converting from single fuel pump to dual

[CCR Engineering]

I'll just have to pull the pump out and check everything. I just thought it was normal since this is the first E30 I've really run hard. Since its only got one pump I may just look into replacing the pump either way. This body is soon to get an SR20DET so I need to change it anyways. The filter is new so I know its not that but the sock on the pump could be clogged too.

[jlevie]

That's probably a sign that the delivery volume of the pump is low. Which could be as a result of a worn pump, clogged filter, or obstruction in the fuel lines. Low volume reduces the effectiveness of the syphon that moves fuel from the left to the right side of the tank.

[Liam]

My best guess is that something is wrong if it's starving with a half tank, I would check the internal pump for leaks in the delivery side.

[CCR Engineering]

My 91 318iS starves whenever the tank is lower than 1/2 hard turning on the street and will starve when its slightly above 1/2 on track. Any hard right turn for more than a second starves the pump and the motor dies for a few seconds until I straighten out. Otherwise it works perfectly so I know its not the pump. The tank isn't dented or mis-formed in any way either. If anyone knows where I can get any extra baffling please let me know. As long as I have 3/4 tank it never starves but its just annoying to always have to fill it up after each session and lug around the extra weight if I don't have to. And I too have had issues when it cuts out with car control. Its like coming off the gas all the way mid corner. If you're running 100% in a corner a mid corner lift will cause the back to swing and you have no throttle to be able to ride it out and it can snap back on you. I've always caught it but I can see how it can be a major problem.

[guibo09]

good info guys, thanks. ill probably look into fabbing some sort of extra baffling.

[jlevie]

We also relocated the return line to drop the unused fuel to the top of the pump bracket ( bracket from the earlier cars, crazy huh)

You'd have done better to leave the return line where it is as I understand the construction of the tank. That return powers a syphon that lifts fuel from the left side of the tank and dumps it in the right side (where the pump is).

The only times I've seen E30's have fuel starvation issues on the track there were obvious problems with the tank (loaded with rust), pump, or filter.

[Liam]

okay this is very interesting. are you saying the stock late model tank requires a 2G turn almost empty to starve, or an extra baffled tank?

can you give more details on what kind of baffle i need, where to purchase or how to fabricate, etc?

2gs is probably an exaggeration, I just made that up.

The baffle is an aluminum tube about with about 10 6mm holes in the bottom OD rim (about 5mm up from the bottom) and a few more about 150mm above that tube was just the right OD to drop down the hole the fuel pump drops in (I can't remember the size at the moment) we actually ran the tube all the way to the top of the tank so the pump mount secured it to the bottom of the tank.

We also relocated the return line to drop the unused fuel to the top of the pump bracket ( bracket from the earlier cars, crazy huh).

[guibo09]

Baffle drops in right down the hole with the pump, best solution for the problem. But in order to starve the pump the tank would have to be nearly empty in something like a 2+ G turn (just a guess at the G #s)

okay this is very interesting. are you saying the stock late model tank requires a 2G turn almost empty to starve, or an extra baffled tank?

can you give more details on what kind of baffle i need, where to purchase or how to fabricate, etc?

[Liam]

i do auto-x, which sloshes the tank like crazy. an example of a fuel cut prone situation was a complete right hand loop around a ~50ft circle. the loop lasts over 10 seconds and you are pulling alot of g on good tires.

do you suggest i just add more baffling? is this even possible without opening the tank?

Baffle drops in right down the hole with the pump, best solution for the problem. But in order to starve the pump the tank would have to be nearly empty in something like a 2+ G turn (just a guess at the G #s)

[guibo09]

The late model tanks have a baffle that the pump sits in, for the rally cars and lower end group cars we sometimes installed a deeper baffle, on Grand touring cars it's a whole different ball game (fuel cells and completely re engineered fuel systems, more for crashworthyness than anything else).

How hard are you really expecting to drive?

BTW Baffles are still available and are also a fairly simple and effective component.

i do auto-x, which sloshes the tank like crazy. an example of a fuel cut prone situation was a complete right hand loop around a ~50ft circle. the loop lasts over 10 seconds and you are pulling alot of g on good tires.

do you suggest i just add more baffling? is this even possible without opening the tank?

[Liam]

what about on a long hard right hander that sloshes all the fuel to the left side of the tank away from the pump pick up? i dont care how good of a pump it is, it doesnt create fuel. and all it takes is for the pickup to be exposed to air for one second to suck in a bubble of air which eventually gets to the engine and causes a 1 sec fuel cut. there is nothing to bleed the air out of the line.

The late model tanks have a baffle that the pump sits in, for the rally cars and lower end group cars we sometimes installed a deeper baffle, on Grand touring cars it's a whole different ball game (fuel cells and completely re engineered fuel systems, more for crashworthyness than anything else).

How hard are you really expecting to drive?

BTW Baffles are still available and are also a fairly simple and effective component.

[guibo09]

The reason for the low pressure in-tank pump and the high pressure external was because high pressure pumps wont draw very well. The latter system solved all the problems (better pump technologey).

With this system there wont be any fuel starvation problems (unless you are running out of fuel or have a 1000 hp blown V8 ).

what about on a long hard right hander that sloshes all the fuel to the left side of the tank away from the pump pick up? i dont care how good of a pump it is, it doesnt create fuel. and all it takes is for the pickup to be exposed to air for one second to suck in a bubble of air which eventually gets to the engine and causes a 1 sec fuel cut. there is nothing to bleed the air out of the line.

[Liam]

The reason for the low pressure in-tank pump and the high pressure external was because high pressure pumps wont draw very well. The latter system solved all the problems (better pump technologey).

With this system there wont be any fuel starvation problems (unless you are running out of fuel or have a 1000 hp blown V8 ).

[guibo09]

Okay I see.

You really don't need this, the fuel system in the e30 is designed for high pressure, that is a workaround for a low pressure system that cannot flow the pressure and volume necessary for FI.

i know it is essential for a carb to FI conversion. but it also mentions how it can be useful for fuel starvation issues on a FI car.

the above diagram, is basically how most surge tanks work for FI cars anyway. im just wondering, if i use a high pressure pump in the tank instead of a low pressure one if i will run into any problems. i dont think so since the pump will not build much pressure without a FPR inline, but i have never tried it.

[Liam]

Okay I see.

You really don't need this, the fuel system in the e30 is designed for high pressure, that is a workaround for a low pressure system that cannot flow the pressure and volume necessary for FI.