[CobraMarty]

There are many 'boost a pump' devices out there that increase the voltage. Mustangs have a similar problem. Something like prochargers boost a pump.

[AltecBX]

Originally Posted by shiv@vishnu

For the sake of perhaps morbid curiosity, we drove the pumps at 14v and conducted the same tests. This higher voltage environment represents a condition that cannot be replicated by the factory fuel pump controller (EPK). But something that can be accomplished with fairly simple/inexpensive circuitry that the user can install. The extra 3 volts makes the pump spin much faster. And it showed on the flow test bench:

Why can't the Procede send the extra voltage to the factory EPK? (We are only demanding it for a few second sat higher boost application).
And if it can't be done because of the 11.0 volt limit, can future Procede have a built in circuitry to handle this job?

Originally Posted by Doug007

Shiv,

Can you go into a bit more detail about how the amount of fuel fed to the HPFP is controlled?

The HPFP is an engine driven positive displacement pump, unlike the LPFP which is centrifugal and variable speed. Fuel is incompressible so the HPFP should be pumping an amount that is proportional to rpm (since it's engine driven) all the time. I don't really understand how a valve can affect the amount of fuel "gulped" by the HPFP.

Even if it reduces the pressure of the fuel, pressure has a negligible effect of fuel density so the HPFP would gulp the same amount that would only really change with engine speed.

Is the displacement of the HPFP pistons variable somehow? What am I missing?

I'm very interested in this as well. Shiv, please go into this in part 3.

[Rob@RBTurbo]

What makes anyone think the HPFP just "gulps" what it wants? It's a simple concept really, the HPFP needs to be "forcefed" approx. 72psi of fuel at all times to it's inlet to function properly. If there is a weak link in the LPFP system in that it can not maintain volume flow (due to pump flow capacity or resistance in line(s) and/or fittings) the pressure will decrease and affect the HPFPs ability to exponentialize fuel pressure to the injectors as its design intends. The volume flow is very important, and the LPFP is the primary driver in that department.

[AltecBX]

Has anyone looked at the plumbing and Low Pressure Fuel Pump in the S63 engine?

[stressdoc]

Perhaps BMW is also interested in Part III. I am curious what specs the M5 V8 tt LPFP has -- perhaps we will be snagging parts from the M3 fuel delivery system soon.

[Rob@RBTurbo]

That would be interesting if there was an upgrade to be found there. I was looking at my LPFP and FPR assemblies (I ordered new from Tischer) last night to get a feel for the whole intank system... And concluded that there are several fittings in the feed line leaving the pump that are fairly undersized for making good power. If some other hardware dropped in with bigger lines and fittings and with a higher capacity pump that our EKP could still control without hiccup that would be great. For now though it seems Shiv has something already concocted that will work for us so thinking too much maybe just a waste of time.

[Clap135]

I'm curious to see shivs upgraded fuel system however I am worried that all this emphasis regarding the lpfp wont be enough. On every other di engine the hpfp is the main limiter of flow. Judging by this thread it seems that everyone is under the assumption that the hpfp is limitless if it is given proper flow....I simply doubt this is the case here but I guess we will find out. I saw that terry just hit roughly 500 wtq downlow and claimed to have no fueling issues which is a good sign for the hpfp limits cause as we know it is driven off the engine. The lower the rpm the less fuel it can pump. As Rpms increase the hpfp will need to hold more and more pressure to acomidate the fuel demand and this is where the main problem will lie. But that's just a theory of mine based on previous experience with di engines.

[Rob@RBTurbo]

Nobodies saying the HPFP is limitless, we are just attacking a very weak link here piece by piece. If we can free up another 60-100rwhp of fuel in a modified LPFP... Well that is outstanding. Surely there is a volume limitation of the HPFP, but we will have to cross that bridge when we get to it.

[indy99gpgt]

Originally Posted by Clap135

I'm curious to see shivs upgraded fuel system however I am worried that all this emphasis regarding the lpfp wont be enough. On every other di engine the hpfp is the main limiter of flow. Judging by this thread it seems that everyone is under the assumption that the hpfp is limitless if it is given proper flow....I simply doubt this is the case here but I guess we will find out. I saw that terry just hit roughly 500 wtq downlow and claimed to have no fueling issues which is a good sign for the hpfp limits cause as we know it is driven off the engine. The lower the rpm the less fuel it can pump. As Rpms increase the hpfp will need to hold more and more pressure to acomidate the fuel demand and this is where the main problem will lie. But that's just a theory of mine based on previous experience with di engines.

I agree with you. I have a feeling that this new fuel system upgrade will help us achieve higher power output but we will then run into another limiting factor at some point which will be the hpfp.

[CobraMarty]

A 10% smaller pulley for the HPFP might help it's output if that later becomes the limiting factor.

[AltecBX]

Shiv, have you also checked the fuel filter to see if there's any restriction in the fuel flow?

