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2010 FXT Auto4
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409 Posts
Discussion Starter #1
I noticed that if I accelerate hard under 3200 rpms in 4th or 5th gear the car surges and is slow to build boost. Does this sound normal? Any ideas ? Someone said could be fuel pump.
 

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2016 Outback and WRX CVT
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2,551 Posts
^ With your setup, I'm almost wondering if you're bogging.....?
 

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2015 Forester X 6MT 6-Gear Manual
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1,373 Posts
Ask your tuner. How can we know without seeing the tune on a NS tune? But sounds like octane limiting issue if you have a good tune and the K-sensor is op. Then you could have have wastegate issues ...
 

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2015 Forester X 6MT 6-Gear Manual
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1,373 Posts
Inadequate fuel volume would show up at full throttle higher RPM, improper fuel pressure could have issues at all rpm. You have a FP gauge?
 

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2010 FXT Auto4
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409 Posts
Discussion Starter #5
I did talk to my tuner he mentioned it could be the fuel pump and I do not have FP gauge.I just seeing if anybody had some opinions. The peak Ft-Lbs(360) are about 3200 RPM's. HP are 5500rpms(307)
 

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05 FXT Broken 5-speed
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239 Posts
Even w/ a 2.5liter, you will still have some lag on a VF39. W/o seeing the tune, there are only a limited amount of things that can be checked. I have never seen a Walbro 255lhp go bad. I have been tuning for over 10 years. But the tune could definantly have something to do w/ it. Are you running an aftermarket boost solenoid or stand-alone boost controller???
In the tune, there could be AVCS timing in those areas, maf scaling, you could be fighting closed loop/open loop transition. Also, depending on your boost control, there could be way too much duty cycle on ramp up, causing boost oscillations/surging.
W/o seeing everything done, engine wise, hard to say. I have an 05 FXT VF39, stock topmount, Walbro 255lph, and supporting mods. I am running E85. I put down 300 wheel hp and 354ft-lbs on 17psi. I am limited on my stock 550cc injectors.
Dynograph shows it spools up the same as a TD04, but I have noticed a slight amount of more lag w/ the VF39.


I am in the South Denver area. Do you know anyone w/ a Tactrix cable, so you can atleast log, using RomRaider?
Ecutek locks your computer, so we really can't retrieve your information.
Absubtle
CO
 

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2010 FXT Auto4
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409 Posts
Discussion Starter #7
Here is dyno sheet 18Psi at3300 rpms.I'm not running any boost controllers. My setup is VF-43,STI topmount,CAI, Custom open source tune,Rebuilt short block one size over pistons,Racing bearings,turbo inlet pipe.
 

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Registered
2010 FXT Auto4
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409 Posts
Discussion Starter #9
Yes it is a new problem and it started about a month ago. I have an appointment to see Harvey but he is booked till mid June. Also does your car have engine surges at low speeds?I have this surging at low speeds 2nd and 3rd Gear at 20 to 30MPH.Not sure if related to other problem.
 

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05 FXT Broken 5-speed
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239 Posts
No, I dont have that problem. But I do know what you are talking about.
Maybe as simple as a suction leak. You could just be leaner-than-normal, when you load up your car like that. It would be worth just visually checking the suction pipe. But a pressure test would find the problem instantly. But requires compressed air. That is how I check for suction/boost leaks.
You don't own a Tactrix cable?
Absubtle
CO
 
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