Hot Surge Tank

[shanef]

You could try a one way fuel system - what alot of modern cars are using.

Basically you mount the FPR at the rear of the vehcile so that the fuel gets pressurised sent to the front - that way fuel only goes forward and not cycled around and around.

I can see that having pressure drop issues up at the rail. You won't have the same pressure at each injector if you regulate the fuel before the rail, whereas with the fuel regulated after the rail, you wont ever have pressure issues i.e not all injectors will see the same pressure with it regulated before the rail. Probably fine for the family run around, but on a hi peformance vehicle i wouldnt even dream of doing it.

[rob82]

I can see that having pressure drop issues up at the rail. You won't have the same pressure at each injector if you regulate the fuel before the rail, whereas with the fuel regulated after the rail, you wont ever have pressure issues i.e not all injectors will see the same pressure with it regulated before the rail. Probably fine for the family run around, but on a hi peformance vehicle i wouldnt even dream of doing it.

Plenty of hi performance gen3 and gen4 egnines run this setup. Some of the supercars use this setup as well.

[aDrew_C]

Being a 31 owner myself I can backup how bad the standard tank can surge. I'm only making around 250rwhp and get surge turning corners even slightly aggressively under 3/4 tank, under half a tank i get surge when accelerating hard.

My 2L surge tank is going in shortly, I was planning to relocate the battery to the boot and mount the tank where the battery is located and use my walbro 500hp pump as a lift and 044 as main pump after the surge tank. I know the walbro is going to cause issues with overfilling the tank, but will the tank being being in the engine bay help this at all or greatly increase the heat issue due to... being in the engine bay

[Tangles]

id leave it as is but try an in-line fuel line cooler

and add heatwrap (or foam, or thick rubber, or similar) around the current fuel lines

[blind_elk]

blind_elk: They may be high pressure standard pump but there shit house. what part of THE STANDARD PUMP WOULDNT KEEP UP didnt you get?

I fully understand what you are saying about the ability of the standard pump to supply the engine. What I am saying is that using it - or any other high pressure, EFI pump - to supply a swirl pot is simply massive overkill.

The problem you have is the fuel equivalent of why you need an intercooler for the intake air. Compressing the fuel introduces heat into the fuel. So, when you compress it to feed the swirl pot, it gets hotter. Then you compress it again to feed it to the injector rail. Added to this is that fuel is the coolant for EFI pumps, just as coolant keeps the engine block "cool". So, replacing the standard pump with a low pressure pump may help with the problem you are experiencing.

Using heat wrap and the like around the fuel lines will only worsen the problem, in that the heat in the fuel will not be able to escape via heat exchange through the metal pipes to atmosphere.

[RB30TI]

So we have come to a time hwen to judge weather its the pumps that are heating the fuel or the heat from the engine bay, if its the pumps causing the heat issue you would want the fuel rail to be open as possible to help let the heat excape. but if its the engine heating the fuel threw the rail and other metal peices you would want to wrap the fuel rail.

which leaves us with the question of.....whats causing the heat?

id say just with the fuel being hotter due to the weather (summer) its starting off hot befor the cars even thought about starting,.

i would like to hope its as easy as wrapping the rail but i think its ganna be more of a ball breaker then that

[SirRacer]

If my problem continues im going to get a low pressure pump to feed the surge tank. Ive been told by a few different people that this works well.

[RB30TI]

quick question, if i was to install a low pressure pump at a pick up, would it have any issues filling the surge tank in a race?

2L surge tank.

[Scooby]

I heard of a similar problem years ago, the cause was the diameter of the fuel lines being too small. Increasing the diameter fixed the problem. From memory it was to do with the return line in particular, presumably the fuel took longer to recirc back to the surge tank before being pushed into the line at pressure again.

[rob82]

I fully understand what you are saying about the ability of the standard pump to supply the engine. What I am saying is that using it - or any other high pressure, EFI pump - to supply a swirl pot is simply massive overkill.

The problem you have is the fuel equivalent of why you need an intercooler for the intake air. Compressing the fuel introduces heat into the fuel. So, when you compress it to feed the swirl pot, it gets hotter. Then you compress it again to feed it to the injector rail.

You do realise that the std pump will not be under pressure when supplying the surge tank - so there is no heat gain!!! Using a "low pressure" pump wont help anything, there is absolutely nothing wrong with using the std efi pump to supply the swirl pot!!

[Gav]

The problem you have is the fuel equivalent of why you need an intercooler for the intake air. Compressing the fuel introduces heat into the fuel. So, when you compress it to feed the swirl pot, it gets hotter. Then you compress it again to feed it to the injector rail.

Not a good analogy - liquids (unlike gasses) aren't compressible and therefore don't gain heat through compression.

Heat can be generated by mechanical work (agitation) but this likely to be minimal. By far the majority of the heat will come from absorbing heat from the engine bay. Sounds to me that you are recirculating too much fuel between the engne bay and the tank.

If you really need to run a surge tank, then insulating lines and rails in the bay should go a long way to help prevent overheating. Can't comment personally on fuel coolers, but it does seem to expose your fuel lines to the risk of rupture.

