Topic: HPFP or in tank pump... whats the real limiting fuel factor?

[miller11386]

Ive been talking to the diesel folks about the hpfp issues the high HP cars are experiencing. The issue is the stock fuel rail pressure depletes as the HP and RPM rise. Effectively reducing the power capacity of an LNF. 

However a similar issue is solved in the diesel world. By putting in what they call a "lift" pump, they can effectively raise the capability of their HPFP by increasing the fuel pressure to the HPFP on the low pressure side. 

ZZP corroborates this theory by saying that the in tank fuel pump is the limiting factor of the HPFP and should be replaced by an aeromotive stealth fuel pump to get more fuel to the HPFP. Therefore if you increase the capacity of the in tank pump, you can effectively get more fuel into the LNF.

I was always under the understanding that the HPFP was the limiting factor in the whole chain of command, but others are telling me that the HPFP is starved by the in tank pump, causing the low fuel rail pressure.

Another high HP build with upgraded fuel lobe cam is ~458whp on e47, and has no signs of running out of fuel.


So does anyone have data to support this theory? or data to dispute it? is there even a sensor to measure the low side fuel pressure vs the high side? 

[Sol Asylum]

It should be easy to test, you plumb in a fuel pressure gauge between the low and high pressure pumps.  If you see the fuel pressure drop off to zero as you increase RPM then it would support what your hearing about the HPFP starving.

[miller11386]

Yes I dont have a motor to do that. Im hoping someone could help out

[Sol Asylum]

I haven't looked into the specs on the pumps, or if you could even find them, but you might find what you need there.  If the LPFP puts out less volume then the HPFP that would tell you the same thing.

[miller11386]

Agreed. But fueling isnt n the ecotec build book

[snaponbob]

Well sports fans, ZZP is wrong. I have had problems with fuel starvation running E85 and Trifecta tune, and the bigger tank pump did NOT resolve the problem AT ALL. You can send an ocean of fuel to the high pressure pump at the engine, but if IT can not move enough fuel to the rails ......... well ............ the engine starves for fuel. Until there is an effective cam driven pump with greater VOLUME, we are stuck with what we have. If a HVHP engine driven pump comes available, I will be installing one.

[Dave@DDMworks]

Ive been talking to the diesel folks about the hpfp issues the high HP cars are experiencing. The issue is the stock fuel rail pressure depletes as the HP and RPM rise. Effectively reducing the power capacity of an LNF. 

However a similar issue is solved in the diesel world. By putting in what they call a "lift" pump, they can effectively raise the capability of their HPFP by increasing the fuel pressure to the HPFP on the low pressure side. 

ZZP corroborates this theory by saying that the in tank fuel pump is the limiting factor of the HPFP and should be replaced by an aeromotive stealth fuel pump to get more fuel to the HPFP. Therefore if you increase the capacity of the in tank pump, you can effectively get more fuel into the LNF.

I was always under the understanding that the HPFP was the limiting factor in the whole chain of command, but others are telling me that the HPFP is starved by the in tank pump, causing the low fuel rail pressure.

Another high HP build with upgraded fuel lobe cam is ~458whp on e47, and has no signs of running out of fuel.


So does anyone have data to support this theory? or data to dispute it? is there even a sensor to measure the low side fuel pressure vs the high side? 

The easiest way to see if the low pressure fuel pump is not keeping up is put a fuel pressure gauge on the low pressure line feeding the high pressure pump. There is already a port there and very easy to do.

[Brad Kenny]

Sounds like SOB has found a "new" project for one of our trusted vendors... LOL

[Kelu]

Don't forget ZZP has an upgraded HPFP, not put on the market yet but I know they installed it in some customers cars too, I think they said LPFP is the limiting factor after using their upgraded HPFP and doing like 600whp on E90.

With stock pumps I vote that HPFP is limiting factor.

[Arabas]

Don't forget ZZP has an upgraded HPFP, not put on the market yet but I know they installed it in some customers cars too, I think they said LPFP is the limiting factor after using their upgraded HPFP and doing like 600whp on E90.

With stock pumps I vote that HPFP is limiting factor.

Kelu, having less technical knowledge than you (thus it is more probable that i am wrong), i say this: our hpfp has a pressure of 150 psi at WOT. VW group 2.0 TSI has 130 psi at WOT doing the same stock HP numbers. they upgrade it with a 150-160 IIRC hpfp from RS6 and get almost 400 hp with their K04 and aftermarket fuel injectors. this makes me assume that the limiting factor in our stock set up is not the hpfp but either the lpfp or the fuel injectors.

[Kelu]

Arab let's talk based on true facts:
TFSI engine comes with 130 bar HPFP - they have an upgrade solution from APR with a pump which can make 150 bar and it can reach 330-400bhp. After 400bhp they use LPFP upgrades, generally additional inline electrical pumps.

