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CTS-V2 Fuel System Warning - Important!

54K views 115 replies 23 participants last post by  cotty 
#1 · (Edited)
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):

http://www.cadillacforums.com/forum...l-system-warning-important-2.html#post2440763


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:

CTS-V2


ZR1


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 I do NOT quote SAE numbers for component range capabilities, especially the fuel system.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):

http://www.rwtd.com/tuning/gm/fueling/cts-v2/dennis_ducos/dyno8_test6.csv
(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:

http://www.rwtd.com/tuning/gm/fueling/cts-v2/dennis_ducos/dyno2_test2.csv
(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:

http://www.rwtd.com/tuning/gm/fueling/cts-v2/mike_elder/dyno17_test5.csv
(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:

http://www.cadillacforums.com/forum...es-forum-2009/172595-v2-fuel-restriction.html

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).

Regards,

James
 
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#80 ·
BAP Theory Explained.

This part piqued my interest:

"MYTH: “THAT EXTRA VOLTAGE WILL HURT YOUR PUMP”
FACT: The installation of our Boost-A-Pump will actually increase pump life by reducing its workload."

As has been explained in this thread and in that PDF, once the PWM (Pulse Width Modulation) duty cycle reaches 100%, that's it, there is no more work to be had out of that pump. The BAP increases the pulse amplitude, so that each of the pulses can do more work (voltage times duration).

What I don't get is how they can claim it doesn't affect the longevity of the pump. While the duty cycle (pulse width) can be lower for a given flow, the pulse amplitudes are higher (when the BAP is activated). How is a greater pulse amplitude somehow easier on a pump designed for a lower pulse amplitude?

There is no free lunch.
 
#86 ·
Short answer, no. You can, and I have, installed a 9.5" pulley, cai and tune, along with a cam and have not needed to change anything in the fuel system yet. Are those the mods you were thinking of doing? I'm not sure how close you would be with a 10" ring is why I ask.
It has a little room to go and I'm headed to the shop for exhaust today, then do some logging and might need to toss in some injectors.
 
#89 ·
This is a hot topic.... Drumstix is correct,depends on pulley size too... but you also need to have a good tuner shop. Also depends on your elevation.......

IMO I prefer to have more safety..... So I would pick up some injectors if your questionable about your shop.........
 
#87 ·
I'm curious- how does one (who lacks any real knowledge of tuning) determine if a tuner is a "hack" or "legit"? What questions should we be asking?
The primary reason I have not made any modifications to my car is that I still see serious discrepencies with modified "claims". CAI is worthless/header are worthless/watch out for hacked tunes, etc. It's not as if S/C LSx's are new, so why all the confusion?
 
#88 ·
I would say just keep asking questions and gathering your own knowledge of these systems and components and how they interact. Don't just take someones word for it if you are not comfortable in the modding arena, just like anything else you undertake in life. Even if the car is left stock dealers have been know to take customers for a ride. No really. :yup: Knowing what's up can lower that repair bill.
Find a reputable shop that is willing to answer your questions and build a relationship with you. It's not all secrets and black magic, especially when you foot the bill. I would not accept that on a $50m project so I would not accept that on a $65K car.
Also note that some of these shops may raise doubt in public to raise revenue and compete. That can often be countered in the forums with skilled tuners who help out the community as a hobby.
 
#95 ·
I checked the fuel line size today while the car was on the lift. They are .31" outside diameter so they are 1/4" lines X2. 1/2" of fuel line! Also, There are bends in the lines but no real kinks that I could find. The system looks pretty efficient while maintaining clearance from hazards.
 
#104 ·
Thank you for taking the time and helping the community with this - that's greatly appreciated! It's also great to see that the factory lines are plenty sufficient for all but the most extreme setups.

I just want you to explain your open ended question.
:confused: I didn't know that I had an open-ended question, brotherman? Basically, I was asking for was what your power #s were in Actual, and what your injector duty cycle was showing. I don't need your logs, but I figured it would be a good "treat" for the community here to have various comparisons of individual cars. Often, on the various forums I frequent, I have put up tons of logs, for countless amounts of various vehicles I have tuned over the years, of the power breakdown in small rpm increments, along with the datalogs, while explaning the findings, so everyone can study and develop an understanding of what all these various vehicles are capable of, and to help steer them in the proper direction for current and future modifications. I plan on that here, too. The more we have contribute, the closer, stronger, and more knowledgeable this community becomes.

