Stutter in Transient on acceleration/hwy cruise

[Alex_87Scirocco_2T]

Hello All,

I am at my wit's end. I also fully recognize that I am not a tuning expert. Part throttle when cruising the engine runs richer below AFR target. This shaking can be exaggerated if I was to accelerate at low rpm. It makes strange surging sounds. It is a 2L 4cyl engine with a K04 turbo iwg, and a 80mm DBW throttle. It will do this with accel enrichment off + CLL off. Looks like the injector Effective PW oscilates. I am still on waste gate pressure 6psi. This log does not show my fuel pressure, I did start logging that after. It looks smooth (3 bar fpr). I am using a somewhat obsolete LC-1 Wideband controller. It was free air configured. I plan to switch to an LSU-ADV O2 Bosch sensor with Spartan 3 Controller soon.

P.S. does the engine speed signal appear noisy?

Any insight is much appreciated.

Log 2019-08-6 9;05;39 pm.llg

Edited August 18, 2019 by Alex_87Scirocco_2T
Not leaner. It's richer when the stutter occurs.

[cj]

Between 1:45 & 1:50 in that log the dwell time jumps repeatedly from ~3.3ms to ~1.3ms. This combined with the slightly fuzzy rpm line _might_ means trigger issues. Your trigger error counter doesnt increase, but it would be worth taking a trigger scope capture at about 2700-3k rpm to have a look.

Your AFR's look fine in that log. You will likely never get it to hit AFR target immediately on changing throttle position because of accel enrichment, and the fact that CL lambda is a reactive thing. It looks to hit target within about 1/2 a second when you hold the throttle though which is pretty normal.

At about 2:00 there is a 5 second block where you press the gas pedal repeatedly to ~90%, but your throttle target never gets over 50%. This may be intentional in your ethrottle target table, but it does make me wonder if there is something wrong there.

The other thing I notice is around your boost control at 2:50 -2:55 & 3:00 -3:05. your boost pressure jumps up & down and it looks like your wastegate duty cycle jumps from 0 to 55% and back repeatedly. I'd guess you have open loop boost control set up and a pretty big jump from 0 to 55% at about 135-140kpa?

 

[Alex_87Scirocco_2T]

14 hours ago, cj said:

Between 1:45 & 1:50 in that log the dwell time jumps repeatedly from ~3.3ms to ~1.3ms. This combined with the slightly fuzzy rpm line _might_ means trigger issues. Your trigger error counter doesnt increase, but it would be worth taking a trigger scope capture at about 2700-3k rpm to have a look.

Your AFR's look fine in that log. You will likely never get it to hit AFR target immediately on changing throttle position because of accel enrichment, and the fact that CL lambda is a reactive thing. It looks to hit target within about 1/2 a second when you hold the throttle though which is pretty normal.

At about 2:00 there is a 5 second block where you press the gas pedal repeatedly to ~90%, but your throttle target never gets over 50%. This may be intentional in your ethrottle target table, but it does make me wonder if there is something wrong there.

The other thing I notice is around your boost control at 2:50 -2:55 & 3:00 -3:05. your boost pressure jumps up & down and it looks like your wastegate duty cycle jumps from 0 to 55% and back repeatedly. I'd guess you have open loop boost control set up and a pretty big jump from 0 to 55% at about 135-140kpa?

 

Thanks for your insight CJ!

I changed boost rpm activation to 9000 rpm and zeroed boost target values. The car drove without hesitation after. I drove prior to making the change. As soon as boost table was activated, the hesitation started. The pedal input is rpm dependent. The hesitation made it really bad. I can add more aggressive throttle response now that its sorted.

I will investigate the trigger signal next.

I appreciate you good work. Thank you.