Bogging down off idle - sudden symptom - what am I missing?

[marches]

Greetings all!

Recently rebuilt 911 3.0 w/ ITBs, COP, G4X.

Took the car out for a test run and it suddenly started to backfire and behaved as though there was a spark issue.  One of the COP ignitors died a few weeks ago and presented similar symptoms.   The ignitor was replaced and the car drove fine afterwards.   During the recent test run, the car presented similar symptoms to the torched ingnitor a few weeks ago.  Stumbled home, ran ignition test and injector test, all COPs and Injectors replied.  Even though we can prove there is spark, how does one know the energy of the spark is up to spec?  Peeped dwell table to make sure it was not too much for the ignitors, I think it is OK.  

Have been struggling with what must be a ground issue, but that has been true since installation some time ago.  This can be seen by noise in the TPS and MAP signals.  The sudden performance change points to hardware failure of some type, but am not sure what.  Attached is the current tune and a small log file of a start-up and driving the car a few feet to put a load on the motor.  

Fuel table is not perfect, I know.  But the car once ran pretty well with the same map.  There is also a new 'blip' present, this seems to coincide spikes in noise - no surprise. 

Also noticed upon throttle input at ~ 1:16, the idle goes from 1300RPM to 2300RPM and does not settle back down.  

Thanks all!

M.

 

052623_ColdStartStumbleWhenThrottleApplied.llgx 502723_InjDeadTime_IgnitionAxis_FuelSmooth_FromPreviousTune.pclx

[Adamw]

Assuming the problem is mostly idle or just above idle and it runs better with larger throttle openings, I'd lean more towards ITB sync - the few 911 ITB linkages that I have had experience with weren't particularly well designed.  Intake "spit back" is a common symptom of itb's out of sync, especially during warmup.  Have you got a synchrometer?  

You really need to tune this with a Alpha-N strategy, you idle at 80kpa MAP and WOT is 99kpa so your fuel control is going to be pretty crap.  I would use TPS for ignition load also.  Why is it idling at 1500RPM when cold?  I assume it doesn't have an idle valve?  

What coils/ignitors do you have and is it a twin plug or single plug engine?

 

11 hours ago, marches said:

Also noticed upon throttle input at ~ 1:16, the idle goes from 1300RPM to 2300RPM and does not settle back down.  

Im not sure if you have attached the right log then?  There is no throttle movement near 1:16.  I see something possibly similar around 3:34?  This is from the ignition timing jumping from 8deg to 26deg, and the root cause of this is using MAP/MGP as the load reference as mentioned above.

A couple of other things I noticed:

Inj deadtime table is messed up

  

Idle target RPM is zero, and idle MAP lockout is 50kpa so idle ign is not working.  

[marches]

Will recheck the sync across ITB's straight away, maybe locknut on adjustment screw was not sufficiently torqued last time around.  

No discrete idle valve in this install, proper idle has been a struggle.  Idle has been smooth around 1300RPM, but too high.  Maybe its time to consider an idle valve install.

Working on converting the tune to AlphaN over the coming days.  

Single plug, coils are generic Bosch style, ignitors are VEMO V24-70-0027.  Do these components ever partially fail or is the failure mode either good or bad?  As mentioned above, running test mode for coils and injectors results in audible clicks for both components.  It is curious to me that the intensity/volume varies so much from one coil/injector to the next.  Some click loud enough to hear in the cabin, others require an ear in the engine bay to hear.   

Will update the deadtime table and idle target table.  

Thanks a million, Adam!  Will go over this in the next day or two and report back.