I have a close friend, that is an Admin/Mod on ModularFords, named black2003cobra (Eric), that I will see about getting to contribue here (as he's able), so to help contribue an additional style of tech. He's an engineer by trade, and a pure genius when it comes to calculations for vehicles. He can take the datalogs, backcalculate them, throw in formulas out of his head (very complex ones that I often have to research from my college days, lol), and present an amazing scientific explanation. I've made a new thread located below with examples of his work:

http://www.cadillacforums.com/forum...es-forum-2009/217634-tech-black2003cobra.html

And so not to confuse some here, the MAF calibration, IAT sensor, MAP, O2's and all other important sensors work in concert through the ECU/tune to compensate for weather and altitude changes. Hence the MAF! (and not speed density or carburetion.) Set it and forget it.
What you stated is pretty much right on! However, to go a bit more indepth GM actually uses a hybrid MAF/SD base measurement (many of the Oz cars are only SD, however). On the CTS-V2 calibration, like most all other GM Gen3/4 OSs, the system goes to a pure MAF measurement (mostly) above 4000 rpms (the VE system is used in transitional phases at this point). The difference, as you know, but others might not know, is that GM went to more complex predictive filter algorithm that combines the MAF, VE, MAP and TPS transient information. In a nutshell, it's all divided up into many zones, with a coefficient for each zone to form an equation for the system to calculate the VE value (versus a lookup within a traditional table, like the Gen3 processors, and early Gen4 systems). This is very similar to Ford's system in the PowerPC vehicles (most all 2004+ Ford vehicles, including 2005+ Mustangs. Here's a few good reads for those who want to understand the VE system on both the Gen3 and Gen4 pcms:

Gen3: http://www.hptuners.com/forum/showthread.php?t=2359
Gen4: http://www.hptuners.com/forum/showthread.php?t=8490

Also, either system can be simply set to pure MAF mode only, as well, and many tuners have resorted to this method in the past few years. Those of us who tune this new VE system generally use "EQ <> VE" software, which can be found here (latest version is 3.5):

http://www.hptuners.com/forum/showthread.php?t=20539

Some know this, and some don't, but EFIL has these calculations built in for you. It is rumored that HPT will have this in their upcoming 2.24 release (or eventually).

James (RWTD) nice to see ya working on more late model GM Stuff! THis is Mike from G-Force!

On my personal 09 A6 V i just completed a round of mods that netted me 588 rwhp corrected and 604 rwhp uncorrected (actual rwhp)
Mike! Wassup brotherman? I was trying to call you a few weeks ago, but I didn't have your # with me (left my cellie at da house). I'll catchup with you soon. BTW, BRUTAL #s on your car! AWESOME!

(adjust for ethanol content by ensuring the values in the stoich AFR table are accurate so they can compensation for % alcohol)
I'm glad you brought this up, so others can take note! Too many are NOT doing this, and relying solely on the Adaptive system to do this job. Yes, allowing the Adaptive system to do this job will work, but it's not the best method.


Everyone, I hope this all helps!

James
 
#98 · (Edited)
I just got done talking with Dustin on the phone, and here's an email he sent to me earlier today.

James,

Things are good, staying busy. We're feeding boosted power to the FPCM. We’ve run it up to 20 volts, and we’ve made 650rwhp with no real drop at 19 volts.

By the way, there is no real spike in the amp load since the MSD turns on progressively. We ramp up to 16.5 volts for stock SC kits, at around 5psi of boost, so it’s a slow ramp from 14 to 16.5. Hobb switch styles instantly turn on, and charge the system, as they're basically just amplifiers.

We’ve had 0 failures!

Thanks,
Dustin
When he states Hobb switch styles, he's referring to a design like the KB BAP. Also, the Whipple kit has a harness that plugs into the FPCM fuse panel and replaces the stock 20 amp fuse, so it goes BEFORE the FPCM. As you can see, they have ran it up to 20v into the Camaro FPCM without any issues of it overheating. I also do not see any reason why the CTS-V2 and ZR1 FPCMs can't either, but that deserves more attention and discussion before I blindly state otherwise. On the CTS-V2, Jesse states the limit being 14.3v max without overheating the FPCM. Potentially this is the limit of the factory FPCM attempting to drive twin pumps (the Camaro only has 1), and is understandable, as this has occured in the Ford world with the '03-'04 Cobras attempting to upgrade from their factory pumps to GT40 supercar pumps, all while still using the factory FPDM (either an upgraded FPDM is used from mjchip, or dual FPDMs are used, just like on the GT40 from the factory). Jesse, do you have any additional information you'd like to share with the community here in regards to LPE's voltage findings you speak of (they are claiming on their site that the max is 14.8v, due to the current draw)?

