LeForce

I'm using an LS9 in an engine swap project, I'm also using an adjustable fuel pressure regulator. Can someone tell me what's the stock idle fuel pressure for the LS9? (with vacuum hose connected or not)?
I recall that the stock pressure for the LS3 is around 60psi but I suspect that the LS9 needs higher pressure since it's supercharged.

Thanks

redbird555

LeForce

Any tips how to set the fuel pressure?

Unreal

Set it with a base pressure high enough to support what you need to do, and tune around it. You won't have the same functionality as a stock zr1, but you can tune around it and just have to adjust everything in the ecu to accommodate since you can't run the factory PWM controlled pump setup. .

LeForce

I was hoping to run the engine on the stock tune & not have to tune it, is there away to mimic the factory PWM control? I'll set the pressure to 37psi for the break-in duration.

Unreal

37psi is strickly for idle and low load, and once you give it any gas it will go super lean.

You can try to rig up a whole zr1 fuel pump assembly/etc, but that would cost WAY WAY WAY WAY more than just having someone tune it.

LeForce

Well 37psi would be just for the break-in duration as the engine is brand new. The fuel pressure regulator is vacuum referenced, I have set it first to 43psi at idle & I tried a couple of minimal revs & I noticed that fuel pressure would almost instantly climb to 80s psi. I will check the AFR to evaluate whether it requires a tune. Are you familiar with the stock target AFR, mid to high range RPM?

lt1z

You need to tune it when the LS9 is not in a ZR1. What I would do is set base PSI to 58 and boost reference the regulator to raise pressure 1:1. So if seeing 11 psi it will raise to 69 psi under full boost. That will be enough. If you have a crate LS9 controller it will work similar, but a factory ZR1 tune assumes a FPCM that ramps to 6 bar.

LeForce

I'm reading the engine manual, it says "ensure that fuel pressure is capable of 600 kPa (87psi) with the engine running, the pressure regulator must be vacuum referenced" It looks that my regulator would easily achieve 6 bar at high RPM. I don't have a GM tuner anywhere around here, I'm a tuner myself but I never did a GM engine, only Japanese engines. I should be able to fine tune the fuel table myself if I have to, but I need to know what are the stock AFR targets on the LS9.

Unreal

Just look at the maps. ~14.1:1 at part/idle, and look at the PE table, which varies from ~10.5-12:1 or so depending on loads/rpm/etc.

LeForce

I tried 60psi as idle pressure & the engine ran very rich with black smoke when revved, base pressure definitely needs to be lower.

LeForce

I haven't opened the maps yet, I just received my Hp tuners suite, are fuel table numbers represented in actual AFR figures? That sounds good! With other ECMs the numbers are simply fuel injector duty cycle percentages.

Unreal

No, they are typically EQ ratios based of the stoich value programmed in.

NicD

OK so LS9 in a swap application, what controller are you using? That will change everything...

lt1z

LeForce

Thank you for the question, I purchased what's called the LS9 connect & cruise package from GM Performance the kit included the engine, T56 super magnum gearbox, and LS9 controller kit (ECM & harness) GM part # 19354338
https://www.chevrolet.com/content/da...m-19354338.pdf

NicD

Crap I can't remember what the GMPP LS9 tune shows in the injector flow rate table but looking at the guide it says the regulator must be set for 60 psi at idle and then 65 psi at WOT but that isn't a 1:1 boost reference so that's kind of odd. The guide also says the regulator must be referenced so that needs to happen. Either way I would be tuning it afterwards since there are so many variables in a swap application and the MAF tube orientation, filter, etc will all change the calibration.

LeForce

Yes MAF & O2 sensors were installed according to the manual, closed loop seems to work fine as idle is very stable regardless of fuel pressure. I'm using an Aeromotive A1000 inline fuel pump and an Aeromotive fuel pressure regulator. Again, I'll adjust the fuel table if I have to, but first I want to achieve acceptable & safe AFR through a suitable fuel pressure & then I might only fine tune it through the fuel table. I still don't have a definite answer regarding the stock AFR targets, @Unreal mentioned that such figures would be found inside the tune file. Instinctively, I'd shoot for something like 12.5 during spool up, 11.5 at mid range, dropping to 11 by red line.
I really appreciate your feedback, please keep it coming

LeForce

After going through the manual, I'm positive that controller I have is meant for the LS9 as a swap engine not a ZR1 controller. So it's meant to work with a vacuum referenced pressure regulator, not a PWM controlled pump. The manual says that idle pressureI should be at 60PSI, but the complete sentence describing fuel pressure in the manual is a bit tricky, "The required fuel system needs to be controlled to 60psi at idle and 75 GPH @ 65psi for WOT conditions" I don't believe that pressure would be at 65psi only during WOT! I think the sentence is simply explaining what should be the fuel flow at a certain pressure. In a different section in the manual, it says "ensure the fuel pressure i capable of 87psi with the engine running" and "ensure the fuel pump has the following flow capacity, minimum 75 gph @ 65psi. I believe that fuel flow should fine & work well with the controller if I set idle pressure at 60psi then the vacuum controlled regulator would simply increase fuel pressure as air pressure changes. I'll keep an eye on AFR to make sure that the engine isn't running too rich or too lean.
I appreciate your feedback