Edit 12/12/2010 at 7:25 PM CST: If you're just now reading this, or coming back to revisit some of my information, the answer has been found to the pressure limitation of the factory CTS-V2 fuel system. Please see my post within this thread located here (it's the 1st post of page 2 of this thread):
Most of you are aware, but for those who aren't, the '09+ CTS-V, like the '09+ ZR1, and many of the E85 GM trucks, incorporates an electronically controlled fuel system, consisting of variable voltage pumps, FPCM (fuel pump control module), and an LFPS (liquid fuel pressure sensor). Fords from basically '99-'10 use a very similar system (variable output Walbro pumps made for Ford, an FPDM, aka fuel pump driver module, and an FRPS, aka fuel rail pressure sensor). On these types of vehicles, one can modify the fuel pressure within the PCM, which is a huge plus for those attempting to increase injector capability, especially factory injector.
From the factory, the CTS-V and ZR1 utilize an injector that flows approx. 52.x psi at 4-bar (58.x psi). With increased DeltaP, these injectors are capable of 650-700+ rwhp Actual (Uncorrected), as I have regularly obtained such on modded C6 ZR1s.
Here is a screenshot of the injector flow rate table from the CTS-V2:
The factory CTS-V2 pumps are rated at 190lph each at 4-bar, and here are screenshots of the various fuel pressures that the CTS-V and ZR1 will see from the factory:
Anyway, to my subject of this thread:
Note: Power numbers that I quote are Actual (Uncorrected) at sea level. I do NOT quote SAE numbers for component range capabilities, especially the fuel system. If you live at higher elevations, such as Colorado, you will more than likely never run into the issues I'm about to mention below, since you'll have approx. an 18 to 22% lower overall power output than someone at sea level.
I just returned from another week long tuning event in Puerto Rico (I was last there in 2005). I had the pleasure of working again with multiple friends of mine, namely Christian from Auto X Dyno, and also Dennis and his CTS-V2 (auto), C6 Z06, and '03 Cobra. Like many other CTS-V2s I have tuned, Christian and I also found that Dennis's factory factory fuel system is basically done at anything much over 525 to 550+ rwhp/rwtq Actual on the A6 (550 to 575+ on the M6). FYI, these power #s represent approx. 13 to 15 psi of boost at sea level, and these quoted numbers can vary by +/- 25 rwhp, depending on a variety of factors. Also, the reason the A6 hits the limit at lower power numbers is due to the increased drivetrain loss.
Here is a datalog of my friend's CTS-V2 showing the various pids logged, including fuel pressure (I cut out some of them that weren't as pertinent, to decrease file size):
(right click, save as)
Note: The Commanded air/fuel at WOT is 11.6, which was also Actual as measured by Christian's lab-grade wideband (do NOT trust low-cost aftermarket widebands, unless it's at least an NGK AFX with NTK sensor). Part of this is due to the fact that most all gas is now E10 (contains 10% ethanol). Generally, on boosted vehicles one shoots for an AFR of not any leaner than 12.0 for 100% pure gas (stoich of approx. 14.7), and not any leaner than 11.6 on E10 (stoich is approx. 14.1). This isn't a rule that always apply to every vehicle, depending on a variety of factors (such as compression). With that being said, the richer the fuel mixture, the more of both fuel pump and fuel injector is used.
At 6000 rpms in the datalog (frame 190), you will notice the Commanded (aka Requested) fuel pressure is 65.3 psi, which is exactly what it is Requested within the tune (see screenshot I gave above earlier). Then you will notice the "Injector Delta Pressure" is 52.7 psi. Measured MAP (manifold absolute pressure) here is also 195 kPa, which is approx. 13.x psi of boost (see calculator here, then one must subtract atmosphere pressure, which was approx. 14.x the day of the dyno tuning). Commanded Pressure minus boost = Injector Delta Pressure, therefore 65.3 - 13.6 = 51.7 psi, so these calculations are inline with the measured data.
Note: A fellow tuner (Flash Me) once wrote a very easy to understand explanation of fuel pressure versus boost, so I figured I'd quote that for you here:
I find it easiest, when thinking about boost vs fuel pressure, to imagine a fight going on. Fuel rail pressure is on one side of the fuel injector, trying to push fuel thru it at around 39 psi on most Fords. In an NA car, that's the only fighter, so 39 psi makes it thru the injector.
In a boosted car, you have boost psi trying to push that fuel back up thru the injector, say at 10 psi. So one side of the injector has 39 psi, and the other has 10 psi. In this case, the net pressure going into the motor would be 29 psi. This net pressure is called pressure drop across injector.
Note: generally, older cars have fuel pressure regulators that are boost referenced, and raise the fuel pressure from 39 to 49, so the 49 psi vs the 10 psi of boost creates the net pressure drop across injector of 39 psi again. As long as fuel pressure is raised 1:1 with boost pressure, the net pressure drop across the injector remains the same... 20 lbs of boost, 59 psi would be required.
Now you know how boost requires an increase of fuel pressure = to boost psi, in order to maintain the 39 psi. This pressure maintainence means the injector flow rate remains constant... x lbs of fuel at 39 psi, or whatever the injector is rated at, so long as fuel pressure is = to that injector rating.
