Surge Tank Low Level Detection/monitoring

[kitto]

Hey guys, so after hearing some horror stories of the lift pump in the main tank failing and running the surge tank dry causing the engine to fail due to it leaning out i have decided i want to try and monitor the level in my surge tank or more to the point, have a low level detection to set off a warning lamp.

There's a few ways i have thought to do this.

1. You could try and mount a low level thermistor in to the tank (the same type of unit that is used to detect low fuel in the main tank in most vehicles today). This however will be difficult to seal correctly into a surge tank, they do not come in a packaging that you could mount into an already made surge tank. They also tend to fail.

2. Ultrasonic detection from outside of the tank, There are tiny ultrasonic sensors that you can mount to items that detect if fluid is present or not behind the medium they are mounted too. Unfortunately i do not believe there is one on the market that will detect fuel through aluminium.

3. Mount a float switch to the tank, when the level falls below the tank, the switch closes. Simple. However, if the fuel is sloshing around which it will, the level may get low and activate the switch but the sloshing fuel may cause it to be on and off rapidly and you may never see the warning lamp light up. There is also the issue of trying to mount and correctly seal this type of switch on an already made surge tank. I dare say fuel, especially E85 will eat most of these switches.

4. Put a DC current transformer into the mix. These will monitor the amount of current that a device is drawing. For example, the lift pump may draw 5 amps of current under normal operating conditions. If the circuit for the pump fails or a fuse blows the current will drop to 0 amps. The DC current transformer will pick this up and can be set to switch a relay which in turn lights up a lamp. The other way around is under fault/short/overload/pump seizure the pump will draw well over the normal 5 amps. The current transformer will also pick this up and can throw the relay in the same way. The issue with this setup, it doesn't account for a mechanical failure of a split line from the lift pump to the surge tank. They are expensive and are proving very difficult to find in an exact form that will suit this purpose. These are usually used in automation where a PLC will monitor a 4-20mA range.

5. This is the way that i am thinking will be my best bet. Fit a hobb switch that is set to (1-2PSI) inline with the feed line from the lift pump to the surge tank. When the lift pump is working fine the hobb switch is in a healthy state, if the pump fails, the pressure will drop to 0 causing the hobb switch to activate therefore turning on a warning lamp. The only issue i'm having with this type of setup is what pressure does the line between the lift pump and the surge tank operate at? Obviously it is bugger all, but surely there must be some sort of pressure there? Whether it be 1, 2, 3 or 4 PSI or whatever it is. They must have some pressure. I'm using an aeromotive pump as the lift pump. Its a high volume high pressure pump, so one would thinking, pumping stacks of fuel through an 8mm fuel line will create some sort of pressure which is what i want in this case.

This idea is cheap, simple and will work quite well if all goes to plan. Unfortunately this method does not detect the level in the surge tank, however it will let me know very early that the lift pump has failed and that my engine is going to run lean quite soon.

6. Using a flow meter to monitor the amount of fuel being pumped into the surge tank. These devices are extremely expensive and i highly doubt there is an exact item on the market for my specific purpose.

These are my current ideas, im sure there are a few other simple ideas out there, which is why i'm asking you guys. Please let me know your thoughts. Sorry for the long post, but this is a real life scenario and i'm looking for a solution.

Daniel.

[The Mafia]

Set it so that when the surge tank is low and dangerous, to cut the engine. Nto sure how but it seems to be a good solution. Hope you find a way that works!

What ECU do you have?

Edited April 24, 2012 by The Mafia

[kitto]

Set it so that when the surge tank is low and dangerous, to cut the engine. Nto sure how but it seems to be a good solution. Hope you find a way that works!

What ECU do you have?

I dont particularly want it to cut the engine. Just warn me early that it is running low.

Just a NIStune for the time being. So no 'extra' engine controls or monitoring.

[zebra]

Why not set a low pressure switch to kill the engine if pressure drops to nothing in the feed line to the surge tank?

You might have to use a low pressure reg between the main tank and the surge tank and another return

[scotty nm35]

Magnets on a float inside, with a reed switch outside?

[zebra]

Or just use a fuel pressure gauge or a fuel flow gauge

[battery]

Dual lift pumps lol

How big is the surge tank?

[Risking]

Get a propery designed surge tank and lift pump, then you shouldn't have any worries about running the surge low.

All you going to do is create another "worry system" in the car.

Where does it end. Warnings for surge tank, warning for fuel rail, warning for radiator header tank, warning for oil level, warning for everything that has a level.

[zebra]

Get a propery designed surge tank and lift pump, then you shouldn't have any worries about running the surge low.

All you going to do is create another "worry system" in the car.

Where does it end. Warnings for surge tank, warning for fuel rail, warning for radiator header tank, warning for oil level, warning for everything that has a level.

Little cameras inside the bores to check for det?

Or in the sump to see if there is oil surge?

Lol

[kitto]

Why not set a low pressure switch to kill the engine if pressure drops to nothing in the feed line to the surge tank?

