Bigger cam, and timing at idle.
07-30-2014, 08:33 AM
#1
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Bigger cam, and timing at idle. Hey guys...
I have searched, and seen some answers bordering on what I am looking for.
Here is my issue. The LS1 Swap I just completed on my Z seems to run great everywhere, except idle. It will be smooth at about 1150, but if I load the motor down electrically (fans on, headlights on, heater running) it oscillates all over the place.
One of the guys on the Megasquirt help forums tells me I need to drop my timing down to around 15 at idle, but that makes the oscillation so bad it will kill the motor. If I back the IAC steps down to try to lower the idle, same thing.
The cam is an overall lift of 575 int/574 exh, 228/228 duration, with a 112 centerline. If I remember right, it is about 270ish lift at 50 degrees.
Most of what I have read seems to indicate that with cams in this neighborhood, 30 degrees and up seem to make them idle better under all conditions.
I am going to fiddle around with it tonight some more, and try cranking the timing up, but I wanted to know what you guys with bigger cams running for timing at idle?
Thanks.
I have searched, and seen some answers bordering on what I am looking for.
Here is my issue. The LS1 Swap I just completed on my Z seems to run great everywhere, except idle. It will be smooth at about 1150, but if I load the motor down electrically (fans on, headlights on, heater running) it oscillates all over the place.
One of the guys on the Megasquirt help forums tells me I need to drop my timing down to around 15 at idle, but that makes the oscillation so bad it will kill the motor. If I back the IAC steps down to try to lower the idle, same thing.
The cam is an overall lift of 575 int/574 exh, 228/228 duration, with a 112 centerline. If I remember right, it is about 270ish lift at 50 degrees.
Most of what I have read seems to indicate that with cams in this neighborhood, 30 degrees and up seem to make them idle better under all conditions.
I am going to fiddle around with it tonight some more, and try cranking the timing up, but I wanted to know what you guys with bigger cams running for timing at idle?
Thanks.
08-12-2014, 10:35 AM
#3
On The Tree
Stock LS6 here and it's around 16-18* at idle. You would want more timing than that with a larger cam. Keep an eye on MAP too, you want to shoot for lowest kPa or as much vacuum as possible.
08-12-2014, 04:43 PM
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I think I have gotten a lot closer to figuring this out. I finally figured out that the wobble in my idle was coinciding with intake air temps rising over 150 degrees.
So I did some reading and found several references to faulty or incorrect dead time, and pulsewidth programming contributing to instability at idle when the IAT rises. I finally got some hard data on dead time and voltage correction, and the injector latency was way off. After fiddling with it for awhile today, I have gotten a lot closer.
And by the way, I also built an airbox to keep the IAT down. Lost 25 degrees across the board with this 40 dollar, 2 hours of labor investment.
Last edited by MaxxAction; 08-12-2014 at 04:51 PM. Reason: edited to add info
08-13-2014, 06:03 AM
#6
Good job. I'm not very familiar with that ECU and it's programming. The budget ECUs appear nice but I've wondered if they have many of the parameters that are found in the factory setup. Getting idle, idle under load, and transition from idle to load can be a lot more work than WOT.
