. 


Im going to be fitting another -6 return so i end up with 2x -6 returns. 


I think i need to look into the vent on the standard tank as i dont think its working when the fuel expands with heat. 



Also can anyone recommened a fuel cooler i can use please?





Robby, the bit i dont understand is that i have 1 bar of pressure going down the return pipe? surely it shoud be higher than this? defo if it managed to split the surge tank? surely only have 1 bar of pressure down the return pipe shows the -6 pipe at the moment is flowing enough?


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## RB26 240Z (Dec 29, 2007)

mattysupra said:


> The surge tank would run dry as the 044 pump will take more fuel than the nismo intank pump can supply.



Not if you have x2 lift pumps.


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## mattysupra (Oct 31, 2008)

RB26 240Z said:


> Not if you have x2 lift pumps.




True but i dont have to lift pumps :shy:


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## SafT (May 20, 2004)

Piggaz said:


> No... but in the mean time you have the lift pump stuffing more fuel into the surge replacing the fuel that is being taken BY the feed (to engine) pumps.


The only reason why the fuel is coming out of the return from the engine is because it's being forced out by roughly the same volume of fuel entering the system at the other (pump) end. 


Where is the extra fuel coming from in your example?


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## R.I.P.S NZ (May 7, 2004)

mattysupra said:


> The surge tank would run dry as the 044 pump will take more fuel than the nismo intank pump can supply.


Not correct sorry, the only way your surge tank will run dry is if you BURN more than the intank pump flows unloaded (ie. around 6 liters per minute) and even then it would only empty the surge tank slowly.

Basicly unless you can maintain susatained full power at more than around 6 liters per minute you'll never empty your surge tank as long as the return from the engine goes back into the surge tank.

We always use a stock intank pump to feed the surge tank, even when we have 3 x 044s drawing from the surge tank. 

Robbie.


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## mattysupra (Oct 31, 2008)

SafT said:


> The only reason why the fuel is coming out of the return from the engine is because it's being forced out by roughly the same volume of fuel entering the system at the other (pump) end.
> 
> 
> Where is the extra fuel coming from in your example?



I think i understand what they mean SafT, what they are saying is that the fuel in the surge tank is being removed by the 044 pump. 

The removed fuel is then replaced by the NISMO intank pump. 


Then... the 044 fuel is returning to the surge tank from the fuel rail BUT there is no room for this fuel as its already been replaced by the intake pump! 



HOWEVER! All i can see this doing is increasing the pressure as we end up pumping to lots of fuel to the same 2 litre tank? So this is the problem???? 

If this is the problem then how come there is only 1 bar of pressure in there? Surely the return is flowing enough fuel as it only gets to 1 bar pressure! 



Like i say, in my case the pressure build up i think is in the main tank. 


For instance i could have 5 bar of pressure in the surge tank and the fuel tank at the same time? So as the pressure is equal both sides of my gauge in theroy the gauge thinks there is no pressure there as its equal both sides? 


So i have 1 bar of pressure on the return pipe to the tank. This i guess actually could be 6 bar if the pressure in the tank is already at 5 bar. 

Does that make sence?


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## R.I.P.S NZ (May 7, 2004)

SafT said:


> The only reason why the fuel is coming out of the return from the engine is because it's being forced out by roughly the same volume of fuel entering the system at the other (pump) end.
> 
> 
> Where is the extra fuel coming from in your example?


The fuel from the engine is returning to a fully flooded catch tank as the in tank pump will continually keep it flooded (it will easily replace the fuel being burnt at the engine), when you have 2 x 044s, especially at idle, they then pump against the in tank pump keeping the surge tank flooded and you then have 3 pumps trying to get fuel OUT of the surge tank to the main tank through a -6 line, hence the pressure build up.

If you turned OFF the intank pump, you would just be circulating fuel from the surge to the engine and back again.

Or if you turn OFF the 2 x 044s you are just circulating fuel from the main tank through the surge tank and back again.

Have all 3 pumps going at once and a single -6 can not flow enough to keep the surge tank at 0 psi or an acceptable pressure.


