Article: VTT working on 1200+ whp 100% E85 ethanol capable BMW N54 fuel system

[psychosinmylobby]

Good catch:

So with OEM pump and a tank with effective volume of 2.7L - 3.2L you get 36.6s - 43.43s to deplete

With 455 pump you get 99.59s - 118.03s to deplete

Enough for a standing mile(s)

[Terry@BMS]

True I didn't consider the volume in the return line prior to starting a run. Assuming the two primary pumps are oversized enough to push that fuel back to the bucket. Which may or may not be the case depending on the power level and fuel pressure.

net/net I'm happy we've at least done some sort of a reasonable analysis on this. It would be nice to get actual flow numbers through the factory and 455 in tank post siphons and filter. The OEM pump probably is very limited in that regard so I'd consider the 455 in tank a must to attempt this setup. I think if you were going to go this route a 3l surge tank would make more sense.

[psychosinmylobby]

Yeah the numbers are all theoretical anyway.

Reading the Radium page, 2L is the fluid volume with 2 pumps; add that to the fact that you don't want to deplete tank till the point you are counting on the fuel in the return lines (defeats the purpose of a surge tank).

Say 1.5L effective volume will give you ~20s with the OEM pump and still about ~55.3s with the 455.

[The Ghost]

True I didn't consider the volume in the return line prior to starting a run. Assuming the two primary pumps are oversized enough to push that fuel back to the bucket. Which may or may not be the case depending on the power level and fuel pressure.

net/net I'm happy we've at least done some sort of a reasonable analysis on this. It would be nice to get actual flow numbers through the factory and 455 in tank post siphons and filter. The OEM pump probably is very limited in that regard so I'd consider the 455 in tank a must to attempt this setup. I think if you were going to go this route a 3l surge tank would make more sense.

It is in my two posts that I tagged you in explicitly and in the video you didn't watch

Yeah the numbers are all theoretical anyway.

Reading the Radium page, 2L is the fluid volume with 2 pumps; add that to the fact that you don't want to deplete tank till the point you are counting on the fuel in the return lines (defeats the purpose of a surge tank).

Say 1.5L effective volume will give you ~20s with the OEM pump and still about ~55.3s with the 455.

And 55s at sustained WOT, no lift, is plenty for nearly all scenarios.

[The Ghost]

have each pump wired to a relay, one pump is triggered by the factory signal, second pump comes in at 10 psi, 3rd at 20 psi.

Do you have any more pictures of the surge mounting from under the car? Where do you route your lines from & to surge tank (how does it leave the trunk)?

One other thing I'm wondering is if the Walbros have an internal check valve. Otherwise, before all pumps are on, there is lower pressure in the Y that isn't being used, possibly reverting fuel flow from one pump backwards through the disabled pumps.

Thanks,

[Boardsandwhores]

can anyone post a diy???

[Sticky]

can anyone post a diy???

For what exactly?

[Eracer76]

One other thing I'm wondering is if the Walbros have an internal check valve. Otherwise, before all pumps are on, there is lower pressure in the Y that isn't being used, possibly reverting fuel flow from one pump backwards through the disabled pumps.

Thanks,

I know this thread is an old thread, but I'm considering this type of fuel system for my Z4, since there is no Stage 3 pump option for my car... I'm going to try and make 700whp on 100% E85, so I'm curious to know what everyone's take is on this type of setup a year later? Does anyone know the answer to the above question about Walbros having a built in check valve or not? So, in a multiple pump setup when only one pump running, is it losing some of its output back through the non-running pumps?

Im also wondering about the operation of the pumps... Will the stock lpfp run constantly now, even with the engine turned off because there is nothing to pressurize, now that its just looping fuel through the surge tank back to the gas tank?

And what about the new surge tank pumps, do they (or at least one) run full blast constantly, even with the engine off? I'm assuming the second and or third pump will turn on via a Hobbs switch when called upon.

Is anyone concerned that this type of system will eventually heat up the fuel in the tanks considering it'll be looping through at least two pumps at all times?

Thanks for anymore info on this topic!

[R.G.]

Why would any pump be on when the engine is off? Are you talking about the priming after it's been sitting for a while?
This has been done for such a long time in every platform and is still the best LPFP solution for high hp cars. Just do a general search - Surge tank fuel system and pick any platform.

[Eracer76]

Why would any pump be on when the engine is off? Are you talking about the priming after it's been sitting for a while?
This has been done for such a long time in every platform and is still the best LPFP solution for high hp cars. Just do a general search - Surge tank fuel system and pick any platform.

Yes, I'm talking about the priming you hear when you turn the key on. So if the key is left on, what is it that shuts off the pump once it is primed? Is it the pump control module via a pressure switch/regulator? If that is true, then what shuts off the factory pump with this surge tank system that doesn't ever pressurize? Even with the engine off, there is no dead end in the fuel line, because it just loops through the surge tank and back to the gas tank.

I get the mechanics of this type of system, but I'm not understanding the electronics/control of the pumps.

[R.G.]

Yes, I'm talking about the priming you hear when you turn the key on. What is it that shuts off the pump once it is primed? Is it the pump control module via a pressure switch/regulator? If that is true, then what shuts off the pumps with this surge tank system that doesn't ever fully pressurize due to the fuel just looping through the system via an overflow to back to the gas tank, and a return line back to the surge tank?



I get the mechanics of this type of system, but I'm not understanding the electronics/control of the pumps.

I got ya.
Here is how I understand it.
DME wakes up, triggers EKP (fuel control module) to run 100% duty cycle for a few seconds to bring fuel to the hpfp, then shuts off. With or without the surge tank the fuel just loops since none is being used. This was part of the software update during the hpfp recall debacle. Both in tank and a single surge pump would follow that cycle prior to start up.

[Eracer76]

I got ya.
Here is how I understand it.
DME wakes up, triggers EKP (fuel control module) to run 100% duty cycle for a few seconds to bring fuel to the hpfp, then shuts off. With or without the surge tank the fuel just loops since none is being used. This was part of the software update during the hpfp recall debacle. Both in tank and a single surge pump would follow that cycle prior to start up.

Oh ok, so its just a preset time then, and has nothing to do with reaching a certain pressure.

So in this type of surge tank system, how would the main pump in the surge tank be wired? Just a simple 12v relay getting power directly from the battery and being triggered by the lpfp wiring? The whole PWM thing confuses me when adding additional pumps. I get that the 2nd and 3rd surge pumps get activated by hobb switches, correct?

[R.G.]

The whole PWM thing confuses me when adding additional pumps. I get that the 2nd and 3rd surge pumps get activated by hobb switches, correct?

Hobbs is a clean solution but not the "best" or the way I would run it. There is another recent thread floating around where a member built a controller that is triggered by PWM signal.

how would the main pump in the surge tank be wired? Just a simple 12v relay getting power directly from the battery and being triggered by the lpfp wiring?

Yup, that is how I plan on wiring


I've got a couple of other projects being finished but this 3rd/4th on the list. Will share any insights from my install set up once I get there.

[Kirk@DOCRace]

They have used surge tanks in high HP turbo cars and race cars for years. Try giving a turbo car (Especially on E85,98) full throttle after coming out of a steep corner with out one. The G forces stick fuel into corners and away away from the pump especially in most BMW's, as they have a saddle bag style tank. These have been around for a very long time. Only in the last few years since Radium came on to the stage have I seen this big swing towards them in street cars.

Think about it.. Im going to spend $XX,XXX on my build and run the risk of fuel starvation? This is a no brainer for any high HP , aggressive daily driver or track enthusiast. Radium makes GREAT products by the way.