As 2xLS1 said, id be running a pair of 02s, you can run pre cat 02s no problem.
As 2xLS1 said, id be running a pair of 02s, you can run pre cat 02s no problem.
Speed Cost Money - How Fast Do You Want To Go?
Okay, I'll see what I can do about getting the upstream 02s in. Now, just for future reference, let's say I needed to cut fuel across the board. How do I do that? With injector timing, or the VE table?
My suggestion is, trying to F around with it while the injectors are an unknown is going to leave you more confused and frustrated than you already are.
If you want to cut fuel across the board you'd be taking it out of the VE Table
Speed Cost Money - How Fast Do You Want To Go?
Well not necessarily. The OEM ecu is not like a stand-alone where the VE table usually just affects fuel only. The OEM ecu has an airmass calculation that it uses to adjust myriad features which is far more delicate a web than any stand-alone. There is a consequence to removing VE in that it will reduce the predicted airmass. So even though it may correct for fueling it could also have a negative impact on any number of downstream calculations, for example shift pressure will be reduced, not just the fueling. There are algorithms in place which keep track of torque, friction, energy loss, etc... and reducing the VE will influence them all. Thus we can't go right to the VE table to remove or add fuel without considering the airmass first.Originally Posted by PREDATR
The most important globally influence fueling table is the injector size table. The injector size will control global fueling for a stated pressure without affecting airmass- or it may be more precise to say that injector size table can be used to dial in the airmass predictions by correlating ideal VE table values to realistic airmass values over the course of tuning by using a wideband sensor and datalogging (the way most people tune the engine is by logging the wideband values over the course of driving a vehicle many sessions).
Its also worth mentioning that the airmass doesn't necessarily need to be correct in order to be ideal. For example a higher than realistic airmass value could result with increased transmission longevity due to heightened shift pressure in affected areas. It may also result with unnecessarily harsh shifts; the point being, it could go either way, and its up to us, the engine tuner in control to decide how the engine should be tuned, and not the other way around. Don't let it fool you into thinking you need to be exact in terms of airmass or torque predictions or whatever in order to fully control or tune the engine, but also be aware that if you are a novice engine tuner the least resistance pathway is likely going to be the one where the computer is accurately configured to predict realistic values that, as a novice tuner, you would be unable to reconcile with using the myriad various other maps to which an experienced tuner would be able to affect the necessary changes to take advantage of the skew prediction variables set forth by non-realistic VE table values or similar.
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I want to thank everyone for the input on this issue. A lot of great info is here. I believe the previous owner's capabilities are coming to light. Upon inspection (first chance I've had to get a good look) , I find that this thing is so pig fat that he had to leave the EGR valve loose to keep it running. I tightened up what I thought was an oversight, and it stopped running altogether. If I loosen the EGR valve, cause a massive vac leak, it runs. My guess is that he uncapped the injectors and they are simply hosing in fuel. I can't see where this relatively mild cam and a set of headers could demand that much more fuel. I've built a lot of high performance small blocks in my day and have never had to pour fuel into them like this. I'm going to start, as soon as the weather warms up, by removing and inspecting the injectors for tampering. I'll replace them with some stockers and go from there. The whole thing looks to me like the last owner opened up the injectors, figured out it was much too much fuel, and created a massive vac leak to compensate! I really, really hate hacks!! Thank you, guys!! MUCH appreciated!!
Stock injectors, as in correct for the truck via a parts lookup, will let you go back to stock injector data and make it run and respond to changes in a rational way. But stock 25lb injectors will not be big enough for a 'stage 3' cam & headers, you will be RPM-limited before you hit 100% injector duty cycle.
I'm not completely opposed to you going back to stock injectors even if they're ultimately going to have to be changed again later. It's a good way to build some confidence, being able to see it work like it should even if just temporarily as a kind of diagnostic way to rule out some problems so you can see if anything else needs addressing.
Does the truck have fuel pressure regulator on the rail or is it returnless?
Truth be told, I don't even know. I have to get back out to my son's garage and give a it a good look. Basically, I should look for some larger injectors to pop in there, like something from a 6.0 or something? Maybe a 6.2? As I said, this is like a dentist doing brain surgery for me. I COULD go with a little larger injector, but then I would need to enter the correct info into the tune to compensate, right?
Yes but if you get larger GM injectors it is easy to copy very accurate OEM injector data from the vehicle they came out of, stock tunes for most everything are on the tune repository.
If you are going to do anything other than the stock injectors, I'd go straight to the 50lb L96 injectors. Cheap. Depending on what parts you have now you may need top hat spacers and/or harness adapters. You really need to at least pull the fuel rails off and make a thorough inventory of what's there before you go making any lists of stuff to buy. What intake is it? What rails? What injectors are they - stock-height Gen3 truck? And etc.
innjector dimensions.jpg
Following along it looks like you haven't given up, and I'm glad...
