idle tuning on 408 motor

[mrr23]

added Russ K idle config to my config to make it work.

here's the log and file. did just like Russ k said. started it with no throttle input.

tell me what you think.

seems to me that commanding the 10.56 a/f ratio is really rich. i do have a wideband, just not wired into the MPVI interface, yet. idle is choppy. granted it's a 408, but the cam is a 232/240 LSA 117. once warmed up, it idles pretty good. some surging.

[Russ K]

mrr23

Looking at your idle scan, it appears that the TB has been drilled larger than stock, or the idle screw is holding the throttle slightly open. Fix what ever was done, then do another cold start idle scan.

Russ Kemp

[mrr23]

the TB is a NX 85mm, no hole. idle screw is most likely slightly open. at this point, 850-900 is where it likes to idle. would like to get it down to the 700 rpms, if possible.

here's a pic of the TB.

[camarokid94]

same thing i got going on

[mrr23]

i loaded your tune last night, but did not start the car. didn't do one this morning as i had to go to work. i can tell you it did not want to idle. outside temp was in the 70s. i had to hold the throttle. i adjusted the TB to get try and get to 800 rpms will running.


ok. here's a somewhat cold scan, from just now. if you need one colder than 104* engine temp (welcome to florida), i'll do another tomorrow morning.

question for you. rather than give me the fish, can you teach me to fish? i greatly appreciate you making the changes for me, and am willing to send some money your way, for you taking time out of your life to help me. i compared yours and mine to see what you did. just wondering what you saw in the scan to dictate the changes you made. you may have went over this in another thread. if you could point me to it, that would be great.

[Russ K]

You need to return the RAF table back to stock and then add 2 g/sec to the whole table. Then close the throttle blade stop screw 1/2 turn at a time to raise the desired airflow to be close to the RAF table. Then fine tune the RAF table. The idea is to have the LTIT +- .5 g/sec, and the desired idle airflow to be close to the values in the RAF table of the editor.

Russ Kemp

[mrr23]

thanks for the explanation. i just did a cold start on the car. with your tune, it won't run. with my original tune, it would start and run. had to hold the throttle to about 1200 rpms for about 2-3 seconds for it to settle in. let me give this a shot and see where i can go with yours.

[Russ K]

Just compared your tune to a stock one. Why are a lot of tables changed in the Dynamic Airflow page? Try returning these tables to stock, then start the car by holding the gas pedal till the engine starts. Then let off the gas once the idle catches, and continue scanning till operating temp.

I would raise the idle speed another 50 rpm with your camshaft.

Russ Kemp

[mrr23]

i was using a borrowed tune. i think i might be getting close. once i'm done playing, i'll upload it for your review. i, actually, might be understanding what STIT is doing. right as if this moment, my STIT is -0.17 lb/min and idle is pretty steady. engine temp is 163* and IAT is 93*. i'll let it cool down some more and se how it does in the under 100* area.

[Russ K]

You need to switch the STIT to g/sec, to agree with the RAF table in the editor.
The LTIT is the long term idle trim, and the STIT is the short term.

Russ Kemp

[mrr23]

correct. i have been using the conversion tool calculator for that.

[Russ K]

Just change the units to metric in the chart display.

Russ kemp

[mrr23]

thanks for the tip. now i just have to convert the temps back to *F. or convert the editor to *C (which i did)

[mrr23]

well, i've stopped for now. just getting aggravated over it. it's in ok status. just the whole under 80*C area is still not going well. i set my startup airflow delay to 500 (about 52 seconds). doesn't look like i can get the idle below 850ish.

i played with the following tables:
Idle Airflow
Startup Airflow Initial
Startup Airflow Delay
ST Adapt Airflow Max
MAF table
Open Loop EQ Ratio
Idle Spark Advance (used tables Russ K provided)
IAC Steps vs. Effective Area

we'll see how it goes tomorrow morning. i may restart from scratch, if it doesn't work out. been mixing so many things around, i've lost track.

[mrr23]

ok. did the world a favor and started over. combined a little of what you taught me and what i've learned through trial and error. started right up and idled. unfortunately, the throttle was opened a little too much. so, while i was scanning, i started closing it until the STIT was near zero and as close to 800 rpms where the target idle speed was set at. you'll see this happen at frame 1175. when i tried getting to 800 rpm idle, it started surging. so, at this point, looks like 850 range is it.

getting the desired idle airflow to be close to the values in the RAF table of the editor is being difficult. desired airflow is hovering in the 3.50 g/sec range. RAF is set at 6.20 g/sec at the given temp.

the LTFT are way lean right now. in past tunes, i've been compensating with the MAF table.

here's what i have. i'm going out right now to redo the idle start up with the new throttle blade setting and see what happens.

