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Idle tuning, high VE

Practical Standalone Tuning

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Hi! I finally started tuning my drift car. Currently setting Idle when warmed up. I have had some success, but there's room for improvement.

1JZ-GTE VVTi, Ecumaster Classic, stock cams, stock throttle, no IACV, pump 100 octane fuel

https://drive.google.com/drive/folders/1r43UvXq-WpbZoXBK9hSjyyTslAdSxOgE

Map and log in the link

Idle target RPM 900

Idle RPM 890-920

3% throttle plate opening (before reset for 0 reading)

47KPa

Fuel pressure 2.41Bar

Ignition map base angle 10 degrees

Idle target AFR 0.95

62 VE%

Controlling idle with ignition correction

How could I retain the RPM level, but perhaps decrease VE? Burn less fuel essentially. I had it running pretty steadily at 1000 RPM and 54VE%, but I would much prefer lower RPM if possible. Throttle plate can't close more or no more cold start. One thing I haven't tried yet is going for 1.0 AFR.

When coolant fans kick in I get a temporary lean spot, from 0.95 to 1.10. Voltage does drop, but not drastically. Goes from fluctuating 13.85-14.15 to 13.70-14.0. Are there any tools (maybe even Ecumaster Classic specific) I could use to enrich that spot?

Idle Ignition correction works, but it won't correct enough, even though there's still range (goes from 20 to -20). Can someone shed some more light on this? I guess it has to be set mechanically first and correction to fine tune only.

Matej,

For a given airflow, all else equal, a typical engine will idle at a higher speed when hot vs. cold, the opposite of what's usually desired in terms of target idle speed.

It sounds like this is a cable throttle setup with no idle air valve, so you've set the throttle stop in a place which has just enough airflow for cold idle, too much airflow for hot idle. That's the best you can do if you don't want to have to use your foot to keep it idling while cold. Tuning will not bandaid a lack of airflow control.

Be careful in your attempt to reduce hot idle speed via ignition timing retard as beyond a certain point, you create a ton of exhaust heat and under hood heat, which can melt things. You mentioned -20 degrees. That is more than 20 degrees from as low as I generally go. Adding an EGT probe will really help see this in action and help you make those timing decisions.

If you don't want to have to use your foot to keep it idling while cold, hot idle will be high.

If you don't mind using your foot to keep it running while cold, you can reduce minimum throttle opening so hot idle isn't so high. That's the bandaid I suggest until someone can execute a proper solution, which would commonly be adding and tuning an idle air valve or drive by wire system.

For what it's worth, I admire the precision you're striving for in terms of idle fueling, but it sounds like air/fuel ratio is only shifting 0.15 AFR when the fans go on/off, which is quite small, not enough to worry about functionally, but I like that you're wondering how you would account for it if you had to.

I would confirm your dead time tables are appropriate for the injectors, confirm fuel pressure doesn't shift during high electrical load, then monitor engine load (likely MAP in your case) as the fans go on and off. Oftentimes engine load changes when high electrical loads occur, so you may be operating in a slightly different area of your VE table, which may need a tiny adjustment.

Some ECUs have compensations for fan on/off, or high electrical load, but they're usually airflow based, related to idle control, rather than fuel based.

Although your ignition timing and fuel settings are just like stock you also need to tune idle stepper motor ( the one with 6 wires) in order to bring idle RPM down.

At the aforementioned 3% propped throttle plate opening I does run even when cold, although tuning that is on the agenda for this week. Just to idle when warmed up, 1% throttle opening was enough. That would never work for cold starts though.

I logged everything extensively while working and the actual timing after correction was normally around 5 degrees. The -20 I brought up is just what the correction table is limited to. That actually confirms that the current iteration I use is better than what I had a few days ago, because at that time it did in fact try to retard by up to -20 which did set actual timing into negative numbers at times. Another thing that kind of confirms improvement is the cycle time between fans coming on. Now it takes longer for the engine to warm up back up after fans cooled it.

The only thing that I would wish to improve on is really the high VE. The rest, I can life with

I openwd a separate post under General about Injector dead times. They are Denso, so hard to find info. Have a look if you can maybe shed some light on those.

Georg, my manifold is thebone without the IACV hole and I am not prepared to add an IACV at this time.

Have you tried to retard ignition timing let's say to 3-5 degrees instead of 10? If you have no meand of restricting the air flow at the idle there is only one thing left wjich is ignition timing sonce changing AFR will not have great effect on idle RPM.

I have tried that. Idle timing correction compensates for it

So what idle RPM do you get when you set ignition timing at 5 degrees BTDC?

Lowest I went was 0 base. And rpm was slightly below 900, wit correction chasing 900

Can you change target settings for that correction?

Sure. If I do though, I would rather have it idle lower than higher. You think 0 degrees (or even lower) base and lower RPM target is the way to go? Is that even acceptable, to have Idle base that low? Don't most run 15-20 advance at idle base? Or is that specific to having an IACV?

Any ignition timing is acceptable as long as you are satisfied with outcome. In your case if you'll get lower idle RPM with less ignition timing and the engine will not be stalling - sure it's a way to go...

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