I doubt that even mounting the sensor back at the tank will matter. It' just the physics of a non-compressible fluid. You almost need a level sensor with the pump reservoir housing to pull it back before the pump runs dry.

 

https://mercedessource.com/store/190...re-accumulator


hmmmmmmmmmmmmmmmmmmm

 

I wonder if the pressure drop to 55 is due to fuel line size and flow rate. Your still on the stock line?

If your sensor is at the pump it would see less pressure drop. The closer to the injectors the faster the response rate will be.

That accumulator looks too small.

 

What boost level can u do without it dropping to 55psi?

 

good question ...... not easy to test that though !

 

I think its time for a #6 fuel
Line

 

Doesn't really solve anything that can't be tuned for but placing sensor close to pump might give me a few micoseconds as i might be able to set alarm at a higher psi without getting........ falseies

 

If the sensor is closer to the pump you may never see a pressure drop, due to line friction.

A bigger line would allow you to maintain full pressure at your injectors until your surge tank goes empty.

If you are making 380 whp thats 475 at the engine with a 20percent drivetrain loss. A 5/16 line is too small to flow that much fuel without a significant pressure drop.

Id bet that is more of your problem than running your surge can empty. If you move your sensor to the pump and do not see the pressure drop there then it is definitely one problem.

I just realized you said tuned for. Yes you can but i still think your response time would be greater if you move it closer to the pump.

 

Interesting thought , but , what I got was not a reduction in gas . It was a sudden and total loss of gas . The fact that it was after a corner and while low on fuel plus the fact that the issue isn't present on other occasions tend to support the pump starvation theory .

 

I think I have figured out what is happening in the video above .

*At 1/4 of a tank the fuel level is such that it wont fill the pump bowl by sloshing over the top .
*Also at 1/4 tank there is no help from the siphon as fuel is probably gone from the other side of the tank and is all concentrated on the pump side .
*When you take a corner at high gs fuel is dragged away from the bottom of the bowl .
*The one way valve at the botttom of the bowl stops fuel from draining from the bowl but if you start accelerating while 1/2 way round the corner ,as you do, you are using up the fuel inside the bowl.
*When you accelerate away from the corner the fuel is still not able to slosh over the top of the bowl so has to be drawn through the one way valve .
*At full noise my pump would be draining that half full bowl at a higher rate than what can be sucked through that very small check valve .
* So even though there is fuel there .... it is not getting through the hole fast enough and eventually the pump starves .

Another possibility is that it's just that the check valve is uncovered the whole time , both while cornering and accelerating ..... But I'm leaning more toward the check valve being too small as the problem doesn't seem to appear during straight line acceleration at 1/4 tank.

Realising this is what is happening is half of the battle ..... I have devised and implemented a solution to this and will be able to test it once my tank gets down to that level again ..... Fingers crossed !

 

There you go. This is exactly what is happening.


The check valve is not big enough to support the need for more fuel to be supplied to the bigger fuel pump and the venturi syphon is to small for that amount of flow that the pump is trying to push. The pump starts to suck air and the venturi stops working preventing it from drawing fuel from the other side of the tank. This is all going on inside the assembly before we even bring into consideration the fuel sloshing around inside the tank at the same time.

Plus I would bet your donut filter in the assembly is pretty much done for and blocking the flow aswell.

Maybe some tank foam strategically placed around the assembly?

A while back I contacted Aeromotive to see if they would sell me or point me in the right direction about there venturi syphon assembly that they use in there replacement pump assemblies but to no avail.

Great info here so I'm going to drag this over to the fuel pump thread and edit my post there.

 

I'm thinking that the venturi does nothing at 1/4 tank anyway so isn't part of my particular issue. It probably is the issue for tthe track guys on lefthand high g corners though.
Do wonder about the filter donut , that has 200,000 kms on it !

 

Correct that's the way the Venturi is designed to do is to empty the other side of the tank till its bone dry way before the 1/4 mark.

Sure it plays a huge part in this. The Venturi plays its part. If the pump is sucking air then the Venturi is blowing bubbles stopping fuel from getting into the bowl. Its also helping to prevent fuel being drawn from the other side of the tank and getting into the assembly.


Err I think its done too. Mine Started to crap out at a 100,000 Km.


Im pretty sure I read in the service manual somewhere that mazda recommend to replace the fuel pump assembly at a certain service interval. I'm guessing for this very reason.

 

I guess if the venturi is sucking air into the bowl assembly , that air is displacing fuel so yeah it must be part of the problem.



The manual says "replace fuel filter every 160,000 kms" . What they mean by the 'fuel filter' is not clear however .

I also noticed an 'air filter' as part of the fuel tank setup ..... not sure what that does .................

 

Yup that's what is happening and it cant be resolved without redesigning the whole assembly. People have tried to make the one way valve orifice on the bottom of the pump bigger and drilling the venturi out and both have failed.

The only thing that seems to be a valid fix is to use the stock pump as a lift pump feeding a surge tank with a bigger primary pump controlled by a trigger from the stock pump.

Gotta love the guy that was tasked with the job of translating the manual from Japanese to English when his first language isn't English.

I'm guessing that service point will vary depending on how crappy the gas is in your area. The quality of the gas in Canada is really poor and thinking about it I may have put a walbro in at that point. Mistake number 1.

I think they mean the charcoal canister that's part of the tank breather system for emissions purposes. If that sucker gets plugged up man it can reduce your tank to something that resembles a used chip bag and only hold a few litres of fuel in seconds. I did it to my company car.

 

Neither of those is what I'm trying
But i might increase the one way valve orifice size as well .....

 

Hmmm got my attention.


Try raising the bottom of the assembly off the floor of the tank from 2mm to 5mm to allow more fuel under there. The thought behind that is say the one way valve size is adequate but the pool of fuel underneath the pump isn't.

 

That wasn't something I had thought of , but ironically , the pump will be higher anyway ....

 

Interesting


Need somebody to come up with something like this with a high flow venturi.


Job Done.

 

I havent seen anything about people increasing the one way valve size. Are they just trying to shave some material from the current one? I bet you could add a second one using a second stage regulator flapper and a little patience.

This is about 1" in diameter, very flimsy and can be picked up at most scuba shops for 5-10 dollars

 

I'm getting another pump so i will have a spare flapper . I might try incorporate that so I can have a dual flapper arrangement .
That way I know it will work in that environment , and two flappers are always better than one !

 

Thats what she said

 

OK ...some promising news ...

Same corner i was starving on previously Went round it 5-6 times on full boost .....
Went from 1/4 tank down to 1/8th tank .... all good .

More testing needed before I'm confident I got the design right .

 

Awaiting info!!

 

waiting for your good news!