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> Not correct sorry, the only way your surge tank will run dry is if you BURN more than the intank pump flows unloaded (ie. around 6 liters per minute) and even then it would only empty the surge tank slowly.
> 
> Basicly unless you can maintain susatained full power at more than around 6 liters per minute you'll never empty your surge tank as long as the return from the engine goes back into the surge tank.
> 
> ...




I dont think you have read/ understood the question i was replying to rob. 


The quote of mine above is my answer to someone who was asking 'if' we was to return the fuel rail to the main tank rather than the surge tank. 


As your answers says, only if it was to return to the tank rather than the surge tank! 
:nervous:


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## R.I.P.S NZ (May 7, 2004)

mattysupra said:


> Robby, the bit i dont understand is that i have 1 bar of pressure going down the return pipe? surely it shoud be higher than this? defo if it managed to split the surge tank? surely only have 1 bar of pressure down the return pipe shows the -6 pipe at the moment is flowing enough?


You should have NO pressure going down the return pipe thats the whole point.

Imagine 14.7 pounds per square inch working on the surfaces of your surge tank, even with a small tank you could have several 100s of pounds (even into the 1000s of pounds) working on just 1 face of the tank, then add to it that its pulsing and flexing all the time, its not surprising the tanks crack.


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## SafT (May 20, 2004)

The surge tank is going to be under basically the same pressure with the 044(s) on or off.

When the 044(s) in this example are on, they are simply shifting roughly the same amount of fuel out of the surge tank (small + volume from fuel heating, small - volume for consumption at idle) as is coming out of the return from engine. Its continuous. Assuming it's pumped from, and directly returns to the surge tank its going to have a near zero net effect on volume of fuel in the surge tank.

Its a closed system. 

The pressure on his surge tank is coming from the lift pump.

edit: that will be the same pressure he is seeing on his return from regulator.

Your return line from the surge tank needs to free flow as much as your feed from the lift pump supplies.

If this isnt the case, you will get some pressure in your surge tank.


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> You should have NO pressure going down the return pipe thats the whole point.
> 
> Imagine 14.7 pounds per square inch working on the surfaces of your surge tank, even with a small tank you could have several 100s of pounds (even into the 1000s of pounds) working on just 1 face of the tank, then add to it that its pulsing and flexing all the time, its not surprising the tanks crack.




Personally i cant see it possible to have zero pressure at the tank when two pumps are forcing fuel into it! 

However who am i to argue with you when your the chap i look upto with your knowledge LOL! 


O.k then so i can see what your saying. Like i say i will fit another feed back to the main fuel tank. 


But im still stuck with the fact i have pressure in the whole system. Yes im showing 1 bar of pressure down the return pipe which again i cant see being enough pressure to split alloy, personally i would of thought the braided pipes/joins would go first. 

However like i say im only taking a reading of 1 bar if the whole system is not under pressure (both sides of my gauge) 

If teh whole system is under pressure ,5 bar in tank and 6 bar in the surge tank and my gauge is reading teh difference between the two ( 1 bar) then i defo have another issue!


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## R.I.P.S NZ (May 7, 2004)

mattysupra said:


> Personally i cant see it possible to have zero pressure at the tank when two pumps are forcing fuel into it!


What if your surge tank had no lid, would there be pressure in there then?

Pressure is only a measure of resistance, reduce/remove the resistance and there is no pressure.

Rob


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> What if your surge tank had no lid, would there be pressure in there then?
> 
> Pressure is only a measure of resistance, reduce/remove the resistance and there is no pressure.
> 
> Rob




UMMM.... now i think i understand. 


So basically i should be able to remove the lid from tank and have no pressure there? So the fuel should be able to flow in and flow out without over filling basically? 


O.k like i say i will increase the fuel return size. 



Do we have any ideas on the main tank building pressure?


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## R.I.P.S NZ (May 7, 2004)

SafT said:


> The surge tank is going to be under basically the same pressure with the 044(s) on or off.
> 
> When the 044(s) in this example are on, they are simply shifting roughly the same amount of fuel out of the surge tank (small + volume from fuel heating, small - volume for consumption at idle) as is coming out of the return from engine. Its continuous. Assuming it's pumped from, and directly returns to the surge tank its going to have a near zero net effect on volume of fuel in the surge tank.


