2018 5.3l On3 Performance single turbo Kit and suggestions

Matthew Fontana · September 11, 2020

Kind of jumped the gun about 6 months ago and bought a single turbo kit for my 2018 double cab 5.3l Z71 package. I’m still planning on installing it but have decided to wait until the warranty is up in roughly a year or so before in install it. In the mean time, I’ve decided I can probably gather a few other parts to make fuel and air delivery better and also wanted to ask about high flow cats as I’ve read in some places that factory 5.3l gm cats are high flow? I’m not planning on running crazy high boost just wanted something fun to toy around with and maybe it will help with towing every once in a while too. In any case, I’ve read that bigger injectors will help but if it’s still going to be a daily driver. Do I need to do this? I’ve also considered putting a catch can in, cold air intake and maybe a fuel pump depending what everyone here thinks? I’ve had a range 4cyl disabler in the truck since it had roughly 500 miles on it. Plan on having it disable through the tune once I have it tuned for the turbo install. Really just looking for some input and ideas here since I’ve got a little bit of time for the install. Would rather be over prepared for what I will need I guess. Thanks in advance.

CamGTP · September 12, 2020

With the way the turbo is you won't be using your stock y-pipe with cats anymore and I wouldn't want to chop that up just to snag one cat from it. Besides you'd be trying to push all 8 cylinders through one cat that only have 4 going through it before. The 3rd cat after the y-pipe merge is larger but still I wouldn't want to cut that up. Those y-pipes are super expensive if you ever decided to remove the turbo kit and return it to stock.

If anything I would get one high flow cat, like a 200 cell or whatever they sell now. I think magnaflow makes one, it's mainly just used to tame down the exhaust smell.

As far as the injectors go, lets put it this way. A bolt on TVS or Whipple blower on the low boost setting is good for about 100-125hp give or take a couple. That is designed to work with the stock fuel pump and stock injectors on regular 91 or 93 octane fuel. You are basically at the limit of the injectors at this point.

If you want to run a decent amount of boost and over that 100-120hp increase you are going to need larger injectors and a larger high pressure fuel pump. Going with the LT4 injectors and LT4 fuel pump is the way to go. That will give you way more headroom with power.

You don't really need a cold air intake with the turbo because it has an intercooler. Just make it so the filter location is pulling in fresh air all the time. I don't know much about the On3 Kits but some let you keep the stock airbox location that pulls air from the inner fenderwell.

Don't forget that you will need/want a GM 3 bar MAP sensor for logging boost when tuning. I don't know if On3 supplies such a sensor but if it's not a GM sensor, throw it away because only a GM AC Delco sensor is proven to work and they have good MAP sensor data for tuning.

flyingfool · September 12, 2020

why keep the cats anyways? its a new truck so there are no emmissions for like 8 years. i got a 2016 and never had to smog it. just run it dirty 'til its emmissions time.

if you want Perf cats.. the Isuzu NPR HD has extreme high flow cats on the 6.0L LS motor, these things are huge 12" diameter

CAI are a waste of money, as the stock system out flows the heads when you pull the restrictor panel out.. I like the idea of swapping out the entire muffler and running a remote turbo, , with no intercooling.. if boosting the TB and Manifold is a cheap fix restriction by swapping to the 6.2 induction. . would luv to see what a 5.3 with the entire 6.2 Induction does, from cam , manifold TB

I believe you can flash our ECU's with the S/C vette or Camaro ECU software file for a quick safe tune, after you improve the fuel system to LT4

instead of Boosting, you might be able to make 80-120hp with a stock N/A set up with simple bolt in upgrades. the weakest link is the trans tuning and torque converter

i would say $6-8000 would get it done right..

Edited September 12, 2020 by flyingfool

Matthew Fontana · September 12, 2020

In my state vehicles 3 years old have to pass emissions tests, in some counties you have to get one every year after the vehicle is three years old until it’s 25 years old. Some counties don’t have emissions requirements but I’m not fortunate enough to live in one of those. I will look into the LT4 injectors and fuel pump and the MAP sensor. The kit is “bolt on” but anyone who’s ever worked on any vehicle before knows how that goes. I did also get an electric oil pump which will return into the oil fill cap instead of having to tap into the pan as well. As far as the air box I haven’t been able to find anyone who has installed this particular kit on this particular truck but there’s no air filter relocation in the kit and from what I’ve read on their website it doesn’t have to be relocated.