Define "keeping up" as it relates to fuel pumps

[LS1_Disciple]

How much (if any) is an acceptable amount for the fuel pressure to drop at WOT?

After I installed the Maggie, I used a BAP with the stock pump. Fuel pressure barely ever dropped below 53psi or so. Now 7000 miles later, pressure was dropping to like mid-40s even at relatively low rpm (like 4500). So I just swapped in the ZL1 pump and disconnected the BAP. With no help from a BAP, fuel pressure drops to about 45psi and stays there to redline.

So do I reconnect the BAP to help out the ZL1 pump, or is 45 psi acceptable? I seem to remember Shane and Buford not having issues up to 600hp with the ZL1 pump by itself.

[XXFire]

Why was pressure dropping?
Just got my Maggie installed and guess ill have to watch this...

[Firehawk]

not sure where the acceptable threshold is.

i am just now ordering my gauges. the gauges and centerstack plastics should be here from down under in a couple of weeks. once its all installed i can tell you what my Squash / Aeromotive setup drops to under full load.

alternately Andy from Squash performance may be the best person to answer this question directly.

[LS1_Disciple]

Why was pressure dropping?
Just got my Maggie installed and guess ill have to watch this...

Under WOT the engine obviously requires more fuel. If the pump is not up to the task (say after strapping a blower or a huge cam to it), then the fuel pressure will drop. If the pressure drops enough, the A/F ratio will be off, the car will go lean, and the engine will pop. Not sure what the definition of "enough" is yet.

I assumed that the stock pump had crapped out and couldn't even keep up with the extra help from the BAP. So far, the ZL1 pump w/o a BAP can do what the stock G8 pump could do with the assistance of the BAP. Since it all really depends on the A/F ratio, I intend to get it strapped to a dyno again here shortly and see what's actually going on. If it can maintain the correct A/F ratio at "only" 45psi, then I suppose that's "fine."


not sure where the acceptable threshold is.

i am just now ordering my gauges. the gauges and centerstack plastics should be here from down under in a couple of weeks. once its all installed i can tell you what my Squash / Aeromotive setup drops to under full load.

alternately Andy from Squash performance may be the best person to answer this question directly.

Please do let me know, though I suspect your proper set-up will not drop much.

[mooredata]

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[TooManyHobbies]

How much (if any) is an acceptable amount for the fuel pressure to drop at WOT?

After I installed the Maggie, I used a BAP with the stock pump. Fuel pressure barely ever dropped below 53psi or so. Now 7000 miles later, pressure was dropping to like mid-40s even at relatively low rpm (like 4500). So I just swapped in the ZL1 pump and disconnected the BAP. With no help from a BAP, fuel pressure drops to about 45psi and stays there to redline.

So do I reconnect the BAP to help out the ZL1 pump, or is 45 psi acceptable? I seem to remember Shane and Buford not having issues up to 600hp with the ZL1 pump by itself.

According to this thread Shane used a BAP with the ZL1 pump:

http://forum.grrrr8.net/showthread.php?t=29878&highlight=zl1

[TyG8GXP]

What injectors are you running?

[LS1_Disciple]

According to this thread Shane used a BAP with the ZL1 pump:

http://forum.grrrr8.net/showthread.php?t=29878&highlight=zl1

This is true, but he was making more HP than me, and he had the BAP turned "way down." Interesting though as I read through that thread again, he mentioned in post #2 that the pressure was low-40's at the end of the gear. That's why he stayed with the BAP.


What injectors are you running?

LS9's

[KANGA2]

Subscribed.

[XXFire]

This is true, but he was making more HP than me, and he had the BAP turned "way down." Interesting though as I read through that thread again, he mentioned in post #2 that the pressure was low-40's at the end of the gear. That's why he stayed with the BAP.



LS9's

Wonder if I'm gonna need a BAP...
We shall see...

[EcoBrick Bob]

If you have it, why did you disconnect it???? I still have my KB BAP connected in my Brick, and I am otherwise stock... just have it turned off. Of course my Ford system is return-less which means my pump voltage regulates the amount of fuel pumped, so at low RPM it is below 9 (without BAP) and maxes out in the 13-14 volt, again without the BAP. KB BAP increases voltage up to 50%, and in the Flex, it made a difference of over 200 PSI on my DIFP which can see pressures as high as 2,400 psi. I watch LAMBDA # and the key is to make sure it doesn't go up much, and stays below .82 in my turbo'd application. As long as your A/F or Lambda number stays within your acceptable operating limits, the FRP is likely fine.

