1994 C2500 383TBI tuning newbie

[C2500ERIK]

Hello all,

I recently replaced the engine in my 1994 Chevrolet C2500 and I’m sure I’m going to need some tuning advice. The truck originally came stock with the 5.7L 350 and the M30 4L60e transmission. After 270,000miles it still ran well but felt a little tired.

I decided to replace it with a 383 Stroker crate motor. Here are the specs:
383 Stroker, Vortec iron heads, 9.2:1compression, hydraulic roller camshaft and lifters, spec's (206/216` duration at .050" with .475" lift on 114`LSA), dual plane aluminum intake(pro-comp), no egr.

I purchased a new throttle body from SPR:
46mm TBI Kit w/ Carb adapter 1994 4L60E-New TPS, New IAC, 350 high flow-matched injectors, 18psi, thinned shaft, bushed shaft, 1/4" pod spacer, shaved air horns, custom cut 46mm base gasket, air cleaner gasket, fuel line o-rings, adjustable regulator cover, 4150 carb intake gasket and mounting hardware. Open element air cleaner.
Installed a new EP381 fuel pump in tank at the same time.
I installed everything and set the initial timing to 6* and started tuning.

I’m using TunerproRT, Moates Autoprom, Stock ecm is 16196395, BJLH $0D.
Since I didn’t have the ability to read the bin from my original chip I downloaded one from here and started editing.

First things I changed were constants for injector flow and cylinder volume.
I set injector flow to 80 lb/hr and cylinder volume to 47.86cid.

I then changed the main spark tables using a vortec chart that FAST355 posted. This timing change made a huge difference in how the engine runs.

My next step will be to smooth the VE table and make some datalogs so I can adjust the VE using Dave W calculator spreadsheets.

I'll be posting some datalogs soon so everyone can see whats going on.

I’ll be looking for any advice as to the order in which to tune and any helpful info or comments.
Please feel free to point out what I’m doing right or wrong as I’m very much just learning how to tune.
Thanks, Erik

[Roadknee]

Hi Erik. I think you have an excellent start. That combination should really wake up the truck. What are you running for exhaust?

Since you don't have EGR, and if you haven't done so already, turn off EGR by setting the minimum temp for EGR as high as it will go.

I also prefer to zero out the PE spark table for initial tuning. You might add some PE spark later when fine tuning.

Did you set the initial timing in the bin to 6°? If not your engine is seeing 6° more than what is indicated in the timing table. I prefer to set up the bin so that the timing delivered to the engine matches the values in the timing tables. If you set the initial timing value in the bin to 6° you'll need to increase every value in the timing table 6° for the engine to receive the same timing as it is now.

Set all the values in the PE AFR table to 12.5 for initial tuning. You can tweak these when fine tuning later.

Set all the values in the TPS for PE vs AFR table to 60% and TPS for fast PE vs AFR to 70%. This will hold the engine in closed loop in the upper MAP areas of the VE table and allow you to get BLM data for VE table tuning.

Set the PE delay to 0 seconds. It's 15 seconds in most factory bins.

You'll need more AE for the larger engine, larger cam and larger plenum non-heated intake manifold. You can probably double the values in both the AE vs TPS and AE vs MAP tables to start. There are also tables with multipliers that add AE when coolant temps are colder. The factory multipliers are as high at 5. with a non-heated intake I've found you can cut the multiplers in half at least.

The non-heated intake can also benefit from increased deceleration enleanment. Don't concern yourself with this now, but when you get into fine tuning you'll see advantages.

Is your 4L60e stock? You'll probably want to bump up the line pressures and remove some of the negative pressure profiling to help keep the trans alive with the increased torque of the 383. There's a lot of performance benefit adjusting upshift/downshift and TCC lock/unlock tables too.

[C2500ERIK]

Roadknee,

Thanks for the reply. Right now I'm still running the stock exhaust manifolds but I have a free flowing cat and muffler. I plan on installing full length headers in the future.

I have turned off the egr as you described. The timing is also set as you described. After reading your post I have set the PE AFR to 12.5 and the PE delay to 0 seconds. Thanks! I'm now working on the AE, thanks for the info there.

I'm awaiting a Wideband O2 sensor probably after Christmas and I'm looking forward to some WOT tuning then, but first the drivability has to be squared away.

I do want to make some adjustments to the 4L60e, and would love to hear anyones advice/recommendations on how to go about this.

Thanks again for the great info.

[Roadknee]

Here's my trans tuning thread

http://www.gearhead-efi.com/Fuel-Inj...E-tuning-in-0D

The WB is a great idea. In addition to tuning WOT it will save so much time getting AE and decel enleanment dialed in.