COS5 Turbo 5.3 falling on it face off of idle.

[C450]

Hi guys, I have bought a tune and can't seem to figure out what is keeping it from revving. The combo is a 5.3 running on a COS5 tune, TH400, MP70 turbo, 2 bar MAP, Boost referenced fuel pressure regulator, 60 lb/hr injectors @43.5 psi, LS7 cam, 1.7 rockers.
The truck will start and idle just fine but once you try to open the throttle it just falls on its face and dies. I do not yet have a wide band o2 sensor. The data I've looked at on the data log all looks fine to me. I'm assuming I'm not looking at the right information. Just to make sure it wasn't the engine itself I flashed a stock tune back into it and the truck would not idle but I could rev it up. I was hoping someone here to take a look at it and notice anything I'm missing on this base tune. I would greatly appreciate the help.


2002. 5.3 MN6 COS5 Adam Divine Basetune_0000 newest.ctz

[C450]

I have just replaced my 2 bar ebay MAP sensor with a genuine GM Cobalt SS sensor. Still no difference in how it ran but I did finally notice that when the truck is missing while at idle, it's because the injector duty cycle goes from 1% to 0%. When I get into the throttle the duty cycle may come up to 2 or 3% and then back to 0%. Also, I know my injectors are rated to flow 60 lb/hr at 43.5 psi. I adjusted the fuel pressure using a gauge and with key on engine off set the pressure at 44 psi. So this is where the gauge is at while running at idle.


Also, here is a log of it running in the driveway.
Log 6-23-15 Injector duty cycle going to 0.efi


Again, thank you for looking over this data and any help is greatly appreciated.

[joecar]

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I adjusted the fuel pressure using a gauge and with key on engine off set the pressure at 44 psi.

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If you do it like that (KOEO) the fuel pump has to be running constantly.

[ScarabEpic22]

Also GM uses 58psi for fuel systems, Ford uses 43.5. I have never run a GM LSx at 43.5psi, just left it at 58psi and adjusted the IFR accordingly (60lb/hr at 43.5 is more like 82lb/hr at 58psi). This difference in injector size would cause the PCM to try and reduce pulsewidth to maintain idle AFR.

Does your boost-referenced FPR need a flat IFR or a sloped IFR? Return or returnless fuel system?

[joecar]

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Also, I know my injectors are rated to flow 60 lb/hr at 43.5 psi. I adjusted the fuel pressure using a gauge and with key on engine off set the pressure at 44 psi.

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Erik brings up a good point... GM FPR's are set to 58 psi, so GM has scaled the IFR from rated pressure (43.5 psi) to 58 psi.

C450, when you set your FPR to 44 psi, did you then scale your IFR to 44 psi...? Also, is your FPR manifold referenced or un-referenced (see Erik's question... boost-reference requires flat IFR, un-referenced requires sloped IFR (goes as squareroot of pressure across injector))...?

[johnv]

I agree with above, fuel pressure and injector data are probably where your problem lays, post up your tune otherwise we are just guessing.

[C450]

Also GM uses 58psi for fuel systems, Ford uses 43.5. I have never run a GM LSx at 43.5psi, just left it at 58psi and adjusted the IFR accordingly (60lb/hr at 43.5 is more like 82lb/hr at 58psi). This difference in injector size would cause the PCM to try and reduce pulsewidth to maintain idle AFR.

Does your boost-referenced FPR need a flat IFR or a sloped IFR? Return or returnless fuel system?

Ok I totally misunderstood the injector flow rate. The injectors I purchased were rated at 60 lb/hr @ 43.5 psi. Therefore I assumed that they had to be ran at 43.5 psi. I have since then increased the fuel pressure to 55 while running. I do have a return line in my fuel system. My IFR is flat. So I have the IFR set at 68 lb/hr. The truck is running better but it's still plenty rich. Should I set IFR to 82?

[C450]

I agree with above, fuel pressure and injector data are probably where your problem lays, post up your tune otherwise we are just guessing.

I posted up a tune and datalog in the first two post but I'll post the updated tune. The data shows that it is running plenty rich. At part throttle is tries to make some power but when it goes into OL-Drive it falls on its face. Doesn't gain any RPM. This is the first time I seen the OL-Drive show up on the scan tool so I'm going to read more into that. I only have a 2 psi spring in the wastegate so I'm not trying to burn it down. Since it is running better, would I be able to run the Auto VE?
2002. 5.3 MN6 COS5 Adam Divine Basetune_0003 6-24-15.ctzLog_6-24-15 running better.efi

[C450]

Erik brings up a good point... GM FPR's are set to 58 psi, so GM has scaled the IFR from rated pressure (43.5 psi) to 58 psi.

C450, when you set your FPR to 44 psi, did you then scale your IFR to 44 psi...? Also, is your FPR manifold referenced or un-referenced (see Erik's question... boost-reference requires flat IFR, un-referenced requires sloped IFR (goes as squareroot of pressure across injector))...?

Joecar, no I did not have it scaled appropriately. I increased the fuel pressure to 55 running with the vacuum lined hooked up but I need to find the correct information on scaling the injector correctly. I know I shouldn't be trying to learn all of this on a turbo LS swapped truck but I am learning and I do appreciate everyone's help.

[joecar]

Engine idling, temporarily remove FPR reference hose (block off to prevent airleak into manifold), set FPR to 58 psi; reconnect reference hose when done.