IAC counts high

[PlayingWithTBI]

Here's an example from mine with aluminum heads. Your Vortec heads will want a little different ramp. HTH

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Note: I'm idling at ~850 RPM in Open Loop with this cam (I'm sure I could get it to run in CL but, I'm lazy). That's why the lower end of MAP/SA is flattened. Usually at ~55 - 65 MAP.

 

[Scooterwrench]

Ditto with your success!

Here's a link that may help with your timing. @84Elky Includes a great explanation of how and why. You may want to start with something like this, then adjust based on Knock Counts. Post #3 starts with the "how and why", post #8, @Sharp38 modified the spreadsheet to eliminate a loop in the formula.

www.thirdgen.org/forums/diy-prom/761049-spark-advance-table-example.html#post6301288

Spark Advance table example needed - Third Generation F-Body Message Boards

DIY PROM - Spark Advance table example needed - Trying to understand the sa tables vs actual engine excelleration vs mph at the foot pedal. Found this graph from older thread here and compared it to my bin which is a lot different. Can there be a good/simple reason?...

www.thirdgen.org

That's good stuff.
That's more like a mechanical advance curve where the weights sling out gradually and the vacuum advance retards when you step on it and gives more advance at the off idle point when you step on it. That was always a problem I tried to overcome with the weights in my HEI. Never could find that sweet spot.

 

[PlayingWithTBI]

That's more like a mechanical advance curve where the weights sling out gradually and the vacuum advance retards when you step on it and gives more advance at the off idle point when you step on it

Yes, and infinitely more adjustable. You don't have to rely on weights when they're too light at one point and too heavy at another. The MAP acts like your vacuum advance which, based on KCs can be adjusted and smoothed in any area. I'm sure you know this stuff, I'm just explaining it for anyone that may not.

My engine has almost no KCs on acceleration but, it does at idle ( ~850 RPM and 65 - 70 MAP), and cruising at ~2000 RPM and 40 - 45 MAP. I kept pulling timing until it turned into a dog and still had those KCs. I went back to the original RPM/MAP settings and called it "phantom" KCs. I have no idea why...

 

[Scooterwrench]

Yes, and infinitely more adjustable. You don't have to rely on weights when they're too light at one point and too heavy at another. The MAP acts like your vacuum advance which, based on KCs can be adjusted and smoothed in any area. I'm sure you know this stuff, I'm just explaining it for anyone that may not.

My engine has almost no KCs on acceleration but, it does at idlew ( ~850 RPM and 65 - 70 MAP), and cruising at ~2000 RPM and 40 = 45 MAP. I kept pulling timing until it turned into a dog and still had those KCs. I went back to the original RPM/MAP settings and called it "phantom" KCs. I have no idea why...

Is that table you posted the table you are running now? That's quite a bit of low end advance. What?,about 25deg?

 

[PlayingWithTBI]

Is that table you posted the table you are running now? That's quite a bit of low end advance. What?,about 25deg?

Yeah, with higher SA, I get lower MAP. That makes it a little easier to tune Speed Density. I had it as high as 28° on my previous cam (08-430-8) in a 350. Now, I even have longer duration (08-432-8) in my 383.

 

[docstoy]

I'm glad you found your problem (s). So some of what was going on was due to setup in your programming ? I'm totally stupid on that , is there a sticky on it ? Would it help with stock engine setup or is it more for performance setups ? Just wondering if it would help efficiency of stock power train.

 

[PlayingWithTBI]

Would it help with stock engine setup or is it more for performance setups ?

Stock would want it, performance engines would need it.

Just wondering if it would help efficiency of stock power train.

Yes, GM left a lot on the table with conservative SA and VE tuning. You can get a performance upgrade without failing emissions standards too.

 

[docstoy]

It would be nice to have a 30 mpg or better 4x4 truck. So look in stickies to get started and then ask questions ?

 

[PlayingWithTBI]

It would be nice to have a 30 mpg or better 4x4 truck

That'd be a challenge,

So look in stickies to get started and then ask questions ?

What do you have? Is it TBI or Vortec? Start reading from there, to a certain extent, you don't need to worry about tuning a TBI when you have a Vortec. Or visa versa.

 

[Scooterwrench]

I'm glad you found your problem (s). So some of what was going on was due to setup in your programming ?

And way too much fuel pressure. I'm guessing the ECM was trying to lean it out to the point it was shutting the injectors off at cruise.