All in all, if the MSD Pump Booster can be used on the CTS-V2 and ZR1, just how it can be on the Camaro (pre-FPCM), then this would be a very inexpensive method of increasing the maximum range of the factory pumps (for those needing such), while allowing the FPCM full control still over the voltage input to the pumps (just like on a Ford with their FPCM arrangement), and allowing for proper fuel pump voltage delivery, thus pressure control. It still doesn't solve the factory injector limitation of the CTS-V2's max 4.5 bar (65.x psi) fuel pressure. However, as we've already discussed, replacing the factory 4.5 bar relief valve off of the pump assembly to one from say a ZR1 (6-bar, 87.x psi), or with the solid plug that ADM supplies, would allow an additional factory injector headroom of 100+ rwhp Actual. So two simple updates would pretty much solve 99% of those wanting to make power up to 700 Actual (Uncorrected).

Regards,

James
 
#99 ·
James (RWTD) nice to see ya working on more late model GM Stuff! THis is Mike from G-Force!

On my personal 09 A6 V i just completed a round of mods that netted me 588 rwhp corrected and 604 rwhp uncorrected (actual rwhp)

Mods were 9.55 lower and ls9 cam. Boost was 14 psi. I too noticed the drop to around 51 psi. But the pressure holds at 51 psi. I used Shorty siemans 63lb injectors (with the correct injector data:shhh:) and set commanded wot fuel to 11.4 and tuned the MAF to get there. 50psi and a 63lb injector is safe enough for me!

Ive been beating the crap out of my V with no issues.

Heres a vid.

 
#101 ·
James the kennebell boost a pump cant be turned all the way up in our cars, We install them PRE fpdm like you say, but you can only turn the dial to 2-3 on the selector. If you go higher it WILL reset the car when you enter 4psi and higher. It happens on EVERY ctsv. The kennebell boost a pumps are only good for 40 amps as are most others. The Current draw of the pumps is much larger than that 60+ while going to full pulse width.

Without programming the fpdm.


Having a ramp in controller might help, but when i contacted the bap people at the time of testing all this, none seemed interested in supporting the 09 up V...
 
#108 ·
Hi,

In reading this thread, I have a question. Early in the thread, you state that the fuel pump is variable speed. Are you certain about this? From the tune side, I see that while the car has a FSCM, i see that PWM is disabled.

I am wondering how, then, does GM provide for variable pressure? Is the pressure regulator controlled by the FSCM to accomplish this?
 
#109 ·
Yes the fuel pressure is controlled by the fuel pressure control module. The ecm only tells it what Pressure to make. Then the FSCM changes the pulse width to the pumps to make the fuel pressure it needs. It will adjust the duty cycle to maintain the set pressure. It learns how much it needs and at what time also. So the first time might have errors, but the next time it will be closer to correct... But it can only go so far.
 
#110 ·
OK, then, this is where I am confused.

In the stock tune fro GM on the '09 CTS-v, it shows that there is NOT a variable speed pump, and further, the table that defines the PWM is set to all 90's.

Does the FSCM have it's own parameters that it runs, which make the ECM parameters moot?

And, even if it were PWM, wouldn't installing a Boost-a-Pump not work? Meaning, that, even if you boosted voltage, the PWM would be scaled back to make the pressure it wants to make?
 

Attachments

#111 ·
If you look at F0585 I put in that you can see if the car has a fscm, Then the numbers lower tell the computers on the buss what the ecm is asking for during each fuel flow commanded. For example, When the temperature of the engine is 1 degree outside, the car is going to be asking for F0588 which is a fuel rail pressure of 60PSI. Then as the temp gets to 76F then it will start to follow what it was supposed to be depending on flow commanded. So say low at idle, then the computer just puts out on the buss that the commanded pressure is 36psi...

Then at that time, the FSCM which is being reported to because you have F0585 turned on, Will listen to that requested fuel pressure value, then it will adjust pwm to the pumps to achieve that psi goal..

There are safey factors built in though, and also voltage limits that make it so you cant use the boost a pump like on the previous years if it is a direct on off full power. "until i see one personally on a car and how it is hooked up, and fully working all the way turned up, my saying stands"

The fscm also will only allow you to ask for a certain fuel pressure before it will ignore the request and go back down to a safety value. So say you ask for 70psi, it wont give you 70psi, as it cant. There is an internal bypass valve that opens up in the tank that will bleed off access pressure. You can cap this a little bit to restrict flow, to give you 70@wot, but it is hard on things.
 
#114 ·
the more i read about V2 fueling,, the further i get lost in the details,,
my 09 V is modified and previous owner doesn't seem to recall any of fuel upgrades his tuner did to the car,, in the other hand,, the car doesn't run properly and have a lot of the symptoms of improper ecu/ifr calibration mentioned here and other related threads,,
the car auto shifts bad,, goes rich despite how bad we raped PE/VE/MAF tables,, even with 15psi of boost with a TVS2300,, the one thing i noticed that pumps sounds noisy compared to stock V,,
how can i clean this mess?
 
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