Idle Tuning with large TB and large Cam

[bmorrow8]

hello,

I am having a hard time setting my IAC and getting my truck to start cold.

set up:
1986 c10
ls1
prc heads - 10.5:1 CR
btr stage 4 car cam
long tube headers
4inch CAI
ls3 MAF/IAT
holley 102mm TB
Stock replacement IAC
MSD atomic air force intake
stock ls2 injectors
return style fuel system
t56

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I am following tuning material I purchased from ERM tuning. (rest in peace Ed). I have maf and VE very close, especially idle values, When i set my TB to less than .8v and IAC sitting at 40-60 at operating temp. It idles fine, I usually set BRAF for 198 Degree cell and disable timing control while doing it, just to get things running right. I let it sit over night and attempt to do a russK config to do BRAF. IAC count is 310 and wont idle or even start for nothing. Could you give me some ideas to try? attached is current tune and idle scan tonight when attempting to BRAF cold to hot. This is my first tune from scratch on very modified motor/ LS swap. Feel free to ask me why I did this or that in my tune, I am learning and love tuning and want to be able to tune efficiently.

*excuse my really long .hpt file name, it helps me learn and keep things in order when trying new things*

[anniversaryss]

Im here for the information but its funny bc all my file names are about as long as yours lol.

On a side note did you drill the the throttle blade?

Ed has a spreadsheet to figure hole size out as well

[bmorrow8]

I have not drilled yet because I honestly couldn’t figure out how to use his calculator.

[anniversaryss]

On a side note hows the car run with your injection timing aimed at PPV?

[aw1980t]

I'm trying to put a choppy idle tune on a Gen 3 5.3. Can someone give me a hand?

[Ben Charles]

What part of TN you from?

[Ben Charles]

Don’t ever drill a 102mm TB... plenty of adjustment on that TB

[bmorrow8]

On a side note hows the car run with your injection timing aimed at PPV?

It seems to like it alright. I noticed it doesn't smell no where near as bad. With a cam this large, It only seemed right to shift the SOIT to PPV. At 6700rpm and 100% TPS. I'm running around 87% Inj Duty. More than I like to be but will work for now.

[bmorrow8]

What part of TN you from?

Chattanooga, TN

[bmorrow8]

Don’t ever drill a 102mm TB... plenty of adjustment on that TB

That is why I haven't drilled it yet. I just can't seem to figure out why I set my IAC to 40-60 at hot idle and set BRAF and then it won't start without pedal on cold start. I can't even get it into Adaptive Idle but increasing or decreasing start up air flow and/ or friction airflow doesn't help either. Makes me think it needs the throttle body cracked more but when I do that, The IAC sits at 5-10 and seems to try and stall every once in a while when letting out of throttle coming to a roll?

[bmorrow8]

I kind of wonder if i'm not fighting a crappy IAC and it doesn't have enough range for cold start

[anniversaryss]

It seems to like it alright. I noticed it doesn't smell no where near as bad. With a cam this large, It only seemed right to shift the SOIT to PPV. At 6700rpm and 100% TPS. I'm running around 87% Inj Duty. More than I like to be but will work for now.

Would u mind sharring your cam and injector info with me? You can PM me if ya like. I have been thinking about trying to move my injection timing closer to PPV with my cam. Ive tried after the exhaust valve closed but i dont think my car liked it, dont think thr fuel was mixing well.

[Ben Charles]

Sometimes I have had to open up the iac passage on some aftermarket TBs (much smaller then stock.)