Although it might not be much I think you'd find, seeing as the lifter is continually replacing the fuel the engine is burning, and the fuel from the motor is not comming back to a tank with some fuel removed (the burnt stuff) there would be extra pressure from the 044s pishing against the fuel trying to come in from the lifter.




SafT said:


> Your return line from the surge tank needs to free flow as much as your feed from the lift pump supplies.
> 
> If this isnt the case, you will get some pressure in your surge tank.


Agreed.


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## SafT (May 20, 2004)

Matty, your pm box is full  but here is what i was going to reply with

I went thru it with mine - I have a 45l plastic fuel cell as a surge tank/extra fuel capacity (as well as the stock r32 gtr tank).

I have 044 in tank lifting thru a -8 line.I didnt think about the flow/return too much until after i fired up the pump and found even with a -8 return it was inflating the fuel cell. (really obvious with a plastic tank)

I added an extra -10 return but I still get a small amount of pressure (acceptable, similar to opening a normal gas tank on a hot day) with the combined -8 and -10 returns.

Your issue with the main tank sounds like something blocked in the stock venting setup - find a copy of the 34 workshop manual i guess and see if there are any check valves/roll over valves that may stick.


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## SafT (May 20, 2004)

R.I.P.S NZ said:


> Although it might not be much I think you'd find, seeing as the lifter is continually replacing the fuel the engine is burning, and the fuel from the motor is not comming back to a tank with some fuel removed (the burnt stuff) there would be extra pressure from the 044s pishing against the fuel trying to come in from the lifter.


I think we are close to agreeing here 

Basically the effect of running the 044(s) on the level of the surge tank is very little, since the volume of fuel they are drawing out of the tank is basically the same as whats going back in. Its all happening at exactly the same time. The pump(s) are simply shifting the fuel in a loop


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## R.I.P.S NZ (May 7, 2004)

It would be interesting to compare pressures a surge tank has with a -6 in and -6 return with the 044s on and then off, I'd bet there's pressure with the lifter and I'd also bet the pressure increases some more with the 044s running.

I'd also bet that there's nowhere near the pressure you think in the surge tank with a -6 in and a -6 out of the surge tank, IMO its when the 044s are added to the mix the pressure gets excessive.

Think about this...........lets say the lifter flows 6 liters per minute unloaded through a -6 line, putting a surge tank in line isn't going to change that much if the hose lengths are kept as they would be in a typical install.

6 liters per minute is only 100mls per second, imagine how little pressure there would be to fill a cup in 2 1/2 seconds, in fact I'd say you'd almost be able to push that much water through a -6 hose with your mouth and you can only push around 2psi max with your mouth. 

In any case, we all agree you should run a return at least one size larger than the feed from the main tank.

Rob


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## GT-R Glenn (Nov 9, 2002)

I thought I answered this about 100posts ago ...
lol


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> It would be interesting to compare pressures a surge tank has with a -6 in and -6 return with the 044s on and then off, I'd bet there's pressure with the lifter and I'd also bet the pressure increases some more with the 044s running.
> 
> I'd also bet that there's nowhere near the pressure you think in the surge tank with a -6 in and a -6 out of the surge tank, IMO its when the 044s are added to the mix the pressure gets excessive.
> 
> ...



Tell you wait, i will check in 10 mins! 


I will check to see what the pressure is with a surge tank and without and with the 044 running and without! 

Guess i will stinking of petrol next time i reply!


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## mattysupra (Oct 31, 2008)

o.k, surge tank by passed i have (on the return to tank pipe) 

.6 bar off the intank pump
.8-1bar (pulsing ) when i turn the 044 on. 


Be back in a minute as going to connect the surge tank back up.


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## R.I.P.S NZ (May 7, 2004)

GT-R Glenn said:


> I thought I answered this about 100posts ago ...
> lol


True, what you said in post #15 is what I have been agreeing with all along.

