[urr2slo]

Originally Posted by cmitchell17

How is the low side pump controlled? I tried looking at HP tuners tune, but didn't see anything specific for the low side duty cycle or anything? I'm wondering if there is any way in the tune we can boost output on the low side with a max duty cycle change or something?

The chassis control module has the logic to PWM the low side pump. If you have access to HP Tuners latest beta you might have access to some of it. They recently posted that most OS's 09+ have access to the FPCM (which is the CCM on these cars). I haven't tried to access it so I don't know how much access is there.
Our CCM also control exhaust valves and the magnetic ride if I recall....So that's why it's no longer called FPCM since it controlling more that just the fuel pump.

[toohighpsi]

Originally Posted by parish8

let say the low side fuel pressure is at 45psi and I run out of hpfp at 600hp on e85. would getting that low side fuel pressure up to 60 or even 70psi help the hpfp go any farther?

I am looking for someone that has tried this in the real world and either saw an improvement or didn't see an improvement.

Increasing the LPFP pressure into the HPFP will not have much impact on fuel delivered from the HPFP. Fuel is essentially an incompressable fluid so the change on an positive displacement pump will be very minimal.

Now, with falling pressure from the LPFP there is a point where the restrictions between the LPFP and HPFP will prevent complete filling of the HPFP. I haven't tested to determine what pressure/flow that this will begin to occur at, but I have run down to 25psi LPFP pressure without any reduction in flow from the HPFP.

I have no intention of testing lower pressure, now with the addition of the ZL1 LPFP along with the Big Bore HPFP and LT4 injectors I was running a minimum LPFP pressure of 40.5 psi @ 730RWHP.

[Atomic Ed]

Originally Posted by urr2slo

The chassis control module has the logic to PWM the low side pump. If you have access to HP Tuners latest beta you might have access to some of it. They recently posted that most OS's 09+ have access to the FPCM (which is the CCM on these cars). I haven't tried to access it so I don't know how much access is there.
Our CCM also control exhaust valves and the magnetic ride if I recall....So that's why it's no longer called FPCM since it controlling more that just the fuel pump.

This is intriguing. It would be nice if we had some control via the CCM module that would be similar to a Boost-a-pump setup.

I will comment also that that local tuners and I have talked about tuning my E-Force in the future and they state that they can tickle the LT1 fuel system to handle power levels up to roughly 620 rwhp without any mechanical upgrades. When I press them, they just smile and state that its one of their trade secrets. They will even warranty their work. (They have done dozens of corvette LT1s already and are now offer an FBO kit through the local Chevy dealer with full factory warranty, so one has to assume they know what they are doing.)

My only guess is that they are going beyond the typical HP Tuners tuning capabilities and manipulating the firmware directly(?) Are they possibly managing the HPFP via firmware changes to achieve this? This is way out of my league here, but I am interested in hearing from others on this.

[parish8]

600+hp with gasoline should not be an issue with all stock fuel system.

[exxit]

Originally Posted by Atomic Ed

This is intriguing. It would be nice if we had some control via the CCM module that would be similar to a Boost-a-pump setup.

I will comment also that that local tuners and I have talked about tuning my E-Force in the future and they state that they can tickle the LT1 fuel system to handle power levels up to roughly 620 rwhp without any mechanical upgrades. When I press them, they just smile and state that its one of their trade secrets. They will even warranty their work. (They have done dozens of corvette LT1s already and are now offer an FBO kit through the local Chevy dealer with full factory warranty, so one has to assume they know what they are doing.)

My only guess is that they are going beyond the typical HP Tuners tuning capabilities and manipulating the firmware directly(?) Are they possibly managing the HPFP via firmware changes to achieve this? This is way out of my league here, but I am interested in hearing from others on this.

I guess that would depend on two things... 1. Is there a firmware lock or failsafe that keeps the pumps from working too hard and breaking? 2. could you boost both and achieve what other non DI motors do without mechanical changes?

It's a matter of software or a limitation of physics at this point. You'd think with the LT1 out for as long as it has been; they'd find a cost effective solution to all this.

Want e85? Cool it'll run you about 10k with cam and fuel + labor. Yay.

[urr2slo]

Originally Posted by Atomic Ed

This is intriguing. It would be nice if we had some control via the CCM module that would be similar to a Boost-a-pump setup.

I will comment also that that local tuners and I have talked about tuning my E-Force in the future and they state that they can tickle the LT1 fuel system to handle power levels up to roughly 620 rwhp without any mechanical upgrades. When I press them, they just smile and state that its one of their trade secrets. They will even warranty their work. (They have done dozens of corvette LT1s already and are now offer an FBO kit through the local Chevy dealer with full factory warranty, so one has to assume they know what they are doing.)

My only guess is that they are going beyond the typical HP Tuners tuning capabilities and manipulating the firmware directly(?) Are they possibly managing the HPFP via firmware changes to achieve this? This is way out of my league here, but I am interested in hearing from others on this.

