FRP dropping, FDM failure? (w/datalogs)

hawkeye93 · September 05, 2016, 03:02:40 PM

Today I went to datalog my latest Unleashed revision, and on both of my 2 runs, the car went into limp mode. Didn't get a DTC until after I loaded an older tune, and I got a P0305 (misfire on #5) right on startup. Looking at my logs, I see that my fuel pressure is dropping to below 1000 PSI. Is this indicative of an FDM failure, or could it be related to my tune? Bad gas? I have noticed stumbles with this tune when I wasn't logging.

91 octane tune, running 92 octane gas

ZSHO · September 05, 2016, 03:56:49 PM

I would start off by checking the front middle #5 plug and check the electrode.. . are the plugs the the MC- Sp-534's ?any noticeable smell of gas? Z

FoMoCoSHO · September 05, 2016, 04:07:39 PM

Have you noticed any FRP drop prior?

Did you flash back to stock and take a log to see if the behavior carries over?

hawkeye93 · September 05, 2016, 04:26:03 PM

Quote from: ZSHO on September 05, 2016, 03:56:49 PM
I would start off by checking the front middle #5 plug and check the electrode.. . are the plugs the the MC- Sp-534's ?any noticeable smell of gas? Z

Plug looks OK (cell phone doesn't take great pictures), only the slightest hint of gas. Plugs are NGK 6510s, which I understand are equivalent to SP534s.

Quote from: FoMoCoSHO on September 05, 2016, 04:07:39 PM
Have you noticed any FRP drop prior?

Did you flash back to stock and take a log to see if the behavior carries over?

I have noticed "stumbles" under load. I haven't flashed back to stock, but I did flash to a previous tune revision. Haven't driven it hard since. I'll go back to stock and give that a try. When I first got the car, it did go into limp mode once while cruising on the highway. I think that was with my first Unleashed revision. Pulled over, stopped & restarted the car, and it was fine.

ZSHO · September 05, 2016, 05:03:49 PM

Did you check the relays,fuses by by the engine compartment....try swapping them around. Z

SHOdded · September 05, 2016, 05:08:04 PM

How long (miles) have these plugs been in the car, and what is the gap? More often we see a fueling issue than an ignition issue once plugs have been changed and gapped properly. How many logs have you done on the latest revision prior to the limp home incident occurring? If there are no codes, it could be the car adjusting to the tune, as it seemed to do before.

hawkeye93 · September 05, 2016, 05:21:33 PM

Quote from: SHOdded on September 05, 2016, 05:08:04 PM
How long (miles) have these plugs been in the car, and what is the gap? More often we see a fueling issue than an ignition issue once plugs have been changed and gapped properly. How many logs have you done on the latest revision prior to the limp home incident occurring? If there are no codes, it could be the car adjusting to the tune, as it seemed to do before.

About 2K miles on the plugs, gapped @ .030. These were my first recorded logs with the new revision, but a few days ago, I did notice (after one of the stumbles), that I had 10* of spark retard (see Min value in photo). I assume that's a result of knock?

Quote from: ZSHO on September 05, 2016, 05:03:49 PM
Did you check the relays,fuses by by the engine compartment....try swapping them around. Z

Haven't swapped any fuses or relays yet. I'll have to look up which ones are which.

SHOdded · September 05, 2016, 05:24:33 PM

could be really bad gas for sure. same station as usual? top tier? OAR looks good tho ...

Load is hitting 2.0 after you reach 40 mph. I remember AJ pointing that out as an issue, looks like Torrie will have to dial it in further.

hawkeye93 · September 05, 2016, 05:32:28 PM

Gas is 92 octane premium from Fleet Farm, a sort of general store here in the midwest. Don't know if it's Top Tier. I've been buying there because it's hard to find 93 around here.

SHOdded · September 05, 2016, 05:50:23 PM

There are variances between LPFP pressure desired and actual upon demand. Possibly a FPCM issue? I haven't seen both the desired and actual logged before, at least recently, so I have nothing to compare against ... Almost like the LPFP is in overdrive, shutting down the HPFP?

AJP turbo · September 05, 2016, 07:02:57 PM

I will try an ld look later but do your logs have wot in them?

You might not have anything wrong at all....if you are hitting 2.0 load then without looking at a log i would guess you are just out of fuel...if that 2.0 happens lower than 5k and or is a spike in load then your fuel system is simply taxed.

That is usually a symptom from having the throttle wide open during shifts

hawkeye93 · September 05, 2016, 07:14:22 PM

The logs are WOT from a dead stop, no brake boosting. Sport shift mode, AdvanceTrac off, climate control off. For my datalogs, I generally try to get a 0-100 run at WOT.

What does load 2.0 indicate?

AJP turbo · September 05, 2016, 07:23:43 PM

Quote from: hawkeye93 on September 05, 2016, 07:14:22 PM
The logs are WOT from a dead stop, no brake boosting. Sport shift mode, AdvanceTrac off, climate control off. For my datalogs, I generally try to get a 0-100 run at WOT.

What does load 2.0 indicate?

2.0 is more than likely over 20 psi..maybe 22 ish psi...too much boost basically....ive noticed that actually the fuel system is pretty robust and 20 psi at high rpm is not the problem but when there is fast load spikes and fuel demand goes up fast for some reason the pressure drops....if load is controlled better the fuel system seems to keep up better

Ive seen 1.7 load kill rail pressure when load spikes to 1.7 but if 1.7 load is sustained smoothly that is no problem for the stock fuel system

hawkeye93 · September 05, 2016, 08:04:12 PM

Just got an update from Torrie, said he took the boost down. I'll give it a try tomorrow.

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AJP turbo · September 05, 2016, 10:07:31 PM

Hawk you have a couple different things going on that can make it hard to isolate the problem from those logs...Your boost is kind of aggressive...In one log you had spikes to 240KPA or 20 psi. Couple that with a LAMBSE or commanded afr of .75 which based on the stoic of the fuel in your tune is like 10.5 air fuel ratio

That boost with that commanded afr will deplete the rail of pressure. When you command a rich afr it takes more injector duty cycle to achieve that and rail pressure falls because injectors are wide open and spraying as much fuel as possible.

You have some knock retard....Maybe from low fuel pressure.

also you have a discrepancy bank to bank as far as stft's and measured AFR. They are more different than what you should normally see BUT that could be a product of the super rich commanded afr and or the low fuel pressure

The stft for bank 2 is wonky and jagged.....Could be from what I said above and trims are adjusting rapidly because pressure is low OR the bank 2 primary o2 sensor is bad. But a bad O2 sensor won't cause bad fuel pressure.

Command lower boost and see if fuel pressure improves...That will tell you if there is a fuel delivery problem which I suspect there is not....Then once you have fuel pressure see if afr and stft balance from bank to bank improves, that will tell you If you have a bad o2 sensor.

That's all I got