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So I just got my car fired up after swapping the cam from a 226/242 on 117 to 242/250 on 114. 402 stroked LS2, E40 ECU, stock LS2 throttle body, stock ls3 intake and heads. It sounds cool, but I'm having some strangeness with the idle. The video is just for cool sounds. I was able to force the idle down by taking a ton of timing out of it on the scanner.
My tune before the cam swap the engine idled very smooth at 850 rpm at about 16 degrees of spark timing and more base running airflow than stock as expected.
Anticipating needing more timing and airflow due to the large cam I bumped idle airflow up, and put another 10* of spark in the tune. It idled at 1400 rpm with adaptive idle turned off.
I have been fighting to get the idle down to ~850-950.
Right now I have less base running airflow 30% lower than before, and the timing is being forced down to 2-6 degrees by adaptive idle and is still trying to idle higher than my 950 rpm commanded idle.
For reference, my base running airflow is in the 6.5-7.3 g/s range between 800 and 1000 rpm. I've opened up other cammed engines and I'm getting close to half of their settings.
What am I missing here? I need to get some timing in this thing.
Otherwise than the weird idle I was able to drive the car around and the throttle response is good and the engine is idling pretty good. Fuel trims are consistent and the O2's are switching. It doesn't seem like anything is horribly wrong. It needs some love to get the tune dialed in of course, but some rough running is to be expected with the larger cam.
I would suspect a fairly large vacuum leak or un-metered air coming in from somewhere, but the engine is consistent and stable other than this odd issue. Any thoughts?
I rambled a bit in the first post and I think confused the primary concern I’m dealing with haha sorry.
I don’t know where it’s going to want to idle cleanly but I’m targeting 950 right now.
My issue is I can’t get the idle to come down without dramatically decreasing running airflow and the timing is all the way down to 2-6 degrees.
A bigger cam should want more airflow and more timing.
I don’t believe I have a vacuum leak or unmetered air getting past the MAF because my fuel trims are near 0 at idle, and are consistent. The car is also running the same bank to bank, and is running pretty good. Vac leaks or unmetered air usually makes it run like ****.
I'm going to keep forcing the idle down and see if I can get the timing to come back up to where it should be, but I'm getting below where like...a stock LS2 is at. I'm already less than a stock LS7, and 30% less airflow than I was with the much smaller camshaft.
I've never seen this behavior before, and other tunes I've checked from the repository I'm way out in left field.
Spanks, I chased a high idle for months until Darth told me I likely had It too rich at idle, due to camshaft overlap causing a false lean condition from reversion. He was exactly right as usual. My wideband showed 14’s at idle before, but it’s now at mid 15’s idling and it’s good. Spark plugs agree. I had 4 degrees timing in it before to get it to idle. Now at 15 degrees. Idles at 980 ish...
Last edited by Che70velle; 08-18-2020 at 08:10 PM.
How are you setting up idle? OLO2 idle I assume? What map is it idling at? Did you do any TB drilling or cracking the idle set screw for the old cam?
Zero out the timing adaptives until it's over a couple hundred rpms so it's not swinging back and forth, just so you can get in the ballpark. You should be able to lock the timing and vary the AFR and vice versa to see what it wants to get best map. A cam that size is not going to idle best at stoich.
Spanks, I chased a high idle for months until Darth told me I likely had It too rich at idle, due to camshaft overlap causing a false lean condition from reversion. He was exactly right as usual. My wideband showed 14’s at idle before, but it’s now at mid 15’s idling and it’s good. Spark plugs agree. I had 4 degrees timing in it before to get it to idle. Now at 15 degrees. Idles at 980 ish...
Damn, that sounds like the ticket! I haven’t put it open loop yet at idle. I’ll give that a shot and see what happens I bet it dies quick.
Short terms are showing near 0 at idle but the narrow bands also aren’t switching too well so I don’t doubt it’s off.
I’ve setup cars to be OL at idle and closed loop above that before maybe I’ll give that a shot if I can’t make the narrow bands switch better.
I just got a terminator X setup so this doesn’t need to last me forever I just need to sort a few things out before I install it, mainly the switch from DBW to DBC.
I think I made some progress tonight. No lie I don't think I can point to really anything specific I did but it is working better tonight, but I did massage a bunch of stuff after my last drive. It'll probably run like **** next time I drive it lol.
I did try open loop idle but stupid me didn't set the PE enable high enough MAP before driving it around. Once warmed up the cam is making it idle at 67-68 kPa and I had the threshold set to 65 lol.
It is idling around 15* spark which is just a hair under what I commanded w/ the idle control doing its job. The rpm is averaged pretty well around 950 rpm commanded. I have the idle control really desensitized because I hate choppy idles...don't get it. Narrowbands are switching and wideband is showing ~stoich, whether that is real or diluted by misfires the throttle response is good when blipping the gas and it is idling stable.
