2010 Camaro LS3 Injector Delta Pressure?

[10_SS]

I just installed a whipple with 4" pulley on an otherwise stock 2010 LS3 Camaro, using the Whipple tune copied to the 2bar OS.. things seem like they are working great. Im using the Whipple MSD Boost A Pump.. but who knows if it's working. I'm not running lean under the low RPM I've tested it at so far, in fact I just richened up WOT so the settings I entered to do that work fine.

I've been searching for Fuel Pressure information, and found Injector Delta Pressure, but when I log it, it shows lower PSI when at WOT/Boost than when driving normal, out of boost/PE.

Is this normal? What exactly is Injector Delta Pressure and is it actually reading fuel pressure, or just calculated fuel pressure? All the posts I find about it are confusing.

Attached is a picture of the datalog where delta pressure drops to 58psi during WOT/Boost and stay's there.

[DSteck]

-100% LTFTs? Good lord.


http://www.injectordynamics.com/Stec...reArticle.html

The car has a fuel pressure sensor and uses that along with manifold absolute pressure to calculate effective pressure. However, it won't function in boost and defaults to 58psi until actual rail pressure begins to fall.

[10_SS]

-100% LTFTs? Good lord.


http://www.injectordynamics.com/Stec...reArticle.html

The car has a fuel pressure sensor and uses that along with manifold absolute pressure to calculate effective pressure. However, it won't function in boost and defaults to 58psi until actual rail pressure begins to fall.

-100 LTFT... haha, no that's an artifact from updating to the latest .767 beta.. alot of my PID's arent reading including all of the status bits. I know I freaked out too for a minute.

OK good so in boost is that 58psi showing actual real (correct) pressure delta and the fuel pressure system/pump is simply defaulting to 58psi, or are you saying the Pressure Delta reading defaults to 58psi even though the actual pressure delta could be 30psi?

BTW that air theory had to be true since that log is a new WOT, and the 02's are rock solid at whatever unknown (but richer) AFR (I added fuel to the PE Boost table and it works).

[DSteck]

As soon as you're in boost, the number you see is actual rail pressure so far as I've seen from the cars I've done. That's part of why I prefer return 1:1 systems for boosted applications.

[10_SS]

As soon as you're in boost, the number you see is actual rail pressure so far as I've seen from the cars I've done. That's part of why I prefer return 1:1 systems for boosted applications.

cool, good info. I was thinking it was still measuring something since it's wavy as if it's measuring fuel pressure. I can watch this and if I see it falling then I know i'm running out of supply.

Now, do you know if it's before or after the fuel filter? I was under there running my MSD boost a pump and saw a pressure sensor on the side of the pass side tank connected to a line, hope that's not it (I'd prefer after the fuel filter, as close to the rails as possible).

Thanks DSteck you've been a huge help Chapter 2: 2010 LS3 Whipple Install.

[10_SS]

Well I'm hoping it's measuring Delta pressure since this graph shows the Injector Delta dropping as Inj Pulsewidth and RPM go up, cause, if it's just measuring line pressure then I'm losing it, and if that's true maybe the BAP isnt workin as it should. 02's are steady though.

[Area47]

i have poked through these threads for fun a few times. if you're running headers on this car and you're still trying to tune off the narrow bands, which IMHO is a massive mistake in the first place, you're going to have some serious issues.

[10_SS]

I'm not running headers, and I'm not really tuning with NB02's, just using them to figure out why weird things happen.

[MikeOD]

-100 LTFT... haha, no that's an artifact from updating to the latest .767 beta.. alot of my PID's arent reading including all of the status bits. I know I freaked out too for a minute.

Go to your My Documents/HP Tuners/VCM Scanner/Vehicles folder...and delete everything. The scanner will re-scan for PID's, and for me, has fixed when something stupid like that happens in the scanner. It won't affect your configs, or user defined PID's or anything else.

[10_SS]

I tried that, Bill told me to do it. I found if I have 38 parameters everything is OK, and 39 then this happens. He's looking into it, not sure if it's normal or not. I think when I when over 38 in the past the logging rate was slower, that's all.

[mkent93]

The mass flow out of the fuel injector is primarily a function of PW, but also varies with the voltage applied at the injector and of course the pressure across the injector.

Delta pressure appears to be simply the pressure across the injector.

Mathematically it is:
Delta Pressure =(Fuel Rail Pressure [psig]) - (MAP [psig])

I work in SI units, so your 58psi is same as 400kPa. If your engine is at idle, your MAP is probably somewhere around 30kPa. Since that's 30kPa absolute pressure, and assuming Baro = 100kPa, your manifold gauge pressure is actually (30 - 100) = -70kPa.