[mrr23]

with the new throttle blade setting, it would not start by itself. so, gave it a little help. LTFT are maxed out at 25% add. idled really rough. about 7 minutes into it, the idle started to smooth out.

question - should the desired airflow match the MAF reading? i would think so, as that's what the engine is requiring, but the desired airflow is 6 g/sec lower.

to fix the extreme lean condition, seeing as i'm running the MAF, should i just fix it through the MAF table? with the MAF in the way, i know not to change the VE table. or, is this fix able through the RAF table by setting it to match the desired airflow?

[mrr23]

i decided to try a different approach to startup and idle. instead of controlling it with the base running airflow, i made changes to the friction airflow initial. what i did was watch to see how much airflow the MAF reported right as soon as the engine turned over. it was reporting 15.95 g/sec. so,what i did was, i left the base running airflow table stock and added the rest to the friction airflow initial table. this took care of startup. then, i took friction airflow decay and reduced it by 10%, to slow the decay down.

also, changed the target idle rpm to 900 in park and 850 in gear. when in gear, the STIT went up to just over 1 g/sec. i may set the in gear to 900 rpms as well, unless i can get the STIT fixed. seems 900 rpms is where it wants to be. when i raised the target idle rpms, it raised the STIT. so, i opened the TB up to get it around -0.50 g/sec. would really like to get it to 800, if at all possible.

for now, i made MAF changes, to get the LTFT in line.

attached is where i am at now.

[ALB]

Wow a bit new to this hptuners stuff and can't believe how complicated it seems to be or guys are making it out to be.

In my highly modified turbo talon with race cams I simply up the idle speed to where it runs smooth as glass. So what if its 1000rpm instead of 950?Then I can lower it once in awhile if want to hear some lope but still above stalling point. I simply welded my fast idle so use right foot to keep the car fast idling when cold. Factory idle in those cars is never very steady since they use a wax think in the throttle body that don't work so well when it gets old. And I simply took out timing at the rpm points where was getting some surging. And thats about it.

But now have all these different things to much with to tune my ls1. Sure seems like overkill. If the cam idles even with a big of lope and don't stall out when warmed up and don't have noticeable surging isn't that good enough? Maybe not for some. I guess I am old school hot rodder. Don't expect my cammed up car to run like 100% stock cam. But if you do want that there are several more stealth type cams like lingenfelter gt3 or my new not installed lingenfelter gt7 that should idle like a baby especially in my planned 408 or 427 build.

Some cams are just not going to tune that well they are too wild. But I think higher idle is the simple key to most of this wild cam running better problems. And take out some timing at low speed if you get surging.
I realize this is pretty simplistic. Also can't see a huge problem with drilling a tb if need be. Whatever works.

[mrr23]

looks like you are reading too much into this. i'm not looking for it to idle like a stock motor which is 500-650 rpms. this isn't my first rodeo with modified engines. 950 is too high. there isn't any need for it to idle that high. this cam is on a 117 LSA. at least it's being easy to tune.

here's a sound clip of it's idle. really not that radical.
http://www.stealthram.com/familypics...08/408idle.wmv

i'm closer to 850 right now. if that's where it's going to settle in at, then so be it. rather would have 750. my current issue is cold start (40*C) and once idle is settled in, surging. of course, if i hold the pedal for 2-3 seconds, then slowly let off, then it idles. this is a minor issue.

my bigger issue is the surging and wanting to stall when i let off the throttle. and this is where i'm at now. once this is gone, i'll pretty much leave the idle stuff alone and move on to VE tuning in SD. maybe that's what i need to do, instead of chasing this. maybe it's in the VE.

[mrr23]

read some more on the forum. made some more changes. decided that 900 rpms is the place to settle on for idle rpms. startup and idle is acceptable, at this point. surging is minimal. i took a break last night and made no changes. i wanted to let it 'learn', to see how it would be.

thanks to russ k for pointing me in the directions i needed to go. you are a great help in the idle department. if i owe you anything, let me know.