Mild lq4 fuel upgrades
02-11-2017, 11:44 PM
#1
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Mild lq4 fuel upgrades
Hey guys i have a mildy built lq4 i swapped into my 1500 sierra, its got a decent cam, milled .030" and ported 317 heads with full comp cam kit including trunion upgrade. full bolt ons with longtubes and custom tune by a local guy. (was previously a custom tuned cammed 4.8) before I get my trans rebuilt and have it all tuned again for this year I was wondering about some fuel upgrades.
What is the stock flow rate of the fuel pump? and what would be a simple and better upgrade pump. I'm looking at a few on summit but I'm not sure what flow rate would be ideal considering I don't know stock.
With injectors I believe the 4.8-6.0 had 25# injectors correct? My tuner recommends nothing more than 42# injectors so I'm wondering if there is a budget injector swap from similar Lsx engines, I've heard about 8.1 injectors will swap in but I cant find if they're direct bolt in (correct length and pigtail plugs) or not.
Thanks in advance guys!
What is the stock flow rate of the fuel pump? and what would be a simple and better upgrade pump. I'm looking at a few on summit but I'm not sure what flow rate would be ideal considering I don't know stock.
With injectors I believe the 4.8-6.0 had 25# injectors correct? My tuner recommends nothing more than 42# injectors so I'm wondering if there is a budget injector swap from similar Lsx engines, I've heard about 8.1 injectors will swap in but I cant find if they're direct bolt in (correct length and pigtail plugs) or not.
Thanks in advance guys!
02-12-2017, 12:11 AM
#2
I might be wrong but I thought it was somewhere around 190-200lph, going to a 255lph like a walbro will work just fine if that is all the mods you plan to do. It can handle more than what you have but if you wanted boost you'd need a larger pump.
Correct, factory injectors are 25lb/hr. You can buy some 31lb/hr 8.1 injectors and swap them straight in. They should be all the same because the early 2000's 8.1's all had them. Find the data from the stock 8.1 tune file and swap it in.
Correct, factory injectors are 25lb/hr. You can buy some 31lb/hr 8.1 injectors and swap them straight in. They should be all the same because the early 2000's 8.1's all had them. Find the data from the stock 8.1 tune file and swap it in.
02-14-2017, 09:27 AM
#5
You don't have to up your fuel pump if you don't want to. All you need is the 31# 8.1 L injectors. My stock fuel pump keeps up just fine with my truck. Fuel pressure never falls even up to 6000 rpms. I'm sure it's just about maxed out, but for heads and a cam you should be fine. When the stocker fails, then slap a 255L in there.