surge tank setup

[loner]

Pretty sussed on how this stuff works... and have done one setup before... but just wondering if a filter after the surge tank and before the external fuel pump, is required in addition to the filter that is right before the rails... I\'m guessing it will protect the external pump... but can\'t think of any other benefits... also wondering if a standard type filter will do in that position (between surge tank and external pump) or if I would need an inline filter? I\'m worried that a standard filter would itself suffer from surge... or maybe that\'s not possible. hmm.

[funkytown]

i run an inline one,

And i\'d need to check to be crystal but 99.999% have the factory sock on the internal, and one after the surge tank before pump as you\'ve described.

[loner]

yeah I have the two standard filters... i.e. the sock and the standard filter before the rail... was thinking about putting an additional one between the surge tank and external pump...

anyway... just got an inline one from extreme for only $20... so will just use that... no need for one of those ridiculously expensive "performance" units.

[funkytown]

oh.. i took out the factory one on the firewall Loren.

[loner]

oh okay... I think I\'m going to leave that in... I figure if the external pump explodes or something that filter will stop crap getting to the rails...

[nztintin]

I run the factory sock then an inline in the engine bay in place of the factory filter

Less filters = more flow imo

[loner]

yeah true, but I only have the one filter after the external pump, and the flow before the external should be massive because the in tank pump is not loaded.

[funkytown]

 nztintin said:

I run the factory sock then an inline in the engine bay in place of the factory filter

Less filters = more flow imo

actually i think is the way i did it too, given i\'d removed the filter on the firewall.

so. inline is post external pump, not before it.

[thorpy]

I run the sock on the intank walbro , then an inline filter out of the surge tank before the external , then the factory one in the engine bay.

Probably overkill but I figure each one saves things if anything before it explodes.

[gotasuby]

 titian said:

Common mistake with surge systems is bringing both returns back to the surge tank without ensuring correct pressure drop. This can limit return flow from engine supply pump/system.

A pressure drop must be present between both system returns. I.E. the surge tank "fill" system and the engine supply from the surge tank system.

If there is not a good pressure drop,(as in the return from the surge "fill" system pressure must be lower), lack of circulation and possible "boiling" of the fuel can occur in the injector rails.

Careful consideration is required for these systems to be effective and not cause lean out due to this fuel heating on open loop tuned vehicles. Many engines have been killed due to this.

In short:- Ensure there is a "free" return to the fuel tank from injector supply rails/fuel regulator. That is not affected by the surge tank pressure at all.

You want the return from the rails to surge tank then a return from the top of the surge tank to factory return on in tank unit as it helps drive the transfer between humps in main tank

[lachlan]

man you completely missed his point . read it again aye

[rex-leggy]

he didnt miss it. he rarely misses much

[funkytown]

so im skeptical as hell as to what you\'re saying, can you draw me a picture please and post it up

[gotasuby]

I\'m not confused at all or wrong. But am highly amused haha. If designed correctly then there should be no pressure in surge tank

[loner]

There maybe some pressure... but it\'s not high pressure, like between the external pump and the regulator.

Anyway, I\'d like a diagram as well, because what you wrote is incomprehensible.

[funkytown]

 

To create a pressure drop at this point a small orifice can be fitted on the surge tank vent/return to tank prior to where the engine return tees in. this will allow venting of the surge tank and ensure no back pressure from the tank pump/surge tank system.

wait so you want to punch a hole in the top of the surge tank? and vent to atmo? thats going to end up with fuel EVERYWHERE ?????????

[Koom]

Guys, what he is saying is that the pump from your tank to the surge tank will create pressure inside the surge tank. This is what drives the return from the surge tank to the standard fuel tank.

Then he is saying that the return from the fuel lines needs to have somewhere of low(er) pressure to flow to otherwise it just won\'t return any fuel flow and the fuel sitting in the fuel lines will just stagnate as the only way it can flow out of the fuel lines is into the injector as effectively the return from the regulator is blocked by the high pressure in the surge tank.

So, what you do is tee the return from the regulator into the surge -> fuel tank fuel line. BUT, you put an orifice in the surge tank outlet as this will provide low pressure downstream which will allow a decent amount of return FLOW from the fuel rails through the regulator and back out the return line to the fuel tank.

If you think about the pressures from the point of view of a river flowing from one lake into another, you will see that if you have high pressure in the return, you are effectively asking the stream to flow uphill. or something like that. I need to draw something in MS Paint to make that last sentence make sense...

[Koom]

 funkytown said:

 

To create a pressure drop at this point a small orifice can be fitted on the surge tank vent/return to tank prior to where the engine return tees in. this will allow venting of the surge tank and ensure no back pressure from the tank pump/surge tank system.

wait so you want to punch a hole in the top of the surge tank? and vent to atmo? thats going to end up with fuel EVERYWHERE ?????????

