Need some idling help

Tuning concepts, methods, tips etc.

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pbreaction
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Need some idling help

Post by pbreaction »

I am not sure what steps to take to get my car to idle in the 850 range with out babying the throttle I figure some of you might have some advice. Keep in mind most times the IAC is fully open.



I do have a big cam which may not be helping but every time i put it in either reverse or 1st it will die unless i give it a decent amount of throttle so i am not sure if that means it needs more gas or it needs more air and i am flooding it... i played around with the fuel tables a certain fixed timings and i didnt really see any sort of change. Granted i didnt go too extreme for fear that i might lean out the engine too much and blow it.

Anyway here is my log and my tune maybe yall see something i don't.

Thanks,

Mark
2000 Firebird V6 to LS3 swap.
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pkm123
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Re: Need some idling help

Post by pkm123 »

your cam is has very low vacuum at idle and the vacuum increases as the rpm increases. I had the same problem, it makes the engine hunt and is difficult to tune. I changed from SD (%Baro) to Alpha-N hybrid (multiply: on) and everything settled down. See my tune in Success Stories: 452 cu. in. FE in 1968 Mustang. I am including a log of my engines idle. Open mine with MegaLogViewer and do a scatter plot of MAP vs. RPM vs. AFR and compare to your log.

When you have a long duration cam, you only use the top half of the VE table. You can rescale to eliminate the map values below 45%. This will give better resolution, but it won't fix the idle.
kaeman
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Re: Need some idling help

Post by kaeman »

where does your cam info card say the engine should idle at, if you have very large camshafts they usually have a idle recommendation, larger cams usually end up idling in the 1000+ rpm range, big cams can have a recommended idle of more than 1500 rpm. Several of my friends have large cams above 300 duration and .650 lift and they have idles in the 1300 rpm range before it will run smooth.
Your 850 target may be the problem in itself. if the cam card says it needs to idle at 1200 then set your idle speed there. Good luck.
64 el camino, 383 SBC, 11.7 to1 CR, accufab tb/rhs intake, 44lb injectors, trick flow heads, xr292r solid roller cam, belt drive camshaft, dry sump oil system, 2400 stall, turbo 350, spooled 9 inch, strange axles, 3.89 gears, dual wideband, full sequential fuel/cop, MS3x using 1.4.1 code.
pbreaction
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Re: Need some idling help

Post by pbreaction »

Wow good call this is my cam

http://www.race-mart.com/Crane_Cams-416478.html

so that means i should be idling at 2400 rpm???
2000 Firebird V6 to LS3 swap.
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pbreaction
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Re: Need some idling help

Post by pbreaction »

i bought the whole un-assembled engine from a guy on Craigslist and got it rebuilt to an LS3 about a year ago so the cam spec sheet slipped my mind.

Also i tired alpha N and it surges pretty bad but i know i am assuming because my rpm was way too low.


And i am assuming if i get it to idle correctly for the cam then i wont choke my engine out when i ease into 1st.
2000 Firebird V6 to LS3 swap.
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pbreaction
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Re: Need some idling help

Post by pbreaction »

Also i had another thought what would yall say my ignition table 100 kpa values should reflect between. Cuase my intial research said 24-25 degrees should be for max power but with my limited knowledge i would assume have such a high lift cam i would have to increase the timing advance.


edit:
found this article... http://www.masterenginetuner.com/ls-big-cam-idle.html
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billr
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Re: Need some idling help

Post by billr »

That 2400-6500 rpm range is where the best torque will be, where you should be trying to operate the engine for best over-all power. It will idle at a much lower speed. For comparison, I have a similar cam with a 3500-6500 "range" and it will idle under 1000 rpm. Put a load on it (get MAP up) and it will pull pretty strong at 1000, just not as strong as when above 3500...
pbreaction
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Re: Need some idling help

Post by pbreaction »

awsome thanks bill.

do you mind showing a screenshot of ur ignition table to posting up ur tune... just so i can get a ball park idea of ur tables

Thanks
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S.Bretz
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Re: Need some idling help

Post by S.Bretz »

I have found that more throttle opening and less timing gets it close.
You can play with the injection angle to get it a little smoother too (thought not much in most cases).

Have you enabled any of the advanced settings for idle? You can set it to pull timing as the engine speed picks up and adds timing back when the rpms are dropping. Fast 10-15 degree timing swings 25-50rpm off the target idle rpm can really make difference in somce cases.
kaeman
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Re: Need some idling help

Post by kaeman »

When reading the description for using the camshaft.. choppy idle means not smooth.....does your engine have the high compression, better heads, etc.. that the cam usage is asking

Crane Cams 1449161 HR-228/347-2S-15 0A Hydraulic Roller Camshaft Chevy 4.8 6.2L LS V8 1997-2010 Weekend driver, for modified 5.7L thru 6.0L, choppy idle, upgraded cylinder heads and valvetrain required, headers and aft cat exhaust required, 11.0+ compression ratio advised, low ratio gearing required, auto trans w/3200 - 3600 stall converter, computer upgrades required.
Part Number: 1449161
Grind Number: HR-228/347-2S-15 0A
RPM Power Range: 2400-6500
I would expect your idle to be 1100 or a little under.. but the description says choppy idle...... I would pick a number where you feel good about the engine not trying to die going into gear etc. and tune for best idle... knowing it probably wont be SMOOTH...good luck
64 el camino, 383 SBC, 11.7 to1 CR, accufab tb/rhs intake, 44lb injectors, trick flow heads, xr292r solid roller cam, belt drive camshaft, dry sump oil system, 2400 stall, turbo 350, spooled 9 inch, strange axles, 3.89 gears, dual wideband, full sequential fuel/cop, MS3x using 1.4.1 code.
pbreaction
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Re: Need some idling help

Post by pbreaction »

Thanks will do
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Yves
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Re: Need some idling help

Post by Yves »

That's by no means an agressive cam if you ask me.
pkm123
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Re: Need some idling help

Post by pkm123 »

Hello again, I have a cam thats 248/254 at 0.05 on a 452 cu.in. motor. It will hold idle at 850 rpm. Your cam is much milder than mine. You must have a vacuum leak somewhere. If your engine has a compression ration of 10 or better, the ignition idle setting should be about 14 to 16*.
Yves
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Re: Need some idling help

Post by Yves »

his cam is 228 at .05
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