Saft seems to think the 044s have no effect on the pressure increasing in the surge tank.

Its one of those things, who's going to take the time to do the test to prove anything one way or the other when we all know the solution to the problem.

Rob


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## SafT (May 20, 2004)

Basically, yeah, im saying the effect the 044(s) will have will be negligible, because they arent adding any volume of fuel into the surge tank system (apart from a small increase in volume from the heat)


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## mattysupra (Oct 31, 2008)

mattysupra said:


> o.k, surge tank by passed i have (on the return to tank pipe)
> 
> .6 bar off the intank pump
> .8-1bar (pulsing ) when i turn the 044 on.
> ...





Right then, reconnected the surge tank and ran car. (again on fuel return to tank from surge tank) 

It is .8 bar with 044 running. (but not pulsing pressure, pump is also quiet running off surge tank) 


044 turned off and the surge tank return pressure is now 1.2 bar????? im going to guess this is because the engine is not taking its fuel? 




So basically with the surge tank connected i have less pressure down the return to tank line and the 044 runs smooth. 

If i connect the 044 inline the pump pressure is up and down and the pump is noisy and there is more pressure down the return line!


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## R.I.P.S NZ (May 7, 2004)

1.2 bar is alot for a -6 in and a -6 out?

I can't see anyway your pressure can be lower with the 044 running but I havn't seen your system design or install.

Interesting...............


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## SafT (May 20, 2004)

1 way that a local racing workshop told me they like to do it to prevent excess heat in fuel (Homewoods for Colin/Glen) is use the same model pump as a lift and supply. and run the return from regulator straight back to the fuel tank.

It makes sense. the Lift pump will always flow more since its running at much lower pressure.


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## R.I.P.S NZ (May 7, 2004)

SafT said:


> Basically, yeah, im saying the effect the 044(s) will have will be negligible, because they arent adding any volume of fuel into the surge tank system (apart from a small increase in volume from the heat)


I'd agree but I still think the pressure would have to increase somewhat.

Anyway it seems Matty has thrown a curve ball as his figures don't add up so far.


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> I'd agree but I still think the pressure would have to increase somewhat.
> 
> Anyway it seems Matty has thrown a curve ball as his figures don't add up so far.


LOL ye i think i have! Them figures have confused me also? Not what i was thinking was going to happen!


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> I'd agree but I still think the pressure would have to increase somewhat.
> 
> Anyway it seems Matty has thrown a curve ball as his figures don't add up so far.


Do you think it will help if i remove that dodgy looking RIPS 044 clamp you supplied me LOL (joke, it looks the dogs bollox) 



Would picture help? maybe me draw how it works? maybe even i video whats going on?


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## mattysupra (Oct 31, 2008)

where has everyone gone? we off thinking maybe LOL


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## R.I.P.S NZ (May 7, 2004)

pix or confirm exactly how it is plumbed with sizes etc would be interesting.


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## mattysupra (Oct 31, 2008)

R.I.P.S NZ said:


> pix or confirm exactly how it is plumbed with sizes etc would be interesting.


Will do in the morning mate, bed time for me now. 

P.S hows robin (it is robin isnt it? going off memory here) getting on with the borg! LOL i bet he has soiled a few sets of under wear!


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## GT-R Glenn (Nov 9, 2002)

Rotary Extreme


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## R.I.P.S NZ (May 7, 2004)

mattysupra said:


> P.S hows robin (it is robin isnt it? going off memory here) getting on with the borg! LOL i bet he has soiled a few sets of under wear!


He's on his way home now, had a fantastic week with us, had a ball thrashing his car and doing lots of other cool stuff.

And yes, he was a little scared at times but well worth it he said, lol


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## pupsi (Aug 29, 2006)

I bet Robin left a few soiled boxers behind in N.Z when he left. I'm missing a hell of a lot of performance after reading about the Borg's achievements so far.


