I could use some help interpreting Torque app data

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guy48065

Joined
Mar 4, 2009
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60
Location
MI
My truck just got a reman engine (ATK) installed & I picked it up Tuesday.
2010 Traverse 3.6L
128k, bought 2/22 with 103k
Broke timing chain.

It's running fine with the rebuilt engine but there's a couple things I've noticed when watching real time data that are causing concern.
My fuel rail pressure maxxes out at 1700 where before it hit 2700psi. It's my understanding 2700 is normal.
My long term fuel trims are -4% and -7%.

I'm not clear whether the OBD2 data is telling me it's compensating for rich mixture, or it's displaying a lean condition--possibly related to the low fuel pressure.

In short I really don't know if I have a problem. It seems to be running 100% fine. No codes--but I've only driven 300 miles.


Screenshot_20230919-184736_Torque.jpg
 
I thought it was the other way around--short term trims can be high but long term should be near zero?
 
And should I be concerned about the low pressure to this direct-injected engine?
Should I be asking this in another section?
 
These apps are tricky. Is it normal? Is it a problem? It runs fine. Just leave it. That was my verdict after checking my truck a year or ago. My guess is injectors are no longer 100% balanced
 
My LTFT on my Accent were always really high . Got up to +10 at one point. It ran good and got good gas mileage. I noticed when I went and drove on the intestate at highway speeds the LTFT would drop into single + digits. The high numbers were when I was putting around and driving it like a diesel.

So in my case it's the less than ideal factory fuel mapping.
 
guy48065 said:
And should I be concerned about the low pressure to this direct-injected engine?
Should I be asking this in another seection?
Click to expand...

If you are really concerned, have a look at "demanded" "commanded" or "requested" fuel rail pressure and compare it to the measured value ............... you may need a better OBD dongle and software to do this

They will never ever be an exact match for extended periods of time, but it will tell you a much better story about the ECU's ability to control and monitor the fuel rail pressure that is super critical on direct injection engines.

Eg - had a Citroen DS5LS here this week with a funky HPFP ................... ran with difficulty from cold if at all - once up to temp it was as if normal ...............

Lots of moans about fuel pressure control and possible cat damage as a result in the ECU with the engine light on to warn you.

On modern ECUs you will most likely find the ECU will shout at you about fuel pressure regulation way before you can figure if there is a problem
 
"ECU will shout at you"
Is there a code for that?
I'm surprised that it seems to be running perfectly fine 1000psi below what it was a month ago.
What regulates the pressure from the HPFP? It's a mechanical pump... Is there an electronically-controlled regulator or is it the low pressure pump in the tank that is varied?
I'm guessing it's the former because the HP varies a LOT from idle to high rpm, but the LP only changes about 10psi.
 
guy48065 said:
"ECU will shout at you"
Is there a code for that?
I'm surprised that it seems to be running perfectly fine 1000psi below what it was a month ago.
What regulates the pressure from the HPFP? It's a mechanical pump... Is there an electronically-controlled regulator or is it the low pressure pump in the tank that is varied?
I'm guessing it's the former because the HP varies a LOT from idle to high rpm, but the LP only changes about 10psi.
Click to expand...
The ECU shouts via the EML light on the dash .............. once the ECU sets the engine light on the dash you will find a fuel rail pressure control fault code in the ECU

During your engine upgrade, there exists a possibility that the ECU's contents (MAPs, etc.) also got updated - something that often is overlooked when vehicles' operational parameters are compared................. this MAY explain your observation but not necessarily - there may be other factors involved

The lift pump in the tank supplies around 4-7Bar to the HPFP - HPFP may be mechanical, but the rail pressure is electronically governed by the ECU (MAPs, etc.) ............. read the rail has a return flow to the tank with a governing valve.

again

LvR said:
If you are really concerned, have a look at "demanded" "commanded" or "requested" fuel rail pressure and compare it to the measured value ............... you may need a better OBD dongle and software to do this

They will never ever be an exact match for extended periods of time, but it will tell you a much better story about the ECU's ability to control and monitor the fuel rail pressure that is super critical on direct injection engines.
Click to expand...
 
To get a general idea because everything involved simply cannot be typed up here.


