MPFI Version 2 - 1227730 ECM

[Bill usn-1]

I have already showed you how to do a TBI with the older C3 1227747 ECM.

I have showed you how to upgrade that to the newer P4 16197427 PCM.

Then I showed you how to convert that PCM to run a MPFI system.
All this was done using the same old wiring harness.


So now I will show you how to do a MPFI system with a factory GM P4 1227730/7727/7749 PCM. This will be a fresh install with new harness. The old harness could be used and the crossover diagrams are avail, but this will start with a complete harness for those wanting to start with MPFI from the beginning.

This is one of the older P4 PCM's but it is the faster baud rate and since it has been around for a while, it is very well documented and "hacked" so there are many options avail for it. There is elec fan control, turbo and supercharger 3 bar map control...etc.

So it makes it a pretty good candidate even though it's a little dated.

NOTE- see all the attachements in each post.

This is my red scout that I built back around 2004 to take to Europe. The TBI has worked perfect and has not let me down since the day it was installed. It made 2 trips around Europe. 3 years of wheeling in Sicily. Then another drive across country here.
But after doing my first MPFI install, I'm kind of hooked. It's a smiles per miles sort of thing.
First remove the old manifold and clean everything. I also replaced the 4 center screws on the valley pan in preparation for the RPT alum (bling) manifold. You can leave your bolts in if using a factory manifold drilled for MPFI.




Then I installed the gaskets. Before you drop the manifold on you will need to either remove the valve covers or trim the gaskets since the hang over the head and will hang on the manifold.



Then set the new manifold in place.
You will need a strong back or an engine hoist if working with the stock 70lb manifold. The alum is definately lighter.






Then add the injectors and fuel rails.



This allows you to mark the location of mounting bolts for the fuel rails. (if your using the RPT manifold)

[Bill usn-1]

I got everything pretty much slaved in on the scout. At least enough to try it out.
I just made some simple fuel rail connections with 3/8 fuel inj hose.
It will work fine but definately not bling quality.

There are a couple sensor differences from the older 7747.
This one is set up for the IAT/MAT sensor. This measures the temp of the incoming air. This was used on the car version of the 8746 so if you used the caprice airfilter it's the sensor on the aircleaner.

It also uses the 4000 pulse VSS.


After hooking it all up I bump the key with the coil wire off and got a great arc off the post.
So I hooked it up and touched the key. It immediately fired up and then died just as quick.
I thought I missed a VATs (anti theft) setting in the base chip. So I stated trouble shooting a no spark condition. Ended up being an ignition module.
Lesson learned to not allow the coil to arc over without a coil wire on it and have it arc to a good ground. Those electronics gon't like all the arcing just looking for a ground.

Once fixed I hit the key and the excess fuel lit off in the exhaust and scared the crap out of me. But she roared to life and idled great. See video below.

Even with just a basic chip with the unused sensors turned off, it ran really good.
So it looks like a pretty straight forward MPFI system will be available for the DIY'r and in kit form shortly. I still need to get a good tune done.

And i guess my initial drilling of the injector ports and fuel rails worked pretty good. This is the second system installed and no leaks. Guess doing things the old fashioned way still works. With the right tools and a lot of time measuring 3 times before drilling!!

But I have now found a machine shop that I provided all my measurements to so they can replicate the process faster then I can. I have to set up every hole one at a time to drill. They can set it up on a machine and have it auto feed.






Video link

If you listen you will hear some tinking at the beginning. That's from the OBW belt I left flopping. About 45sec in you will hear my knuckles hit the fan as I grabbed the belt on the fly. No blood and I held my tongue. I still don't have the IAC wired up yet so that's why I plugged the IAC port on the top as it was running.
Hopefully you have some 5.1 speakers with a subwoofer to get the full effect.

[Bill usn-1]

Speaking of IAC.
The throttle body I am trying out is a holley 4 barrel TBI that I picked up off ebay.
I removed the injector pod an then I had to drill the IAC ports and mounting since they are cast for an IAC but do not have one.
Since Holley makes or copies the standard GM and Dodge stuff, the IAC from a 454 TBI can be made to work with a little machining.

I had to open up the main hole to about .750 and then drill the passage to the air above the throttle plate and another below the throttle plate to allow the IAC to regulate the vacuum leak for idle speed control.

[Bill usn-1]

Finally got a little time to work on the scout.
I had to find a way to connect the throttle and auto kick down linkage to the new throttle body with the MPFI fuel rail right where it used to mount. Not to mention the injectors now sticking up out of the manifold.

Well I thought about it quite a while trying to come up with something that could be duplicated by someone else who wants one of these systems without having to fork out more money on the lokar parts.

What I did was remove the fuel rail and drill and tap the bottom of it to accept 1/4 x 28 bolts. The lower portion of the rail is 1/2" thick so I drilled 3/8" deep and then tapped the holed.
I drilled 3 holes so the throttle bracket could be moved forward or aft as needed.




Then I took the kickdown part of the bracket (my scout used a 2 piece bracket with the top part the throttle and the bottom is the linkage) and cut the mounting holes off.




Then with a little tweaking of the kickdown arm to the throttle and I moved the pivot rod to the outer position by just moving the E clips, it all fell into place.

No binding, full throttle, and the kickdown works. And it was all free.

And even my audiovox cruise control still hooks up.




Time to log a little data and do some tuning.

[Bill usn-1]

I didn't realize how long it's been since I updated some of these projects.
Been running the old girl on the 7730 MPFI for a while.
Sets for ever and I just walk up to it and turn the key and she roars to life.

Tuning takes a little longer since i had to learn the program, then had to set up the data logging and the bin tuning files. i had really hoped since this was so well hacked in the past that the files would have been complete. But no such luck.

I still need to rework the IAC port to get it a little smoother on the 4 barrel throttlebody.
But i think i will take a couple days and yank it off and throw one of the big 2 bbl TBI on it for air and see how it does.


After all the systems I have done, I haven't found one I don't like.
TBI or MPFI, they all work good.