620rw should be achievable with optimum conditions (race gas preferred). The low side fueling just has to keep the HPFP fed, that's all. The HPFC is mechanically driven so there's not much manipulating available, though there is a relief valve that is electronically controlled and setting the limits higher may help high RPM fuel delivery. While I don't doubt some people have greater access than most people can have access to, there's still only so much the factory LPFP can actually output. Most people add a voltage booster, like one from JMS that can be dialed in for specific applications. That way the pump only works as hard as it has to and you can "ramp in" your added voltage. There's a few things that you can change without physically changing the parts, but the end result is how much fuel you can get in the cylinder at the appropriate time? And that's what most people are learning on these GenV engines, you have approx. a 6ms window to get the fuel into the combustion chamber, anything longer than that and you and you increase the chances of an incomplete burn or an irregular burn than has potential to damage the engine. Basically you are "out of fuel" over 6ms.
Currently I am at 681rw and I have all stock LT1 high side parts and a ZL1 low side pump. I do have a cam with a 38% fuel lobe though. My injection time is 5.2ms and my high side pressure is 2241psi and my low side drops to 45psi during the pull. I am still playing with the injection timing to see how much more room I have to go to a smaller pulley and more boost. Before the ZL1 pump I was seeing 7.2ms 1700ish high side and 32 low side and power was peaking around 660. I changed the low side pump and it went to 5.8ms while maintaining 45psi and over 2000 high side. Playing with injection timing I am down to 5.2ms and power is peaking at 681rw.
So there's a lot to consider when talking about tuning the fuel system.

[parish8]

Whoa. Some good info there.

Repeating what you said going from 32psi low side to 45psi low side had a significant improvement in the high side fuel delivery.

What all are you doing with your injection timing?

[Atomic Ed]

Good comments. I learned something today. I should have stated that my criteria to the tuners was it has to be tuned to 92 octane and no meth or E85.

I am just beginning to understand the "why" of the whole injection timing window restrictions and understand that minor changes are possible, but not a lot of room. (as you said, 6ms. limit.) I've also heard that minor tweaks to the SOI can help a little.

I don't plan on changing out the cam, so as a safety factor, I'll probably add the LT4 HPFP myself before the tune. Maybe even the injectors.

But I still want to hear from the local tuner how are they accomplishing this level with no changes in the mechanical portion of the fuel system. The electronically controlled relief valve on the HPFP may be the key as you stated.

[Hyper SS]

What about adding a LS7 lash cap?

[urr2slo]

Originally Posted by parish8

Whoa. Some good info there.

Repeating what you said going from 32psi low side to 45psi low side had a significant improvement in the high side fuel delivery.

What all are you doing with your injection timing?

Well, I haven't concluded any formula to work when switching cams. Currently I have been retarding the cam during WOT and increasing the SOI in small increments. So far all is positive results. I wish there was a way to calculate the appropriate number so I am not doing trial and error, but I have not come across any definitive way of doing that. So I just keep trying a little here and there and see where it goes.
As far as stock cam goes, when boosting I have seen positive results increasing higher rpm and higher airmass areas by 5 to 7 percent.

[urr2slo]

Originally Posted by Hyper SS

What about adding a LS7 lash cap?

Heard too many horror stories from the Vette forums. I have not tried it and doubt I will. When I run out I am looking at buying the Lingenfelter big bore pump and whatever injectors may be out there by then. I know there's a ridiculous amount engineering on these DI injectors. That seems like a more reliable way, to me that is.

[Atomic Ed]

Originally Posted by parish8

Whoa. Some good info there.

Repeating what you said going from 32psi low side to 45psi low side had a significant improvement in the high side fuel delivery.

What all are you doing with your injection timing?

My first thought was; well you have the sum of the pump curves playing into this. But the small incremental change in pressures from the ZL1 pump to the stock pump at WOT doesn't seem it would account for this.

[ProCharger]

Originally Posted by parish8

let say the low side fuel pressure is at 45psi and I run out of hpfp at 600hp on e85. would getting that low side fuel pressure up to 60 or even 70psi help the hpfp go any farther?

I am looking for someone that has tried this in the real world and either saw an improvement or didn't see an improvement.

It only helps in a very narrow range.

A Camaro that I was tuning would drop from 80psi to like 35psi under a short dyno pull. And then yes HPFP readings were dropping as well.

After House of Boost installed a Boost-a-Pump, the system maintains a full ~80psi on the LP side, and runs exactly my commanded HPFP pressure.


However, I see WAY more junk HPFP's that just have no prayer keeping up, then I do LPFPs.

[ProCharger]

Originally Posted by urr2slo

Well, I haven't concluded any formula to work when switching cams. Currently I have been retarding the cam during WOT and increasing the SOI in small increments. So far all is positive results. I wish there was a way to calculate the appropriate number so I am not doing trial and error, but I have not come across any definitive way of doing that. So I just keep trying a little here and there and see where it goes.
As far as stock cam goes, when boosting I have seen positive results increasing higher rpm and higher airmass areas by 5 to 7 percent.

SOI is the key to making power in these cars, and properly dialed tables.

As far as "cam timing" most if not 99% of the cams made for these cars are made for "0" on the cam table. Any change usually results in MORE boost, and LESS power. (aka: flow issues)