Low Idle Vacuum Tuning
I've attached the engine build sheets. Perhaps someone can extract something from them.
The advertised LSA is 108° (https://www.jegs.com/i/Crane-Cams/271/521211/10002/-1). Is it being suggested that the engine has an internal issue?
FiTech unit isn't controlling timing and no vacuum advance. There was no hanging idle issue with the carburetor.
The dropbox link to the log file is below. Further down the spreadsheet you can see where I tapped the throttle and the idle eventually returned.
https://www.dropbox.com/s/dod9d6xel4zoq6v/DashBoard14.csv?dl=0
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Idle looks fine to me. Don't think you are going to do any better than that. If you want it to come down quicker, just increase your loop down rate a little at a time.
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If it was my car, I would do something about your low vacuum, but it's the AFR learn that is pinging -35, indicating you need to change your cam setting to a lower number. It's trying to take out too much fuel from your table.
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Your Iac returns to 0 in about 3 seconds after the throttle blip but as you said the rpms dont drop for another 7 or so seconds. At 0 the iac isn't controlling the idle. Your target rpm is staying high though matching the actual rpm. Have you watched this video? https://youtu.be/Mf078dj6LLU
Or this one? https://youtu.be/2g4iujVqjG8
Under idle control under procal go to open iac decel and take 10 counts from it to see if that helps.
I agree that you need to try different cam settings because your afr learn is way off. 20s would be better. You might also try hooking up vacuum advance if you have it. Hook it up to full vacuum. I'd advance the timing some too listening for spark knock.
Is your vacuum level cold the same as warm? I also agree your vacuum is very low. As I've said my vacuum is about 6 in gear (auto trans)with a very lumpy cam.
Yes, I've watched both YouTube videos. I'm maxed-out negative on the Decel Open IAC.
It's currently set to Cam 4. I'll try Cam 3 and see where the AFR learn goes.
Yes, vacuum reads the same cold and warm.
What is your timing at idle and how fast does the mechanical advance come in? At what rpm is it all in and what is the timing all in?
Here's the major plots together from you last log. I'll put in the new one when you post the new and improved log file.
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When the idle is hanging, have you tried to manually close the butterfly and/or links as much as you can (both front and rears)? If you do this, does the idle goes down to the set point? All this looks very similar to my issue.
The primaries and secondaries can't close any further since they're up against their respective adjustment screws. I did try backing out the secondary screw so it just contacts the arm...I wasn't able to get the IAC down from triple digits. Idle still hangs.
Thank you for the RPM vs Time plot. Nearly 20 seconds to return to idle looks Ok? Seems excessive when I'm shifting gears. Perhaps my expectations for idle return with EFI needs to be reevaluated if this is the case.