AUSSIROC

iTrader: (1)

When i start the car (cold or hot), it flares up, comes down to 1000rpm, sits there for about 15 seconds, then settles down to 800rpm (Side Note: even though i have it set at 750rpm it idles at 800rpm?!?).

Why does it take so long (15secs) for the idle revs to come down?? If you dont wait it clunks into drive harder than i would prefer. Is there a parameter/timer i can adjust so it settles virtually straight away after the flare up?

I'm using TunerProRT...

DSmith

Check your idle RPM startup position, its about 25 from the bottom of the constants. The higher the steps added the longer it will take to return to normal.

Its been a couple years since I messed with this stuff, The last couple weeks I have been trying to refresh my memory.

Orr89RocZ

iTrader: (20)

are you going by the tach when you say it idles at 800? stock tachs can be off so even if you set the chip to idle at 750, the motor could be shown to idle higher on the tach. But dont worry, its probly idling at 750 or so.

as far as cold starts go, the idle will flare up and hold there for a while as coolant starts to warm up. as it warms up the idle comes down and the car will enter closed loop. it will keep coming down to the hot idle target speed once operating coolant temp is reached

AUSSIROC

iTrader: (1)

Cool, will do.
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I have a new Autometer SportComp monster, so im hoping it would be accurate, unlike the stocker?
Also, it does it when its warm too. Should it take 15secs to go into closed loop when hot?

Orr89RocZ

iTrader: (20)

not sure but once warm it shouldnt take all that long to go into closed loop. I know when its cold, it takes a while to get down into closed loop and to have the rpms drop down to idle speed warm.

It shouldnt be hovering high like that for a long time while restarting warm tho.

AUSSIROC

iTrader: (1)

Yeah, its probably some sort of voodoo curse. It may take some tinkering and hopefully i'll jag it.

Changing the subject, you have prob mentioned this before, but how much ET did you shave off with your HSR compare to TPI?
Also, i have a set of 3.45 gears coming to replace the 2.77s i currently have. How much ET gain can i expect with a gear change, assuming i can improve my tune to where it needs to be....??

327_TPI_77_Maro

iTrader: (8)

Are you going by the datalog, or your tach? If your tach, your tach is wrong. Also there is an idle speed deadband, within which the ECU won't make corrections. The dead band is around 50 rpms. So w/ 750 commanded idle, it will let it idle at 700 or 800, or anywhere in between, w/o correcting via the idle air motor.

Orr89RocZ

iTrader: (20)

trying to compare to similar weather conditions, i shaved off atleast 4 tenths and gained 4 mph by switching to HSR and tuning for it.

with street tires, gears are hard to see gains sometimes because you cant launch to hard. on some sort of sticky tire, that gear change will improve your 60 foot and help you pull thru more gear during the run, i'd say 2 tenths gain wouldnt be out of the question.

AUSSIROC

iTrader: (1)

Yeah i'm lookin at the tach. I just didnt expect an Autometer tach to be out thats all.
I might fiddle with the deadband...

AUSSIROC

iTrader: (1)

Kool, good to know. Thats what i was thinking.

327_TPI_77_Maro

iTrader: (8)

You can't get 50 rpm accuracy even with a good analog tach -- the angle you view it from will change the reading more than 50 rpms. I have an autometer tach too and it does not "agree" with the datalog down to that kind of precision, but I'm never looking at it dead on anway, so it doesn't really matter.

I would leave the dead band alone. If you make the dead band narrower the engine will hunt up and down as the computer does a feedback loop.

AUSSIROC

iTrader: (1)

This is the first aftermarket tach i have purchased, and considering its autometer, and i have it positioned so i look at it dead-on, i expect it to be accurate. Anyway, if thats how it is theres not much i can do about it.

Thanks for the tip on the deadband. I tried that, and know i know why it didnt work lol.

327_TPI_77_Maro

iTrader: (8)

Yeah, I have had to make my deadband larger w/ a big cam so the rpms did not hunt, but it does result in some loss of accuracy. IE the datalog shows my commanded 850 idle is in the low 900s, but thats good enough.

tequilaboy

If hot spark retard is active, 150 rpm will be added to the desired idle speed.

From ARAP_hac.src:

;------------------------------
; PID HOT SPARK RETARD
;------------------------------
LC57B FCB 25 ; 25 sec's, MIN ENG RUN TIME TO ENABLE HOT SPK RETARD
LC57C FCB 12 ; 150 RPM/12.5, ADD RPM OFFSET IF HOT SPARK RTD ACTIVE

I usually see this active for 30 seconds following a warm re-start. In my case its only a 100 rpm offset instead of 150 rpm.

It may be responsible for the rpm offset that you are seeing following start-up.

Update: I verified this function last night. I zero'd the equivalent parameter in my car ($32B based bin, so the address is different: LC68B in $32B FWIW). I no longer see the 100 rpm offset added on restart. I can live without it since my normal warm idle rpm is 900 rpm.

Note: there is another parameter in $32B that also offsets the warm park position under the same conditions (hot restart spark retard). I don't see an equivalent in $6E.

AUSSIROC

iTrader: (1)

Sweet, i'll try that, cheers.
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That sounds like it could be it. Thanks for the input, appreciate it. I'll try that too, sounds like that may just be it.