Fuel Pressure on Vortec Motors

[twebuh]

After building out my truck (heads. cam. exhuast, tune, the works) my tuner told me im at 100% duty cycle and that I needed bigger injectors to get that lower for more tuning potential. I have already done the MPFI upgrade before he tuned it. I have seen a lot about the marine intakes but I have also heard how expresive they are. I saw that TBI 350s have adjustable fuel pressure regs, is that true for vortec motors too? I just dont want to have to drop a bunch of money on making the marine intake work. It seems like a common issue people have and im not even sure if its that big of an issue. Thank yall!

 

[1998_K1500_Sub]

IIRC, @L31MaxExpress and / or @Supercharged111 have commented that the reported duty cycle can be greater than 100%, meaning you may have some margin left.

Let's see what others say.

You've come to the right place.

 

[Supercharged111]

What exactly does the build consist of? Maxxing out stock injectors equates to making some good power.

 

[99xcss4]

you can get higher psi mpfi spiders but they are very expensive https://www.ausinjector.com/categor...rmance/chevrolet/k1500/v8-5-7l/1996-99-3.html they come in 36 psi 48 psi and 62 psi

 

[Caman96]

@L31MaxExpress has also mentioned a few times correct injector data to pcm for MPFI upgrade is also a noticeable improvement.

 

[twebuh]

What exactly does the build consist of? Maxxing out stock injectors equates to making some good power.

I mean its really not a lot of power prob because its lifted 6 1/2 inches. Mild comp cams cam with supporting valve train mods, ported the heads and intake, MPFI conversion with stock injector size, CAI, EGR delete, stuff like that. Dyno said it makes something like 280hp on 35s

 

[twebuh]

you can get higher psi mpfi spiders but they are very expensive https://www.ausinjector.com/categor...rmance/chevrolet/k1500/v8-5-7l/1996-99-3.html they come in 36 psi 48 psi and 62 psi

wow, yeah thats expensive too. I just dont know if its bad that Im max duty cycle. Ive been told its fine by my tuner and that i might just get an injector stuck eventually. Just wanna be sure im not missing out on any power

 

[Moofus02]

Increasing Fuel Pressure on Spider Injectors

Does anyone have any experience increasing fuel pressure on the spider injectors? Its my understanding that there is a torx adjustment screw on the fuel pressure regulator. Some people have said they were able to increase pressure up to 70psi. Currently seeing over 100% injector duty cycle at...

www.gmt400.com

 

[L31MaxExpress]

Increasing Fuel Pressure on Spider Injectors

Does anyone have any experience increasing fuel pressure on the spider injectors? Its my understanding that there is a torx adjustment screw on the fuel pressure regulator. Some people have said they were able to increase pressure up to 70psi. Currently seeing over 100% injector duty cycle at...

www.gmt400.com

I ran 70 psi for several years. Best guess is that unless you are over 400 hp, you are actually losing pressure up top rather than the injectors being too small as is.

 

[Amsterdamned96]

I ran 70 psi for several years. Best guess is that unless you are over 400 hp, you are actually losing pressure up top rather than the injectors being too small as is.

What kind of pumps were you running? I only recently found out mine had a bypass in place of the drop-in fuel pump, unsurprisingly though as there were two high pressure 45psi inline-pumps. As of rn, I’ll be using the in-tank pickup-pump as well as one of the higher pressure Bosch units, seems more sensible than two inline in the frame rail.
My setup is a gen v with an aftermarket mpfi intake using the 36lb/hr injectors, the intake has rec intake ports so I imagine they didn’t have tbi in mind and it has a RV cam, flat-tops and lightly ported (tear-drop) peanut ports.
I have yet to tune it though so I’m uncertain how justified larger injectors are in naturally aspirated application.