09 Z06 Blown odd behavior at wot on dyno

[IDRIVEAG8GT]

don't rape the PE table. The problem with this car is a funky MAF sensor, or placement of it.... I've gotten away with 23psi boost on a 427 via a 50% scaled MAF tune.

[HoP]

don't rape the PE table. The problem with this car is a funky MAF sensor, or placement of it.... I've gotten away with 23psi boost on a 427 via a 50% scaled MAF tune.

/agreed.

Looking at my last log you will see that the INJ DC went through the roof, which was a result of having 20-30psi of fuel pressure on a return style system. However it was still pegging the MAF even after a scaled 50% tune.

[IDRIVEAG8GT]

/agreed.

Looking at my last log you will see that the INJ DC went through the roof, which was a result of having 20-30psi of fuel pressure on a return style system. However it was still pegging the MAF even after a scaled 50% tune.

Get more pressure, then you can turn the MAF way down.

[Asylumwarp]

How do you turn the maf way down? Just up your psi, and lower the maf as needed for fueling adjustments?

If thats the case, wouldnt that screw up your lower rpm region?

[IDRIVEAG8GT]

How do you turn the maf way down? Just up your psi, and lower the maf as needed for fueling adjustments?

If thats the case, wouldnt that screw up your lower rpm region?

Exactly, and no not really if your regulator is boost referenced. It may mess with it a bit, but is still easily tuned using the MAF.

You achieve good results by flat lining the IFR table, setting the regulator to 58 psi, and then make sure the pump can keep up. I run anywhere from 70-78 psi fuel pressure according to the regulator with twin Walbro 255's. One runs all the time, the other triggered by a Hobbs Switch set at 3 psi, which is reverse fed power by a Kenne Bell BAP in case I ever need to turn it up or down.

[Asylumwarp]

What about if fuel pressure is good, and the injector duty cycle is above 80%? Im seeing 105% at 5200 but have good a/f numbers on wideband, somewhat rich. Im not leaning out like i am losing fuel pressure, and now with the scaled tune, it didnt lean out at high rpm, it stayed rich, just slapped my inj cycle...? I also noticed hop is running 125%, if were scaled tune by 50% and telling the Injector flow is half of normal, in my case 56.42 is now 28.21, is 105% now really 52.5%?

[IDRIVEAG8GT]

What about if fuel pressure is good, and the injector duty cycle is above 80%? Im seeing 105% at 5200 but have good a/f numbers on wideband, somewhat rich. Im not leaning out like i am losing fuel pressure, and now with the scaled tune, it didnt lean out at high rpm, it stayed rich, just slapped my inj cycle...? I also noticed hop is running 125%, if were scaled tune by 50% and telling the Injector flow is half of normal, in my case 56.42 is now 23.21, is 105% now really 52.5%?

Well, no you need more fuel pressure. Remember, for every 1 pound of manifold pressure=1 lb lost of flow. Therefore your injectors would only flow 51.5lb/hr @58psi rail pressure, or 52.5lb/hr @59psi rail pressure. You can quickly see how crappy things get without ample fuel pressure to excessive boost. My ID1000's in the truck flow 114lb/hr @58 psi rail pressure, and my Injector Duty Cycle hovers around 55-60% at WOT with 70+psi rail pressure.

Also, corrected at 22 lbs of boost with a 50% scale, my MAF levels off at about 60 lb/min.

Even though your AFR is good, you're having to command the injectors to stay open for a ridiculously long time to get your AFR right.

I used to run LS9's in my G8 at 112% INJ DC at a constant 58psi rail pressure with no issues whatsoever, till I went to a different fuel system. Now LS9's are at 80% INJ DC making 612WHP on pump gas.

[Asylumwarp]

It has a 1:1 boost referenced vacuum regulator at 58psi. Is it time for more fuel volume? I can adjust the psi, but heck, i may be running low on psi, were still not sure as we are installing a rigged windshield psi gauge to check under boost.

Or since im commanding the right afr, i have the fuel i need, do i need bigger injectors?

[Asylumwarp]

Also this is a 6.0 lq9 with l92 stage 2 cnc heads with a ls9 reground cam. Making 8 psi on a whipple 2.9l, 52lb bosch replacement ls9 injectors.

