Courtesy of Wolf Engine Management: You know, sometimes people talk about an idle control system, whether it be a stepper motor, or a pulse width modulated solenoid, as if it can overcome fuel and ignition tuning issues. That is not always the case. BEFORE you start playing around with the idle control system on your ECU, you must make sure that the engine will idle as well as you possibly can, without the idle control system taking control. Let's talk for a minute about the most basic concept on how to set up your fuel and ignition maps so that you have the best chance of having a stable idle, even under varying load conditions such as when you turn the headlights on, or when the A/C comes on. Let's say for example that your engine idles at 20% load and at 1,000 RPM. If your engine goes to stall, the RPM will drop and the load will increase. So, you need to increase the amount of engine torque generated as the engine begins to slow down. This will then try to increase the engine speed, and hence this will stop the engine from stalling. How do you do this? Let's say that at idle (20% load and 1,000RPM) your ECU is delivering 3mS of fuel and 10 degrees of ignition timing. We will assume the engine is running at an air fuel ratio of 14.2:1. As the engine starts to slow down (you will see the increase in load and decrease in RPM), you want to increase the amount of torque the engine is producing. So instead of 10 degrees of ignition timing, you might have 13 degrees at 875 RPM. This will increase the amount of torque the engine is producing and the engine will try to speed up. As it speeds up it returns to the 20% load and 1,000RPM point where there is slightly less engine torque, so it will begin to slow down again. Now, and this is the important bit. The idea is not to have the engine cycle faster, slower, faster, slower. The idea is that the engine ends up "sitting" on this new torque slope. Even though it may actually be going faster, slower, faster, slower, it may only be doing that by 20 -50 RPM, and you will not even notice that. You can do the same thing with fueling, giving a little extra fuel as the engine slows down will increase engine torque, and help keep the idle stable. NOTE: Don't make these fueling and ignition slopes too steep, otherwise you will get cycling happening and the engine will not have a smooth idle. Now that your engine is idling smoothly, you can activate the idle control system. The idle control system can now be adjusted to take up any slack caused by headlights and other loads that the fuel and ignition torque ramp cannot completely control. I'll be sending out a future email with more specific info on setting up the idle control system, but that is it for today.

You like?

Now this tuning season I am closer to that good idle. this morning idle was very good 15 minutes into ride on country roads a few stops to observe idle. Idle was 825-850 and steady. IAT was 55 degf and coolant 185. At end of ride IAT was 85 and coolant 185. Now I see the idle drop to 700 and stall saver pulls it to 900 and it is cycling. I fattenned up the VE 1200rpm and below so I think I am OK with fuel. I idle 24d sa. But reading the article maybe I need to add some spark 400-800? M WB reads about one point leaner that OL tables at OL idle.
Quote:
NOTE: Don't make these fueling and ignition slopes too steep, otherwise you will get cycling happening and the engine will not have a smooth idle.

That may be part of it. I may have a drop off in SA too STEEP?

what??????????? lol glad im carb

Why are you then peeking into the zone?. Carb guys should be required to obtain a password. Moderators?

im peeking becuase i like to learn things u have a great post here just read it and was lost

Couple of things. Need to open the throttle blades to get the IAC steps down to 5 - 10 at idle. This will provide the best idle and tip-in off-idle response. Do this with the trans in park/neutral and no other loads (A/C, headlights).

For the SA during idle, there are already tables to do this. Look at the tables:

SA - Idle Low Compensation
SA - Idle High Compensation
SA - Idle Low Map Multiplier
SA - Idle High Map Multiplier

They are designed to stabilize the idle RPM.

Use those in conjunction of the set idle SA option. This way the idle SA is divorced from the main SA table.

You can also use the open loop idle option. This will remove the prop gains along with the INT/BLM corrections to the fueling during idle. I like to use open loop idle when dialing in the best SA values/tables.

RBob.

Thanks.

IAC at idle is zero steps in my .bin above 160F coolant.

SA Compensation and SA Multiplier I have already modified. I dont recall which way I went but I reduce all by 50% or greater vs EBL.bin. I can check .bin and report back later. Did I misinterpret on that one? Is that compensation favorable or a hindrance assuming use of stock values?