[Doug Hilliard]

Just to chime in for any who are considering a change, the CTS-V pump with VaporWorx controller on mine holds the pressure at 56 psi all the way through WOT and still has headroom. That's well over 750 hp at the crank (need to dyno it to confirm the numbers).

[LS1_Disciple]

If you have it, why did you disconnect it???? I still have my KB BAP connected in my Brick, and I am otherwise stock... just have it turned off. Of course my Ford system is return-less which means my pump voltage regulates the amount of fuel pumped, so at low RPM it is below 9 (without BAP) and maxes out in the 13-14 volt, again without the BAP. KB BAP increases voltage up to 50%, and in the Flex, it made a difference of over 200 PSI on my DIFP which can see pressures as high as 2,400 psi. I watch LAMBDA # and the key is to make sure it doesn't go up much, and stays below .82 in my turbo'd application. As long as your A/F or Lambda number stays within your acceptable operating limits, the FRP is likely fine.

The BAP's only disconnected electrically. 5 mins with a soldering iron, and it's back running (Magnavolt doesn't have an "off" switch like your KB). I don't really like relying on a BAP, so I wanted to see what the ZL1 pump could do by itself. But it appears it will need some help.

[LS1_Disciple]

UPDATE:

Got my tub strapped to the dyno this morning to check this out. A few days ago, I wired up an external switch for the BAP so that I could run both with and without the assistance of the BAP. On the street, the assistance from the BAP has provided very little increase in fuel pressure, if any (1-3ish maybe; hard to accurately read a FP gauge on the street while going WOT).

Started off without the BAP. At idle and at low RPMs (low enough to stay in the "vacuum" region), the ZL1 pump holds 55ish psi (not surprising). Once the blower starts making boost, it drops to about maybe 50-51 psi. As the RPMs continue to climb, it drops to about 45-46 psi by 5500 rpm, and then maintains that until 6500. The entire run the AFR is dead-level at 11.5:1. I didn't bother getting a copy of the graph, but if you want to see one, imagine what a straight line looks like ;) This was repeated for 2 or 3 runs with the same results, and it ultimately dyno'd 515rwhp 502rwtq (same numbers it put down in my sig about a year ago). Duty cycle on the LS9 injectors was 95% at 6000 rpm and 100% at 6500.

So then just for comparison's sake (and so that my wiring work was not in vain), I wanted to make one run with the BAP. We only got about 1% into the run, and it blew the fuel pump fuse. This never happened on the street the last few days. Anyway, not wanting to temp fate, we replaced the fuse and called it quits.

So bottom line is I believe the ZL1 pump by itself works "fine" in that it's maintaining 11.5:1 all the way to redline. Perhaps not ideal but at least adequate. I need to upgrade injectors and then perhaps reattack this. Will be pulling out the BAP stuff soon and selling it to offset some costs.

Thoughts? Disagree?

[Doug Hilliard]

The only additional thing to think about is what happens with heat. I had the condition, with my stock pump with a BAP, on the road course that my pressure was apparently going a little low. I didn't have a gage but as the day wore on, I didn't have as much power on the seat dyno. After discussing with Rick, he advised it was likely that my fuel was getting warmer in the tank, then under hard driving at the track the fuel rail is hot, as the pressure drops, the fuel will boil easier and you don't get the fuel you're trying to and you go lean. In my case, Rick's tune protected the motor. I replaced the pump a couple months later. If you drive hard for extended periods in hot weather, you may see this same condition and that may be risky. Just food for thought.

[DSteck]

Pressure is not as important as flow. Fuel pumps actually flow more fuel at lower pressures. That's why you see pressure drop without completely leaning out. There's really no "floor" for pressure as to what's acceptable, although usually you'll see things completely crap out when it drops to about 35psi. If your injectors are large enough to give the pump a break and allow it to still flow enough through lower pressure, then I wouldn't worry about it. That said, LS9s with that low of pressure won't get very far in power production.

A duty cycle of 95% is effectively maxed out. There's a hard coded 0.8ms off time for injectors to prevent them from literally staying open, plus you have to factor out the voltage offset. I think you need to consider stepping to large injectors, or supplying more flow at higher pressure.

[ZiM]

Just to chime in for any who are considering a change, the CTS-V pump with VaporWorx controller on mine holds the pressure at 56 psi all the way through WOT and still has headroom. That's well over 750 hp at the crank (need to dyno it to confirm the numbers).
I'm running this setup and can confirm....