 
LvR said:
The lift pump in the tank supplies around 4-7Bar to the HPFP - HPFP may be mechanical, but the rail pressure is electronically governed by the ECU (MAPs, etc.) ............. read the rail has a return flow to the tank with a governing valve.
Click to expand...
The HPFP used on this platform is an on-demand pump that has no return line back to the tank. Single plunger, driven off an extra lobe on one of the cams.
The video you linked is a diesel fuel pump.
 
guy48065 said:
I thought it was the other way around--short term trims can be high but long term should be near zero?
Click to expand...
The main job of the long term fuel trim is to keep the short term fuel trim as close to 0% as possible. The main job of the STFT is to keep the O2 sensor near stoichiometric. +/- 10% fuel trims are considered normal for most systems.

You need to use a good scan tool to see what the desired fuel rail pressure is and see how it compares to the actual pressure.
 
wtd said:
The main job of the long term fuel trim is to keep the short term fuel trim as close to 0% as possible. The main job of the STFT is to keep the O2 sensor near stoichiometric. +/- 10% fuel trims are considered normal for most systems.

You need to use a good scan tool to see what the desired fuel rail pressure is and see how it compares to the actual pressure.
Click to expand...
Ok thanks for the details on the short vs long term numbers. Kinda opposite what I thought.

I don't have a "good" scanner. I have an Innova 5160RS. It shows the fuel rail reading but neither it nor the Torque app displays the Command. I don't think it's a limitation of the OBD2 adapter--HPFP Command isn't in the large number of greyed-out display choices.

When I first got this truck 19 months ago I was amazed to see 2800psi fuel pressure. I had never heard of anything that crazy. I searched online & learned that was normal for these DI motors.
1700psi is a long ways from those earlier readings so something isn't right. I haven't been able to find anything online that tells me if it's enough. I'm still in the 600 mile break-in so I haven't pinned the throttle to see if it has the same spirit it used to have.
 
I want to add that i'm glad I posted this question here. Even tho it isn't a lube topic I knew I would get to a level of technical detail not possible in the normal car & truck forums. I had posted this in a Traverse forum I frequent and got nothing but crickets.
 
guy48065 said:
The HPFP used on this platform is an on-demand pump that has no return line back to the tank. Single plunger, driven off an extra lobe on one of the cams.
The video you linked is a diesel fuel pump.
Click to expand...
As I said it's a general idea.

You seem to know more about the exact details of the design of your vehicle's injection system so why the uncertainty then? Get a decent scanner and go from there

If there is no return line from the rail like on that diesel design then you have a SCV (suction valve) (and again generalized) that is controlled by the ECU.

guy48065 said:
I don't have a "good" scanner. I have an Innova 5160RS. It shows the fuel rail reading but neither it nor the Torque app displays the Command. I don't think it's a limitation of the OBD2 adapter--HPFP Command isn't in the large number of greyed-out display choices.
Click to expand...
If the software is oblivious to the existence of the specific parameter (demanded pressure) it cannot display info about it - Torque et al can only do what it was designed to do.

You need a scanner that can display all the live info available from the ECU ............... ito money something like the Autel AP200 (white)


............. and as others have said - if it's driving okay and the ECU is not complaining, then what you see on the data is probably within acceptable tolerance limits coded in the ECU.

We can keep talking generalities but unless you can confirm the ECU to be running the exact same firmware version as before and somebody with exact mapping info comes along who knows the differences we are all guessing
 
If you are not running the Torque Pro app, then you are missing out on all that Torque Pro has to offer. Torque Pro has a one time "registration" fee of ~$5.00. After paying the "registration" fee, you can then go into the settings and enable manufacturer specific settings to monitor much more than what the free version of Torque offers.

Also, Torque Pro allows one to choose which live data streams it will store in an Excel-like file for viewing on a PC.
 
chemman said:
If you are not running the Torque Pro app, then you are missing out on all that Torque Pro has to offer. Torque Pro has a one time "registration" fee of ~$5.00. After paying the "registration" fee, you can then go into the settings and enable manufacturer specific settings to monitor much more than what the free version of Torque offers.

Also, Torque Pro allows one to choose which live data streams it will store in an Excel-like file for viewing on a PC.
Click to expand...
I do have Pro... But I'm having a hard time finding the spot in their endless menus that tells me whether I've paid for all the extras. I can't remember.
 
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