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

[rlhammon]

bottom line, someone who has the fueling issue needs to replace their in tank pump with a double pumper/similar crazy volume low pressure pump.

I started this thread on the theory that a higher pressure  & volume on the low side may increase pressure/volume on the higher side. Diesels have done this for years to increase their power.

Throw this in the tank and see if it solves your fueling issues. .. 800lbs per hr at 80psi!

 http://aeromotiveinc.com/products-page/fuel-pumps/11104-eliminator-fuel-pump/

I believe Bob is already running a bigger LPFP in the tank, and saw the issue.  We'll need him to speak up, but he's mentioned it previously.

The GM Fuel Engineers I've spoken with have repeatedly told me we need a high flowing HPFP in order to achieve what we need.  That's why I was talking about a modification and trying to understand what the Buick LHU engine is using.

[snaponbob]

The tank pump is something I addressed somewhere else. To put in absurd terms, we could unleash the Grand Coolee Dam on the HPFP and the same problem would be there. REGARDLESS of whether or not the HPFP is drowning in fuel, if it can't move it fast enough, it will NOT get there. If the HPFP can not get the job done, it can't get the job done. It is NOT a pressure issue, it is a VOLUME issue. Hydrodynamics can't be cheated.

[tazz]

 

[snaponbob]

        

[miller11386]

So there is no bleed through on the pump lines? If I supply 30psi vs 80psi there is no change in fuel rail pressure as long as the volume is up?

Can any of our members who are GM employees get a print and PM me a link to photobucket? or Mail me a hardcopy? I want to see how it looks internally before I jump to conclusions of what can and cannot be done.

GM P/N: 19168380

[joshmass]

The GM Fuel Engineers I've spoken with have repeatedly told me we need a high flowing HPFP in order to achieve what we need.  That's why I was talking about a modification and trying to understand what the Buick LHU engine is using.

REGARDLESS of whether or not the HPFP is drowning in fuel, if it can't move it fast enough, it will NOT get there. If the HPFP can not get the job done, it can't get the job done. It is NOT a pressure issue, it is a VOLUME issue. Hydrodynamics can't be cheated.

I'm following along now. Maybe I'm slow or maybe I just wasn't getting the full picture all at once. I don't know.

So you're saying that you've used up all of the available injection window (and then some) to spray fuel and it's been determined that the effect is that fuel pressure is dropping to 900 psi and throwing the car into limp mode.

You've also said that increasing the commanded fuel pressure has no effect. If the HPFP can't keep up with the demands of the injectors then increasing the pressure to the pump wouldn't do anything at all. It's only capable of pumping a maximum volume of fuel, regardless of the pressure used to spray it. Therefore increasing the pressure on the low side isn't going to help because the high pressure side still can't keep up to the demands of the injectors.

Now Rich says that GM engineers are recommending a higher flowing HPFP but looking back at the specs of the HDP 5-FCV HP, and comparing it to our current pump, I'm not seeing anything that shows that it's capable of any higher volume of fuel at all. It has the ability to spray over 200 bar of pressure but the fuel delivery maximum appears to be the same (1.1cm3/Rotcam). Reading through the spec sheet, the only direct reference to increased volume is through the number of cam lobes and cam lifts.

Is there a chance that we're failing to realize that our current HPFP IS actually fully capable of handling the fueling demands of E85 but only with a different cam profile like what ZZP has already done? And what exactly does the increased pressure of over 200 bar accomplish if volume is the key here and you've already shown that volume trumps pressure?

[snaponbob]

Measuring pressure assumes resistance. As you have said, the pulse period is so long that eventually the injectors are RELIEVING the pressure in the fuel rail faster than the pump can refill the rail, and THAT is what is causing the pressure drop - lack of volume. Number of lobes and/or profile can increase the volume. BOTH are needed for big increases as lift only is good for maybe 15% +/- in volume.

[joshmass]

Measuring pressure assumes resistance. As you have said, the pulse period is so long that eventually the injectors are RELIEVING the pressure in the fuel rail faster than the pump can refill the rail, and THAT is what is causing the pressure drop - lack of volume. Number of lobes and/or profile can increase the volume. BOTH are needed for big increases as lift only is good for maybe 15% +/- in volume.

