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Author Topic: Idle torque reserve me 7.5?  (Read 756 times)
Kacpern
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« on: November 17, 2024, 03:19:45 AM »

Hello, what is the idle torque reserve in me 7.5 responsible for? Will increasing it improve thrust when starting?
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aef
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« Reply #1 on: November 18, 2024, 01:51:33 AM »

https://s4wiki.com/wiki/Idle_torque_reserve
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doktor
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« Reply #2 on: November 18, 2024, 07:05:24 AM »

Since we are in the noob questions area... Why is the idle stabilized only with ignition timing but not also with injection time ("load")? I get it that the engine runs quite inefficiently at idle with retarded timing. Why not use an ignition timing map (rpm/load) similar to the one for normal driving? The idle speed feedback controller would simply request load and look up timing, that would be the logical and efficient way to do it IMO.
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Kacpern
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« Reply #3 on: November 18, 2024, 10:10:39 AM »

Thank you.
So the torque reserve map has no effect on thrust when starting?
Which map is responsible for pulling power when starting?
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nyet
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« Reply #4 on: November 18, 2024, 03:21:13 PM »

Since we are in the noob questions area... Why is the idle stabilized only with ignition timing but not also with injection time ("load")? I get it that the engine runs quite inefficiently at idle with retarded timing. Why not use an ignition timing map (rpm/load) similar to the one for normal driving? The idle speed feedback controller would simply request load and look up timing, that would be the logical and efficient way to do it IMO.

certainly you mean stabilize via throttle plate angle? Variation in lambda at idle torque would have almost zero effect on RPM.

you don't want to do via throttle plate angle because its slow as fuck that way.
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doktor
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« Reply #5 on: November 18, 2024, 03:24:32 PM »

certainly you mean stabilize via throttle plate angle? Variation in lambda at idle torque would have almost zero effect on RPM.

you don't want to do via throttle plate angle because its slow as fuck that way.
Yeah thats what I meant, so speed is the problem. Thanks for the reply.
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prj
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« Reply #6 on: November 18, 2024, 04:36:29 PM »

Actually it has fast path and slow path torque intervention.
Slow path is throttle and fast path is ignition.

It uses both.
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nyet
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« Reply #7 on: November 18, 2024, 04:47:19 PM »

Actually it has fast path and slow path torque intervention.
Slow path is throttle and fast path is ignition.

It uses both.

Apologies, i was mixing idle control with torque reserve

not sure if there is any meaning to having a throttle plate reserve Smiley
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prj
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« Reply #8 on: November 18, 2024, 05:00:40 PM »

Apologies, i was mixing idle control with torque reserve

not sure if there is any meaning to having a throttle plate reserve Smiley

Not sure what you mean, when you increase the torque reserve it opens the throttle wider and to keep the idle at the same spot it reduces the ignition timing.
Thus you have more timing "in reserve".

Idle control is also done with both. Slow path through FUEDK and LLR and fastpath through ignition...
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nyet
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« Reply #9 on: November 18, 2024, 06:03:05 PM »

Not sure what you mean, when you increase the torque reserve it opens the throttle wider and to keep the idle at the same spot it reduces the ignition timing.
Thus you have more timing "in reserve".

Idle control is also done with both. Slow path through FUEDK and LLR and fastpath through ignition...

Understood. The point is, you reserve a bit of headroom for increased ignition efficiency (reserve) so if you need a bit more torque you can add timing instead of opening the throttle. That is to say, the reserve exists solely for the purpose of the fast path. The slow path (more open throttle, worse timing) provides the reserve.
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doktor
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« Reply #10 on: November 19, 2024, 06:08:13 AM »

Thanks for the replies, interesting info.
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prj
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« Reply #11 on: November 19, 2024, 08:16:07 AM »

the reserve exists solely for the purpose of the fast path.
I disagree because the idle controller works on both slow path and fast path, it is constantly trying to reach the target torque reserve with the slow path and it is using the fast path to compensate for the speed of the slow path.
Torque reserve gives the idle controller more leeway to respond.

I understand what you mean, but the way you say it makes it seem like the throttle angle is fixed once you reach idle speed.
It's not. It's closed loop. If you turn on e.g. AC then the ignition will momentarily advance, and then as soon as the slow path controller catches back up the ignition retards again to provide the target "reserve".
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« Reply #12 on: November 19, 2024, 11:17:38 AM »

Agreed. This is why is said "slow path provides the reserve". literally Tongue
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Kacpern
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« Reply #13 on: November 19, 2024, 01:50:16 PM »

Does the torque reserve map for idle control handle starting from a standstill, or is it only responsible for stabilizing idle RPM during AC turn on?

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prj
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« Reply #14 on: November 19, 2024, 08:16:14 PM »

Does the torque reserve map for idle control handle starting from a standstill, or is it only responsible for stabilizing idle RPM during AC turn on?
It also handles you being bad with the clutch.

No, you are not going to make antilag with it, the monitoring will tell you to gtfo.
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