Tuned Vortec TBI to MPFI on 7427

**woody80z28** · 03-07-2019

I built a Vortec TBI in 2011 and tuned it so it runs pretty well. A little bit lazier than I expected to be honest, but the BLMs are all really good and driveability is good.

I'm taking that engine and putting it in a new truck (also a 94 with 7427) and would like to convert to MPFI at the same time. The hardware stuff is easy and I've looked at the how-to and changing the resistors on the ECM and adding a jumper on the PROM looks pretty straight-forward. My question then comes to the changes I'll need to make in the BIN. I went through the noted flags and checked/unchecked them, but the calibration stuff is where I'm stuck.

Anyone have a clue about my used blue top Bosch/Accel/Ford 280150967 injectors? So far the Googles have failed me on finding the voltage offsets. I couldn't confirm that that are high impedence either.

For Crank BPW vs temp, do I just change the pulse width based on the total injector math? So 2x80lb=160, and 8x36lb=288, so I multiply the current numbers by 0.55?

I'm excited to get started on this. It's a project I've wanted to do on my current truck for years, but haven't had a chance. My new truck2.0 will have a lot of those procrastinated projects...haha

**Fast355** · 03-07-2019

Originally Posted by woody80z28

I built a Vortec TBI in 2011 and tuned it so it runs pretty well. A little bit lazier than I expected to be honest, but the BLMs are all really good and driveability is good.

I'm taking that engine and putting it in a new truck (also a 94 with 7427) and would like to convert to MPFI at the same time. The hardware stuff is easy and I've looked at the how-to and changing the resistors on the ECM and adding a jumper on the PROM looks pretty straight-forward. My question then comes to the changes I'll need to make in the BIN. I went through the noted flags and checked/unchecked them, but the calibration stuff is where I'm stuck.

Anyone have a clue about my used blue top Bosch/Accel/Ford 280150967 injectors? So far the Googles have failed me on finding the voltage offsets. I couldn't confirm that that are high impedence either.

For Crank BPW vs temp, do I just change the pulse width based on the total injector math? So 2x80lb=160, and 8x36lb=288, so I multiply the current numbers by 0.55?

I'm excited to get started on this. It's a project I've wanted to do on my current truck for years, but haven't had a chance. My new truck2.0 will have a lot of those procrastinated projects...haha

Try leaving the cranking BPW alone. Once I had mine in MPI mode it started well with minimal changes. For that matter it started and ran on a stock TBI tune suprisingly well after setting the injector size to match. 4x24=96 lb/hr.

Most would probably laugh but I had pulled the PCM out of my G20 when it layed dormant for ~5 years. I lost the chip and file that ran it. I wanted to load it onto a trailer to bring it home. I hooked a TBI PCM to it, timing still set to 10° BTDC, put a battery into it, sprayed a shot of ether into the throttle body feeling the injectors were probably gummed up anyway, hit the key never even hearing the fuel pump run and the cammed 383 ported head Vortec TPI with SLP runners roared to life and stayed running. After a few seconds it settled down to a normal idle and after about 1 minute or so went into closed loop and ran as well as any OEM TBI 350, lol.

https://youtu.be/VvmK__hH-Fg

Even on 5 year old gas it still ran good.

https://youtu.be/t5O1if1DpRo

The videos above were running a completely stock junkyard pull 95 Van computer and a stock GM BJYN Memcal. It ran a little rich but honestly I could of driven it to and from work the way it was running and other than the annoyingly low TBI shift points it actually drove really well.

**woody80z28** · 03-07-2019

Damn, that does sound good! haha

This is probably the best exhaust video I have of the Vortec TBI:

https://www.youtube.com/watch?v=dHipLkOYmL8

**Fast355** · 03-07-2019

Originally Posted by woody80z28

Damn, that does sound good! haha

This is probably the best exhaust video I have of the Vortec TBI:

https://www.youtube.com/watch?v=dHipLkOYmL8

Sounds good!

I am actually suprised it ran as well as it did on the TBI PCM. I thought it would at best limp onto the trailer. I actually did a little burnout in the street after I unloaded it off the trailer. It was parked when I lost 3 & 4th on the 3rd 4L60E that was in it.

That exhaust setup was thorley tri y headers into dual 2.5" pipes, X pipe where the cat usually sits on those vans and dual flowmaster 40s with the OEM style dual pipes in stock location for that year van. Sitting at a redlight you would never suspect it had a cammed 383 TPI lol.

**woody80z28** · 03-22-2019

I measured my injectors and they are 14.5ohm, so I'm good there. Would still like the know an estimated offset if anyone knows how to figure that out.

However, that new 94 truck is a rusty POS, so I'm buying a clean 92 with the 7747. I still want to use the 7427, so I see I can either repin or I should be able to swap the harness from my current 94 donor truck. Which do you think would be easier? I'm worried about damaging pins during the repin process. I had trouble with it when I tried just one pin on my Beretta with a mini screwdriver, but this how-to makes it look easy with a homemade paper clip tool: http://www.dynamicefi.com/RePinHowTo.php

Any other tricks to the process? I suppose I can try to repin and then swap harnesses if it goes south...