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

[RD in SD]

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.

[swingtan]

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.

[RD in SD]

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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.

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.

14186

[swingtan]

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.

[RD in SD]

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?

[swingtan]

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.

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.

[RD in SD]

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?

[swingtan]

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.

[RD in SD]

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

[swingtan]

Do you have the EFILive V2 with you?

[RD in SD]

OK I put the tune back in and my trouble code is ECM P0606 MF-HX-CI

[RD in SD]

I raised B 1650 all the way back up to 4500 before I gave up. What should I try next?

[swingtan]

Sorry, I got caught in traffic on the way home....

P0606 is an issue I've seen when changing B1650 too much. I've had one car that will throw the code when it's set to 4600, but not at 4900, so try 4900 and then work around to see what gives the best results. Your only other option is going to be to drill a hole in the TB blade to try and get some more air flow. I normally don't like drilling a hole as it can cause other issues, but it may be your only choice if B1650 won't play nice.

Simon.

[RD in SD]

Sorry, I got caught in traffic on the way home....

P0606 is an issue I've seen when changing B1650 too much. I've had one car that will throw the code when it's set to 4600, but not at 4900, so try 4900 and then work around to see what gives the best results. Your only other option is going to be to drill a hole in the TB blade to try and get some more air flow. I normally don't like drilling a hole as it can cause other issues, but it may be your only choice if B1650 won't play nice.

Simon.

4725 is where B1650 (max throttle area) was before. What about those other settings for max throttle area B16151 and B16152? Are those causing the code? It seems like just those setting alone would help the situation but I guess I don't understand what is going on. Would it make sense to try increasing them to a higher number or put B1650 back to where it was and leave those at 4%? Why would those settings alone not be an effective way to increase idle air?

If I am able to get B1650 (max throttle area) to decrease to lets say 4600 then what would I do with my idle air table? I guess start moving it back up to higher numbers? It seems like what you are saying is that the idle air table does no good beyond a certain point with the max throttle area set to 4750 is that true? This is why we were able to set it at 40 and it did not solve the problem. What point is it that it is no longer effective how do I know when I reached that point or is it just trial and error?

My original tuner did drill a hole in my throttle plate but I replaced it with a new one (still have the old one). Perhaps he already did this excessive. However he was unable to get the car to do much of anything right. It didn't start well hot or cold and did not idle well hot or cold. My new tuner asked me to get rid of the hole and we started tuning from there, now I am down to cold idle only problem, as soon as it warms up it is OK.

Last night when I decreased B1650 both the hot and cold start and idle did improve dramatically, at one point I was able to lower the idle from 800 to 700 and it was still pretty smooth, so I agree it does seem to have us on the right path. In fact when it was learning it idled down to 600. Idling lower is important to me becasue I have a stock converter.

I just had another idea what about 102mm throttle body would that help with the idle airflow?

[swingtan]

{B1651} and {B1652} set the maximum amount of throttle for idle control, so I don't think these will help with cranking, though they may help slightly. As I mentioned previously, there seems to be a fixed max setting that we don't have access to, hence why we try to fool the ECM into thinking it has a smaller TB, so it opens further. I would however, try setting these to around 4% to see if it helps. The idea to to get the base idle air flow correct, so the ECM doesn't need to adjust by too much. Ideally we would set these very low if we could get the min idle air flow tables spot on.

Changing {B1650} to a lower number doesn't seem to have a great effect on the min idle airflow table {B1829}. I really think it's a setting that is only used in the theoretical calculation of how far the ECM has to open the TB for a given air flow, but {B1829} is an actual measured air flow setting. So one will not impact the other. though I think there is some rational checking between the settings. To get a working value for {B1650}. I'd try a bit of binary sorting..... If 3600 throws a code and 4725 is stock, try half between the two, about 3900. If that doesn't throw a code, but doesn't have sufficient impact, try half way between 3900 and 3600. If 3900 still trows a code, try half way between 3900 and 4725. then just continue making smaller steps till you get as good as you can get.

Here's my thoughts on drilling holes. It helps for some things, it hurts for others. My main reluctance to drilling holes is trying to balance hot vs cold idle. With a hole in the TB blade, you need less commanded air flow, as the hole lets more air in to the motor than the ECM is commanding. so you may only command 5gm/S at idle, when really the engine is consuming maybe 10gm/S. So as an example, the hole may be letting in 5gm/S of additional air. When the engine is cold, you command much more idle air to help it idle after starting, may cammed cars will want 2X the airflow when cold, so you max out the ECT idle air correction to 2X. The problem is that you are only commanding 5gm/S of idle air in the ECM, so 2X is only 10gm/S, and in the 5gm/S from the hole and you only get 15gm/S instead of the desired 20gm/S. You can see how balancing hot and cold idle air flow becomes difficult. It will come down to the trade offs you are willing to go for. Hole or no hole they both have good and bad points.

The NW 102 would in theory help, as it is bigger than stock so should give more idle air flow. However, I've not seen any specific tuning data for the NW, which is a bit of a shame. It also has a tendency of introducing idle correction over shoot as it gives more throttle opening for each degree of shaft movement, especially at small openings. This can introduce hunting issues that cause the ECM to over correct at idle. If NW was to release specific idle tuning data, it would help a lot. just like some of the better injector companies provide specific tuning data for their injectors.

Simon.

[RD in SD]

I have not yet had a chance to get back to the car yet.

My cold problem is idle only, it starts fine, no cranking issues so it sounds like maybe B1651 and B1652 alone might help me, would you agree? Do those ever throw codes when you crank them up to 4%?

