Entry level EFI tuning

[travis]

I’m slowly putting together a mild L31 based 383 for my ‘99 3/4 ton suburban. I will be basically duplicating the GM HT383...factory spider injection system, Vortec heads, ramjet cam, etc. Undecided if I’ll run headers or not at this point. I’m assuming it’s going to need some tuning changes to the factory computer system to run its best, especially since everything I have read says that this system will run extremely lean after pretty much any engine modifications.

Is there a novice friendly tuning setup that isn’t too expensive? Also...any suggestions on reading material to help tune one correctly? Or is this one of those things best left to someone that knows what they are doing?

[rebelrouser]

I am not a guru, but will give you some of my personal experience. HP tuners are about the most common, YouTube is your friend, sit down and watch a lot, and be ready to figure out who knows and who doesn't. My main issue is when tuning OEM computers, is because of emission laws, the OEM does not give out a lot of info. When you open up a OEM computer program, their is not a really good reliable source to tell you what all those tables do. Most of the tuners I talk to know how to do some stuff, but frankly they are kind of limited on what they know about how the fuel and ignition system is supposed to operate on a stock vehicle.
I say that because before I started to use a programmer, I paid money to have computers flashed, and seldom did they get it right. Many times I had to send them back multiple times to even get the engine to start.
To give you a good example helped a guy that bought a street rod, with a LS engine, basket case. I helped him and it turned out that it had sat so long the injectors stuck do to fuel varnish. Got it running and the throttle would not work, it would just idle, drive by wire. So a guy came by, hooked up his lap top and flashed it so the throttle would work. The reason the throttle would not work was because the other modules on the CAN bus were not installed so the ECM could not do a diagnostic to make sure the network was able to safely control the throttle. So I asked the guy did you install some resistors in the harness, so the ECM could do a CAN bus diagnostic? He gave me a puzzled look and just left. So yes the throttle worked, but all the factory safety checks were disabled, so what happens when the throttle on a hot LS goes wideopen in a 2,500 lb fiberglass body car with no roil cage?

My personal preference is that if you want EFI on a performance vehicle, buy an aftermarket computer and system, they have the info, changes are easy to make and it just works out a lot better and safer.

[travis]

I have read that few people REALLY know how to tune a factory computer, for the reasons you stated.

My fear is trying to integrate some sort of aftermarket EFI with the factory PCM, VATS, etc. It sounds like something that could get real complicated and expensive, real quick. This is no hot rod at 5700+ pounds empty, more of a family hauler/tow vehicle.

[englertracing]

I'm not sure what's avaliable for a gm, but after a bit of a learning curve the tweecers let you do a whole lot to many ford vehicles.

If you can find something similar for a gm it would do what you want.

[vannik]

The very basics of Canbus explained and the requirement for a terminating resistance explained and the effect of not having it shown:

https://www.youtube.com/watch?v=uKnQI2IScPU

[Belgian1979]

I’m slowly putting together a mild L31 based 383 for my ‘99 3/4 ton suburban. I will be basically duplicating the GM HT383...factory spider injection system, Vortec heads, ramjet cam, etc. Undecided if I’ll run headers or not at this point. I’m assuming it’s going to need some tuning changes to the factory computer system to run its best, especially since everything I have read says that this system will run extremely lean after pretty much any engine modifications.

Is there a novice friendly tuning setup that isn’t too expensive? Also...any suggestions on reading material to help tune one correctly? Or is this one of those things best left to someone that knows what they are doing?

Don't waste you time on a factory ecu. Get yourself a programmable aftermarket efi and be done with it.

[BigBlockMopar]

If you know how to tune a carb and ignition... properly tune a carb AND ignition, then you are miles ahead of the average 'computer/tech-nerd' who flies through the settings like a robot, but for instance has hardly a clue why you would need 'acceleration enrichment' or limiting spark-advance at high intake air temps.

Knowing a bit of everything gets you on the road quicker.
If you're handy with carb, ignition and wiring, and you know your way around computers/software, then it won't be all that difficult.

[PRH]

Get yourself a programmable aftermarket efi and be done with it.

Exactly.

It’s the difference between a system that’s not designed to be adjusted by the end user..... and one that is....... along with the tech support to help you with it.

[S10LS2]

Your first problem is you asked here lol. As you can see by most of the replies not alot of knowledge on oem ecm,s here so far fro the replies.. You have a basic setup That about anyone with a wideband and stretch of road can tune.. Your combo has been done to death for 15-20 years. A 99 l31 is not drive by wire so no worries. Read up educate yourself a bit on the subject. Early ecm's 98-05 ish do not have complex tables in them like the new GM stuff. Go out and buy efi live or hp tuners make a few logs and post them up on the appropriate forum.. You wil get lots of help from guys who have 20 plus years on factory ecm's. Learning to read the logs and adjust maf and ve tables according to what the wideband says is not that difficult anymore. I have not seen anyone with efi live or hp tuners on this forum help someone tune something efi ever. If you posted a log file in one of those formats here I bet not to many educated responses.

[S10LS2]

Lots of reasons to aftermarket ecm. Your is not one of them.. In my state only cars that are 25 years and older do not have to go through emission testing which requires a functioning check engine light and verification the sensors are working and valid ,of which only a factory ecu can do. A $2500 holley efi or a $300 mega squirt will not be able to do that. Dig in and start reading at those two forums or many others. There is a learning curve but it is not a big one for what you are doing right now.

[Belgian1979]

Engine Check lights can be done with MS as well.

[CGT]

If you know how to tune a carb and ignition... properly tune a carb AND ignition, then you are miles ahead of the average 'computer/tech-nerd' who flies through the settings like a robot

I agree...but there tends to be a lot of either/or in the efi tuning world. Computer guys that don't have a clue how an engine works, and engine guys that don't have a clue how a computer works.

[Belgian1979]

You don't need to be able to program them (although I admit it might have been useful) but you just need to be able to use the program such that the engine does what you want. If you have a fairly simple engine with a fairly standard setup it shouldn't be too difficult imo. When moving away from simple, things get complex very rapidly. This is furthermore made more complex by the enormous amount of different setups that it can accomodate.
The most difficult aspects I faced were (i) wiring issues, (ii) proper ignition setup and (iii) some aspects associated with my specific engine. As far as tuning is concerned: fueling is relatively easy to set up but ignition is virtually impossible to set up correctly without a dyno.

I cannot say that an efi system will make an engine produce more power but it will do away with the difficulty to get it to idle properly with a large cam and it will elimate any vapour lock, fuel boiling issues you might have had before. You also do not need a choke anymore and you can have your engine adjust its idling rpm automatically independant if the engine is hot or cold and independant what devices you switch on.

[travis]

Would an aftermarket EFI and the factory PCM/trans controller be able to work together, or would I need a stand alone trans controller? It’s a 4L80 if that matters

[Belgian1979]

Would an aftermarket EFI and the factory PCM/trans controller be able to work together, or would I need a stand alone trans controller? It’s a 4L80 if that matters

I don't know what the trans uses as input to change gears and such but can imagine that it uses some sort of signal that represents rpm and/or load. You can setup a analog output signal that would vary depending on the factor that needs to be monitored. You can even setup a frequency signal in the same way and you can even send out a can signal if you can get the protocols to work together (that last one is a bit too complex for me I'm afraid).

For example, I use a ford fuel pump controler that uses frequency output of my ecu to regulate the speed of the fuel pump. All it needed was the correct output from the ECU.