down rev with extremely light flywheel and idle control

[vwnut8392]

so this is and yet another problem i seemed to uncover. what i have is an 8lb billet aluminum 034 motorsport flywheel in a project car with tilton OT-II twin disc clutch set so very light compared to stock. problem is when the engine is coming down ibn RPM it does it very fast and the idle control cant seem to catch it in time and the car stalls. sometimes it wont stall but most of the time it stalls. not really sure how to approach this one. do i do something with timing and fuel to slow the engine down or catch it when coming down in RPM? tried a 1000RPM idle and it didnt help at all and i dont want it idling any higher than that.

[jonn48]

so this is and yet another problem i seemed to uncover. what i have is an 8lb billet aluminum 034 motorsport flywheel in a project car with tilton OT-II twin disc clutch set so very light compared to stock. problem is when the engine is coming down ibn RPM it does it very fast and the idle control cant seem to catch it in time and the car stalls. sometimes it wont stall but most of the time it stalls. not really sure how to approach this one. do i do something with timing and fuel to slow the engine down or catch it when coming down in RPM? tried a 1000RPM idle and it didnt help at all and i dont want it idling any higher than that.

Hello! I have a lightweight flywheel and also have a problem, but the engine does not have time to stop. I assumed that this is a malfunction of my car, but now I will try to solve this problem by setting it up.

[Error404]

I have no experience with Motronic, but if possible I would try to increase the idle air DC slightly, at and just above the idle speed, and tweak the PID.
Do you have an anti-stall timing trim? Making that more aggressive could help, Idle tuning is always going to be more difficult with less inertia.

[Bowie69]

If you have fuel cut on overrun switched on, raise the point at which it is switched back on, I. E. If 1200 then move it up to 1500.

I've found can stop the engine being able to react properly to a fall engine speed.

Otherwise, as said, you need to work on the damping of the idle speed control to suit your engine. It is a pain to get right at times, and can lead to bouncing idle, but perseverance pays off

[jonn48]

If you have fuel cut on overrun switched on, raise the point at which it is switched back on, I. E. If 1200 then move it up to 1500.

I've found can stop the engine being able to react properly to a fall engine speed.

Otherwise, as said, you need to work on the damping of the idle speed control to suit your engine. It is a pain to get right at times, and can lead to bouncing idle, but perseverance pays off

I now have the beginning of the introduction of cylinders to work - 1400, the value when all cylinders must be activated - 920. I think 920 is too low, there is little time for reaction. We must try to add this value.

[Bowie69]

The other thing you can do is increase timing advance in the bins under the target idle speed, this will help bring the engine back up to idle quicker.

[vwnut8392]

iv'e tried a lot of what has been suggested already with no positive result. i'll keep working away at it though, if i figure something out i'll report back so everyone else knows for reference.


Just for reference here are all of the constants from the DAMOS relating to idle control. PRJ already covered the maps for the most part except the actual P I and D maps for the ISV.

These are the constants for idle control.
Idle 2.JPG
Idle 1.JPG
Idle 4.JPG
Idle 3.JPG

These are the constants for idle adaptation
adap 1.JPG
adap 2.JPG

[vwnut8392]

Here's all the tables related to the idle control from the damos. im giving this up in hopes that it will not only help me find a solution to the problem for myself but for others too.

Table 1.JPG
Table 2.JPG
Table 3.JPG
Table 4.JPG
Table 5.JPG
table 6.JPG
table 7.JPG
table 8.JPG
table 9.JPG
TABLE 10.JPG
table 11.JPG

[vwnut8392]

I adjusted these 3 tables like this and it appears to have fixed the stalling when coming down from idle.

Idle drop.JPG

[d_anev]

Hi guys,

why you rediscover hot water!!! Everything that you need to solve that problem is described in M232 Wiki:

• Idle ISV Linearization - target ISV DC based on RPM and ECT. Simply rev up the engine and then release the throttle, and see how slowly the idle drops. Keep in mind that the ISV can control airflow slowly - you want to have a stable base value, and then have adaptive control and ignition fast path to do the rest.
• Idle ISV Linearization, AC ON - same as above, but when the AC input signal is received by the ECU.
• ISV frequency during cranking - these two maps are added together and the duty cycle of the ISV during cranking is output from them. If you have more displacement or funny cams you might want to increase this somewhat. Same effect as slightly leaning on the throttle when starting the car (which you should never be doing if this map is tuned right).

Then read about "ignition fast path" to be able to have fast idle speed control .... here are your decisions....

[Acki]

Shutdown restart speed? Fuel cut limit or something like this sounds way better ^^

[jonn48]

I adjusted these 3 tables like this and it appears to have fixed the stalling when coming down from idle.

Idle drop.JPG

Which damos maps were used to convert these tables to xdf?

[vwnut8392]

to give everyone an update what i did to get the car to not stall and idle correctly with the lightened flywheel was i lowered the lambda threshold map at 1000RPM to 0 so that it would not interfere at idle than i simply went into the VE table and in the idle area of the table i set the ECU to idle around 13.0AFR. also i made some small tweaks to the idle ISV linearization table and all is working perfectly now. car idles smooth and doesnt stall at all anymore.