Delta Pressure at idle = (400kPa rail pressure) - (-70kPa manifold pressure) = 470kPa.

You can see at WOT in an NA engine, your manifold absolute pressure will approach 100kPa (or 0kPa gauge pressure) meaning your delta pressure would be 400kpa - 0 = 400kPa.

Pressurize the intake manifold and now you are subtracting positive numbers from your rail pressure. This is decreasing the pressure across the injector, and effectively decreasing your fuel flow rate potential.

To answer your other quesiton--Yes, this is normal.

If you are still confused, let me know and I can try to explain it another way.

[griffincox]

I have begun logging Injector Pressure Delta in my 2008 TBSS - E67 - TVS1900 truck. This vehicle operates at a fixed 58psi rail pressure. I have a Aeromotive 340lph pump and have no doubt it can hold the rail within a few PSI of 58. The Injector Pressure Delta varies from 58 psi at 105kPa MAP up to a maximum of about 69psi at maximum manifold vacuum or around 20kPa. Above 105 kPA MAP (boost) it reads a constant 58 PSI. Basically with the higher manifold pressure fuel flow decreases and it seems the ECM is not accounting for it. Lambda follows commanded pretty well even at MAP of 105-140kPa. Is this decreased fuel flow being accounted for in the ECM somehow or is this error effectively baked into the Airflow calibration now? Rough estimate would be about 4 lb/hr of fuel expected to be flowing is not flowing at max boost. Help me wrap my head around this.

[scv_guy]

The mass flow out of the fuel injector is primarily a function of PW, but also varies with the voltage applied at the injector and of course the pressure across the injector.

Delta pressure appears to be simply the pressure across the injector.

Mathematically it is:
Delta Pressure =(Fuel Rail Pressure [psig]) - (MAP [psig])

I work in SI units, so your 58psi is same as 400kPa. If your engine is at idle, your MAP is probably somewhere around 30kPa. Since that's 30kPa absolute pressure, and assuming Baro = 100kPa, your manifold gauge pressure is actually (30 - 100) = -70kPa.


Delta Pressure at idle = (400kPa rail pressure) - (-70kPa manifold pressure) = 470kPa.

You can see at WOT in an NA engine, your manifold absolute pressure will approach 100kPa (or 0kPa gauge pressure) meaning your delta pressure would be 400kpa - 0 = 400kPa.

Pressurize the intake manifold and now you are subtracting positive numbers from your rail pressure. This is decreasing the pressure across the injector, and effectively decreasing your fuel flow rate potential.

To answer your other quesiton--Yes, this is normal.

If you are still confused, let me know and I can try to explain it another way.

Please forgive me, but I'm new to the world of efi tuning.
Im trying to crawl before I walk or run for that matter!
So if the Delta injector pressure is dropping under a boost condition is this corrected via tune or fuel pump just can't keep up?

[schpenxel]

Please forgive me, but I'm new to the world of efi tuning.
Im trying to crawl before I walk or run for that matter!
So if the Delta injector pressure is dropping under a boost condition is this corrected via tune or fuel pump just can't keep up?

The best way is to use a fuel pressure regulator that increases fuel pressure as boost increases, thus keeping the delta from manifold pressure to fuel pressure the same.

Some ECM's are capable of having injector flow rate tables that go into boost (with a patch from HP Tuners), but others are not

[scv_guy]

The best way is to use a fuel pressure regulator that increases fuel pressure as boost increases, thus keeping the delta from manifold pressure to fuel pressure the same.

Some ECM's are capable of having injector flow rate tables that go into boost (with a patch from HP Tuners), but others are not

I would agree with you, but I'm working with the returnless system, how is this corrected in the tune?

[DSteck]

I would agree with you, but I'm working with the returnless system, how is this corrected in the tune?

You can't always fix everything in the tune. There are mechanical things that need to be right for a given setup.

[scv_guy]

You can't always fix everything in the tune. There are mechanical things that need to be right for a given setup.

the issue I'm seeing is the delta pressure is dropping under boost casing a lean condition, this is a returnless system.
The pump should be more then enough.

[schpenxel]

the issue I'm seeing is the delta pressure is dropping under boost casing a lean condition, this is a returnless system.
The pump should be more then enough.

VE or MAF tune? Or both?

[scv_guy]

VE or MAF tune? Or both?

It is a MAF tune

[DSteck]

the issue I'm seeing is the delta pressure is dropping under boost casing a lean condition, this is a returnless system.
The pump should be more then enough.

There's a mechanical regulator in the fuel pump assembly within the tank. You're going to be clipped at 58psi rail pressure if this is a LS3 Camaro. In boost, it's automatically going to drop delta pressure.



You cannot tune away a mechanical limitation.