surging on idle after driving

[Seight-v8]

hello all,

so been out today doing some road miles, and logging.

Finally feel like i am getting somewhere.

A few problems i need to work on, so here's the first one.

After driving, and then stopping, idle surges 580-1000rpm for about 8-10 secs, then idle returns to steady 750rpm.

got the stepper motor to follow tps - disabled

and the close delay at 40secs.

or is something else amiss somewhere.

cheers

scott

[dnb]

There's a number of things that can cause this.  Here's a couple to look at (non-exhaustive list!)

The PID settings for the idle controller are a little off, but not much - consider decreasing P a fraction or increasing I a fraction (but remember that I can be made asymmetric)

The VE table is a little lean at one or more points as you approach idle.

[Seight-v8]

thanks dave,

i have from the log i took today, redone the vetable, so will try again tomorrow.

found on thrusday i have a leaking exhaust gasket on the lambda side, which when fixed, changed all the lambda readings.

scott

[Sprocket]

Its always a good idea to have a higher value in the ignition table, in the lower RPM region around idle, to help speed the engine back up as it dips below the desired idle speed

[Seight-v8]

i've noticed that at idle, it is right in the middle of two load sites, and i think this is also changing the readings slightly enough to affect idle quality.

i only have 6kpa between load sites and wondering if at idle (about 44kpa) i should make this bigger, so the fueling is more constant.

Idle is currently running at 44-48kpa, and my load sites are 40,46,& 50kpa.

how much between load sites is too much?

cheers

scott

[rob@vems.co.uk]

You'll tend to have the bottom 3x3 rpm and load cells quite close together in order to get a clean, stable idle.

[mattias]

Make sure to have the same ignition advance for all load sites that are considered "idle".
If you don't the idle will "hunt" because of it.

We should really have a special idle ignition table if you ask me, or at least a fixed advance at idle. Some large V8 engines or inline 6 tend to use the same load sites for idle and low speed city driving in high gear and having to compromise the optimal advance between idle and driving is not good.

You can enable ignition advance idle control to complement the idle air valve later, I feel that +/- 5 degrees is all it takes if the valve is tuned well.

[Seight-v8]

done 212miles today to a kit car in newark (UK).

Car ran pretty well, 60-70mph is great

I enabled iac to follow tps before i left, and idle is much better when stopping.

Think my VEtable is still about 3-5% off, as lcd showing ego correction.

Cant fault the acceleration.....wow thats some fun.

More tuning to be done, but so far getting much happier all the time, with the way it runs.

cheers everyone.

scott