16197427 PCM swap

[JeepsAndGuns]

No, change only the one for TBI, because thats what you are running with that pcm. If you are running mpi, or cpi, then you would change those.
All I had to change was the injector flow rate. The other one (grams/sec) was automaticly calculated when I put in the flow rate.
You will need to know what your injectors are flowing for the psi you are running. And if I remmember correctly, its the flow of only 1 of those injectors. I cant remember. But I think its in the comments box.

[babywag]

Bah, you guys and those 401's with big injectors...
Makes me envious.
I didn't have to change it for my lil' 'ol 360 engine

Anyone planning on using a wideband with their 7427?

[FSJ Guy]

No, change only the one for TBI, because thats what you are running with that pcm. If you are running mpi, or cpi, then you would change those.
All I had to change was the injector flow rate. The other one (grams/sec) was automaticly calculated when I put in the flow rate.
You will need to know what your injectors are flowing for the psi you are running. And if I remmember correctly, its the flow of only 1 of those injectors. I cant remember. But I think its in the comments box.

Perfect. That's what I needed to know. Thanks!

[FSJ Guy]

SUCCESS!!!!

Well, as in I didn't fry my new PCM or any of my existing sensors.

It wouldn't run when I carried over my existing fuel map and injector flow rate so I plugged in the Chevy 350 fuel map and flow rate and got it to at least idle (poorly) and move out of the garage.

I have no datastream, but I think that's due to Howell switching the data lines in the original harness. I may just bypass the harness completely and go right to the ALDL port.

And I must've turned off the correct flags because the CEL (Check Engine Light) stayed off.

[JeepsAndGuns]

Only thing I carried over from my 7747 bin was my timing table. The 7427 does fuel diffrently, and has two tables. So all I did was smooth them out just a little. Definately keep the correct cylinder volume and injector flow entered into the bin so it can correctly calculate the injector BPW, then keep the stock chevy fuel tables and adjust from there.
I didnt have to swap any wires on the aldl plug?
When I first tried mine, I could not get aldl connection (tried before I even started) and the fuel pump came on and never shut back off. I did a little checking and found out I had put the eeprom in backwards.
Just remember 7747, pin one goes twards the middle of the ecm, on the 7427, pin one points to the outside.
Once I put the chip in right, it fired right up and instantly ran WAY better than the old 7747 did.

[FSJ Guy]

According to diagrams on the internet, I need to move the data feed from Pin E to Pin M (right below Pin A).

Any hints on how to remove the pin connector? I've been fiddling with the paperclip I used on the ECM connectors but so far am having no luck.

I'll check the ads file and see if I can't tell it to look at a different pin location, too.

It idles really nicely with the Chevy 350 fuel map and the injector rating set correctly at 81 lbs/hr.

[FSJ Guy]

Well, I got the pin moved to position M, but still no data stream. :-( I tried it with and without the 10K resistor. I will continue poking around.

UPDATE: Poking around was successful!!! I had to go into Preferences and play with the data stream settings. But now I've got datalogging!!!

Compared to the '7747 ECM, it's awesome to see the gauges and flags change INSTANTLY when they actually happen!

[JeepsAndGuns]

The faster datastream is awesome! Its like you finally got all the molasses cleaned out of the wires....hahahahaha.

[FSJ Guy]

Even after one datalog and adjustment to the the fuel tables, the difference is night and day!

[Revhendo]

God I hate you guys. Looks like a trip to the pick a part in my future.....

[JeepsAndGuns]

Even after one datalog and adjustment to the the fuel tables, the difference is night and day!

I couldnt believe the diffrence myself either. I was like wow, there is a very noticeable diffrence here. Couldnt believe it was from just the pcm.

Told you you wouldnt be disappointed with the swap

[FSJ Guy]

Tomorrow I'll take it out on the interstate and get it up to 75 mph. In town, I've only got BLM data up to 2,400 rpm or so.

I wish I could drive it to sea level, too, so I can get valid data for the higher map areas. MAP reads 85 with the key on, engine off at my elevation (~5,000ft).

[Bill USN-1]

I think you guys are blowing it up to be a little more then it really is.
The conversion is nice in that it allows for more future options like electronic trans and such. For an engine with a big cam the idle tables do allow for improved idle. The faster baud rate is a plus when tuning. Elec fan control.

But if the 7747 ECM was tuned properly then the swap to the 7427 PCM with the same good tune is not going to show a performance improvement.


So while it is something new to play with, it really makes no "performance" gains.

So if a guy already has an ECM based TBI system running fine on his basically stock engine and no real plans to go to an electronic overdrive trans in the future, then the only reason to swap is to have something new to play with.

Just don't want every guy reading these, thinking it's something he needs to do.

But learning new things is always a plus.

[babywag]

My eventual goal for doing this swap is to also control the 4l80e I have sitting on the side of my garage.

Staying with my 7747, would have required an addition TCM or a standalone unit.

If I ever get enough $$$ stashed away for the adapter kit I need that is.

[FSJ Guy]

I see your point, Bill. But for me, having essentially "real-time" data is a performance boost all by itself! And I like how the PCM adjusts timing to help control idle speed. That's a nice touch.

So now when something goes wrong, I have loads more data to look at before I scratch my head and wonder "Wow, I still have no ideal what just happened!"

I would still recommend the 7747 computer for someone just starting, however. It's a little "easier" to jump into.