With the 102mm throttle would it be safe to assume we could expect about 10% more air for any given situation? Seems this might be a possible solution. My engine builder seemed to think that I was leaving some horsepower behind with out one anyway. Frankly I thought it would just create another tuning problem? The engine is a 440 with a large cam so it does need a lot of air.

I know a trick that can be done by making a physical adjustment to the TPS. This is done by elongating the mounting holes in it and rotating it. This will change where the car thinks the throttle is and can work to increase or decrease air to some extent. I do have experience doing this on another car and it did work for a different situation by by tricking the TPS into believing it was further open that it really was to reduce air, we might do that same thing here to have the opposite effect and increase air. What do you think?

[swingtan]

I think I'd rather drill a small hole in the blade rather than elongating mounting holes

B1651 and B1652 may work for you, if it does then go that way. Really there's no single fix for everything, so use what works ;) They don't throw codes, but are still governed by the maximum TPS opening limit. SO setting them to 50% may not help, just like setting the min idle air to 40gm/S didn't make a difference.

Perhaps the 102 is the best choice here, though I'd still test out B1650 to see if that does the trick. Then I'd probably look at the 102 to help the top end of the bigger motor.

Simon

[RD in SD]

I think I'd rather drill a small hole in the blade rather than elongating mounting holes

B1651 and B1652 may work for you, if it does then go that way. Really there's no single fix for everything, so use what works ;) They don't throw codes, but are still governed by the maximum TPS opening limit. SO setting them to 50% may not help, just like setting the min idle air to 40gm/S didn't make a difference.

Perhaps the 102 is the best choice here, though I'd still test out B1650 to see if that does the trick. Then I'd probably look at the 102 to help the top end of the bigger motor.

Simon

Success, I increased B1651 and B1652 to 4% and got a code. Changed them both to 3% and it worked great except the idle was a bit to high so I lowered the idle air tables down to 15 and its better. I have some more tweaking to do to make it perfect but overall that solved the problem, it started and idled cold and hot with no code. What a simple solution to a problem I have been doing battle with for a while. Thank you very much for your help. I will post again after I get it all dialed in so others can learn from it.

[RD in SD]

Update,

As I said in my last post the cold idle stuff is all worked out after lots of playing with the idle air table, the coolant correction and the idle speeds. Lots and lots of trial and error and probably over 100 tunes.

Right now I have it idle pretty smooth in gear at 725 and 750 in P/N. However with the idle that low and everything else working well at low speeds it does not like to shift from D to R, it dies about 25% of the time and when it does go in without dying it slams in hard and the car jumps back. I have played with the reverse idle air and the in gear correction table a lot to try and smooth this out. I have come to the conclusion that it is the shift pressures or shift timing in my highly modified transmission tune that won't let it slip into gear nicely. It only does this when transitioning from D to R all other shifts are fine. It goes like this: shift from D to R, 1 second delay during which time engine revs to 900 or 1000, car slams into reverse and car jumps, sometimes engine dies and sometimes is stumbles.

In addition when decelerating to a stop at around 2 MPH the transmission downshifts from 3 to 2 and the car jumps forward as the engine revs up a little and it shift. It used to do it twice until I lowered the 2 to 1 shift point to 0 now it shifts after I stop. The strange thing is that the 3-2 downshift is programed at 24MPH. This problem does not occur if I hold it in second in tap up tap down mode.

Lastly the car transitions from the idle table to some other table at 2MPH (factory setting that can be changed) what table does it go to? When it transitions my idle goes from 725 to 900 and the car accelerates to 6 or 7 MPH so I am driving around parking lots with the brake on. I think the table it goes to has to do with in gear RPM at idle that I have seen in HP tuners but can't find it in EFI live. I wonder if that is what is causing the problem described above as well?

Any suggestions would be helpful.

[MyM8V8]

Hi Guys.

Just seen this and I have just installed a 457 LS2 in my Maloo. I'm running a fast 102 intake with the NW 102 TB through a Duspeed OTR. Its got a big cam 25x 26x with some lift too. I've got a base tune in a looking to get it to idle.

Not wanting to be a parasite, but I would just love to see your idle tables now you have sorted yours??? Did you drill or not drill?

Regards.

[RD in SD]

Hi Guys.

Just seen this and I have just installed a 457 LS2 in my Maloo. I'm running a fast 102 intake with the NW 102 TB through a Duspeed OTR. Its got a big cam 25x 26x with some lift too. I've got a base tune in a looking to get it to idle.

Not wanting to be a parasite, but I would just love to see your idle tables now you have sorted yours??? Did you drill or not drill?

Regards.

No need to drill it can be done with programming. I don't have my tune on this machine but if you PM me with your email address I will send it to you.

[MyM8V8]

Hey just got back from a trip abroad today. Thank you so much for your kind offer. I PM'd you.

Regards.

[MyM8V8]

Any Moderator who can help???

I don't think my PM facility is working. I am trying to send a PM to RDinSD. I have sent two but they don't appear to be getting through.

Thanks.

[joecar]

I sent a pm to both, let me know if it gets thru.

[joecar]

I'm wondering if he has PM's enabled...?

[MyM8V8]

thanks Joe. I got yours.

[MyM8V8]

Might not have. Hope he just comes back on here.

[LS1FREEK]

I could really use some help on this subject as well guys! 2006 GTO, 408ci, big cam (24x/26x) fast 102, nw102. I don't have my tune file on me but would greatly appreciate if one of u guys could send me yours. I'm having alot of hunting issues (surging).

[swingtan]

It would be easier to post your tune, and a matching log that shows the surge issue....