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06 AT OBXT Cobb +pro tune?


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I'm still fighting something here. HW or Tune??? Not sure.

Car has for a while been rough after startup until heat soaked.

There are Group N motor mounts and now the Rallytech street insert with a new trans mount installed.

As I recall was like this before the new motor with 100mm forged pistons and +1mm valve upgrade. The rest of the motor is stock ish.

JMP vf40 and a clear up pipe with resistor mod.

Trans was just rebuilt so lockup is good. TransGo kit installed. Yes it's pretty firm. 1 to 2 and 2 to 1 shifts are smoothing out, depends on how aggressive the accel or decel is being performed.. The rest all depends on how far into the torque request is being pushed. Very smooth otherwise.

Tuner has settled me and were not knocking as was happening after the initial dyno tune. Currently on Rev 2.

Issue is also the dreaded stumble. Seems any time it's at or near early boost it's hesitating. -1 to +2 psi. before and after that it's smooth.

Went for a quick drive with the tuner in the car and he's not seeing any misfire, AFR look good. No granted this was a quick test. I just stopped in and he had 10 min to look with me.

I have already changed the vac source for the fuel regulator.

Pump was replaced before... Still happening.

Average gas mileage is less than ideal.

So last items to just chuck money at would be a new fuel regulator or injectors. Trying to avoid this if it's not the problem.

Car has 258K on the clock.

Edited by kzr750r1
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Have you checked fuel pressure?  Verified voltage to the pump?  Checked fuel pump controller and wiring?  From your post appears you have been changing parts with little troubleshooting and no data. 

You had knock issues immediately after a dyno tune?  Should be no revs to a dyno tune unless there were mechanical issues to sort that were realized on the dyno. 

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1) No

2) No

3) No but it's all un modified. Will read up on how to confirm if the controller is healthy.

4) Yes. After revision 1 he killed off the knock. Rev 2 is an attempt to help this stumble. But right now the learning tables A, B and C are all at or going to -7.10.

This weekend I went back to Rev one for a test and the long term was worse.

I'll look into a way to monitor fuel pressure, check voltage and component test.

I agree on the tune. Not really clear what he's changed on the revisions. He's keeping it to himself. Not many options I can trust any more. Only variable I changed post tune was putting the stock mufflers back on. But as I've understood they are not a huge restriction. Was tuned with the Nameless 5" OBXT cans on it.

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Until 08 when Subaru started using the larger gauge wiring (like in the STi) the LGT had insufficient wire gauge to supply correct voltage to aftermarket pumps.  Which caused low fuel pressure under certain conditions.  There are write ups detailing the wire upgrade and verification of correct voltage.  Fuel pressure can be checked with a temporary gauge installed in the line. 

Dont buy any more parts until you get some troubleshooting done.  Better to change whats needed and know what the root cause was rather than throw money at it and hope you get it.  Even if you do, you would still not know what went wrong if it happened again.  The tuning situation is troublesome.  I cant assist much on that remotely. 

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Yeah. I've read that thread on the wire/controller upgrade. But your telling me 06 was lacking and what I need to do here.

Was hoping not to go too much farther down the rabbit hole. But I'm already in and need to get back out.

Will re read it the fuel pump fix thread again today and get some materials together.

Was thinking about static gauges anyway so may go the send unit route. But up for a temp if I can get it visible while driving to see if there is a dip. Calling a friend in a moment to see if he has one.

I appreciate you taking the time.

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2 hours ago, kzr750r1 said:

4) Yes. After revision 1 he killed off the knock. Rev 2 is an attempt to help this stumble. But right now the learning tables A, B and C are all at or going to -7.10.

What about fuel trim D? Is it 'turned' off? I think I asked you this before and you may have said yes.

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Since Rev 2 map was applied.

As Mike said above I'm in need of more data before making any other changes. Totally agree.

A friend has a temp fuel pressure gauge I'm going to install to see if I'm getting a dip in line pressure during the stumble.

Also looking at adding a couple of static gauges anyway. Fuel pressure may as well be one of them. Oil pressure with alarm as well.

Current tuner may be working around this by adding more duration in the injector cycle that is not needed. Hence the over all learning view pulling fuel.

Talking to my friend last night this was similar to what was happening when I was E tuning with Cryo. So it's not new, but now with the larger valves the scaling is farther off.

Kind of pointing to the power delivery at the pump at the low duty cycle. When it's at 100% I feel zero stutter.

This is the same pump model both have been tuning with, DW 65c.



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Just ordered two AEM pressure gauge kits. Plus the block adapter for the oil and the bezel label so one can be used for fuel.

Have wanted a static oil pressure reference on this car for a while anyway.

Going to prep for cubby install. Have a dual gauge bezel already in the horde.

Need to open up the dash anyway and get these HVAC actuators replaced.

Reading thru the FP Wire/FPCM thread. Kind of a messy thread. Looks like the STI FPCM is a good item to place as well.

But first I want to see this FP information and check voltage at the pump to be sure the pump is not getting the proper voltage.

Using this thread to keep it specific to my setup since those other threads are just a mess.

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Had the chance to drive the car for several hours yesterday.

Learning A and C locked at -7.10 but B started at 1.2 but dropped to .70 by the end of the day.

What's interesting is the main learning and correction monitors are 0.00 when duty cycle is 100%.

I'm seeing the stumble happening almost always at 66% pump duty cycle. 33% and 100% is ok and strong.



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6 minutes ago, kzr750r1 said:

What's interesting is the main learning and correction monitors are 0.00 when duty cycle is 100%.




I am guessing when your fuel pump duty cycle is around 100%, you are pushing the car and therefore are in open loop. So, no fuel correction at this point and you are most likely in the MAF range corresponding to fuel trim D, which has been set to zero no matter what.

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Ok thanks. Waiting for some HW to show up.

In the mean time I'm going to try and measure voltage at the pump while driving.

Hopefully I can get the leads of my meter to stay in place.

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Curious to see what kind of voltage you'll get. My 06 has been acting up when RPM are 4000+ and load is between 1-1.5 g/rev. It gets quite lean. Weird. But WOT and other driving conditions are fine. Searched for boost/vac leaks, etc.. Nothing. Now suspecting fuel related issue..

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14 hours ago, m sprank said:

18 yr old tuned car running side feeds?  Odd fuel issues?  No way.  Sorry, could not resist. 

Dammit Jim! I'm a Dr not a mind reader... ;)

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