Ls1 injector upgrade

[Kc686]

Hey guys
Upgrading injectors in my skid ute and was just curious if I should set my adjustable reg's psi higher ? Currently running stock ones on 58psi but got a Holley efi manifold and 102mm t.b to go on now and doing injectors to maybe 650cc or even bigger.
Will be re tuned anyway but just thought I would ask someone if I should up the psi

Cheers

 

[Munz]

nah i wouldn't think there'd be much benefit in increasing pressure

what other mods does the engine have?

 

[Bigfella237]

Injector flow rate and fuel pressure go hand-in-hand, any injector you buy will be rated with a certain flow @ a certain pressure.

For example, you mentioned injectors with a flow rate of 650cc/min, if the manufacturer specified that figure @ 4 bar (58 psi) then lowering the pressure to 3 bar (43.5 psi) would mean those same injectors will now only flow 563cc/min, conversely if you were to crank the pressure regulator up to 5 bar (72.5 psi) then those same injectors will now flow 727cc/min.

A lot of the high-end pressure regs these days are "boost referenced" too, that means they have a vacuum hose from the inlet manifold attached and they vary the fuel pressure with intake manifold vacuum/pressure. So you would set the base fuel pressure with manifold vacuum at idle, then as the throttle opens the fuel pressure (and therefore fuel flow) increases. These are really designed for forced induction but still work without, normally increasing fuel pressure 1:1

BTW, unless you're making about 650 N/A horses on E85/Alcohol those injectors you mentioned will be way big, unless your current setup is pinned at 100% duty cycle and still going lean at WOT it's a little overkill. Although if you can still get the thing to idle then I guess there's no harm in having a little extra room at the top end.

From memory a standard LS1 injector is rated around 295cc/min @ 4bar (28lbs/hr @ 58psi)

 

[Bigfella237]

I forgot to mention, if you're thinking about cranking up the fuel pressure to get a little extra flow out of your standard injectors, you'd better make sure the fuel pump and the rest of the fuel system is up to the task first?

Also if you want to supply 8x 650cc/min injectors running at 80% duty cycle then you're gonna need a fuel pump capable of around 80 USGPH (300 litres/hr) and ½" (-8AN) supply line.

Andrew