The orifice is inside the pipework. The high pressure fuel has to flow through it and because it is an orifice, it causes a pressure drop. Its how refrigeration systems work. Its also how you calibrate a flow bench. Fluids and orifices go together like cookies and cream.

[loner]

 Koom']

Guys, what he is saying is that the pump from your tank to the surge tank will create pressure inside the surge tank. This is what drives the return from the surge tank to the standard fuel tank.

ok... but it\'s low pressure.

[quote name='Koom said:

Then he is saying that the return from the fuel lines needs to have somewhere of low(er) pressure to flow to otherwise it just won\'t return any fuel flow and the fuel sitting in the fuel lines will just stagnate as the only way it can flow out of the fuel lines is into the injector as effectively the return from the regulator is blocked by the high pressure in the surge tank.

This doesn\'t make sense to me... the fuel post regulator has to go somewhere... it can\'t go back through the regulator, so pressure will build up

and it will be pushed into the surge tank. The surge tank pressure is not high... it\'s only what is created by the restriction in the lines themselves.

Also, the external pump is sucking fuel from the surge tank, lowering it\'s pressure more.

[gotasuby]

 titian']

[quote name='gotasuby said:

I\'m not confused at all or wrong. But am highly amused haha. If designed correctly then there should be no pressure in surge tank

/quote] Oh really? how do you come to that conclusion? Plenty of pressure in my setup. 10 psi in the surge tank! 40 on the rails and 5-6 in the return to tank.

No pressure in the surge tank??? WRONG! :o

If there is no pressure in the surge tank then either the key is off the pump has stopped or fuel has run out. :)

Further:- With your advised setup and no surge tank pressure there will not be any return flow to the tank and therefore no transfer over the hump A?? Think about it! 8) ??? ???

Your must be set up awful to have 10psi in the surge tank. We have around 1psi.which is nothing compared to the restriction caused by the return line it self. Also only 40 on the rails? Why so low?

Just got off your high horse . There many ways to skin a cat, I just prefer to have my surge tank as full as possible during surge while racing.

[Koom]

 loner']

Guys, what he is saying is that the pump from your tank to the surge tank will create pressure inside the surge tank. This is what drives the return from the surge tank to the standard fuel tank.

ok... but it\'s low pressure.

Then he is saying that the return from the fuel lines needs to have somewhere of low(er) pressure to flow to otherwise it just won\'t return any fuel flow and the fuel sitting in the fuel lines will just stagnate as the only way it can flow out of the fuel lines is into the injector as effectively the return from the regulator is blocked by the high pressure in the surge tank.

This doesn\'t make sense to me... the fuel post regulator has to go somewhere... it can\'t go back through the regulator, so pressure will build up

and it will be pushed into the surge tank. The surge tank pressure is not high... it\'s only what is created by the restriction in the lines themselves.

Also, the external pump is sucking fuel from the surge tank, lowering it\'s pressure more.

All he\'s saying is that you want to create conditions where you can get the maximum flow through the regulator/return so that it is constantly flushing out the fuel rails.

If you have 10psi in the surge tank, and your regulator is also trying to return fuel to that same 10psi spot, then the flowrate will drop accordingly. Which basically means that the fuel in the rails will sit there for a longer period of time (heating up etc).

We all seem to spend a lot of time maximizing everything else on our cars, why not look into other area\'s that are often missed.

[quote name='gotasuby said:

I\'m not confused at all or wrong. But am highly amused haha. If designed correctly then there should be no pressure in surge tank

/quote] Oh really? how do you come to that conclusion? Plenty of pressure in my setup. 10 psi in the surge tank! 40 on the rails and 5-6 in the return to tank.

No pressure in the surge tank??? WRONG! :o

If there is no pressure in the surge tank then either the key is off the pump has stopped or fuel has run out. :)

Further:- With your advised setup and no surge tank pressure there will not be any return flow to the tank and therefore no transfer over the hump A?? Think about it! 8) ??? ???

Your must be set up awful to have 10psi in the surge tank. We have around 1psi.which is nothing compared to the restriction caused by the return line it self. Also only 40 on the rails? Why so low?

Just got off your high horse . There many ways to skin a cat, I just prefer to have my surge tank as full as possible during surge while racing.

I know that there is quite a lot of dislike for Titian floating around, mostly based on his typing style that comes across as yelling. But I have to ask the question, if he\'s got 10psi inside the surge tank, and you\'ve got 1psi, how do you calculate that yours is full and insinuate that his is somehow half empty (yet at an elevated pressure)?

