Strange new acceleration issue - input appreciated

[Underdog]

I plotted two more sets of data. The MAF voltage is definitely starting to drop off at the 4,500RPM mark prior to the event occurring. *Note: the X-axis is time, not engine speed. Engine speed is plotted on the secondary axis. I kept the x-axis scaling constant so the event duration would look similar between data sets.*

 

3rd gear, letting off the accelerator prior to event

http://imageshack.us/a/img72/2679/3rdwlift2.jpg

 

http://imageshack.us/a/img844/8179/3rdwlift.jpg

3rd gear, with the event

http://imageshack.us/a/img443/2103/3rdwevent.jpg

 

http://imageshack.us/a/img855/6438/3rdwevent2.jpg

[ehsnils]

Nils, why do you suspect a valve clearance problem? This looks like a sudden event where, despite target & reported throttle positions being 100%, after the car has already reached full boost and with healthy timing and AFR readings, the MRP just drops off a cliff and in fact goes into full vacuum as if the throttle had slammed shut. All the other relevant parameters behave similarly, as if the throttle actually has closed (engine load, total timing, AFR, MAF voltage, IDC).

 

I just wanted to rule out something that could be a problem, even if it's unlikely. But it's always good to verify that the mechanical side is healthy to avoid serious trouble while trying to diagnose the problem.

 

What about the turbo? Is it in good shape? Shouldn't be a problem according to the charts.

 

But no log of the cam/crank sensors? If one of them stops giving signal at high rpms it would certainly cause problems.

 

Another idea I have is the ECU mapping - is it stock or is it modified? If the problem always appear at the same rpm maybe the mapping is corrupt?

[Underdog]

Fair enough. Checking valve clearance isn't a trivial procedure though, and to me it seems less than likely given the symptoms as described thus far.

 

The OP mentioned in earlier posts that he has tried swapping to earlier maps (from a different tuner than current map) and the problem persists. Also, the car had been driving fine on the current map for months.

 

.:Catalyst:., if you rev it to 5,000 RPM in neutral (no load) does the event still occur? Can you get a log? Maybe one with the engine still cold (as cold as you are comfortable with revving to 5k) and another one at operating temp. The one at operating temp is more important.

[.Catalyst.]

Rick - I'll try revving without load and log cold/operating for this. I haven't done that to see if the event persists without load.

 

Nils - turbo is less than a year old and has been solid. Outside of this one particular situation (100% WOT @ 5-5.5K RPM), it pulls strong and hits boost targets.

 

iNVAR - the BPV has been swapped with the OEM as well and no change. Both seem to hold boost as expected and releases pressure when it should.

 

It is correct, I have loaded another map completely (previous stage 2 tune), and the event still occurs (just at a slightly higher RPM).

 

After discussions with my mechanic (who also talked with Tim Bailey at Cobb tuning Surgeline since he is close with him). He thought it's acting like when at 100% throttle input, something occurs causing the throttle plate to shut. My mechanic wondered if I should just adjust the throttle table and never hit 100 since otherwise it's running really well and pulls hard at 90% throttle. The other thing he wants me to try is to do a log with the MAF unplugged to see if it still occurs to see if either the MAF sensor is going bad.

[iNVAR]

My mechanic wondered if I should just adjust the throttle table and never hit 100 since otherwise it's running really well and pulls hard at 90% throttle.

That sounds like a bandaid for the problem, not an actual solution. I wouldn't go with that.

 

Also, does the BPV/BOV vent when the event occurs?

[Underdog]

It certainly looks like the throttle plate is closing. It seems so unlikely though, because of the way the throttle plate is coupled to the sensor and motor.

 

It will be interesting to see if it does it at no-load as well.

 

Still waiting on that 5th gear log... surely you can find a school zone to do this in.

[.Catalyst.]

LOL at 5th gear

 

iNVAR - no the BPV isn't releasing at the event.