[IDRIVEAG8GT]

Also this is a 6.0 lq9 with l92 stage 2 cnc heads with a ls9 reground cam. Making 8 psi on a whipple 2.9l, 52lb bosch replacement ls9 injectors.

You're most likely running out of fuel pump, monitor it, tell me where your at, and we'll go from there.

[Asylumwarp]

Lost fuel pressure. Updating fuel pump with inline or a1000 intank pump. Already have -6an lines with a Aeromotive return style 1:1 regulator, we are at 58 at idle, and 66 under boost. At 5200 or 84% duty cycle, the psi falls off. Not badly, as we already upgraded to a intank stealth aeromotive 340lph@40psi stock pump, more like 260lph at 65ish.... So we dont lose much pressure, but losing is losing. Once this is fixed, i'll see what my IDC looks like after solid pressure. Customer had spoken with aeromotive, and aeromotive said their "intank" pump would handle this power level. They were wrong.. Customer was upset he already spent the money, so i recommended a booster inline pump to compensate for the problem. This also fixes having to pull the fuel cell. Makes life easier.
I doubted the fuel system and injectors from the start when i heard the build. This did not suprise me, but sure did the customer after they were confirmed it "should" be ok, but "call" if not!
This took the customer installing a dash mounted hard line -4an fuel pressure auto meter gauge to "verify" for himself. In my opinion, any build like this should have this installed anyway along with oil pressure, normal Coolant ECT, WB02, Boost, Head temp coolant sensor, and EGT, but thats just me being cautious.. I like my auto meter gauges just for safety..

[Asylumwarp]

Ok update, HoP, this may or may not help you later in life also. We just got off the phone with areomotive, an engineer they said.. they said why are we stuck on running 58 psi? That was for a gm vaporlock issue on non return style systems. Since we are updated to a return style, he said we should lower our pressure to 40 psi, that gives us the needed room for the flow thats needed, but up our injector size to 72lb injector dynamics. The pump loses volume at high pressure. Lower our overall pressure to 40 and tune accordingly. While this makes some sense, we are gonna give it a shot i believe. The customer would rather upgrade injectors. I said ok, lets give this a shot.

[IDRIVEAG8GT]

Coincidentally, pumps do flow more at lower pressures, but 40psi under boost ain't gonna cut it.

[HoP]

Coincidentally, pumps do flow more at lower pressures, but 40psi under boost ain't gonna cut it.

Could do 40 psi and boost reference it.

[Asylumwarp]

We are getting some ID1000's and they recommended running a 12ga power wire to the pump, and relay isolate it. They said the stealth intank pump works great, just needs bigger power wire. Were gonna try that, we are boost referenced. If we need a booster pump, its still not out of question.

[IDRIVEAG8GT]

We are getting some ID1000's and they recommended running a 12ga power wire to the pump, and relay isolate it. They said the stealth intank pump works great, just needs bigger power wire. Were gonna try that, we are boost referenced. If we need a booster pump, its still not out of question.

HUH?! Unless this thing is going to be with me in the 1k rwhp range you do not need ID1000's! Try ID850's ID1000's hate any condition that's lower than 51psi, the 850's should be more suited to the task.

For the pump power supply, I think you're on the right track.

[IDRIVEAG8GT]

Could do 40 psi and boost reference it.

True, but not with gargantuan injectors.

[DSteck]

ID1000's hate any condition that's lower than 51psi, the 850's should be more suited to the task.

Uhhhhhhh, what are you talking about? Those core injectors come from a 3 bar application.

[IDRIVEAG8GT]

Uhhhhhhh, what are you talking about? Those core injectors come from a 3 bar application.

Personal experience. My set doesn't operate correctly at any lower rail pressure than that.

The banks recorded msec of open time starts jumping around and the idle becomes unsteady.

[DSteck]

If the delivered pulse width in the scanner is freaking out, you have something else going on. The injector itself isn't going to impact the pulse width shown in the scanner.

My rail pressure falls to 48 or so during hard decel, and they have no issues. I run 58 base.