But to get back to the miller's original question then, it wouldn't appear that either the HPFP or low pressure pump are truly the limiting factor here. It's really the fact that the cam needs to be upgraded to provide more volume, correct? And if that's true, what is the performance ceiling of the upgraded cams?

[snaponbob]

Josh, in stock form the HPFP is the limiting factor with E85, but that really is a car by car situation, what sort of driving is being done, and how aggressive the tune is. As for the answer to how much power can be produced, looking at some Cobalt forums might be more informative as more has been reported there. Caveats - 1) forum based dyno racing is as much a function of how truthful the reports are, 2) if the tuning was done for actual driving or just dyno bragging rights, and 3) lots of peak torque can be produced on E85 using stock pieces (north of 425 wtq) but that does not translate to how driveable the car is.

[rlhammon]

But to get back to the miller's original question then, it wouldn't appear that either the HPFP or low pressure pump are truly the limiting factor here. It's really the fact that the cam needs to be upgraded to provide more volume, correct? And if that's true, what is the performance ceiling of the upgraded cams?

On a stock engine, if you can do anything you want... the best solution is to change the cam to a four lobe situation to provide more fuel per RPM to the high pressure fuel rail.

If you went that route, you'd also change to a Late Intake Phasing model, such as BOSCH has indicated to gain the most power from that setup.

Under SCCA rules that Bob and I race under, we can not change the cam.  So... our only route is to increase the fuel delivered with a 3 lobe driven HPFP.  This means we need to increase the bore of the pump, and replace the diaphragm accordingly.  I haven't a place that will do this... yet.

I know Josh has seen this in e-mails today, but I wanted to put it on the forum for all.

[snaponbob]

So, there are parts and specs for modifying the HPFP?

[miller11386]

im still waiting for a pump or a print to look at to see if I want to try to make a better pump. its obvious that many others have not put in a ton of time to get it nailed down. and its not "worth it" for many of the vendors at the volume. However at this point if I could get to 600whp on hpfp and sustain it, I would be willing to pay north of 1k for the pump, because that is what the other hardware will cost to get above that level.

I still cannot believe nobody has a failed hpfp I could rip apart.....

[rlhammon]

im still waiting for a pump or a print to look at to see if I want to try to make a better pump. its obvious that many others have not put in a ton of time to get it nailed down. and its not "worth it" for many of the vendors at the volume. However at this point if I could get to 600whp on hpfp and sustain it, I would be willing to pay north of 1k for the pump, because that is what the other hardware will cost to get above that level.

I still cannot believe nobody has a failed hpfp I could rip apart.....

Frankly I'm glad there isn't a failed fuel pump... that would scare me!

You could always check junk yards.

[rlhammon]

So, there are parts and specs for modifying the HPFP?

Bob, no there are not.  It's my understand that doing something like is isn't as easy as boring out the cavity... there's actually a fair amount of precision machining work and custom parts that need to be done.  Is it technically possible... yes, most things are, is it worth the time and money.... yet to be determined.

[miller11386]

Frankly I'm glad there isn't a failed fuel pump... that would scare me!

You could always check junk yards.

They fail all the time, however almost all are replaced under warranty, so GM takes them back

Junkyards wont sell pcs like that. motors are sold whole

[LatinVenom]