 

Here's logs for free revving (no load) both cold (shortly after starting), and operating temp. Doesn't hang at the RPM and revs to redline.

 

Did another 3rd gear pull. I can't see a way to log Cam or Crankshaft position sensors in RomRaider outside of whether they are on/off. I did add VVT and tumble valves in the 3rd gear pull.

romraiderlog_Troubleshooting_06LGT5MT_NoLoad_20130204_075046.csv

romraiderlog_Troubleshooting_06LGT5MT_NoLoad_20130204_075639.csv

romraiderlog_Troubleshooting_06LGT5MT_3rdgear_20130204_080926.csv

[.Catalyst.]

That sounds like a bandaid for the problem, not an actual solution. I wouldn't go with that.

 

Totally agree.

[ehsnils]

The more parameters I see the more I start to think it's the ECU that's FUBAR.

 

Or is there a rev limit value that's wrong?

 

Anyway - a few new parameters to log:

 

• Mode/Service 0x01, PID 0x03 - Fuel system status, this will tell if the system is in Closed Loop, Open Loop and in some cases also special conditions for Open Loop.
  
• 0x1EE - Engine Speed Target
  
• 0x1F0 - Boost Pressure Feedback
  
• 0x232 - Final Initial Torque
  
• 0x299 - Over-Rev Count (High RPM)
  
• 0x298 - Over-Rev Count (Very High RPM)
  

I'm not sure that you have any of them in your ECU though.

 

 

A deeper dig into the Romraider definitions gave me a few more ideas:

 

• The EGT value - is that reasonable? The log says 1292F, which is 700C, and you did state earlier that you were using a resistor. Is that resistor OK? If it's on the high side it may trigger a fail safe behavior. As long as it's below "EGT Limit (Failsafe)" it should be OK.
  
• That you actually have a problem with the ECU when it transits from Closed Loop to Open Loop due to engine load/rpm/throttle.
  
• Look at the "Speed Limiting (Fuel Cut)", "Rev Limit (Fuel Cut)", "Speed Limiting (Throttle)", "Speed Limiting A (Throttle)", "Speed Limiting B (Throttle)" and "Speed Limiting (Wastegate)" (and a few more in those categories) tables.
  

I know that some of these are long shots. But so far we have been drawing blanks on the things we have suggested.

 

And if you do a pull in second and in fourth gear do you yield the same result?

 

One thought that I got in addition - if there is a secondary sensor for detecting overboost (besides the MAP sensor) that for some reason kicks in.

[.Catalyst.]

Interesting. I do have the 2.2kohm 0.5 watt resistor from the resistor mod fix and the CELs are disabled in the tune. I have extra resistors and can easily swap that out when I get home.

 

I've been questioning the health of the ECU as well. I can dig around the RR logger and see if any of those additional parameters are available to log.

 

I have logged 2nd gear (posted earlier in the thread). 4th gear the event occurs but I have not logged. I try and avoid 4th gear pulls both for the sake of my clutch and the safety factor since this is not on a dyno.

[BarManBean]

Regarding the possible resistor problem, you may want to check with Dave that he's disabled that CEL via software. I do not have and EGT sensor and I also do not have a resistor, I just had Dave delete that issue through the tune.

[.Catalyst.]

That's what I have done in the past and read that the resistor may assist and have been using this since I was on my Infamous tune. I am pretty sure I looked at the tune and the EGT codes were disabled.

[iNVAR]

If the BOV definitely isn't releasing at the event, that means that the pressure between the manifold and the BPV is equal, or close enough to being equal. Otherwise, the valve *would* release. This indicates that your throttle plate actually is open at 100%.

 

I would think that this means that whatever the problem/restriction then is likely upstream from the BOV.

[.Catalyst.]

Verified the 3 EGT codes are disabled in the tune.

[.Catalyst.]

If the BOV definitely isn't releasing at the event, that means that the pressure between the manifold and the BPV is equal, or close enough to being equal. Otherwise, the valve *would* release. This indicates that your throttle plate actually is open at 100%.

