I just finished my 383/CC306 build and I'm still on the stock tune. I started the car and it does not idle, RPM goes up and down and dies sometimes. I am new to tuning, but I want to learn, can you guys tell me what I need to adjust on tunercats to make my car drivable. I"m not hoping to get a killer tune yet, I just want to make sure it is safe to drive it.

TIA!

 

Here is my first guess and this in ONLY to get it idling. LOTS of tuning needs to be done to make it perfect.

You need to open up your blades on the TB to let more air in because the overlap caused by your much bigger cam than stock is sucking more air. If it does not have enough air, it will have a hard time idling. I assume you have a scanner. You will see that your IAC counts are stuck wide open on startup.

This is not the real way to resolve the issue because your split BLM problem will be exacerbated but you should get it to idle.

GL and tell us how it goes.

 

First thing you should do is change the cylinder size in the constants table if you havent yet.

Then if you're auto pick an idle rpm that is not 600 because it aint gonna be happy there.

Then go into closed tps timing and set 400-800-1200rpm to something like 28 degrees.

Zero out the idle overspeed and underspeed spark advance/retard for about 100 rpm on each side of target idle. Your new engine isnt going to be as rock solid and steady as a stocker so it needs a little room not to chase its tail.

Make sure your injector constant is correct in the constants table if you have changed them.

I will second cracking the tb blades a bit, its gonna take quite a bit more air to idle this engine. Generally when all is said and done you would want to see iac counts up near 100 with a cammed engine imo.

 

Thanks for the help, I will try to do that as soon as I can get the definition file to open on tunercats. I am running vista and I am lost

EDIT: Ok, I got it installed, I don't ever know how I did it but it looks like it works now.

 

thanks for the help

 

383 cubic inches / 8 cylinders = 47.875 in^3/cyl

1 cubic inch = 16.387 cubic centimeters

47.875in^3/cyl * 16.387 cc/in^3 = 784.53cc per cylinder.

 

Ok, I made a tune on tunercats but when I open it and click program PCM, after a while it says "No Response From PCM" or something like that.
I'm confused AGAIN!!! lol.

 

turn the key to the "run" position and try it again?

Also depending on what kind of cable setup you have you might need to select a different comm port.

Try datalogging first before you program to make sure you have everything set up correctly.

Uploading a tune is not the place you want to find out you have troubles.

 

I am doing it with the key in the run position.

I can run freescan and read the PCM in tunercats just fine, just when I try to program the PCM I comes up with that error message.

I have the USB to OBD1 cable (OBD2 style connector) and I am using comm port 4.

Edit: turns out I wasn't using comm port 4. I uploaded my tune and it idles a little better (still surges up to 2000rpm and down to 650rpm), but the IAC couts are in the 80s, pretty close to the 100 you mentioned earlier.

It doesn't smell like gasoline anymore though

 

Post a log of the surging.

 

not surging at idle any more!!!

It was a vaccum leak, the little rubber seal on the MAP sensor was missing, I replaced it and IT IDLES, lopes real nice too.

I really apreciate all the help guys, thanks alot.

any other things I should change on the PCM?

 

Tons of things. Vague answer I know, but that was a pretty vague question.

Tuning is very much a cut and check thing start at low speed and cruise and work your way up. Make only a single change at a time unless you REALLY know what you are doing.

 

OK, I'll take it slow on the tuning for now.

I got what I wanted. It Idles

Thanks alot WS6T3RROR

 

I am kinda in the same boat you are. I want to learn how to tune, but don't know where to start. When I get my 383 done, I'm going to get a mail order tune 1st. Just so I have a close baseline to start with...

 

I was reading THIS website about tuning LT1 PCMs. It says to advance timing in the "Closed TPS% Spark Advance vs. RPM" table just enough to not cause knock retard and to lower your KPA reading at idle.

the first tune I made, I had timing at 28* in 400-800-1200rpm, The kpa reading at idle was 48-51.

I modified that table to 33* and my kpa reading at idle went down to 40-43.
Thats good right?

so can I advance timing for part throtle accross the rpm range til I get knock retard, then just back it off a degree or two?