CA18DET deceleration issues

[mattlovo]

Hi guys,
I have a stock CA18DET with a GTX2863 and 550cc R35 injectors.
ECU is
Car idles fine and drives fine except when off throttle. AFRs are good in boost and on cruise.

Upon releasing the gas pedal, there will be a pulling sensation as the engine rpm drops and AFR runs into rich 10s before going to 22.
Once it reaches idle rpm of 1k, it will snap out of that deceleration mode. If you add gas to it while the engine is deceleration, rpm goes up and it smoothen out then goes back into that draggy feel as it drops again.

Not sure if it has to do with timing.
No error codes. Done my boost leak test as well.

Any input is appreciated =)

[louiswun]

what injector latency on your setting , me and my customers are running the same injectors, usually 850ms works fine.

[louiswun]

most of my tuned CA18 do the same, when let off throttle, not just R35 550cc injectos, AFR runs into rich to around 13s before going to 22, R32 444cc do the same thing, no matter how I try different setting, the off throttle fuel cut always delay a hair, what I thought is the injected fuel on the runner wall wetting, while throttle closed, it consume the rest of the fuel on the runner, but most others newer ECU like S13 SR or S14 SR does not have this symtom.

[Matt]

Can we have a log file please with AFRs included showing the issue?

[mattlovo]

Hey matt, will get to it.
I am lacking the db9 male to connect the innovate to it.

Louis, k values and Injector latency same as yours.
Cruises and accelerates well. Only on deceleration, it's rough.
Tapping the pedal when decelerating results in a slight jerk.
Clutching in when decelerating (zero gas pedal) results in a clunk as well. Doesn't clunk or jerk when u let the rpm fall to near 1k rpm before your clutch in.

Rpm still does that dip to 500 600 rpm in free rev.

Tps shows idle switch engaged and neutral switch ok.

[mattlovo]

Seems like the rpm dip is related to the light flywheel from SPEC.

Anyone has any tips on how to set it to "catch" the motor before it dips to 400-500 rpm and up again ?

I have tried to raise fuel recovery and adjust target idle to 900 rpm.

[Matt]

Try tpmin table if fuel related

[mattlovo]

Hi Matt thanks for the suggestion.
What should I do with the TP min? Changing it too much will affect the way the load is processed to my knowledge.

[raddy]

try to increase ign. timing vs rpm at neutral table..

[Matt]

The 'load' values in the TP min table are the minimum TP clamp values allowed

If you suspect it is too lean here, you can increase the values for example but you will need to watch TP and AFR in your logger to see what is going on and then make adjustments based on your observations

[mattlovo]

Hi Matt and Raddy,
Thanks for the tip.

I have tried to do a fuel recovery up the rpm range at 1700 ish.
Does help abit as the dip isn't so bad.

However it still doesn't solve the light wheel flywheel issue.
Cracking the throttle stopper higher got things better as the car idled at 1300-1400 and it did not dip in rpm upon revving. I am not sure how nissan dealt with the tune for a stock flywheel haha.

Raddy, If i increase ignition timing... That would result in a slight increase in rpm. Not sure what is the exact logic behind your suggestion though.

[raddy]

increased timing will increase torque that will lead to engine do not dip that deep-it will compensate light flywheel. increase of the rpm will be compensated by aac then. more modern engines like sr use ign. timing change to adjust idle rpm...

[mattlovo]

Awesome Raddy,
let me give it a shot at trying to increase the timing.

What do you guys use to detect knock anyway ? I don't have a dyno in the area sadly.

[Matt]

We use head phones (see sticky on main thread) or there are various knock detection devices around

[mattlovo]

Hi Matt and Randy,
Tried to raise the ignition vs rpm. Seems to help better.
I also tweaked the fuel recovery higher at 1500 rpm.

I am uncertain about the Fuel cut which is set at 1400rpm. Does this affect as the drop still is harsh.

Lastly, ignition vs rpm has 2 set of value row. Not sure if I am doing it right.