TSI engines (newer ones)- comes with 150 bar HPFP from factory and can be electronically tuned up to 180-190 bar iirc and they can make up to 450hp

Our pumps are similar with TSI ones (150 bar stock, tuned up to 180-190 bar) and can push up to 450 bhp on gas maybe a little more.

Believe me, I did many researches in the past with romanian guys from VAG engines, our stock injectors are far better their stock ones,  are same iirc with the one which they are using as upgrades, same as HPFP.

Our Kappas prove already that we can do 400bhp easy using stock fueling parts on gas, ZZP had no problems with LPFP even they used Ethanol blends up to over 550 hp.

P.S. The fastest Audi S3 is from Romania, 10.7s also there are another 2 - 3 highly tuned ones doing 11.9s and I have direct contact with the owners and local tuners. Also a 600 bhp Skoda Octavia using APR kit also.

[Arabas]

 

thx for the info Kelu!

[miller11386]

Me:What is the max WHP that you have got to with just the HPFP setup?

Tim:On our Cobalt Matt made it to 500whp on e85 where the premechanical injection fuel pressure started to drop.  BUT I hear that the Sky/Solstice cant even get that far.  So a replacement in tank pump will be necessary.

Me:So from your experience, the HPFP works at these levels as long as you upgrade the in tank pump to feed the hpfp? I was under the impression the fuel rail pressure drop was due to the inability of the HPFP to keep the volume up.

Tim: We literally have hundreds of pulls on Matts LNF, what I mentioned is all that you need.  The setup that I have been recommending you will love when its done.  If you over complicate it, then it will less confortable, driveable and it wont make any more power.

Me: You are literally the first person to mention this issue of the hpfp starving rather than being maxed. everyone is spraying the mani over 500whp that I've seen.

Tim: We started that, lol.  But now with the fuel pump lobe and injection window tweaks in our 1.0 file.  The “fifth injector” idea is old school.

I am not going to lie, this seems plausible. This is exactly what the diesel group does to get their fuel up on the high HP motors that starve for fuel. They just upgrade the "lift" pump in line and that gives them more fuel through the HPFP setup. So I have all kinds of conflicting information now.

[Brad Kenny]

Sounds like a Net Positive Suction Head (NPSH) problem to me... A higher pressure and flow pump in the tank would definitely increase the supply to the high pressure fuel pump. Only problem would be needing an internal "bypass" during low demands to allow flow back to the tank to prevent burning out the LPFP.

[snaponbob]

Both pumps do what they are designed to do. The tank pump gets the fuel to the engine pump, and the bypass system is already in place. Having already installed a lift pump (Walbro from DDM), I am here to tell you that the HPHV pump at the engine can not keep up with the injectors when they are programmed to supply what is needed for E85 with a stock turbo.  I was in discussions with ZZP to sell me a "prototype" pump, and after they agreed to do so, never did. Also, they told me that the Walbro pump pushes LESS fuel than the stock pump (yes, you REAR that right and I HEARD that right) but would not clarify if that was on the Cobalt or Kappa.

As I said, when a higher volume HPHV pump comes available (that does not require a cam change) I will buy it. Still waiting. 

[cdnite]

Bosch MotorSport has a new higher volume and pressure HPFP available.

Y'all need to make friends with Bosch MotorSports, our LNF engines are basically designed and made by them.

http://www.bosch-motorsport.de/content/downloads/Documentation/Bosch_Motorsport_Catalog_2012.pdf

--Christian

[kennysabarese]

The 2012 Buick Turbo is FlexFuel, so I would look to see if they have a pump that can deliver more volume.

[miller11386]

I dont have restrictions like SOB, so if a upgraded in tank pump and a cam change will solve the issue, I am going that route for sure.

[miller11386]

So does anyone know what our fuel pump flows?
Aeromotive is rated at 340 lph
Walbro is rated at 255 lph
Stock is ?????

[snaponbob]

So does anyone know what our fuel pump flows?
Aeromotive is rated at 340 lph
Walbro is rated at 255 lph
Stock is ?????

Which pumps? There are two. Is the Aeromotive an in tank pump? If so, is it a drop in like the Walbro?

[miller11386]

Im talking ab the in tank pump. Idk what the stocker is. If anyone has had one out or has photos that would help

[tazz]

My question is would there be enough demand to justify a vendor to produce a  higher flow rate HPFP Probably not, Maybe? 
I would have thought when ZZP did some tests of there HPFP upgrade that they would produce one that would be up to the task but there must have been some sort of hangup or limitation without a cam change.  Also anyone can rule out HPT being able to tune for it since Chris said something about the it's a hard wired parameter that can not be changed if I remember the discussion correctly.

[tazz]

Im talking ab the in tank pump. Idk what the stocker is. If anyone has had one out or has photos that would help

I remember someone over at skyroadster had pics and other info.

[snaponbob]

I remember someone over at skyroadster had pics and other info.

Link?

[LatinVenom]

If he means the GM stock in tank pump Werks had some pictures I think.
I will try to find them and post.