Miller,
Maybe if you contact one of these folks for the fuel rail.
2007
Fuel Pump / Injector Pump
Pontiac Solstice 2.0TRBO A A0052 $200 M and M Auto Parts, Inc. VARA USA-VA(Stafford) Request_Quote 1-800-586-5492 / VA Beach: 1-866-263-5985 Request_Insurance_Quote
 831
2007
Fuel Pump / Injector Pump
Pontiac Solstice   A 10F133 $150 Denton County Auto Salvage - ARA Gold Seal USA-TX(Denton) Request_Quote 1-800-245-0647 Request_Insurance_Quote
 1107
2007
Fuel Pump / Injector Pump
Pontiac Solstice Pump Assembly, 2.0L A $FF234 $140 LKQ Foster Auto Parts USA-OR(Portland) E-mail 1-888-578-5548 2659
2007
Fuel Pump / Injector Pump
Pontiac Solstice   A H238 $125 American Auto Recycling USA-AZ(Gilbert) Request_Quote 1-480-889-7700 Request_Insurance_Quote
 1939
2007
Fuel Pump / Injector Pump
Pontiac Solstice     S140P $100 East Coast Auto Source VARA USA-VA(Moneta) Request_Quote 1-800-869-0655 Request_Insurance_Quote
 734
2007
Fuel Pump / Injector Pump
Pontiac Solstice 2.0L, IN CAR A 120011 $100 Tompkinsville Auto Salvage USA-KY(Tompkinsville) Request_Quote 1-888-482-0016 Request_Insurance_Quote

[tazz]

I have a used one coming next week for $50 off Ebay.

[miller11386]

awesome tazz! be sure to take some good pics! I want to get my machinists and engineer friends brains turning on this one.

[snaponbob]

Some time ago someone at ZZP told me they had been working on modifying the OEM HPFP but the results were not sufficient to move forward with it. That said, it makes sense. If the pump body is "opened up" to flow more, there must be a method for more to actually flow. THAT seems to boil down to either MORE strokes per cam revolution, or LONGER stokes. Absent one of both, the rail apparently can empty faster than the pump can meet demand.

BTW, as for the in tank pump, there may be a different, or at least additional flow issue. There are two methods for the pump to grab fuel - either it pours over the top of the bucket that it sets in, or come up from a small (and I mean small) rubber one way (passive) diaphragm. When I ran straight gas, I could run Solo laps almost empty. With E85 I had to run 3/4 full, and with E60 I continued to do so. I'll try it "low" at the upcoming T&T and Solo events at the end of the month. (You can be certain I will have more gas and E85 with me as well to fill 'er up.)

[miller11386]

Im thinking longer stroke + increased spring pressure on the pump should do it. After looking at photos, I am now curious if the HPFP is floating at high rpm.

[snaponbob]

Im thinking longer stroke + increased spring pressure on the pump should do it. After looking at photos, I am now curious if the HPFP is floating at high rpm.

Longer stroke is a function of the cam lobe. As for high rpm "float", I can not see that as viable. I have been running a 7000 rpm limit since my first ECM tune. RPM is RPM, and I have not had issues until changing to E85, and it was mostly resolved with E60.

[miller11386]

but you run out of fuel on the top end... right? Ever run out in the mid range?

I was thinking along the lines of valve float. Could be wrong, but until I see one in hand its hard to visualize how it works. There has to be a way to increase the affected volume the piston moves... IE port the pump and add a bigger piston

[snaponbob]

Part of WHEN I "run out" has depended on fuel on board. Once I was running full, it was above 5000, but only under rather specific situations of vehicle position, transitions, and load. NEVER had a problem in a straight line on the road.

[miller11386]

almost sounds like you need a better sump/ pickup design on the tank to alleviate the sloshing you are seeing.

If you never have an issue in a straight line, it sounds like a "fuel not getting to the pump" problem rather than a "pump cant keep up" problem... two totally different issues.

Ever have an issue on the dyno/straight line driving? Have you ever ran your car down the drag strip  with the current setup?

[snaponbob]

almost sounds like you need a better sump/ pickup design on the tank to alleviate the sloshing you are seeing.

If you never have an issue in a straight line, it sounds like a "fuel not getting to the pump" problem rather than a "pump cant keep up" problem... two totally different issues.

Ever have an issue on the dyno/straight line driving? Have you ever ran your car down the drag strip  with the current setup?

First - the in tank system is OEM. I, for one, am not so bold  to believe that I am smarter than GM engineers. Second - drag strip, no. Blasts to equivalent speeds on the road can not be discussed here. FWIW - I am not a moron. I know a little bit of stuff. The "school of hard knocks" is a brutal teacher.