Thanks Bink. I was wondering if that is where it was. My throttle cracker table is set to stock levels too. So you're saying I should lower the values in lets say the 0-36mph up to 1600rpm cells? What happens if they are at 0?

I was also wondering if it could be linked to my MAF Calibration table throwing everything off. It too is still at stock values even tho I have billet MAF ends & a ported TB. Tho I didn't have this problem until I added the cam.

 

Did they "Zero Out" your Throttle Cracker Decay table????

 

No, but I was wondering if that was the thing to do in those cells. Like I said it's all stock right now. (as are all the throttle follower tables)

My Throttle Cracker Table
400rpm 1000 1600
0mph 0 0 0.2
4mph 1 0 0.6
8mph 0 0 0.65
12mph 0 0 0.7
16mph 0.4 0.5 0.7
20mph 0.4 0.5 0.8
24mph 0.5 0.55 0.8
28mph 0.5 0.6 0.9
32mph 0.6 0.65 0.9
36mph 0.65 0.65 2

 

No, I wouldn't zero them out. Does it cruise indefdinitely with the throttle closed - i.e. no decay whatsoever?? If so, then I would try reducing the Throttle Cracker Airflow by 15% 2000RPM, 36 mph and down. Leave the 1.000 island, at 400 RPM and 4 mph, alone - don't change it. Take it out and see how it does - scan it.

 

OK, Ill try that. Thanks! The 1 @ 400rpm is so it doesn't stall, correct?

 

That's my take on it ... it needs additional airflow at 400 -800 rpm and > 0 -4 mph. You may need to reduce this some, also - eventually.

 

I have been looking over my logs, and it looks like each IAC count equals .1 g/sec. It starts to stray a little once my car is warm, probably because my running airflow is way higher than it needs to be. gameover...any comments?

 

from my post

 

But that doesn't take the idle hole or set screw into account? I don't see where it "subtracts" this, because it would have to in order to effectively use the running airflow table. So is there a value that is set for "base airflow (non-iac/etc controlled)"? If there isn't, then running airflow can't be measured in airflow, it would have to be in steps.

Like here, his airflow requirements at idle didn't change, but you recommend that he set back his running airflow to account for more flow of the throttle body...

My point is, based on what you say, if the running airflow is right, then there is nothing to trim, regardless of what changes you made to the throttle body. Unless there is a "base airflow non-iac/etc controlled", or the "running airflow" is actually measured in counts.

 

it doesn't care, this the calibration of the IAC. ie. how much airflow thru the IAC do i need to move the engine RPM up or down.

The hole in the TB (or set screw) just adjusts the IAC dynamic range to be "useful". eg. if you want to idle your engine at 1100 RPM it's probably not a good idea to burn ~200 steps of your IAC to get your idle RPM, leaving you only 110 for "adjustment". Far better to drill the blade or adjust the set screw to give you IAC counts in a much lower range at idle.

Chris...

 

Aha. So the value is only the amount of air that should be flowing through the IAC. That's what I wasn't sure about...I haven't had much luck treating it as just IAC running airflow. For instance; when my car is cold I see idle airflow of about 13 g/sec and my desired idle airflow is about 14.5 g/sec with 145 IAC steps, with a stable idle. Is this an issue with 98 vehicles like mine?

 

hard to tell, could be your IAC is clogged up a bit and has to open more to get the same airflow? it's (or the MAFs) calibration could be out? I never pay much attention to the MAF airflow relation to the IAC desired.

 

Well I cleaned everything out with top engine cleaner just a few months back, and I ran a lot through the IAC, but I did not break it all apart. I suppose that could be it... I don't trust MAF calculated airflow at low speeds, there is a big difference between MAF calculated and SD calculated. I'm sure that is thanks to the lid. I'll double check when my Shaner S3 gets installed, but I don't think it's clogged. As for calibration, maybe I will just throw a new one in for the heck of it, but I would expect it to throw a code being that far off.

 

can we get more on regulating spark at idle? all the bigger cam cars i've tuned bounce off their timing quite a bit, i'd love to know how to make it hold steady. What causes it to bounce around like that?

 

idle adapt settings as well as the overspeed and underspeed corrections. my timing and rpms do what i want them to now

 

Thanks for digging this up RHS. Lots of good info here.

 

you can hold the timing at idle steady but deleting the overspeed and underspeed tables. this however will not allow, in most cases, a smooth idle. i adjsuted my spark changes from 25 rpm delta and up in half deg increments starting at 1, i also adjusted the underspeed settings to if the idle dips really low the timing will help it recover on those freak rpm dips on let off. i plan to try and write up a new file of everything i have done so far

 

TTT for new forum

 

What did you change the values to to stop the bouncing?

Bill

 

Sorry to ressurect this old thread, but it has some good info in it...and I have a related question

Is there an algorithm/table that can show us desired idle timing vs cam size/duration/overlap?

My car likes more idle timing with a bigger cam - but it would be nice to know 'how much'