Falling on its face

[brianbr]

What tune is in it, Edelbrock? Did you change something recently and this is a new issue?

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[Torinate]

Nope. No changes. Just out of the blue.

Lund tuned. Never an issue. Runs smoother than stock did.

Thought about sending them a log as well but figured I’d ask here first if anything was obvious. I’m going to do another log this weekend if it doesn’t rain and have another look.

I don’t see anything obvious as to why it occurred and fuel trims look ok as does timing. KnockR didn’t register for some reason - 0’s across the board but SAFTOT showed total timing so I know it’s adding advance timing over base timing. May need to rescan vehicle not sure. The gauge shows the KnockR value though when not logging.

Maybe it’s all in my head lol. I know that pedal commanded and rate at which I command it makes a huge difference in how the car feels. Huge difference in rolling into throttle slowly versus a sharp jab on the pedal.

I know that when I did these logs I was much more deliberate with my pedal even though I only went 50% then like 75% and then more.

I did a smoke test for vacuum leaks as well and all looked great so no issue there. Plugs looked great. No codes.

Stumped but happy!?

I would think if it was a cat problem clogging it would have been noticeable performance wise on any of the runs and not intermittent. Whereas if it’s a fuel pump that’s going it might be a sporadic thing. At least, those are my thoughts.

 

[Jackson1320]

After you disconnect the battery it’s going to run rich until the computer read learns to trims so that’s normal. still sounds like fuel issue. the pump could be wearing out And not keeping up after driving for a while and the pump warms up. i would not worry about the cats normally when they plug up or start to You will be able to notice even at highway driving. It’ll feel sluggish like it has no power even regular driving And lots of times when you shut the car off you’ll be able to hear pressure in the exhaust leaking out. I would guess fuel for some reason could be O2 sensor could be bad pump

 

[Jackson1320]

Have you logged your fuel pump duty cycle. Can your device read preset codes? it’s a code that the computer has detected an issue with but not quite enough to set the light

 

[Torinate]

Have you logged your fuel pump duty cycle. Can your device read preset codes? it’s a code that the computer has detected an issue with but not quite enough to set the light

I have an nGauge, so whatever it can read is what I have. One of my PIDs that I monitor is fuel pump duty cycle. Typically I will see 29-30 cruising and then 49 when the BAP triggers.

Good to know about resetting fuel trims etc.

That’s what I figured as far as cat issues. I’m thinking what you are with the fuel pump. Going to keep an eye on it and see.

 

[Jackson1320]

I have an nGauge, so whatever it can read is what I have. One of my PIDs that I monitor is fuel pump duty cycle. Typically I will see 29-30 cruising and then 49 when the BAP triggers.

Good to know about resetting fuel trims etc.

That’s what I figured as far as cat issues. I’m thinking what you are with the fuel pump. Going to keep an eye on it and see.

With the bap on your only seeing 49% duty cycle?

 

[Torinate]

With the bap on your only seeing 49% duty cycle?

Yes.

I’m told that’s actually double what it reads - so 98%. I wish there was a better way to monitor fuel and fuel pressure other than watching AFRs.

Is there another PID I can watch or log that will show better?

 

[engineermike]

There are pid’s available for lift pressure, desired lift pressure, gdi rail pressure, desired gdi rail pressure, lift pump duty cycle, and gdi pump duty cycle. Both pumps are on feedback control loops.

Regarding the lift pump, 49-50% is max duty cycle, depending on how it’s tuned. I believe in the stock and roush tunes 49 is max. If you’re seeing 49 or 50, it’s at the limit. I have a bap and actually tuned the control loop for it and I went from no bap seeing 50% dc and pressure falling to 55 psi, to now seeing 46% duty cycle and pressure at 75+ psi.

Regarding the gdi pump, 100% is 100%.

 

[Torinate]

Is the GDI stuff for 18+?

Mine is a 16. Using nGauge to log and monitor PIDs. The one I’m using is the fuel pump duty cycle and is 28-30 cruising and 49. under boost.

 

[K4fxd]

I bought a back-pressure test kit and measured 15 psi on both sides at 7500 rpm and wot, which I believe to be normal.

Wow 15 PSI back pressure is a TON.

 

[Torinate]

Wow 15 PSI back pressure is a TON.

What should it be? How is this measured even?

 

[engineermike]

Is the GDI stuff for 18+?

Mine is a 16. Using nGauge to log and monitor PIDs. The one I’m using is the fuel pump duty cycle and is 28-30 cruising and 49. under boost.

My mistake. Gen2 doesn’t have a fuel pressure sensor or feedback control. You’d have to manually check it.

 

[engineermike]

What should it be? How is this measured even?

Ive measured as low as 5 psi and as high as 50 on a turbo setup. I believe lingenfelter said to keep it below 5 psi but it’s not quite as critical on a positive displacement blown setup since the flow is determined by the supercharger size and speed.

I can say that it takes over 40 hp to push the exhaust out at 15 psi at 7500 rpm.

 

[engineermike]

Wow 15 PSI back pressure is a TON.

Ive since measured downstream of the cats and got 13-13.5 psi at 7500 rpm. That means the cats are actually only taking 1.5-2 psi pressure drop.

 

[K4fxd]

the cats are actually only taking 1.5-2 psi pressure drop.

Thats good to know. I saw 15 and started getting out my reciprocal saw.

Ive since measured downstream of the cats and got 13-13.5 psi at 7500 rpm.

Thats still a lot, but to lower it it would get louder.

I see you are boosted,

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