[Greg@PacePerformance]

UPDATE:

Got my tub strapped to the dyno this morning to check this out. A few days ago, I wired up an external switch for the BAP so that I could run both with and without the assistance of the BAP. On the street, the assistance from the BAP has provided very little increase in fuel pressure, if any (1-3ish maybe; hard to accurately read a FP gauge on the street while going WOT).

Started off without the BAP. At idle and at low RPMs (low enough to stay in the "vacuum" region), the ZL1 pump holds 55ish psi (not surprising). Once the blower starts making boost, it drops to about maybe 50-51 psi. As the RPMs continue to climb, it drops to about 45-46 psi by 5500 rpm, and then maintains that until 6500. The entire run the AFR is dead-level at 11.5:1. I didn't bother getting a copy of the graph, but if you want to see one, imagine what a straight line looks like ;) This was repeated for 2 or 3 runs with the same results, and it ultimately dyno'd 515rwhp 502rwtq (same numbers it put down in my sig about a year ago). Duty cycle on the LS9 injectors was 95% at 6000 rpm and 100% at 6500.

So then just for comparison's sake (and so that my wiring work was not in vain), I wanted to make one run with the BAP. We only got about 1% into the run, and it blew the fuel pump fuse. This never happened on the street the last few days. Anyway, not wanting to temp fate, we replaced the fuse and called it quits.

So bottom line is I believe the ZL1 pump by itself works "fine" in that it's maintaining 11.5:1 all the way to redline. Perhaps not ideal but at least adequate. I need to upgrade injectors and then perhaps reattack this. Will be pulling out the BAP stuff soon and selling it to offset some costs.

Thoughts? Disagree?

You don't need injectors. You need to get the pump flowing more via the BAP.
Remember I'm running the stock LS9 injectors at 88% IDC putting down 586rwhp.

[LS1_Disciple]

You don't need injectors. You need to get the pump flowing more via the BAP.
Remember I'm running the stock LS9 injectors at 88% IDC putting down 586rwhp.

Perhaps you're right. Here's Shane's reply from the other board:


You can NOT turn the BAP up much at all with the ZL1 pump due to the higher amp draw of the pump. I had the KB BAP system turned to 20 out of 60 and had it on a Hobbs switch.

My BAP is a Magnavolt which has no adjustment. At about 3 psi, it just gives the pump the full 17V or so. Perhaps just switching to a KB BAP with an adjustment will allow the ZL1 pump to keep up. With that said, anyone have a KB BAP for sale? ;)

[Doug Hilliard]

My BAP is a Magnavolt which has no adjustment. At about 3 psi, it just gives the pump the full 17V or so. Perhaps just switching to a KB BAP with an adjustment will allow the ZL1 pump to keep up. With that said, anyone have a KB BAP for sale? ;)
I'm not sure why putting 17V to the pump wouldn't be OK unless the Magnavolt is not rated for the current draw of the ZL1 pump; maybe that's the issue. I think the KB handles up to 40A.

[DSteck]

Upping the voltage on electrical equipment increases their power consumption. Power consumption directly impacts heat generation. Heat kills electrical parts. Hook an LED rated for 3.7V directly to a car battery, and it'll pop. Voltage ratings are there for a reason. :)

[LS1_Disciple]

I'm not sure why putting 17V to the pump wouldn't be OK unless the Magnavolt is not rated for the current draw of the ZL1 pump; maybe that's the issue. I think the KB handles up to 40A.

I think what Shane (and DSteck) are saying is upping the voltage too much to the ZL1 pump causes it to draw more current than the 20A fuel pump fuse will allow. I don't know what the actual numbers are, but for argument's sake, say the factory G8 pump pulls 15A in normal operation, and the ZL1 pump pulls 18A. Less wiggle room with the ZL1 pump before you hit 20A, and the fuse pops.

[Doug Hilliard]

Upping the voltage on electrical equipment increases their power consumption. Power consumption directly impacts heat generation. Heat kills electrical parts. Hook an LED rated for 3.7V directly to a car battery, and it'll pop. Voltage ratings are there for a reason. :)
True, hence the concern on the current rating for the BAP; if it can't deliver the required current, it will either fail or go into shutdown mode assuming it has internal protection. Automotive DC motors are typically rated for 9-18VDC unless they are on a pretty special regulated circuit. Running the pump at 17V will generate more heat and will shorten the life of the motor as the motor brushes will wear quicker due to higher current density, but there is certainly safety margin built in regarding heat as far the pump motor itself is concerned. My bigger concern is if the car will be driven under boost and hence higher voltage for longer than a quick burst such as in a road course event, not for the motor, but for putting heat from the pump into the fuel, resulting in fuel vaporization under lower pressure mentioned in my previous post.