You might have to use a low pressure reg between the main tank and the surge tank and another return

I can't mount an FPR to the surge tank as my surge tank is not running "pressurized". The return from the engine is at the highest point of the tank, with the return to the main tank being the second largest tank. This is to create a small air pocket so the large main pump is not working overtime to try and pump fuel into the surge tank and then over flow into the main tank. This is a large reason why main pumps run so hot, the main pump is working so hard to do its job. This is off topic though haha.

Magnets on a float inside, with a reed switch outside?

This will be almost impossible to do as the surge tank has already been made. Most setups like this require you to have access on both sides of the plate that you are mounting the reed switch setup too.

Dual lift pumps lol

How big is the surge tank?

Dual lift pumps are an idea, but not practical in an R31 cradle/fuel tank.

Surge tank is approx 4 Litres, but 500-700mL is useless as the inlet for the main pump is 40mm off the bottom of the surge tank.

[XRATED]

Run a frp on the overflow from the surge tank and maintain say 10psi in the surge tank. Then just run a pressure switch on the pressure side. Just make shure you have a decent lift pump...

Cheers

Justin

[kitto]

Get a propery designed surge tank and lift pump, then you shouldn't have any worries about running the surge low.

This doesn't help in anyway if the lift pump fails...

All you going to do is create another "worry system" in the car.

Where does it end. Warnings for surge tank, warning for fuel rail, warning for radiator header tank, warning for oil level, warning for everything that has a level.

This may be so. But its not as bad knowing how many sub woofers to stop at..

[kitto]

Run a frp on the overflow from the surge tank and maintain say 10psi in the surge tank. Then just run a pressure switch on the pressure side. Just make shure you have a decent lift pump...

Cheers

Justin

This is a good idea, i do like it. Its very similar to one of my ideas above, but it involves fully pressurizing the surge tank which puts the main pump under even more strain and heats the fuel further. Which is not what i want to do.

[zebra]

Then return from the rail back to the main tank

Unless you have a tiny feed pump there should be an issue to keep the surge tank full

[XRATED]

^{Ah... beat me to it.}

^{As above.}

^{Constant recirc of fuel, pump speed, cavitation and fuel volume has had more of an impact on fuel temp than pressure in my experience (not just talking about hi-po applications).}

^{Have a look at closed fuel coolers (non tube/fin types), pump speed/pwm controllers, surge tank heatsink and return line size too.}

^Cheers

^Justin

[boostn0199]

Just stick a good quality lift pump in there and get rid of the stock one will prob cost the same as going through this trouble of adding a sensor and it should be reliable.

[battery]

I can't mount an FPR to the surge tank as my surge tank is not running "pressurized". The return from the engine is at the highest point of the tank, with the return to the main tank being the second largest tank. This is to create a small air pocket so the large main pump is not working overtime to try and pump fuel into the surge tank and then over flow into the main tank. This is a large reason why main pumps run so hot, the main pump is working so hard to do its job. This is off topic though haha.

I would have thought it would run harder and get hotter under pressure?

[kitto]

^{Ah... beat me to it.}

^{As above.}

^{Constant recirc of fuel, pump speed, cavitation and fuel volume has had more of an impact on fuel temp than pressure in my experience (not just talking about hi-po applications).}

^{Have a look at closed fuel coolers (non tube/fin types), pump speed/pwm controllers, surge tank heatsink and return line size too.}

^Cheers

^Justin

Fuel pump speed will be varied dependent on TPS posistion. I am installed a big f**k off fuel cooler

Feed to and from fuel rail are 1/2", feed and return from the main tank to the surge tank are 5/16"

Just stick a good quality lift pump in there and get rid of the stock one will prob cost the same as going through this trouble of adding a sensor and it should be reliable.

I've already got a good quality new lift pump. I'm wanting to do this after speaking to a few people that have had relatively new lift pumps fail on them.

I would have thought it would run harder and get hotter under pressure?

Yes, thats what i'm trying to say. The pump works harder and gets hotter the higher the pressure.

[rob82]

Screw monitoring the surge tank side why don't you monitor the injector rail - that's what's important. Use a pressure differential sensor that is set to the pressure you want in your rail and set the bounds to say +/- 2psi. Hook 1 side up to fuel rail pressure the other side to manifold pressure.

Use this http://www.mamcoswitches.com/differential-pressure-switches/mam0071.html

[kitto]

Screw monitoring the surge tank side why don't you monitor the injector rail - that's what's important. Use a pressure differential sensor that is set to the pressure you want in your rail and set the bounds to say +/- 2psi. Hook 1 side up to fuel rail pressure the other side to manifold pressure.

Use this http://www.mamcoswit...es/mam0071.html

Yes i'm going to do this as well using the Engine Monitor 2 kit that Paul is offering on here. It monitors fuel pressure vs boost pressure, coolant temp, oil pressure vs rpm (i love this one). Plus a few other things.

I suppose i'm being a little over the top wanting to put in a surge tank level monitor, butif it can be done a low cost. Why not do it?

I was wondering what you were going to say actually Rob. Would you have any idea what pressure the line would operate at between the lift pump and the surge tank?