 

I would think that this means that whatever the problem/restriction then is likely upstream from the BOV.

 

I'll try and verify this when I head to lunch. I'll keep the window down and listen during the event.

 

If it was pre BPV and both my mechanic and I have checked all intake and vacuum connections? If I'm understanding everything correct perhaps the OEM turbo inlet is collapsing or has an issue at that load/boost moment. That or the turbo itself? When changing BPV and checking TMIC > TB connections there was much more oil blow by than in the past. It's not even a year old but doubt the 1 year warranty on a Subaru replaced turbo is any good at stage 2 mod levels. That would mean time to pony up for a 16G.

[ehsnils]

If the BOV definitely isn't releasing at the event, that means that the pressure between the manifold and the BPV is equal, or close enough to being equal. Otherwise, the valve *would* release. This indicates that your throttle plate actually is open at 100%.

 

I would think that this means that whatever the problem/restriction then is likely upstream from the BOV.

 

Reminds me of a friend that had a similar problem - the air intake collapsed at high rpm/throttle conditions. Adding a support preventing it from collapsing solved the problem.

 

Check the intake so that there aren't any foreign objects/dead squirrels/damage.

[iNVAR]

Yeah, find that out for certain first... I think that would help. Open the BOV full VTA to make it extra audible. Can you do that on yours?

[.Catalyst.]

I can pull off the recirc hose tonight and it would be full VTA.

[.Catalyst.]

Reminds me of a friend that had a similar problem - the air intake collapsed at high rpm/throttle conditions. Adding a support preventing it from collapsing solved the problem.

 

Check the intake so that there aren't any foreign objects/dead squirrels/damage.

The intake itself is 100% clean. I've had it out and ensured there is nothing in the resonator, airbox and my filter is clean as well. Only portion of the intake tract I have not been able to verify is the turbo inlet. I think I could spray carb cleaner on it at the turbo side to see if idle changes to rule out issues? I'd like to avoid buying/installing a replacement inlet unless I know it's the culprit due to complexity of the job. I've already thrown over $500 at this with no improvement.

[mattg]

Was your inlet replaced when they did the turbo, or is it the original?

[.Catalyst.]

Original. Barrett (mechanic) inspected it when the UP/DP were done and said it should be replaced if it's ever touched again.

 

Also just pushed it to event at lunch and I can't audibly tell that the BPV is releasing (normally can hear it release when lifting).

[mattg]

Doesn't seem like the inlet would start sucking shut out of the blue. I'm sure it's just worn out at the turbo end.

[Underdog]

Any new information?

[.Catalyst.]

I wish. I feel like I've reached a dead end. Outside of continuing to replace items and "hope" it works, I don't know what to troubleshoot further. My mechanic says the car runs so good outside of that event I should just adjust the throttle so I don't get to 100%. That's not my style - it bothers me to no end that there is an issue.

 

It's not in the tune, we've ruled that out so I don't have an option there. Since the BPV isn't releasing during the event, iNVAR's input is of note, and I'm considering just replacing the inlet. I've already ordered a replacement post MAF section of the intake track because the Venair piece does not instill a lot of confidence. It's super soft silicone, and not sized correct on the airbox side (too large of a diameter), so when tightening the T-Clamps it is a pain to ensure it's sealed. I'm hoping this may be where a possible collapse is occurring. If not then I'll move to the inlet as I know the OEM has been pretty abused on the turbo side when the dealership did my VF40 warranty replacement. I've sprayed carb cleaner on it with no change in idle, but since this only happens at load, I imagine it needs to be fully pressurized to expose a possible issue.

[12sechatch]

I dont believe this has been mentioned yet, but what about the throttle position sensor?

 

Maybe when it is wide open (full voltage) that triggers it to hiccup (voltage fluctuation) which in turn makes it appear as though you're lifting off of the gas.

 

 

 

?