[BoostedE90]

Curious as to why BMW chose to regulate pressure at 72psi rather than 43psi? From Shiv's numbers our pumps flow better and have less draw at 43psi. I understand the need for the higher pressure from what Shiv said:

Originally Posted by shiv@vishnu

With EFI (Electronic Fuel Injection), fuel system pressure raised to a much higher, standardized and somewhat arbitrary 43psi. This pressure increase was done to improve the injection accuracy and precision. The more pressure behind the fuel injection squirts, the less injector on-time (in milliseconds) is necessary to delivery the necessary fuel mass to the intake port. The higher pressure also improved the atomization characteristics of the fuel. The finer the spray, the better it would swirl with the air in the combustion chamber, creating a burn-friendly homogenous air/fuel charge.

But how much are these things improved at 72psi vs. 43psi?

[Rob@RBTurbo]

Because the HPFP needs higher pressure on the inlet to do it's job.

[Clap135]

Originally Posted by RobBeck

Because the HPFP needs higher pressure on the inlet to do it's job.

Yup. And when the chamber needs more fuel the hpfp steps up the pressure while the injectors increase their durations. When this happens most hpfp simple can't keep up with the requested pressure and begin dropping pressure which can be seen in the low pressure oscillations. I really hope I am wrong but I think this is a waste of time.

[Rob@RBTurbo]

You guys are failing to see he is talking about standard fuel injection in that passage, not direct injection as we have which incorporates a HPFP.

Those standard systems just have one fuel pump (alas the "LPFP" in our cars). It moves fuel STRAIGHT to the injectors at ~43psi.

We have a LPFP that pushes fuel at 72psi into a HPFP which exponentializes it into up to around ~4000psi to be delivered to the injectors that need this much pressure to overcome cylinder pressures as the N54 squirts fuel directly into the combustion chamber via directly injected injectors. The 43psi systems just squirt fuel into the intake path right before the intake valve where this is no pressure (unless it's FI and then pressure needs to be raised 1:1 but that's another topic altogether).

[SennaZ]

One would have to assume that by subjecting the LPFP to +70% electrical loads that its life will be shortened - however, they are readily available for around $200 so replacing them shouldn't be a big issue.

[mycoupe]

Originally Posted by indy99gpgt

I agree with you. I have a feeling that this new fuel system upgrade will help us achieve higher power output but we will then run into another limiting factor at some point which will be the hpfp.

Cart before the horse much??? Let's just let Shiv do his thing and provide us with an upgrade that no one else, even BMW, was able to accomplish and go from there. Even if it frees up a potential 50-100hp before this theoretical HPFP inevitable failure, it will still buy everyone plenty of time at higher hp numbers, to play and get bored, for Shiv to back reanalyze and fix the next issue.

Shiv... if you're ever in Cincinnati, hit me up, I'll buy you a beer!

[BoostedE90]

Originally Posted by RobBeck

You guys are failing to see he is talking about standard fuel injection in that passage, not direct injection as we have which incorporates a HPFP.

Those standard systems just have one fuel pump (alas the "LPFP" in our cars). It moves fuel STRAIGHT to the injectors at ~43psi.

We have a LPFP that pushes fuel at 72psi into a HPFP which exponentializes it into up to around ~4000psi to be delivered to the injectors that need this much pressure to overcome cylinder pressures as the N54 squirts fuel directly into the combustion chamber via directly injected injectors. The 43psi systems just squirt fuel into the intake path right before the intake valve where this is no pressure (unless it's FI and then pressure needs to be raised 1:1 but that's another topic altogether).

^^thanks for clarifying. So I take it all DI engines would use a higher psi?

[Clap135]

Also one last question. Are we using 11v as a standard for testing and assuming the pump runs at 11v or is the pump actually running at 11 volts? If the stock pump is already running at 13-14v from the factory under load then based on the testing above would indicate that the lpfp is not the limiting factor as it provides enough fuel for the 440ish whp limit we are running into.

[Rob@RBTurbo]

Clap that is a good question, on I had myself as well. But there are plenty of factors to think about as well. The fact is this testing was done on a bench through an aftermarket AFPR with likely no line losses. Actually making the whole LPFP system function at these levels may require much modification, considering there are smaller line sizes and fittings ran at say 15ft etc etc. So keep in mind these are bench tests, not actual on car flow figures. Still good data, it's all part of upgrading... It's always good to take small steps.

[Clap135]

Originally Posted by RobBeck

Clap that is a good question, on I had myself as well. But there are plenty of factors to think about as well. The fact is this testing was done on a bench through an aftermarket AFPR with likely no line losses. Actually making the whole LPFP system function at these levels may require much modification, considering there are smaller line sizes and fittings ran at say 15ft etc etc. So keep in mind these are bench tests, not actual on car flow figures. Still good data, it's all part of upgrading... It's always good to take small steps.

This is true. On my other di car I toyed with changing inlet/outlet diameter of certain feeds only to waste my time and not solve a.damn thing. I guess ill just sit back and see what shivs solution is. Until then its all speculation and Bs lol

[mithiral67]

Originally Posted by Clap135

I guess ill just sit back and see what shivs solution is. Until then its all speculation and Bs lol

+1 This is all speculation at this time if any of this really effects our cars. The only proof that will cause me to consider the new product will be before and after dynos with only upgraded fuel systems as variables.