Now, at the same frame (190) you will see that the injectors hit 100% DC (duty cycle) by 6000 rpms (see logged IPW, aka injector pulsewidth - use calculator here). At this point, AFR starts to creep up leaner, thus causing some slight knock at approx. 6200 rpms (until we can rectify this issue, I had to limit Dennis's shift points to 6000 rpms for the time being). So I attempted another test, which was to raise the Commanded fuel pressure to match that of a ZR1. If the output of the pumps were strong enough, and there was no maximum deadset limit of the fuel pressure (such as a regulator built into the pump assembly, like on the 2010+ Camaros), we should be able to increase injector output, thus preventing the injectors from hitting 100% DC. Here's that test:
(right click, save as)
If you go to frame 174, you will notice that the Requested fuel pressure changes from 72.5 to 87 psi. However, take a look at the Inj Delta Pressure, it's only 54.5 psi. Notice MAP is at 194 kPa, aka 13.x psi of boost? 87 - 13.x = 73.x, not 54.5. This tells me we have either a fuel pump limit issue, or a fuel pressure deadset limitation from the pumps (potential mechanical regulator just off the pumps?). If the CTS-V2 does NOT have a max pressure limit, like the Camaros (more on that at the end of this post), due to a mechanical regulator, then the issue is clearly that the factory fuel pumps are NOT enough once the aforementioned power levels I stated are reached. My assumption, at this point, is it's the pumps, but until someone can show me a picture of the pump assembly proving that there is not a mechanical regulator off of them, I'll stand by this.
In regards to the ZR1, the fuel system can definitely reach 87 psi and maintain that. Here is a log from my friend's ZR1 proving such:
(right click, save as)
Go to frame 230, and you will notice that the Requested fuel pressure is 87 psi, and Inj Delta Pressure is 71.2 psi, and MAP is 193 (approx. 13.x psi of boost).
These fueling issues on the CTS-V2 are really nothing new, as others have ran into this problem as well. However, I'm writing this thread because I feel that the issue is not being discussed enough, nor properly, by the community here, nor many of the tuners, as most are blind to the issue at hand (yes, believe it or not). Furthermore, it seems that too many are installing parts/tunes, and then hotrodding their cars without knowing the potential consequences that may face them (i.e. blown engines). I can assure you that 99% of you are guilty of this (can you state you've datalogged your fuel pressures and AFR?). Another thread others have come across the fueling issue in is located here:
I have not measured the output voltage from the Caddy FPCM, but if it is anything like the the 2010+ Camaros, the FPCM limits the output voltage to a max of 12.8v (see here). Currently, we tuners are not able to modify the FPCM max voltage output/limit, since the current crop of tuning software manufacturers do not access the FPCM control module. If we were able to, this would allow us to increase the output limits from the FPCM, thus potentially being able to install a BAP *before* the FPCM (see below). This is all in theory, however.
Basically, you have two options at this point:
1 (easiest): Kenne Bell Boost-a-Pump or a Magnavolt (what Whipple uses on their Camaro kits). If you install this, it is imperative that you install this post-FPCM, otherwise you'll run into issues with the FPCM controlling the voltage going into it, and preventing any additional voltage going out. This is contrary to a Ford with a similar system, in that you should always install a BAP pre-FPDM, as Ford's FPDM (fuel pump driver module) will allow for the additional voltage into it and out, as needed. LPE sells a complete kit that includes a KB BAP here, however you may be able to buy a KB BAP and build your own wiring harness for cheaper. Kenne Bell (BAP) and Whipple (uses Magnavolt) install their systems post-FPCM.
2: Install pumps with the ability to flow more lph at the same voltage output, such as the ZR1 pump (though, from my understanding, it will not fit). Keep in mind, you can NOT install pumps that aren't variable voltage style, otherwise they will not flow properly, and they will eventually burn up.
Another potential upgrade could be upgrading the FPCM to the one from the ZR1 (as mentioned as a potential substitute in the above thread), but ONLY if it outputs more than 12.8v (doubtful). With this being said, I have NOT tested a ZR1 FPCM to see if it allows a higher output voltage, so I cannot guarantee that it'll work. If it does, and if it'll work, then that would be great for increasing fuel volume to the rails.
On a slightly difference vehicle note, in regards to the 2010+ Camaro SS, LPE offers the CTS-V fuel pump assembly upgrade, as well as an FPCM upgrade, as seen here.
Edit: I've been informed that it's kitted together by ADM, as seen here. Lonnie's Performance also sells something similar (I do not know if it includes an FPCM or not?), as seen here and here (scroll down to Gen5 section)
I'm not 100% sure what LPE means by a "reprogrammed" FPCM, but my guess is that ADM is including the factory Caddy FPCM (attempting to ask LPE is worthless, and although they make good products, they are a bunch of pricks and dipsh!ts over there - see here). However, keep in mind, the Camaro is limited to 4-bar (58.x psi) with the factory fuel setup, as there is an in-tank fuel pressure regulator that limits it to such (see picture of such here). Going with the Caddy system, this would allow pressures higher than 58 psi to be commanded via the tune for these cars.
Anyway, I hope this helps. I'll put up another thread in regards to tuning, and information about how to properly do such, especially on forced induction vehicles. A LOT of you would be shocked at how "hacked" tuning is these days (zero MAF table tuning and raped PE tables, raped spark tables, non-renormalized airmass axes, etc).