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## mattysupra (Oct 31, 2008)

Mine is plumbed the same as this (thanks for the link glen)















It plumbed in -6 but uses the standard fuel lines that run under the car to take fuel to the engine and back. So the -6 connects to the standard lines under the car. However the return from the surge tank to the main tank is -6 all the way. 


The pump is wired upto a relay that is switched on by the intank fuel pump that the ecu controls. So the 044 turns on and off the same time as the intank pump.


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## Chris Wilson (Aug 20, 2001)

What a drama!  The pressure in the main fuel tank can only be caused due to a lack of breathing to atmosphere, it's nothing to do with the pumping volume, return line size or whatever. they are separate issues. You need to make sure the main tank is vented for both incoming and outgoing vapours, but with the proviso that if the car rolls it won't vent fuel. You can buy special vent valves for this. In the photo of the swirl post system I built for my RB26 below you can see the vent line tied up to the rear strut brace. It has a valve in the end. I get no pressure or vacuum in the main tank. The valve is in shadow, it's ringed in green.


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## R.I.P.S NZ (May 7, 2004)

mattysupra said:


> It plumbed in -6 but uses the standard fuel lines that run under the car to take fuel to the engine and back. So the -6 connects to the standard lines under the car. However the return from the surge tank to the main tank is -6 all the way.


Change the -6 from the surge tank to the main tank to a -8 but it seems you still have an issue with the plumbing/venting of the main tank which "could" be why your seeing pressure in the surge tank.

Run the engine with the main fuel filler lid off and see if you still have any pressure in your surge tank.

Rob


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## GT-R Glenn (Nov 9, 2002)

Yes Chris, but most people return to the main tank, which IS vented to atmos, so the restriction is in the pipe venting the surge, into the main tank ....
An even easier way would be to put the overflow straight into the fuel tank filler tube ....


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## Chris Wilson (Aug 20, 2001)

"I opened my fuel cap the other day and the pressure was so high that it spat fuel out and blow air at me for a good 30 secounds! Surely the tank cant / should not be allowed to get to this much pressure?"

This is the bit I am referring too, and it's purely an issue with how the main tank is vented to atmosphere


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## blue34 (Jul 28, 2005)

On another note one way valves as well as filters are a must on the 044 output lines. Without these if one 044 fails or partially fails the other can push fuel back through the failed pump resulting in the engine then running with reduced pressure at the rail ie weak running and possible damage. Or a simple conk out where you find yourself stranded by the roadside scratching your head because you can hear the pump running and it will tick over but won't pull away....


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## Chris Wilson (Aug 20, 2001)

blue34 said:


> On another note one way valves as well as filters are a must on the 044 output lines. Without these if one 044 fails or partially fails the other can push fuel back through the failed pump resulting in the engine then running with reduced pressure at the rail ie weak running and possible damage. Or a simple conk out where you find yourself stranded by the roadside scratching your head because you can hear the pump running and it will tick over but won't pull away....



Good point, I didn't need the flow from both my 044 pumps after dyno testing, so I kept the secondary pump as a back up if one should croak. The OE one way valves allow this, as you mention.


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## mattysupra (Oct 31, 2008)

Chris Wilson said:


> "I opened my fuel cap the other day and the pressure was so high that it spat fuel out and blow air at me for a good 30 secounds! Surely the tank cant / should not be allowed to get to this much pressure?"
> 
> This is the bit I am referring too, and it's purely an issue with how the main tank is vented to atmosphere




Thanks for input chris, i think a few people have missed this issue. 


Im going to be checking /modding my fuel tank valve first and then return to the surge tank issue that i personlly think is connected.


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## Chris Wilson (Aug 20, 2001)

If you need a check valve speak to Faye at Speedflow, I get a lot of our race fittings from her. Excellent service and good technical knowledge.

Valves (check, breather, pressure realease & on/off)


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## mattysupra (Oct 31, 2008)

Chris Wilson said:


> If you need a check valve speak to Faye at Speedflow, I get a lot of our race fittings from her. Excellent service and good technical knowledge.
> 
> Valves (check, breather, pressure realease & on/off)


thanks for the link, which part do i need if i was to add a breather to the main fuel tank? 

