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how much timing at idle

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Old 12-23-2005, 10:19 PM
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Question how much timing at idle

just wanted to get a feel for how much timing people are running at idle and at what rpm is idle set at
Old 12-23-2005, 11:05 PM
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Mine is at 35* at 750 rpm. I had this weird idea that i could save a little gas that way.
Old 12-24-2005, 07:54 AM
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Be careful... Too much timing at idle can cause your cats to super heat and start a fire... Don't ask how I know....


Old 12-24-2005, 03:10 PM
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I'm running 25 deg, stock cam and 625rpm. Had the same gas idea too.
Old 12-24-2005, 05:28 PM
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How would more timing cause your cats to overheat?
Old 12-24-2005, 06:52 PM
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Originally Posted by SideStep
Be careful... Too much timing at idle can cause your cats to super heat and start a fire... Don't ask how I know....


Just how much timing did you put in? i'm thinking more timing will help
superheat the cats, but didn't want to reach 'POOF' stage.
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Old 12-24-2005, 06:54 PM
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I think mor etiming should give the charge more time to burn thus the cats not having to work to hard to consume any extra fuel it may see in the exhaust. I would like to know also how extra timing could cause cats to burn and blow?
Old 12-25-2005, 03:43 PM
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I run between 28 and 31 degrees timing at 850 rpm with the f13 cam (230/232)
Old 12-25-2005, 05:53 PM
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you either raise the rpms or the raise the timing, to help out with the idle. 850-950rpm and 28-32 idle timing takes care of most cams. of course the more extreme the cam, the more extreme the measures need to be taken. at 1050rpm, just about any cam's lope disappears.
Old 12-25-2005, 10:52 PM
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thanks for article RedHard Supra
Old 12-26-2005, 03:35 PM
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How do your guys timing profiles look compared to RPM?
In other words, what is the shape of the graph? Does it decline with an increase of RPM? How much timing are you guys running in the upper RPM?
Old 12-26-2005, 06:32 PM
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With a G5X3, and AFR205s (59cc), Kooks (w/cats), SVO #30s, Vararam, blah, blah, blah all the bolt-ons. Sitting in a bank parking lot logging idle, we noticed a funny smell, then we noticed a red glow from under the car. I opened the passenger door and looked under the car to see the cats glowing a bright white-red. We could smell plastic (C5) burning... Not my car but I a horrible sick feeling in my stomach.

The AFR was 14.6 and we had 30 of timing at idle... We backed timing down to 24 and the glowing went away

We were increasing the idle timing to get rid of some of the gas smell...

On my C5 I have LGs with cats all the way back next to the cat-back. If I use the factory idle timing (17*) the cats don't get hot enough to convert. When I set the idle timing to 26* I start getting that slow drip drip out of the exhaust tips, like you do with normal exhaust systems converting correctly. Also this ended the smell I had at idle.

Old 12-26-2005, 08:05 PM
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I'm at about 28 degrees of timing at idle right now.

But, I still get gas smell, and even some smoke at idle. I've leaned out my VE at idle by about 60%, 80% and 90% at 400, 800, and 1200, but I'm still rich.

Should I bump the timing more?
Old 12-27-2005, 12:56 AM
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Originally Posted by silverTA2002
I'm at about 28 degrees of timing at idle right now.

But, I still get gas smell, and even some smoke at idle. I've leaned out my VE at idle by about 60%, 80% and 90% at 400, 800, and 1200, but I'm still rich.

Should I bump the timing more?
Gas smell at idle is normal, especially when cold and catless. Gas doesn't burn, it's vapors do. Temperature is really a measure of molecular kinetic energy (aka how jumpy do the molecules feel), so when the gas is cold (low energy) the molecules don't move around much (vaporize) so it takes a lot more gas than usual to produce the same amount of vapors to keep the engine running.

as for the idle, what's the VE number in the cells you idle in? more like 30 or more like 55? any more info on your setup? (injectors setup especially)
Old 12-27-2005, 12:57 AM
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Have the right fuel pressure regulator? ummm... No idea.
Old 12-27-2005, 08:48 AM
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Eliminate the gas smell by targetting a smooth idle and tuning your VE to within +/-4. Oh, and run cats. Good for the air we breathe.

A well tuned car shouldnt need band-aid fixes like 30* timing at idle.
Old 12-27-2005, 08:53 AM
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Originally Posted by MNR-0
Eliminate the gas smell by targetting a smooth idle and tuning your VE to within +/-4. Oh, and run cats. Good for the air we breathe.

A well tuned car shouldnt need band-aid fixes like 30* timing at idle.
30* of timing is NOT a bandaid fix on a cammed car. It is proper tuning. The extra overlap creates a mushy air/fuel charge requiring more timing down low.
Old 12-27-2005, 07:27 PM
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After Marcin suggested it to me. at idle its good to go a little lean. Im at about 5+ for my ltft's and thats helped with some of my gas consumption at idle. getting better...cant wait for the new o2's and wideband!!




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