[RB30TI]

If you really need to run a surge tank, then insulating lines and rails in the bay should go a long way to help prevent overheating. Can't comment personally on fuel coolers, but it does seem to expose your fuel lines to the risk of rupture.

I agree, im not overly keen about doing the fuel cooler for mainly that reason.

I think ill wrap the fuel line and other metal parts as that seems the easiest thing to do, if that dosnt work/improve then ill have to try something else.

[daisu]

How do you have the pumps connected (electrically)?

Turn the car on and then check the voltage at the pumps. It should be approx 14V.

If you have voltage drop along the cables and end up with 12V or less you will be overloading the pumps. They will heat up and have problems keeping rail pressure up.

How old is your standard pump? It is quite possible the standard pump has come to the end of it's life and can't keep up with the requirements of your engine, in which case you will be damaging the 044 from starvation which will further heat the fuel.

Getting a bit off topic, has anyone ever heard or thought of using a peltier cooler to continuously cool the fuel?

Edited November 2, 2009 by daisu

[RB30TI]

daisu: the standard pump is still run off standard wiring, the 044 is merged into the wires that go to the standard pump, cant remember much more about it, just a relay and merged in.

in the pick i think it was the wire on the right.

[SirRacer]

A good start would be to rewire the pump. Having two pumps running off the stock wires cant be good for maintaining voltage.

Mine are wired seperately and that doesnt make a difference for me. Also have a look at US sites. Fuel coolers look to be pretty common over there with quite a selection to chose from.

Quite a few factory vehicles also run fuel coolers. The DID Toyotas for one are a good example so they cant be too bad for impact damage.

Edited November 2, 2009 by SirRacer

[daisu]

R31Nismoid: I wouldnt like to take it off and take it for a drive because the stock pump wasnt keeping up thats one of the reasons i pump the 044 in.

rob82: One Way fuel system??

blind_elk: They may be high pressure standard pump but there shit house. what part of THE STANDARD PUMP WOULDNT KEEP UP didnt you get?

discopotato03: Yeah its fairly common in the 31's to surge, i have two mates that have had the same problem with theres and also have had to fit a surge tank. Motors not standard, but its not puttin out a great deal of power either.

Id prefur not to run a fuel cooler unless its a last resort.

i cant take the surge tank off and pump off and take it for a drive, well i can but i wont be able to go fast. and if i did take it all off and take it for a drive and it was the problem i would still need more fuel to my motor. id also still need a surge tank as i dont like driving around with over half a tank.

I Think to start with ill try wraping the fuel rail with something and see if that helps at all.

The stock pump wasn't keeping up with the engine before hand. How is it going to keep up now? Even with the surge tank and 044, all the fuel has to flow through the standard fuel pump.

Why don't you like to drive around with more than half a tank? I know that if I have anything less than half a tank I get surge issues. The fuel in the tank is supposed to cool the fuel pump. If the level is dropping below the fuel pump then you will damage the pump internals pretty quickly.

I would be doing the following things, regardless of whether they are the cause of your problems.

Remove the standard pump, check inside the fuel tank to make sure it has not rusted and that any baffles have not come loose.

Purchase and install a high volume, low pressure lift pump. It should flow more fuel than you are going to require at full noise. Make sure it is mounted as close to the bottom of the tank as possible.

A surge tank with greater volume will provide greater surge protection. G-forces and fuel surge can still affect the surge tank itself so you want something as tall and narrow as possible. Look into a swirl pot. They are designed with the fittings positioned in such a way so that the fuel swirls around the surge tank. Supposed to help in removing air pockets and cooling the fuel.

You may be able to keep the 044 if it is still working properly.

Install a fuel pressure gauge to monitor the rail pressure, if it's still faltering then replace the 044 with a new pump.

Make sure the wiring is up to scratch. It is very common for the standard wiring to deteriorate in cars of this age. Run a new wire of decent gauge directly from the positive terminal on the battery (install a fuse at the battery end of the cable). Put a relay in the boot and use the factory pump wiring to switch the relay. Run the new cable to both pumps through the relay. Make sure the negative side of the pumps are wiring is also adequate, connections should not be on painted surfaces.

Not sure if the 044 generates much heat, but wrapping it in foam will only make it run hotter and ensure that the heat is getting into the fuel. Who cares about a bit of fuel pump noise anyway.

[rob82]

Not a good analogy - liquids (unlike gasses) aren't compressible and therefore don't gain heat through compression.

Heat can be generated by mechanical work (agitation) but this likely to be minimal. By far the majority of the heat will come from absorbing heat from the engine bay. Sounds to me that you are recirculating too much fuel between the engne bay and the tank.

If you really need to run a surge tank, then insulating lines and rails in the bay should go a long way to help prevent overheating. Can't comment personally on fuel coolers, but it does seem to expose your fuel lines to the risk of rupture.

Spoken like a true mechanical engineer however your neglecting the fact that an 044 can draw up to 15amps continuous(obviously depandant mainly upon fuel pressure) - thats a shitload of heat that needs to go somewhere - I bet you can guess where it goes.

