Cascade Crew

fiveoformula · Posted: Tue Jan 03, 2012 5:11 pm Post subject: Tune out the surge!

Been trying to get the idle quality a bit better since the cam swap but can't seem to do so... It smells very rich and the car shakes and surges at idle (more so when in closed loop). It actaully "feels" smoother when I disable closed loop. BLM's are way low at idle too. What are some of the tricks to smoothing out idle?
Oh almost forgot to say im using an EBL for tuning.

Twilightoptics · Posted: Tue Jan 03, 2012 5:39 pm Post subject:

First off, you need more timing for a bigger cam.

Second, you need to set the throttle blades as open as you can to get the IAC counts to around 20 or so, that way the computer has less "control" over the idle air which helps to smooth.

If it's too rich, lean it out :O)

Do all these changes fully warmed up.

fiveoformula · Posted: Tue Jan 03, 2012 5:54 pm Post subject:

Ah hadn't thought of that, I still have never punched out the the thing that blocks the screw on the throttle body.
At idle the timing is at roughly 17-20* advanced last time I looked, should I give it more than that? Base is set up on 2*.

aaron_sK · Posted: Tue Jan 03, 2012 6:32 pm Post subject:

Alphius · Posted: Tue Jan 03, 2012 7:00 pm Post subject:

I currently run 22* at idle. Flatten timing and fuel maps in the areas where your engine idles.

I had surging idle problems with my engine, it turns out it likes to idle best between about 13.5:1 to 13.8:1. Any leaner or richer and it starts to surge. Do you have a wideband? I run closed loop until IIRC 1100RPM, can you run open loop under an RPM setpoint? Even wideband AFR targeting at idle makes mine surge too much since the exhaust pulses past the wideband are so far apart.

My IAC is steady-state open-loop at idle, MegaSquirt doesn't touch it, just set and forget. Is there a feature like this in EBL? I run about 750-800 RPM at idle. Maybe bumping your idle speed a bit would help? I don't know what you're targeting right now or your cam specs.

fiveoformula · Posted: Tue Jan 03, 2012 7:11 pm Post subject:

I do have an AEM wideband, I believe I can only set the closed loop enable with a CTS threshold constant. When I run it open loop only, AFRs are around 11.8 at idle, runs alot smoother but you can imagine the gas mileage.

Alphius · Posted: Tue Jan 03, 2012 8:05 pm Post subject:

Twilightoptics · Posted: Tue Jan 03, 2012 9:51 pm Post subject:

Your milage is crappy if you're idling around period. Make it idle good, and don't worry about it.

You can also adjust your O2 swing point then to adjust for the little bit of overlap.

Every motor/cam combo is different for timing. Efficient heads need less timing, big cam wants more.

I ran about 28deg at idle in my 355 with that big ass cam.

Try moving it in 4deg increments.

Your base is set at 2..... did you tell the ECM your base is at two? Now that you can tune with EBL DO NOT LIE to the ECM, because you can adjust in the ecm for MOST lies. Of course I told you about the o2 swing point, that's lying to the ECM but only because of the narrowband functionality.

Or does EBL run off the WB?

Also, you might need a touch higher idle with the larger cam anyway.

fiveoformula · Posted: Wed Jan 04, 2012 7:02 pm Post subject:

EBL runs off the stock o2.
ECM knows its at 2*
Gonna adjust the idle set screw a bit, and I'll try bumping the timing and let you guys know what that does.
Which way do I adjust the swing points? voltage wise.
And it idles rough when it goes into closed loop and the AFR's adjust to around 14.8-15.5. Open loop when its down in the 11.8 area it feels much smoother, so I guess I need to find the happy medium there, for some reason I thought low 15 AFR's should be good at idle.

Alphius · Posted: Wed Jan 04, 2012 7:40 pm Post subject:

Twilightoptics · Posted: Wed Jan 04, 2012 8:36 pm Post subject:

Yes a richer idle can help. However, with a narrow band, part of the problem is the overlap actually gives a leaner reading. Because of the unburnt o2 of the overlap.

So it reads say 350mv and the ecm thinks it's lean so it adds more fuel. So you need to tell it that 350mv is correct, so it doesn't continue adding fuel.