Injector size and fuel system advice needed
Thread Starter
On The Tree
Joined: Dec 2019
Posts: 154
Likes: 22
From: Indiana
Injector size and fuel system advice needed Looking for advice on injectors and fuel system for my build. 6.0, s480, Holley EFI, LS3 head, forged rods and Pistons, either LS3 intake or Holley hi ram. Going in Chevelle street car.
Thanks
Thanks
Thread Starter
On The Tree
Joined: Dec 2019
Posts: 154
Likes: 22
From: Indiana
On The Tree
Joined: Oct 2012
Posts: 124
Likes: 18
From: Jefferson, LA
What type of fuel will you be running? What are your rwhp goals... or ET goals?
If you decide to run e85, you'll need ~30% more fuel than you would with pump 93. If you start with pump 93 but want the option to switch to E at a later date, build the fuel system accordingly. FWIW I got DEKA 80's and regret not going bigger after making the switch to E.
If you decide to run e85, you'll need ~30% more fuel than you would with pump 93. If you start with pump 93 but want the option to switch to E at a later date, build the fuel system accordingly. FWIW I got DEKA 80's and regret not going bigger after making the switch to E.
Ideally you would size injectors so that the fuel actually has time to get into the cylinders before the intake valve closes. That has to take into account time to travel from injector into the cylinder. I can't remember the rule of the thumb but I think it's somewhere in the mid-60's percent duty cycle because my injectors do not exceed low 60% duty cycle and it's something I tried to pay attention to when I selected my injectors. If the injector works harder, then some of the fuel backs into the valve and doesn't get dumped into the cylinder until the next injection cycle. The Holley EFI processor speed is about 10x faster than 0411 PCM so you really can take advantage of stuff like that.
TECH Fanatic
Joined: Sep 2008
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I did a LS2 sleeved and stroked to 427 cubes. L92 heads. 42# Corvette injectors. LS3 intake. -6 SS line. 255 Walbro pump. 480 RWHP. Not big numbers but was easy to tune. Ran great. Tuner said it was a great combo. No worries about leaning out due to lack of fuel.
Make sure whatever injectors you buy has a data sheet for the tuner.
Make sure whatever injectors you buy has a data sheet for the tuner.
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I did a LS2 sleeved and stroked to 427 cubes. L92 heads. 42# Corvette injectors. LS3 intake. -6 SS line. 255 Walbro pump. 480 RWHP. Not big numbers but was easy to tune. Ran great. Tuner said it was a great combo. No worries about leaning out due to lack of fuel.
Make sure whatever injectors you buy has a data sheet for the tuner.
Make sure whatever injectors you buy has a data sheet for the tuner.
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Verdad Gallardo Yeah, the higher the injector duty cycle the closer you are to being "static" and not being able to control the fuel flow. That's disaster in a boosted engine.
There reaches a point where holding the injector open for longer pulse width has little effect on the fuel delivered or loses accuracy of fuel delivered, and that happens somewhere in the mid-90% range. That's one reason why you never want to see >90% duty cycles. Basically injectors are like many other devices that lose accuracy as you approach the min/max limits of operation. Stay away from both ends of the spectrum.
Also, you want some head room in case alternator fails and system voltage drops to battery. The lower voltage will slow the fuel pump and confuse the living hell out of the Holley ECM. The factory ECM has really good voltage compensation but Holley ECM does not, it sucks that way. I lost my alternator at the drag strip and the closed-loop compensation added +25% fuel to hit AFR target. All I can say is it was a damn good thing the CL compensation was on at that point or I would have run severely lean because ECM itself did not know what to do at lower voltage. Size both the fuel pump and injectors so you can safely run on battery (no alternator charging). That voltage will be lower the more electrical demands your vehicle puts on the battery. I'd suggest designing for somewhere between 10.0-10.5 Volt to cover your tail. **** happens, especially when you don't plan for it.
There reaches a point where holding the injector open for longer pulse width has little effect on the fuel delivered or loses accuracy of fuel delivered, and that happens somewhere in the mid-90% range. That's one reason why you never want to see >90% duty cycles. Basically injectors are like many other devices that lose accuracy as you approach the min/max limits of operation. Stay away from both ends of the spectrum.
Also, you want some head room in case alternator fails and system voltage drops to battery. The lower voltage will slow the fuel pump and confuse the living hell out of the Holley ECM. The factory ECM has really good voltage compensation but Holley ECM does not, it sucks that way. I lost my alternator at the drag strip and the closed-loop compensation added +25% fuel to hit AFR target. All I can say is it was a damn good thing the CL compensation was on at that point or I would have run severely lean because ECM itself did not know what to do at lower voltage. Size both the fuel pump and injectors so you can safely run on battery (no alternator charging). That voltage will be lower the more electrical demands your vehicle puts on the battery. I'd suggest designing for somewhere between 10.0-10.5 Volt to cover your tail. **** happens, especially when you don't plan for it.
On The Tree
Joined: Nov 2021
Posts: 127
Likes: 74
Current build that isn't quite complete yet..
5.3
7875 turbo
1050 injectors (Canadian Performance Injection)
8an feed, 6an return
2- 450 walbros (they're cheap and give me room to grow)
Probably going to mostly run 6xx whp on street but would like to shoot for something in the 7xx just because I want to.
Planning on running 91 - as that's what's available but wired in a flex fuel sensor as well so I can play with E85 when I want to.
5.3
7875 turbo
1050 injectors (Canadian Performance Injection)
8an feed, 6an return
2- 450 walbros (they're cheap and give me room to grow)
Probably going to mostly run 6xx whp on street but would like to shoot for something in the 7xx just because I want to.
Planning on running 91 - as that's what's available but wired in a flex fuel sensor as well so I can play with E85 when I want to.
Thread Starter
On The Tree
Joined: Dec 2019
Posts: 154
Likes: 22
From: Indiana
Current build that isn't quite complete yet..
5.3
7875 turbo
1050 injectors (Canadian Performance Injection)
8an feed, 6an return
2- 450 walbros (they're cheap and give me room to grow)
Probably going to mostly run 6xx whp on street but would like to shoot for something in the 7xx just because I want to.
Planning on running 91 - as that's what's available but wired in a flex fuel sensor as well so I can play with E85 when I want to.
5.3
7875 turbo
1050 injectors (Canadian Performance Injection)
8an feed, 6an return
2- 450 walbros (they're cheap and give me room to grow)
Probably going to mostly run 6xx whp on street but would like to shoot for something in the 7xx just because I want to.
Planning on running 91 - as that's what's available but wired in a flex fuel sensor as well so I can play with E85 when I want to.