Beginner in tuning and looking for some help and L31 vortec questions.

[Douglas1300]

I have a 99 suburban that has a GMPP HT383E in it with 0411 PCM swap. I'm trying to start dialing it in. it currently has a stock 02 express van tune on it.

first off, i'm curious of the flowrate of the stock injectors. i don't know if it makes a difference, but i installed the GM replacement MPFI injector spider. i have to measure my fuel rail pressure, but i was hoping to find out the rated flowrate at what pressure so i can adjust the actual flowrate based on my fuel pressure.

also is there a way to adjust the fuel pressure regulator on these to raise it a little so i dont have run more than 80% DC.

The HT383E is rated for like 320hp and 444TQ. i know that is probably at the crank under optimal conditions but i'd like to get as close to that as possible.

The truck has a K&N air filter with the stock intake, stock manifolds to 2" downpipes into 2.5" y-pipe and 2.5" straight pipe with the first O2 sensors in basically stock locations and sensor 2's deleted as there is no need to monitor catalyst performance as the cats are deleted. i built a homemade baffle design muffler that is currently installed to quiet it down for the drive moving across the country, but i will probably straight pipe it unless that sounds too terrible. it also has MSD 6AL ignition box with HVCII coil. I don't want to add too much more hardware right now.

I'm just trying set it up as accurately as possible for now with the current configuration. Also I am using HP Tuner. So far all I know about tuning is what is covered in Greg Banish's books and the basic physics knowledge I have.


any help/advice/information would be greatly appreciated.

[dfarr67]

There is a specific 383 sized spider out there for the vortecs. Davew might be able to help you on this.

How did you handle the harness?

[Douglas1300]

I used a pinout spread sheet from Lextech (Jeff) to pull the pins out of the 4 connector style PCM and install then into the 2 connector 0411 connectors. it was pretty easy really, but I had to chase my tail for a week as to what I did wrong to lose spark when really I just had an ICM go bad coincidentally at the same time as I did the swap.

[Fast355]

I have a 99 suburban that has a GMPP HT383E in it with 0411 PCM swap. I'm trying to start dialing it in. it currently has a stock 02 express van tune on it.

first off, i'm curious of the flowrate of the stock injectors. i don't know if it makes a difference, but i installed the GM replacement MPFI injector spider. i have to measure my fuel rail pressure, but i was hoping to find out the rated flowrate at what pressure so i can adjust the actual flowrate based on my fuel pressure.

also is there a way to adjust the fuel pressure regulator on these to raise it a little so i dont have run more than 80% DC.

The HT383E is rated for like 320hp and 444TQ. i know that is probably at the crank under optimal conditions but i'd like to get as close to that as possible.

The truck has a K&N air filter with the stock intake, stock manifolds to 2" downpipes into 2.5" y-pipe and 2.5" straight pipe with the first O2 sensors in basically stock locations and sensor 2's deleted as there is no need to monitor catalyst performance as the cats are deleted. i built a homemade baffle design muffler that is currently installed to quiet it down for the drive moving across the country, but i will probably straight pipe it unless that sounds too terrible. it also has MSD 6AL ignition box with HVCII coil. I don't want to add too much more hardware right now.

I'm just trying set it up as accurately as possible for now with the current configuration. Also I am using HP Tuner. So far all I know about tuning is what is covered in Greg Banish's books and the basic physics knowledge I have.


any help/advice/information would be greatly appreciated.

Look at the later model 4.3s for the correct injector calibration stuff. I know by 2004 the Astro/Safari vans had the updated spider from GM From memory they are 21 lb/hr and run at 58 psi.

The stock manifolds and 2" pipe are choking it to death. The big vans had 2.25" pipes at the manifolds and kicked up to dual 3" within inches of the manifolds on stock 350s. The Thorley headers I put on mine were 2.5" at the collector and immediately bump up to 3" to mate to the pipes. I used a walker dynomax bus muffler with dual 3" inlets and a 4" tail pipe on my 350. Woke it up ALOT.

[Fast355]

Just FYI it is a very quiet setup even with the Thunderbolt high flow cats on it. Even climbing a 6% grade at 70 mph in the van with some music on you can barely even hear the engine.

https://youtu.be/bpPSgILR6wc

https://youtu.be/UKw3V5f7GIk

https://youtu.be/UgwvwHzk74c

[Douglas1300]

[QUOTE=The stock manifolds and 2" pipe are choking it to death. The big vans had 2.25" pipes at the manifolds and kicked up to dual 3" within inches of the manifolds on stock 350s. The Thorley headers I put on mine were 2.5" at the collector and immediately bump up to 3" to mate to the pipes. I used a walker dynomax bus muffler with dual 3" inlets and a 4" tail pipe on my 350. Woke it up ALOT.[/QUOTE]

good to know it seemed like the exhaust was still pretty hot even after opening it up more than the stock exhaust was.

[Fast355]

good to know it seemed like the exhaust was still pretty hot even after opening it up more than the stock exhaust was.

I think GM used the dual 3" pipes on the vans more for heat management than for flow reasons. More surface area means the exhaust, cats and muffler run cooler under the kind of sustained load a van can create especially towing. Both of my factory manifolds were cracked in less than 70K.

[dfarr67]

I used a pinout spread sheet from Lextech (Jeff) to pull the pins out of the 4 connector style PCM and install then into the 2 connector 0411 connectors. it was pretty easy really, but I had to chase my tail for a week as to what I did wrong to lose spark when really I just had an ICM go bad coincidentally at the same time as I did the swap.

Ah- you had it easy with the 'black box' ecu.

[dfarr67]

I think GM used the dual 3" pipes on the vans more for heat management than for flow reasons. More surface area means the exhaust, cats and muffler run cooler under the kind of sustained load a van can create especially towing. Both of my factory manifolds were cracked in less than 70K.

Are you aware of a good muffler with 4in in/out?

[Fast355]

Are you aware of a good muffler with 4in in/out?

If your rig has a lot of space under it, would be hard to recommend against the Walker HD muffler line like the one I am running in my Express van.

https://www.summitracing.com/parts/wlk-21471?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-walker-exhaust&gclid=EAIaIQobChMI_sqe7abI4QIVxsDACh1Riw-HEAQYAyABEgK64vD_BwE

[dfarr67]

I ended up with the only choice for me is SS that was a decent price- Pro Flow that is configured for my body style 88-2000 truck- but in 6.5 TD? deisel, 4in dia I'm wondering how loud it will be installed.

[Douglas1300]

ever since I did the 0411 pcm swap, the speedometer hasn't worked. Has anyone else had this issue and does anyone know how to fix it?

[dfarr67]

I think there is different ppm vss options- I have a new one in the box to fit the transfer case, I also think there are options on the tuning side. Assuming the wiring is right.