Engine waits before losing RPM with 0 throttle

[rindoze]

E38 LY6 which was 6l90E 2wd and is now manual
So my issue is that after giving it some gas and completely getting off the throttle (between gear shifts and such) the RPM holds for about a second before it gradually falls off. I was wondering what is causing this and if I can make it so the it doesn't happen.

Thanks

[mowton]

the min idle air is too high, coast down spark isnt set right, follower torque isnt set right, throttle control has been messed with etc.

Ed M

[GHuggins]

Go to tune repository on HP's website and find your same vehicle with manual trans setup, compare to your tune, make necessary changes to all idle, spark and torque tables as Mowton pointed out.

All it is is the difference in friction of an automatic held in gear with torque converter coasting down vs manual having nearly no friction with clutch being depressed.

[rindoze]

Thanks for the responses, I didn't now so many things were involved in just RPM dropping. I took those tables and some other spark tables from a 2010 camaro manual and it is improved. I still have the lag though and there is pops out of the exhaust at times. Here is my tune, took me a long time to get it to go past 4k since I am not using any TCM or VSS it was hitting all sorts off different limiting tables. Any advice on the tune?

NewTune3.hpt

[GHuggins]

Sounds like you still need to change some tables over. Have you addressed the trans tables? I would compare all sections of the tunes to see everything that needs to be changed.

[rindoze]

I modified all tables I could see related to the trans in the engine section, in the trans section there are no options but CAGS. Probably should look into getting some cables to hook my TR6060 sensors into the ECM

[Higgs Boson]

before you go through all that trouble, you mentioned it's when you let off between gears. the trans will hold the gear in anticipation of the driver getting back on the throttle before it releases. this isn't what you are experiencing is it? it could be normal. if you had a manual trans then I would go looking at your idle airflow tables.....

[rindoze]

The car responds well now, there was a minor exhaust leak near the collector that I fixed, the engine now revs up faster and falls off faster. I didn't think a small exhaust leak would make such a big impact on the way the motor reacts, but since it was pre O2 sensor it seems to have thrown things off a bit. Still have some popping out the exhaust though. Would increasing or decreasing the idle airflow be helpful for this?

[GHuggins]

The car responds well now, there was a minor exhaust leak near the collector that I fixed, the engine now revs up faster and falls off faster. I didn't think a small exhaust leak would make such a big impact on the way the motor reacts, but since it was pre O2 sensor it seems to have thrown things off a bit. Still have some popping out the exhaust though. Would increasing or decreasing the idle airflow be helpful for this?

Popping while deceling? If it is then you need to start by adding about 8 to 10 degrees timing to your idle advance coastdown table, then under Fuel - DFCO "as long as your still enabling dfco" - set enable rpm down around 950, disable down to 900, enable speed vs gear - lower entire table until 10 is the min for 1st and 2nd gears, lower entire disable table vs gear to appropriate corresponding speeds staying close to OE's trends, entry spark blend time = really reduce this, then exit spark you can reduce or not.

That should get you somewhere close if your indeed talking about decel... Did you ever get your speed cables hooked up to where the ecm could see how fast the vehicle was moving? That would probably help too.

[rindoze]

Speed cables not hooked up yet but now instead of reading 158MPH it reads nothing which seems better. I went in and re enabled DFCO and modified all the parameters you specified, looks like that was the key! Went from having numerous pops out the exhaust every time it reved down to 0, sometimes 1 very small.