You can do this, it will just take patience, you started with a hell of a challenge..
I started with my completely stock and fine running Camaro tuning the MAF and VVE. The first week or so I was kind of like you, I guess this is beyond an old heavy equipment mechanic, I was chasing my tail round and round. This Forum got me straightened up in no time.
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It's become much more complicated than this, actually. I'll give you the Reader's Digest version of this complex story. A few years ago I had a 96 short box Silverado with a 4in 6 in drop kit, a very stoutly built 388 small block that ran extremely strong, 4.56 gears and a sturdily built turbo 350. I found that at my age I could no longer keep it up so I swapped it for an Electra Glide. Well, 950 lb of motorcycle is also way too much for my failing body so I swapped the bike for this hog of a truck. All told, I lost about $15,000 in this horse-trading ordeal. Now I have a wife to contend with because after all the money lost, I still have no truck to drive. So, at this point I would be extremely happy to see a minor progression so that the damn truck at least runs while I make my tweaks. I'm hoping that I can source some take off parts at this point just to get the thing running. I was hoping to find some 36 lb or maybe 40 pound to 42 pound injectors of the stock variety removed from someone's engine. After it runs, and the wife is off of my ass I will be freed up to actually get some work and tuning done to make it right. I know, I'm on a rant now and I apologize. I was hoping maybe to find a stock GM injector such as 12594512, or something similar. I am familiar enough with the software now where I can change gear ratios, enable or disable O2 sensors, EGR valve, set shift points, Etc. This weekend Oh, weather permitting, I will pull an injector just to see what the previous idiot did, and I should be able to determine where to go from there. I really, really do appreciate everyone's input on this ordeal. I understand most people here are used to working with someone who knows what's going on. I will get there, I promise. Thanks again!
Appreciate the encouraging words!! I would have no issues at all if I could start with a stock setup. I MAY swap my son for a stock motor so that all I have to deal with is headers! He has a few LS bullets sitting on stands in his garage. I may have him bolt one in. I'm going to keep going. I've never been one to quit, even though I've been to places that made me want to many many times. Thanks for the uplift!!
Last edited by 2k-Sierra; 04-20-2022 at 03:53 PM.
I recommend the 50lb/hr gm truck injectors. Part number 12613412. The injector data is all over this forum since many of us run them. They are inexpensive compared to aftermarket injectors, and considerably cheaper than new stock truck 25.2lb/hr. I will give you a tune file with the data if you go this route. They fit the 99-06 injector rails/clips pefectly. They do have a different plug (ev6) than the truck harness (multec). So you'll need the harness adapters or splice them into the truck harness. The adapters are relatively cheap and work fine, I have run them both ways.
2001 Silverado 5.3 - 209/217 cam, GT45 Turbo on 7lbs, Aem x-series wideband, 50lb/hr flex fuel injectors, on E85 with content sensor
1999 Silverado 6.0/4L80E Summit Stage one camshaft, 317 heads (replaced cast iron)
This would be greatly appreciated!! I will go this route. My son's buddy has run of a scrap yard and they get vehicles in on a daily basis. I'm sure he can score a harness and such to make this swap. I truly appreciate this. Thank you! That tune should get me running, at least.
Okay, I have some fresh injectors coming, but I have one more concern before I begin tuning. The previous owner installed headers and I just discovered that he has one upstream 02 in one side, and one downstream 02 in the other. I'm assuming I need to use two upstream 02 sensors. Question: What do I do with the downstream 02 sensors? Just unplug them and tuck the wires away? Then what? There is nowhere in the software to disable just two 02 sensors.
You can just disconnect the downstream O2's. You'll need just the upstreams.
Can you post the current tune file? Cause there's a shitload wrong in the only one you posted so far, it'd be good to not waste time recommending changes for stuff that's already been corrected.
Here is the current tune in the vehicle. It came this way, except, I went in there and put the correct axle ratio in.
The DTCs for P0101-P0103 should be set to MIL On First Error, not No MIL. You have no MAF, and setting the MAF DTC(s) is required before it will be in speed density.
Even once you get the injectors in there is a bunch of stuff in that file that need to be fixed.
Have all the EVAP parts been removed, or just turned off because 'smog stuff = bad'?
Truthfully, I don't know. This is the way I received the truck and I am attempting to work it out. Am IK to assume that disabling the DTCs means the component is also disabled? I was under the impression that only prevents the CEL from glowing. This is why, if I had the money, I would build a nice SBC 383 with a carb and call it good. But, I can't do that. I don't care if this is flawless or not. I just need it to run decently at the moment so I can drive it. I can nit-pick at it and tweak it as time and money permit. The MAF is there and connected. I assume you saw something in the file that says differently?
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