383 tuning help

[Kitch]

If no one has pointed it out to you yet, until your motor is up to a certain temperature it will only operate in open loop and when in open loop the engine basically runs of the preset values in your PCM's VE table.

If the values are set on the high side it will generally run rich, if they are on the low side it will run lean.

That's one of the things we change when we tune, to try get the values in the VE tables close to what the engine likes best so to speak.
In theory once you get the VE table set up correctly you could effectively drive around in open loop all the time but I certainly wouldn't recommend that.
During W.O.T. the PCM defaults to open loop and ignores the O2 sensor, thats why it's important to get the values in the VE table correct.

When the engine eventually goes into closed loop the narrow band O2 sensor takes over and tries to trim the fuel to near stoichiometric.
So if your truck seems to be rich when in open loop but better when warmed up and in closed loop, that's just the O2 sensor doing it's job.

Tuner Pro can actually be set to display the point that it changes from open loop to closed loop.

Any time you change your fuel pressure you will need to potentially redo your VE tables.
More fuel pressure = richer across the board
Less fuel pressure = leaner across the board
You need to make sure you have enough fuel pressure with your stock injectors so that are not maxing out their duty cycle at the top end. Then you tune from there.

A bit of a crude description but hopefully it gives you a bit of an idea.

Some of the more knowledgeable guys here might ask you to upload a TunerPro log from your truck and they can then comment on what they see is going on in your log.

[C2500]

Thanks for that last post.. Ill go over to moats and order a cable and get tuner pro.
I’m not sure what chip ed at fast chips uses but can I with the proper equipment reprogram that chip?

[C2500]

I think I should get the aup1 auto prom package??

[myburb]

The apu has always worked well for me. Moates has always been helpfull when needed. Might be an idea to have them ship a few extra chips. If you are going to seriously get into tuning it yourself a zif socket comes in handy and the ( off memory ) g1 adapter

[Kitch]

I'm not sure what Ed at fast chips uses, did the piggy back chip he sent you look anything like the Moates G1 memory adaptor?

I use an APU1 and have been happy with it, I've used it with my 94 Chevy van and my 95 GMC Yukon.
I did buy a GP1 package so I could fit the programable chip to my PCM but if you don't need the quick change ZIF socket and a spare chip then you could just buy the G1 memory adaptor.
I also later bought the HDR1 memecal header only because with the APU1 it allows you to read the contents of the stock chip.

[C2500]

Kitch, myburb, So if I get the apu and a GP1 package I should be set to tune this then? Do I also need the ZIF ? What does that do for me? I want to order what I need to do this..
Here’s a pic of Ed’s piggy back adapter. 9D2DEA51-D0A3-4859-96F7-F95841CFF9BB.jpg

[myburb]

The prongs on the chips are very thin and I tended to get one bent trying to put it in. The zif allowes you to just drop the chip in and flip the lever and you are done. If you want to get the tune really good you will tweak and data log a LOTA LOTA times. The only problem with the zif is it makes the chip sit up higher. Moates does have a low profile zif. What some do is use the zif while you are tuning and when you get the tune done then you can carefully insert the chip without the zif and then the cover on the case will fit ok. That adapter you have looks like it does a similar job to the g1. With the g1 you retain your limp. Not sure if yours does.