I need one that fuel cant flow out of if i was turn the car upside down.


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## Chris Wilson (Aug 20, 2001)

What you need is one my alloy tank top plates that work with the stock seal and plastic ring, then you can add fittings and wire feed outs easily  I would say this one should suit:

In Line Tank breather shut off 610-TPV8


You really need an in line valve as the tank plate is awash with fuel with a full tank, a remote valve will not weep fuel. You then need fittings to get a hose from the tank to the valve. Faye will guide you.


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## nozza1 (Jan 13, 2007)

Need to know if a -10 return to main tank would be sufficient to eliminate any potential pressure build up in my fuel setup.



Okay, got -6 pickup to the surge tank via tomei main tank pump.

Then two -6 bosch 044 pumps feeding from surge tank, joining into a single 10mm aluminium line, then splitting into -8 on either end of the fuel rail.

The return line from the fuel rial will be a -6/-8 adapter from the regulator and a -8 hose back to the surge tank.

-10 from surge tank to main tank.


Should l change the -10 to a -12 return to main tank or is it sufficient?


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## Chris Wilson (Aug 20, 2001)

I run a -8 return with twin 044 pumps. Actually two were more than enough, so I later ran just one and use the other as a spare. But -8 return was more than able to cope without any real build up of pressure. So0me pressure differential does no harm anyway, so long as it's well below the FPR idling setting


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## xxfr (Apr 28, 2009)

A -10 will be fine. Even an -8 will do mate.


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## nozza1 (Jan 13, 2007)

Cheers peeps.

Onwards and upwards..:thumbsup:


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## TTOBES (Sep 28, 2007)

First time I've seen this thread but I have worked out why there is pressure in the surge tank...

The pump circut supplying fuel to the engine and return to the surge tank has little or no effect. There is a slight increase in the volume due to the heat imparted to the fuel, offset by the amount of fuel used by the engine.
The point is the fuel returns to the the surge tank at roughly the same rate as it is drawn out, so balances itself out.

However you have a pump supplying fuel into the surge at 6?? litres per minute.
A -6 return line, with zero pressure in the surge tank will only flow 1?? litre per minute. To get it to return the 6 litres per minute back to the main tank may mean that you need to put 5??? psi behind it.

Connect a -6 line to an open topped container and measure the amount of fuel that will flow thru it in 1 minute. That is the maximum it will return to the main tank and maintain 0psi in the surge tank.....

To calculate the return line size required you need to do the same test as above untill you find a line size that will flow the 6 litres per minute from that open topped container.... And then probably step up one further size...

I would be interested to hear the results....:thumbsup:


As Robbie said, it doesn't take much pressure to blow a surge tank apart.
If you have a 10" tall by 4" square tank you have an internal surface area of 192 sq"....Times the above 5psi gives a total force of close to 1000lb pushing it apart.....:nervous:


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## barbsGTR (Apr 2, 2011)

Interesting thread. Looking at a fuel surge tank at the moment due to my r34 gtr having issues on right hand corners on the track.

I understand most are saying to increase the size of the return line from the surge tank to the main fuel tank. 

I see a user in this thread has fabricated a new lid for the fuel tank. Is this the only option? is everyone doing that to be able to increase the size of the return line?


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## Chris Wilson (Aug 20, 2001)

Working with the stock moulded plastic top is a nightmare, it's far better to turn up an alloy cap and drill that to suit proper bulkhead hose fittings, and to get rid of the fuel pump connector that is not rated to carry much more current than a stock in tank pump draws without the contacts overheating. I made several of these and used two myself. the others are now sold. I am too busy to make more right now. They cost a fair amount due to the size of billet they need to be turned from.


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## BenTaylor200 (Dec 5, 2001)

I'm assuming that the Skyline uses the same jet pump/venturi on the return line to move fuel from the other side of the tank, do you keep this when you install a -8 (or larger) return?


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## luchjeg6 (Jan 16, 2011)

can I have more infos on the custom made metal fuel tank top? Can I ask what's the purpose of the pie coming from the bottom of the tank up to one of the connections of the plastic top?


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