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Thread: 06 Vette, LS2, 440 CI, Auto, 500 RWHP, Fast 102, big cam, ported heads - Cold Idle

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    Default 06 Vette, LS2, 440 CI, Auto, 500 RWHP, Fast 102, big cam, ported heads - Cold Idle

    Hello Everyone,

    I have an 06 LS2 Corvette with an A6 (six speed auto) I use the car for road racing. It now has an ERL built 440 Cubic Inch LS motor that is putting down 500 RWHP (or more with increased timing and race gas). It has a Comp Cams cam with 231 intake 247 exhaust .617 and .624 lift and 113 lobe centers. Ported L92 heads, Fast 102, headers, stock torque converter (part of the problem), lower gears and so on.

    I had the car Dyno Tuned by a local shop and it made good power but they could not get it to start or idle correctly. It runs great at the track, hauls butt and all that stuff. I have been working a local tuner to help me get it tame enough to drive on the street. We have done a great job of getting it to start and drive correctly. Even with the big cam it has good road manners. It cruises down the freeway fine and gets 25MPG at 70 MPH. We have spent hours playing with the idle air, tweaking the timing and playing with the shift times to make it drivable.

    I am satisfied with the car except for the fact that when cold after it starts the only way to keep it running is to give it some throttle until it gets to around 100 to 110 degrees coolant temperature, then it will idle on it's own but not really drivable until about 130 degrees. We have increase idle air until it does want any more and makes the problem worse, I can't remember how much we advanced the timing but we did quite a bit. We played with the table that increases airflow when you put it in gear. We have turned on the fuel trims at I think at 80 degrees coolant temperature. We turned up the cold idle to I think 1200. We tried a few other things that are not coming to mind. I was wondering if anyone has any suggestions as to what we might try next. I would not mind if it would start and idle high for a minute or two to warm up and then drop down but we have not been able to accomplish that except with my foot.

    Any suggestions would be appreciated.

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    Lifetime Member swingtan's Avatar
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    As a test, remove the FAST manifold and return it to stock. Then see how it idles......

    Also, post the tune file and some logs of the problem.

    Simon.
    Holden VZ SS 6Lt L76 M6, 220/224 @114, 0-100kmh < 5 seconds

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    06 C6 A6 Engine Post Gary Runs good cold start needs help.ctd06 C6 A6 Engine Post Gary Runs good cold start needs help.ctd
    Quote Originally Posted by swingtan View Post
    As a test, remove the FAST manifold and return it to stock. Then see how it idles......

    Also, post the tune file and some logs of the problem.

    Simon.
    Well removing the intake is quite a chore and not really practical since I have to put it right back on. Are you saying that because you feel it might have a vacuum leak?

    Here is the file. I don't have the logs handy but I can tell you that when cold the car starts, flares, drops down to about 500 RPM, revs once or twice and then dies. On the second try it is a bit harder to start (cranks longer) but does the same basic thing. If I give it just a bit of throttle it will idle smooth at about 1200. If I let off it drops down, revs up once or twice then dies. I will log it and post logs tomorrow. Thank you for the help.

    Attachment 14186
    Last edited by RD in SD; November 17th, 2012 at 03:50 PM.

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    Lifetime Member swingtan's Avatar
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    In recent days I've heard a number of reports of poor idle when using a FAST manifold. I was suggesting replacing the FAST with a stock manifold to see the impact.

    As for the tune, I think you are simply not getting sufficient airflow when cranking and for cold idle. As a quick test, try setting {B1650} to 3600 and {B1651} and {B1652} to about 4%. You may need to lower your settings in {B1829} though, as 41gm/Sec should be nearly 10 times too much.

    See what those changes do.

    Simon.
    Holden VZ SS 6Lt L76 M6, 220/224 @114, 0-100kmh < 5 seconds

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    Quote Originally Posted by swingtan View Post
    In recent days I've heard a number of reports of poor idle when using a FAST manifold. I was suggesting replacing the FAST with a stock manifold to see the impact.

    As for the tune, I think you are simply not getting sufficient airflow when cranking and for cold idle. As a quick test, try setting {B1650} to 3600 and {B1651} and {B1652} to about 4%. You may need to lower your settings in {B1829} though, as 41gm/Sec should be nearly 10 times too much.

    See what those changes do.

    Simon.
    OK thank you, I will try it as soon as I get back to the car tonight. However I have a question so I can better understand what I am doing. It looks like from what you are saying that the idle airflow table has been limited by the max idle area which has allowed us to increase it by 10 times more air than the car needs. When I open up the max idle area I am now going to have to much air because the idle airflow table is 10 times too high. Is this assumption correct? You said that idle airflow table is 10 times too high do you want me to reduce the entire table by 90% for the test or where should I start?

    On another totally unrelated subject, I noticed you are from Australia, I also have an 09 Z06 with a Harrop Hurricane manifold on it. As you may know that Harrop is made in Australia. The engine is modified in a similar way to this one we have been discussing in this thread except that it has bigger heads a little less duration and more lift. It is putting out 600 RWHP. I have spent a lot of time and money getting this manifold working on the car and it now has better drive ability than the 06 in this thread. It idles nice, starts perfect and the horsepower and throttle response is nothing short of incredible. However I just finished testing it last weekend and do not have extensive seat time. The reason I mention it is that I can't find anyone near me that knows anything about the Harrop. I have found a local tuner to assist and we have been able to dial it in through a lot of trial and error and it's finally perfect except that maybe it would be nice if I could get the idle a bit lower (800 now). My point is that it would be nice to find someone with experience to assist in case we run into more issues. Do you know anyone down under?

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    Lifetime Member swingtan's Avatar
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    1. Yes, the max idle throttle % will hard limit how far open the throttle will ever go. The problem is that I think there's another setting that we don't have access to. The trick is to reduce the ECM's expected maximum throttle area, so it thinks it needs to open the throttle more for a given calculated airflow. Then you can actually command more air and get the throttle to open further. I'd start at 10gm/S for the idles cells and work from there. You may get down to 8 or need to go up to 13, depending on the rest of the setup. Generally though, you start a little high, get the idle settled and work down.
    2. The Harrop Hurricane! I'd love to have one of those, best looking intake I've seen and I'd probably prefer one over a blower.... maybe.... I think it'll come down to the response of the engine to throttle changes, as you've said, it's very responsive. If you want to send me some idle logs and a matching tune, I'll have a look. You can PM me for details.
    Holden VZ SS 6Lt L76 M6, 220/224 @114, 0-100kmh < 5 seconds

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    Wow that was super great. I did exactly what you said. It fired right up, the flare was perfect and it idled right back down cold and had its best idle between 6 and 7 on the idle airflow table. The problem is it threw a code and "reduced engine power" so I can't drive it but it did start and idle perfect both hot and cold. I had to put the old tune back so I can drive it tomorrow. Not sure how to read the codes or where to find them. Can you help me with that?

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    Lifetime Member swingtan's Avatar
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    Use scan tool to read the DTC. It's very possible that {B1650} is set too low for your OS. Some OS's will never throw a code, some are more touchy. Check the codes though and see what was actually thrown. Great news on it getting closer though.

    Simon.
    Holden VZ SS 6Lt L76 M6, 220/224 @114, 0-100kmh < 5 seconds

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    I have no clue what I am doing with the scan tool can you give me some direction. Sorry my tuner guys is not working Sunday at 8 PM

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    Lifetime Member swingtan's Avatar
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    Do you have the EFILive V2 with you?
    Holden VZ SS 6Lt L76 M6, 220/224 @114, 0-100kmh < 5 seconds

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