[Simon-S14]

The stock pump wasn't keeping up with the engine before hand. How is it going to keep up now? Even with the surge tank and 044, all the fuel has to flow through the standard fuel pump.

Why don't you like to drive around with more than half a tank? I know that if I have anything less than half a tank I get surge issues. The fuel in the tank is supposed to cool the fuel pump. If the level is dropping below the fuel pump then you will damage the pump internals pretty quickly.

I would be doing the following things, regardless of whether they are the cause of your problems.

Remove the standard pump, check inside the fuel tank to make sure it has not rusted and that any baffles have not come loose.

Purchase and install a high volume, low pressure lift pump. It should flow more fuel than you are going to require at full noise. Make sure it is mounted as close to the bottom of the tank as possible.

A surge tank with greater volume will provide greater surge protection. G-forces and fuel surge can still affect the surge tank itself so you want something as tall and narrow as possible. Look into a swirl pot. They are designed with the fittings positioned in such a way so that the fuel swirls around the surge tank. Supposed to help in removing air pockets and cooling the fuel.

You may be able to keep the 044 if it is still working properly.

Install a fuel pressure gauge to monitor the rail pressure, if it's still faltering then replace the 044 with a new pump.

Make sure the wiring is up to scratch. It is very common for the standard wiring to deteriorate in cars of this age. Run a new wire of decent gauge directly from the positive terminal on the battery (install a fuse at the battery end of the cable). Put a relay in the boot and use the factory pump wiring to switch the relay. Run the new cable to both pumps through the relay. Make sure the negative side of the pumps are wiring is also adequate, connections should not be on painted surfaces.

Not sure if the 044 generates much heat, but wrapping it in foam will only make it run hotter and ensure that the heat is getting into the fuel. Who cares about a bit of fuel pump noise anyway.

mate the stock pump feeds the surge tank, not the engine... the 2L supply of fuel that the surge tank has feeds the 044 then the motor, in that order. in no situation ever on the face of this planet is his motor is going to strip the surge tank supply of fuel in a few WOT applications.

[Gav]

Spoken like a true mechanical engineer however your neglecting the fact that an 044 can draw up to 15amps continuous(obviously depandant mainly upon fuel pressure) - thats a shitload of heat that needs to go somewhere - I bet you can guess where it goes.

For an external pump, I can guess where most of the heat would go - into the air of the boot. Sure some of the power (210 watts if we assume 15 amps at 14 volts), will be transferred from kinetic energy to heat energy for the moving fuel. Even more will be transmitted from the hot pump to the fuel, but most of the heat will be radiated from the hot motor body into the surrounding air.

I stand by the assumption that most heat is absorbed from the heat of the engine bay. An easy check if I'm right is to operate the fuel pumps without starting the engine (cold engine bay of course) and see how warm the fuel lines and surge tank gets.

[daisu]

mate the stock pump feeds the surge tank, not the engine... the 2L supply of fuel that the surge tank has feeds the 044 then the motor, in that order. in no situation ever on the face of this planet is his motor is going to strip the surge tank supply of fuel in a few WOT applications.

I am well aware that the stock pump is feeding into the surge tank, and the 044 from the surge tank to the motor.

I agree that with a 2L buffer it would be highly unlikely for the surge tank to empty under normal conditions.

But anytime the engine is under decent load (may not even be WOT) the level in the surge tank will be dropping. Without knowing injector sizes, duty cycles, flow rate of the standard fuel pump it would be hard to say how long it would take for the 2L buffer to run out.

The original poster states that R31's are known to have fuel surge problems and that he doesn't like having more than half a tank of fuel.

Imagine on a racetrack, during the corners the standard pump will be starved so there will be no supply to the surge tank. On the straights the standard fuel pump will be supplying the surge tank but the engine will be consuming more fuel than is supplied, so again the level in the surge tank is dropping.

Again, without knowing HP figures, injector sizes etc we can't say how long it would take but you can definitely see that during spirited driving the surge tank level will be dropping. Then imagine skidpans or drifting where WOT and cornering is happening at the same time. If there is no supply to the surge tank it won't take long for the engine to consume 2L doing skids.

For an external pump, I can guess where most of the heat would go - into the air of the boot. Sure some of the power (210 watts if we assume 15 amps at 14 volts), will be transferred from kinetic energy to heat energy for the moving fuel. Even more will be transmitted from the hot pump to the fuel, but most of the heat will be radiated from the hot motor body into the surrounding air.

I stand by the assumption that most heat is absorbed from the heat of the engine bay. An easy check if I'm right is to operate the fuel pumps without starting the engine (cold engine bay of course) and see how warm the fuel lines and surge tank gets.

The original poster states that the fuel pump is wrapped in foam insulation, and from the picture looks like it's mounted on a block of wood? Once the pump heats up all the heat energy will be transferred into the fuel. Running the pump at higher temps is going to shorten it's life. As the fuel heats up it is more likely to cavitate which will cause more damage to the pump internals and cause fuel pressure problems.