Hot Surge Tank

[JonnoHR31]

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 fuel pumps, as pressure drops, flow increases. i understand your theory but emptying a 2L surge tank simply wont be an issue in this case. even if hes making 300 odd rwkw with a really rich tune it would take more than 40 seconds sitting on peak power with absolutely no flow from the lift pump to empty a 2L surge tank and thats being conservative. As per the orignal post, the real issue here is heat and that doesnt come from short bursts at WOT, fuel gets hot after circulating around and around while driving normally. using the standard wiring the 044 is going to be flowing less than its rated for, its only going to get hotter once it gets a full 14v.

Also i'm not sure about other situations but for me i'm almost certain my fuel gets too hot from the pumps (proper low pressure lift pump, 2L surge and 044), not from the engine bay.

Stock 31 fuel tanks are shocking for surge, especially s1 and s2. if you drive them with any sort of aggression it surges to the point of a complete fuel cut with anything under 1/2 a tank.

[RB30TI]

I dont have much time just t ill be back on tomorrow night to answer some of the questions, just want to add, my car isnt putting out much power at the moment, im unsure of duty cycle all i know are there VLT injectors i think 250-260cc and cars only doing about 200rwkw.

like i said not a great deal of power but regaurdless of power the fuel is still heating up.

thanks all for your help.

[RB30TI]

Gav i like the idea of running the pumps with out starting the motor to see weather the fuel heats up.

the foam is on the 044 so it dosnt rub on the bracket or the board mainly, not really for noise.

Is this the best way to run the wiring and is there anything else i should know?

"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."

I dont drift or do any track work, mainly race......stright line

yeah mines series 1/2. and as JonnoHR31 said they do surge even with half tank.

[RB30TI]

i did what GAV mentioned doing and i ran the fuel pumps without starting the motor (cold engine bay) and let them run for 20mins or so, the 044 didnt really heat up at all and the surge tank didnt feel warm either, fuel rail was a tiny bit warm but not overs, its hard to discribe so that is the best i can do. also took most the foam off the pump and just left a little stip around the bracket its alot louder now.

next step it to wrap the rail i guess, i also talk it for a drive last night at didnt have any issues but it wasnt the warm last night.

[Gav]

i did what GAV mentioned doing and i ran the fuel pumps without starting the motor (cold engine bay) and let them run for 20mins or so, the 044 didnt really heat up at all and the surge tank didnt feel warm either, fuel rail was a tiny bit warm but not overs, its hard to discribe so that is the best i can do. also took most the foam off the pump and just left a little stip around the bracket its alot louder now.

next step it to wrap the rail i guess, i also talk it for a drive last night at didnt have any issues but it wasnt the warm last night.

Thanks for the feedback. Nothing like a little bit of real world experimentation to see if various theories are right or not

Unfortunately I haven't got a guarenteed solution for you to the problem. I'm guessing worst case scenario is going to be where engine bay temps are hottest and most of the fuel is recirculating back to the surge and fuel tanks. This will be in heavy traffic or idling after comming off the track etc. Ideally would be better to have a 2 stage pump speed setup which would reduce fuel flow during closed throttle application. You would want to make sure this is very reliable, however, as if it goes wrong I can see horrible consequences of the engine terminally leaning out. Personally I wouldn't do this.

Insulating fuel lines and the rail in the engine bay can't hurt to reduce heat transfer through conduction, however I'm guessing there is also an element of conduction through the mounting bolts and injectors etc. A fuel line cooler on the return low pressure line shoild help, however it would need air flow to be most effective. This by default exposes it to potential damage.

I guess ultimately the safest option as others have recommended is to use a single intank fuel pump. This is what I have done with my GT-R that is now predominantly only a circuit and tarmac rally duty. Sure it doesn't have a surge tank (I need to keep the fuel tank above 1/4 minimum), but it also doesn't have the fuel overheating problems. I also rest easier knowing that if I sustain rear end damage there isn't the exposure of a swirl pot in the boot that is likely to rupture. I run a Nismo intank pump that supports 580 rwhp at close to 2 bar of boost.

[discopotato03]

Look , for the price of some rubber water heater hose /low pressure fuel hose cut to length and slitted lengthwise so it slots over the exposed steel lines and retained with cable ties what do you have to lose ?

IMO hot engine bay and a lot of exposed steel rail/tube to absorb heat , excess fuel doing the roundies between the pressure pump and the pot and IMO a flawed idea of just enough feed from the tank to keep the pot full . More fuel being cycled between the pot and the tank gives more heat sink area but the volume of fuel in the tank will warm up over time .

Sorry to be blunt but if you reduce the heat exposed areas and use a pump correctly sized to do the job you shouldn't have a problem .

I can't see the sense in going to great lengths to cater for a pump that is probably overkill and causing much of the grief .

Your call .

[rob82]

Thanks for the feedback. Nothing like a little bit of real world experimentation to see if various theories are right or not

Unfortunately I haven't got a guarenteed solution for you to the problem. I'm guessing worst case scenario is going to be where engine bay temps are hottest and most of the fuel is recirculating back to the surge and fuel tanks. This will be in heavy traffic or idling after comming off the track etc. Ideally would be better to have a 2 stage pump speed setup which would reduce fuel flow during closed throttle application. You would want to make sure this is very reliable, however, as if it goes wrong I can see horrible consequences of the engine terminally leaning out. Personally I wouldn't do this.