[DSteck]

The ZL1 pump was designed to be operated at 12V. The FPCM even clamps voltage output at 12V and uses PWM to change the output. There's not really a safety margin for it to take almost a 50% increase in voltage. Being in this elevated state for longer sustained periods is definitely the nail in the coffin.

Stuff like this is why I'm not a huge fan of trying to push a stock pump crazy hard.

[Carl@Vaporworx]

The ZL1 fuel module requires approximately 17 amps @ 13.5 volts at 60psi, the approximate operating conditions when using the VaporWorx adapter and regulator. At 16 volts it requires 19.3 amps, so it's not surprising that fuses are being blown using BAPs.

In the above configuration the regulator will be bypassing no fuel when pressure falls 5-6psi from idle pressure. At this point the pump is max'ed out.

I have not tested a stock pump, but based on similar pumps the amperage draw is likely 9-10 amps. That's a lot less than 17 amps. Regular power wiring inspections should be on the list of to-do's.

If the injector is at maximum duty cycle and the pressure is dropping then the pump is too small. One of the rules of pumps is that as pressure decreases, flowrate increases. The tune can accomodate large drops in pressure if the tuner knows what he/she is doing. But, what happens when the pump loses performance, or if the air gets really good, or...... There's no safety overhead. 10% is considered the norm for SF.

[LS1_Disciple]

Good answer, Carl. Let me see if I can ask an intelligent question. Since pressure and flow rate are related, what starts the whole sequence? To clarify, this is a "chicken or the egg" type scenario, and I see a couple different possibilities:

Option 1: The flow rate required/commanded by the engine so high that the pump can't keep up. The pump pushes more flow, which drops the pressure.
Option 2: Similar story in that enough fuel isn't getting to the engine, so the pressure drops. This pressure drop causes the pump to flow more fuel.

So does the pressure drop cause the increase in flow rate, or does the increase in flow rate cause the pressure drop?

[Carl@Vaporworx]

Pressure is created by a flow restriction. When the restriction is small, like putting your finger over the end of a garden hose, the pressure in the hose is high but the flowrate is small. Remove your finger and the flowrate maximizes but the pressure in the hose is nil. Fuel injectors need pressure to work well.

Rules for pumps: Flowrate increases, pressure decreases (no finger over hose.) Flowrate decreases, pressure increases (finger over hose.)

The injector is the flowrate restriction.

If the injector is at 100% DC but the fuel pressure is OK, then the injector is too small (finger over hose.)

If the injector is at 100% DC but the fuel pressure falls, then the fuel pump is too small (finger off of hose.)

[Firehawk]

finally.... gauges installed.

I told you i would tell you my min PSI under WOT with my setup. I should be able to get it tomorrow.

[Firehawk]

FYI
my Squash Performance fuel system using 1 Aeromotive 340LPH 11141 fuel pump is holding a minimum of 53PSI all the way up to 6500 RPM. It normally idles at 58PSI
That setup dynoed at 570RHP

[KANGA2]

Finally installed the CTS-V pump and Vaporworx controller. Fuel pressure holds steady at 58 psi and drops to 53 psi during WOT. Dynoed at 504 rwhp & 478 tq. Personal thank you to Greg@Pace for all his help and to Carl@Vaporworxs for his extraordinary service and support. You both should be commended for the support you provide to the G8 community. Cheers.

[hflores3]

Finally installed the CTS-V pump and Vaporworx controller. Fuel pressure holds steady at 58 psi and drops to 53 psi during WOT. Dynoed at 504 rwhp & 478 tq. Personal thank you to Greg@Pace for all his help and to Carl@Vaporworxs for his extraordinary service and support. You both should be commended for the support you provide to the G8 community. Cheers.

What did the entire setup run you KANGA2?

[KANGA2]

What did the entire setup run you KANGA2?

Can't remember but I'll look it up when I return to the US next week. Cheers.

[STL_G8GT]

What did the entire setup run you KANGA2?

500 for the controller, 100 for various hoses and fittings, + cost of the ctsv pump... Call it 900-1000 all said and done.

[thebeast]

I just bought the Squash twin pump setup with DW300 pumps return style. This will keep up with my fuel demands no matter what