SA Idle option is "set". I idle 24 d. However I see that when the surge occurs I fall out of surrounding cells at set to 24 and at the lower RPM swing point(600) I see I am at 20 d?

Open loop idle "set". I see 15.0/1 on WB commanded to 14.0 in OL tables. Exhaust clean.

Excellent post Ronny

Ronny, rbob is sugesting that you get your iac to 0 as a physical adjustment on your TB.
He is suggesting that you open the throttle plates a little. The iac should then close in relation. open the TB until you get at or near zero on the iac.

I wasn't quite awake this morning. Mixed up IAT and read IAC, at 85 would have been a lot of steps. With them at zero it's OK.

SA Idle option is "set". I idle 24 d. However I see that when the surge occurs I fall out of surrounding cells at set to 24 and at the lower RPM swing point(600) I see I am at 20 d?

Sounds like the set idle SA option flag isn't set. When at idle the basic spark timing is what it is set to in the "SA - Idle State SA" parameter. But need to set the flag to take advantage of this: Option Word 2 - Bit 1 - IdlSa

A low idle can only add timing, can't remove it. This is the idle SA compensation.


Open loop idle "set". I see 15.0/1 on WB commanded to 14.0 in OL tables. Exhaust clean.

Bump up the VE a little to match the commanded AFR. The 15:1 is lean for idle and can cause surging.

RBob.

See prior post "Great Idle"

My settings Idle High Comp all zero
EBL 1-7-7-6-5.

SA Idle High MAP Mult at 20-50 mine all 100... at 55-70 are 90-83-33-33
EBL about 30% less

SA Idle Low Comp mine zero
EBL 0-200 rpm are 1-5-6-5-3

SA Idle LOW MAP Comp 20-40 mine zero
45-70 mine 23-72

It appears I took out the compensation at30% fiquering it would contribute to surge?

I am certain it is set but will double check. I see your point, how can it float when locked.

VE adjustment. now that makes sense. In fact I think my OL operation only is about 1 point off lean all over. CL at stoich(maybe a bit high 15.0/1). BUT is my WB fooled with "reversion" at intake and/or EXT? WB sensor is closer to end of EXT than it is the combust chamber. Dont ask why...

My idle speed is set with throttle stop screw not IAC steps. I think a Grumpy trick?

Option Word 2 - Bit 1 - IdlSa
It is set.

Don't tune to a number (WB AFR in this case). Tune the engine to make it happy.

"Give it what it wants", Grumpy.

RBob.

Ronny, I merged your follow up into this thread.

What you can do is to zero out the two idle compensation SA tables. This way there won't be any +- SA from idle high/low.

Then get the best idle via AFR (VE) and the idle set SA value. Don't be surprised if the idle RPM rolls. If it does then just let it go.

However, if there is surging then the VE values need work.

Then slowly add some compensation SA in to steady out the idle. Just enough to keep the idle from rolling.

RBob.

I assume you mean 4 tables. I will zero out all so no compensation. Idle HIGH and Idle Low I have zeroed now as it is in degrees.

I see Idle Hi and Low MAP is percentages? I see it is VAC.

Should I set percentages to zero or 100? I will zero on a guess that being correct. 100% might double(2X) ?

I have not yet added to VE tables. I will add fuel 40 and < MAP at 400 RPM-1000 RPM and give it a go. Point of interest idle this morning was rock solid. Seems I see a moderate surge only when the underhood temps rise above 85F. It likes cool weather(45F). I will add fuel as stated. Then check the result. Then add back in a little of SA Comp as you suggested. Then check the result.

Just need to zero out the two SA tables.

You mention under hood temperatures increasing. Also shown on the IAT sensor. Is the air intake temperature going up also? Or, is the intake air being pulled from a location that is still at ambient? The IAT should be located that it reports what the true intake air temperature is.

RBob.

There are 4 tables for idle comp? Which two of four? Did I do something wrong?

I see IAT at 45F for quite a while on first ride in morning. coolant is 185F. It slowly rises to 85F on IAT after 25 min ride to office at 65 mph. Now my sensor is tywrapped to
the support of the rad fan about three inches from K+N cone.

The two of the four tables that have SA values.

RBob.