I just wanted to drive it enough to do a couple pulls and hear what it sounds like. I got a whole 3 tenths of a second at WOT in first gear before it sent me into limp mode for a loose TB connector. Plugged it back in and got a rip to 2nd gear and it did it again, and then the scanner crashed and I lost the log I have a new intake coupler and I don't think it likes the vibration from the coupler touching the hood webbing.
Can't wait to get the Holley installed and put these issues behind me lol. Thanks for the suggestions. If I drive it more I'll try to get some pulls on video.
I would also take this chance to retorque the old manifold there not sure what one you got but the plastic ones sometimes need a resnugging of everything. Also the ones that are a clamshell design and bolted together I give a snug to the perimeter bolts.
I would also take this chance to retorque the old manifold there not sure what one you got but the plastic ones sometimes need a resnugging of everything. Also the ones that are a clamshell design and bolted together I give a snug to the perimeter bolts.
Yeah I had the manifold off for the cam swap, and torqued it back down in sequence. When it was idling weird I went back over them.
Nice work getting it sorted! For the 0.3 seconds you got at WOT, how'd it feel?
Man I just want to get the thing to 7200 to see how it pulls and it keeps blue balling me. The first drive I did prior to this it hit a weird fuel cut at 6800 even thought he limiter is set at 7200. Hindsight, I think it was on the verge of going into limp mode there.
It felt good in first gear for sure. It isn't like I saw jesus or anything, but it was the highest airflow numbers I've seen on the MAF even though it is really really hot out here recently. It felt like it was still going up that's for sure, but again first gear is hard to tell. After not driving the car a while with the old cam it is really hard to do an A/B lol.
Man I just want to get the thing to 7200 to see how it pulls and it keeps blue balling me. The first drive I did prior to this it hit a weird fuel cut at 6800 even thought he limiter is set at 7200. Hindsight, I think it was on the verge of going into limp mode there.
It felt good in first gear for sure. It isn't like I saw jesus or anything, but it was the highest airflow numbers I've seen on the MAF even though it is really really hot out here recently. It felt like it was still going up that's for sure, but again first gear is hard to tell. After not driving the car a while with the old cam it is really hard to do an A/B lol.
Lmao so I learned today about codes P0106 and P0068. I guaranteed have a lot more airflow because I never knew about the DTC checks for airflow maximum.
I got a few pulls in at lunch time with my buddy watching things for me, and we had a great 2-4 pull, and then a 2nd gear rip that left me in limp mode AGAIN lol. 3 times in two drives. Very tiresome. I've had issues with the TB going into limp mode previously because of the connector so that threw me off.
He's ridden in and driven the car before and he was very impressed. Biggest difference is I did get to rip off a couple 7000 rpm shifts and it definitely is not nosing over like it did before. I've bumped the limiter to 7600 so I can try to find what it likes.
Back to the topic, idle seems to be behaving as expected now. I put the timing up at 22, and with the super low minimum airflow the throttle is closing down too hard and it is stumbling. With the idle timing set at 16 it did quite well. For whatever reason I seem to be past the high idle/2* idle timing issue for now and feel like I should be able to dial it in no problem now.
This is what it looks like to go from hauling *** into limp mode lol.
So just to close this out, I did find the limp mode issue. I never knew about airflow maximum vs TPS in the engine diagnostics section of HPTuners. Can confirm, getting a lot more airflow since I've never hit the airflow limits before. This is when all the boosted guys are going to roll their eyes.
Easy to just disable the check and go out for a rip. I did one drive to confirm I fixed it at night. At night is important because my dash cluster lights don't come on so I was flying without a tach lol. I bumped the limiter in the tune to 7600 rpm and shifted by feel and was shifting at 72-7300. Power peaked at 6200 previously and fell off pretty quick after 6500. It feels much less peaky now and pulls very hard to 72. No doubt the car is faster.
Here is a before/after cam swap. The before had MUCH better air conditions. We've been in a hot and humid heat wave here in socal. I always treat these tables kind of like an inverted dyno sheet.
Love seeing this thing carry some RPM finally!
I don't want to work anymore on the tune since I took the plunge and ordered a Holley Terminator X setup. Going to get all that installed instead of dicking around with hptuners anymore.
Thanks man. It made me want to get my new motor done. Like, it was a fun side project and all - but time to stop dicking around. It is fast-er, but not 8000 rpm 427 fast. Going to the standalone was one of the final barriers in having the car ready for the ls7. Excited to get all that installed and running then it will be a simple engine swap when the ls7 is built.
So just to close this out, I did find the limp mode issue. I never knew about airflow maximum vs TPS in the engine diagnostics section of HPTuners. Can confirm, getting a lot more airflow since I've never hit the airflow limits before. This is when all the boosted guys are going to roll their eyes.
..... Someone had to. Glad you're getting the tune sorted out!
08-18-2020, 03:55 PM
High idle after cam swap 
I have a new intake coupler and I don't think it likes the vibration from the coupler touching the hood webbing.
.....
Someone had to. Glad you're getting the tune sorted out!