Insulating fuel lines and the rail in the engine bay can't hurt to reduce heat transfer through conduction, however I'm guessing there is also an element of conduction through the mounting bolts and injectors etc. A fuel line cooler on the return low pressure line shoild help, however it would need air flow to be most effective. This by default exposes it to potential damage.

I guess ultimately the safest option as others have recommended is to use a single intank fuel pump. This is what I have done with my GT-R that is now predominantly only a circuit and tarmac rally duty. Sure it doesn't have a surge tank (I need to keep the fuel tank above 1/4 minimum), but it also doesn't have the fuel overheating problems. I also rest easier knowing that if I sustain rear end damage there isn't the exposure of a swirl pot in the boot that is likely to rupture. I run a Nismo intank pump that supports 580 rwhp at close to 2 bar of boost.

f**k thats alot of power for a single pump - is it making that power on pump fuel? An 044 will only flow 3.3L/min at 5bar.

Edited November 9, 2009 by rob82

[RB30TI]

that is a lota power for one pump, what pump is it?

yeah 044 flows 200L/Hour i think.

the 044 may be over kill for how much power i have but at the end of the day a rb30 with 300-400 rwkw (example only) would use roughly the same fuel on idel, buut would need a bigger pump when giving it shit. or am i wrong?

would the set i have be over kill for RB30DET?

completly off subjectn and not sure what its call or how its works exactly but what is the stuff that you can push threw a manifold prior to putting it on the car to clean all the imperfections out of it? i heard of it while ago but forgot now.

its like a foam/sludge/ or something i dunno, but it can be pushed threw the manifold and clears most the roughness outta it.

[gibbau]

completly off subjectn and not sure what its call or how its works exactly but what is the stuff that you can push threw a manifold prior to putting it on the car to clean all the imperfections out of it? i heard of it while ago but forgot now.

its like a foam/sludge/ or something i dunno, but it can be pushed threw the manifold and clears most the roughness outta it.

Extrude honing.

[RB30TI]

Extrude honing.

thanks man, is it as i said? i really have no idea and dont know anyone thats had it done or seen and befor and after shots.

any idea of cost and who does it?

cheers

[SirRacer]

in my experience johnnohr31 has it on the mark.

a fuel cooler does work to a certain extend although it doesnt solve the problem howeve insulating of fuel lines in the engine bay may be necessary as well. my car has the problem, however its a race car and im in new zealand so getting it hot enough wont happen too often.

Edited November 9, 2009 by SirRacer

[juggernaut1]

Specialised Power Porting does it.

I've had a turbo comp cover done, 6Boost ex manifold done and intake manifold done for my SR. None of which I'm currently using haha. I still have intake manifold though - sold off other parts. The 6Boost showed marginal gains in flow at 28 inches of water. The intake manifold showed fairly substantial gains in flow (from memory nearly 40cfm-50cfm improvement across each runner) and all runners were equalised to very similar flow. Of course flow does not necessarily equal go without velocity.

I could snap some pics of the SR manifold if you wanted.

Also re your fuel rail - IMO a fair majority of the heat will be from the engine bay and also being conducted into the fuel rail via the intake manifold which of course is bolted to the head. So of course insulating the fuel rail from ambient heat won't be a cure all if heat is still be transfered from the intake manifold. A vented bonnet may assist in drawing out the hot air when the car is moving and will also allow the hot underbonnet temps to dissapate when the car is stagnent.

Edited November 9, 2009 by juggernaut1

[RB30TI]

thanks for the info man, sounds like its a must do for me.

what are prices like for extrud honing?

pics wouls be great if its not to much hassell.

and vented bonnet is a deff no go. good idea but just not style.

[juggernaut1]

From memory $550 for intake mani and same for exhaust mani - both of these for a 4 cylinder so probably more for a 6. Compressor cover was about $220.

I'll snap some pics for you when I can.

[Gav]

f**k thats alot of power for a single pump - is it making that power on pump fuel? An 044 will only flow 3.3L/min at 5bar.

Nismo fuel pump curve shows the intank pump flows 225 L/h @ 5 bar with a 12.5V feed. I'd expect the flow at the same pressure (I'm running 5 bar at the rail) to be the better with the direct power feed to the battery/alternator that supplies closer to 14V.

Assuming that the pump is only delivering the stated 225 L/h for safety, however, this equates to injector flow of 625cc with all 6 injectors at 100% flow. I'm running 6 HKS 680cc injectors at 90% max duty (i.e. 612cc).

Basically the fuel pump and fuel injectors are maxed out, but then again so are the terbs (2860-5's) at 580 rwhp. I guess the system, although maxed out, is also well balanced.

The caveat in all this is that you need to keep a close eye on AFR's. I do regular dyno checks and also have a reliable AFR logger (Innovate wide band) wired into my Dataloggit that lets me check what's happened on the track. I have a gauge also installed, but I tend to be a bit busy on the track to watch it closely. Matches well on the dyno wity their exhauset meter 'tho.

[RB30TI]

the injectors that ill be running with the twin cam are pretty bit there 850-880cc cant remember exactly, i think there DENSO?? mayb

would the 044 be alright witht that?

[RB30TI]

Ok its been a few days since my last post just been flat out, havent driven the car much lately but when i have driven it it hasnt been playing up much, now what i recon i will do it put the return from the motor to the main tank instead of having it go back to the surge tank, and also install a low pressure, high volume lift pump it,

now what i want to know is whats a good lift pump with a high volume thats ganna fit in my tank hole??

cheers

[RB30TI]

found this pmp just then that may suit? http://justjap.com/store/product.php?produ...=309&page=1 or if theres something better out there please let me know

[RB30TI]

ANyone?