I've been seeing some post regarding fuel pressure regulators and injector data. This is something that I do not fully understand. On my swap vehicle, I have an adjustable FPR mounted on the firewall. Pressure is set at 59psi. The injectors are stock ls7 and as far as I am aware, the injector data hasn't changed in my tune. Does this mean that I will need to change my injector data or am I good as I am? Attached is how I have my fuel line configured:
daily tune vve.hptregulator.jpg
Is there a vacuum hose from manifold to regulator? That's what sets the two styles apart in regards to injector data.
No hose from the regulator to manifold. However, the FPR does have the boost/vacuum port. Any benefits to hooking that up; or is it ok to leave it as is?
Without the vacuum hose it functions just like the stock 'returnless' system and keeps the same type of injector data (flow rate varies with manifold pressure/pressure delta). With a hose connected, the fuel pressure changes in step with manifold pressure so the pressure difference between injector inlet (rail) and injector outlet (manifold runner) stays the same, means the flow rate stays the same, means the IFR & Offset tables have one single value from left to right.
'Return' and 'returnless' are really misnomers, they both return fuel to the tank even if the regulator is inside the tank. A better terminology would be referenced or non-referenced. So when you see someone say returnless they really mean non-referenced where rail pressure stays the same no matter what the engine is doing.
Thanks for clearing that up. I feel like the answer is, yes it need to be hooked up but at the same time, does it really make a difference how its hooked up as long as you are getting the pressure that the engine requires?
If you have enough overhead on injector sizing changing it to referenced will gain you nothing. But if the injectors are really big reducing pressure at high vacuum/low speed can help with idle quality, and if they are borderline too small raising the base pressure as manifold pressure increases can let the same injector support more power.
Changing the manifold pressure has the exact same impact on the flow rate as changing the rail/supply pressure by the same amount - so 20psi boost with a fixed 58psi gives you the same injector flow rate as if you'd dropped the rail pressure to 38psi, and obviously that would limit the power it can make.
Chapter 2Originally Posted by blindsquirrel
LOL.....
(Rob, Inside joke... blind has been schooling me on this stuff in other threads)
2011 Camaro 2SS Convertible L99 Bone Stock for now
2003 Dodge 2500 5.9 Cummins QC 4x4. Airaid, 2nd Gen Intake, Grid Heater Delete, D-Tech 62/65/12, Magnaflow. Bully Dog: Propane Injection, Triple Dog W/Outlook Crazy Larry. Edge EZ, BD Flow-Max, 48RE: Sonnax Sure Cure/Transgo combination, Derale turbulator, billet input, Triple Disc, Super servo, 4 ring Accumulator. :beer
No changes are needed with how you have it set up.
No need to change to vac referenced either.. I've made 600 rwhp easy with those injectors NA.
If you needed a little edge on fuel delivery with a boosted car, or flat out decently high boost car, or if you have injectors that are dirty at an idle.. Then the vac referenced is a good idea and you would need to change the data. Basically copy the flow rate and injector offset at the pressure you are using to the entire table(s).
Tuner at PCMofnc.com
Email tuning!!!, Mail order, Dyno tuning, Performance Parts, Electric Fan Kits, 4l80e swap harnesses, 6l80 -> 4l80e conversion harnesses, Installs
@Dhoagland. Him and a few more definitely got some knowledge tucked away for sure. lol Calibrating is totally different than turning wrenches.
Alvin, Thanks for confirming and elaborating on that a little more.
Reply With Quote