[gotasuby]

 Koom']

Guys, what he is saying is that the pump from your tank to the surge tank will create pressure inside the surge tank. This is what drives the return from the surge tank to the standard fuel tank.

ok... but it\'s low pressure.

Then he is saying that the return from the fuel lines needs to have somewhere of low(er) pressure to flow to otherwise it just won\'t return any fuel flow and the fuel sitting in the fuel lines will just stagnate as the only way it can flow out of the fuel lines is into the injector as effectively the return from the regulator is blocked by the high pressure in the surge tank.

This doesn\'t make sense to me... the fuel post regulator has to go somewhere... it can\'t go back through the regulator, so pressure will build up

and it will be pushed into the surge tank. The surge tank pressure is not high... it\'s only what is created by the restriction in the lines themselves.

Also, the external pump is sucking fuel from the surge tank, lowering it\'s pressure more.

All he\'s saying is that you want to create conditions where you can get the maximum flow through the regulator/return so that it is constantly flushing out the fuel rails.

If you have 10psi in the surge tank, and your regulator is also trying to return fuel to that same 10psi spot, then the flowrate will drop accordingly. Which basically means that the fuel in the rails will sit there for a longer period of time (heating up etc).

We all seem to spend a lot of time maximizing everything else on our cars, why not look into other area\'s that are often missed.

[quote name='gotasuby said:

I\'m not confused at all or wrong. But am highly amused haha. If designed correctly then there should be no pressure in surge tank

/quote] Oh really? how do you come to that conclusion? Plenty of pressure in my setup. 10 psi in the surge tank! 40 on the rails and 5-6 in the return to tank.

No pressure in the surge tank??? WRONG! :o

If there is no pressure in the surge tank then either the key is off the pump has stopped or fuel has run out. :)

Further:- With your advised setup and no surge tank pressure there will not be any return flow to the tank and therefore no transfer over the hump A?? Think about it! 8) ??? ???

Your must be set up awful to have 10psi in the surge tank. We have around 1psi.which is nothing compared to the restriction caused by the return line it self. Also only 40 on the rails? Why so low?

Just got off your high horse . There many ways to skin a cat, I just prefer to have my surge tank as full as possible during surge while racing.

I know that there is quite a lot of dislike for Titian floating around, mostly based on his typing style that comes across as yelling. But I have to ask the question, if he\'s got 10psi inside the surge tank, and you\'ve got 1psi, how do you calculate that yours is full and insinuate that his is somehow half empty (yet at an elevated pressure)?

With my setup all the lift pump fuel fills up surge tank then when it full it vents back to main tank. Same as Titian. Now where we are different, especially with a high flow main pump is say you have 300lph, at cruise you will be using only 10l hour. So his main pump will be flowing back from the surge tank, through rails and back to main tank, not going into surge. So if his lift pump is not as much flow or more his surge tank will slowly empty out which is very dangerous. Do you see the problem? Also with having such a huge lift pump you are heating up the fuel more than say a smaller lift pump and a letting the fuel cool down as it travels through the fuel lines from engine bay. And if it getting too hot get a fuel cooler.

Also the pressure in surge tank has nothing to do with it. It would be awesome to keep it at say 20 psi as it\'s a closed loop system so less work on main pump and a little more on lift pump. So his 10psi is good for main pump but bad for lift pump as it means there a higher chance of running out of fuel in surge tank

[Koom]

There\'s valid points from both sides here. This is great! A discussion on the internet, who would\'ve thought it possible? haha

I\'ve got some graphs in my head that I want to look at putting up tonight as there\'s is maths and logic for both sides of the coin.

Also depends on where in the car your surge tank is located and whether you\'re stuck with using just the factory lines etc etc.

[Koom]

Sorry I got sidetracked by some friends and the pub tonight.

Currently I like both sides of this discussion, there\'s pro\'s and con\'s for each side depending on where your priorities lie.

I want to look at the flowrate of a Walbro (commonly used as a lift pump) pushing into a constant 10psi container, and then compared to something like a Bosch 044\'s flowrate at low and high pressure ratio\'s.

Without doing anything more than daydreaming about it, I prefer Titian\'s setup, as long as the lift pump can handle the flowrate when the main pump is operating at relatively high loads. In that case, the fuel rails can\'t stagnate as badly and overheat the fuel. It just needs to be sized appropriately.

[loner]

I can\'t see how the fuel can ever stagnate in the rails post regulator and not flow back into the surge tank.

The external pump is pumping a high volume of fuel... the suggestion that this just sits in two feet of fuel

line connected to a low pressure surge tank, but does not flow into it... is pure crazy.