StreetSpeed’s DD 500+ MS6 Build

[Enki]

There absolutely is a VVT position PID. This could also potentially be just an especially loose VVT solenoid that can't run well at idle due to lower oil pressure.

Also, If you are on gas or the RPM is not coming down to idle, the rail pressure should always be above 400. If you are WOT and it drops, that's going to be an issue; no need to look at logs to determine that it's an issue.

 

[StreetSpeed6]

There absolutely is a VVT position PID. This could also potentially be just an especially loose VVT solenoid that can't run well at idle due to lower oil pressure.

Also, If you are on gas or the RPM is not coming down to idle, the rail pressure should always be above 400. If you are WOT and it drops, that's going to be an issue; no need to look at logs to determine that it's an issue.

I think for this reason alone I am going to pull the itfp and check it out and then go from there. I run 10w30 and it sits around 20psi at idle and normal driving it is around 40psi and then obviously increases up into the rpms. Would you think that the stock fpr could cause this in any way? It is factory and my car obviously is well into the 200k+ mile range. I was just worried it was doing its job until it wasn't somehow idk.

 

[Enki]

Only if it's dumping pressure. The HPFP needs flow more than it needs pressure; pressure helps prevent cavitation inside the pump at higher RPM, but as long as it's being fed, it ultimately doesn't care.

I'd wager moderate flow could probably get away with as little as 10 PSI, so It seems likely to me that between the HFPP and the gas tank exists a problem. Maybe the factory surge tank isn't staying full for some reason?

 

[Crazycanadian]

First off wow you seem to be full of diagnosis knowledge so thanks lol Secondly, that's what we were trying to do with the voltage. So using desired vs actual hpfp pressures could possibly be used or that isn't enough?

The ECU reads the voltage signal and translates it directly to your actual pid (based on sensor calibrations, which isn't something that gets changed in this case while tuning).. So having the Actual vs Desired pids will help a lot without going into lab scope stuff...

The laptop version of ForScan is free. The Android or Apple versions are $10 or something like that.. you just need to buy a good OBD dongle to use them.. It doesn't care if your ECU is tuned, so it wont ruin anything and doesn't require uploading to your cars ECU.. I suggest getting a dongle off their recommended list on their website.
The down side to this program, it's not the most intuitive to use.

 

[Crazycanadian]

I think for this reason alone I am going to pull the itfp and check it out and then go from there. I run 10w30 and it sits around 20psi at idle and normal driving it is around 40psi and then obviously increases up into the rpms. Would you think that the stock fpr could cause this in any way? It is factory and my car obviously is well into the 200k+ mile range. I was just worried it was doing its job until it wasn't somehow idk.

20 PSI is low.. it should be closer to 30 psi at idle.. by 2500 rpm you should be up to 60psi..

 

[StreetSpeed6]

20 PSI is low.. it should be closer to 30 psi at idle.. by 2500 rpm you should be up to 60psi..

I used to think that but then I realized that from what I could tell a lot of vehicles operate between the 20-60 or 70 psi range. Any higher and they leak and blow seals etc.

 

[JohnnyTightlips]

Part of me still thinks the fuel pressure sensor is not working properly. It should be commanding 430ish psi at idle and in the logs you can see it reading 800 -1300 when the car is hot. HPFP Desired Pressure A table in the tune is commanding 430 psi at idle — so 800–1300 psi reported at idle isn't just high, it's 2–3× above what the ECU is even asking for. The car then tries to compensate for a fuel pressure that is not actually getting and it is creating a domino effect. LTFT in log one is like spot on and then as the car gets hot it goes to +8%. Seems like the ECU is seeing the pressure drop on the afr side but not getting it from the actual sensor and it keeps trying to fix the bad data from the sensor. I would def check the LPFP and make sure that is all good as well. I checked the tune tables for VVT and all that and it is all normal as we have not done anything crazy there.

 

[StreetSpeed6]

Part of me still thinks the fuel pressure sensor is not working properly. It should be commanding 430ish psi at idle and in the logs you can see it reading 800 -1300 when the car is hot. HPFP Desired Pressure A table in the tune is commanding 430 psi at idle — so 800–1300 psi reported at idle isn't just high, it's 2–3× above what the ECU is even asking for. The car then tries to compensate for a fuel pressure that is not actually getting and it is creating a domino effect. LTFT in log one is like spot on and then as the car gets hot it goes to +8%. Seems like the ECU is seeing the pressure drop on the afr side but not getting it from the actual sensor and it keeps trying to fix the bad data from the sensor. I would def check the LPFP and make sure that is all good as well. I checked the tune tables for VVT and all that and it is all normal as we have not done anything crazy there.

What would cause the sensor issue you think? The sensor itself or the wiring? I'll check the ITFP for sure.

 

[StreetSpeed6]

The fuel rail sensor is technically what started all my issues. I may try to get ahold of an original part number sensor. JT sorry but the ones you had given me were in the bag in my garage when it got destroyed unfortunately. I'll try to get ahold of another one to see if it makes a difference.