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Old 06-19-2009, 03:58 PM   #1
wtdash
Scooby Specialist
 
Member#: 59182
Join Date: Apr 2004
Location: N. Idaho
Vehicle:
2002 WRX GG>>
2016 Focus RS

Default Boost Drops to 0 psi @ 5K RPM in 2nd and 3rd (4EAT) - Fixed?

Edit:
I had an extended radiator hose from a custom 'coffee cup/resonator delete' mod to my TD04. The hose was just too long and flexible to hold up under boost when warm.


Short answer is that after I pulled the turbo and re-did my intake - modified to a 45-degree airbox and related hose replacements - it now works OK - no Boost Drop! I put the turbo BACK IN and still ran fine, so it was NOT the turbo, but not sure was causing it!

I've posted this on the LegacyCentral BBS, too.

(Mr. Unabomber suggested I post it here since it was dying of loneliness in the Pre-2002 Factory Turbo Powertrain forum.)
Edit: 6/18/15 - and still NADA....ignored and alone, withers and dies, only to be found in a Search by its owner's eyes.

My Setup:
- '93 EJ22T swapped into a '90 Legacy about 11/15/2008.
- '06 WRX TD04
- '06 WRX TMIC
- Revtronix Stage 2 Chip (plugs into stock ECU)
- 480cc injectors (chip corrects for this)
- JECS MAF (chip corrects for this)
- Stock NGK plugs .030 gap
- Intake modified to remove resonator and snorkus (in fender well) - uses stock air box.
- Turbo 4EAT tranny and Turbo TCU
- 3" Turbo-back exhaust
- Bellmouth downpipe
- STi fuel pump
- Lightweight (not UD) pulley

Issue:
When WOT in 2nd or 3rd gear (auto) @ approx. 5K RPM boost suddenly drops to 0 and the car stops accelerating - but continues to run fine. The boost drops to 0 and stays there as long as I keep the pedal to the floor...I've continued to run the car this way for @ least 5 seconds. The car decelerates but continues to run - not lurching/sputtering/etc***8230;.Just a smooth decrease in speed and rpm. Only after I let off the throttle and reapply it does boost come back normally...until I hit 5K rpm and it drops again.

Here's a list of observations:

- Issue occurs running 17 psi w/the new Revtronix chip that overrides the stock ECU"s parameters, such as max. boost (8.7psi), fuel cut (@ 13psi), and allows me to use a different MAF and bigger fuel injectors.

- It also occurs w/the stock ECU and an FCD/MBC set to 16psi- so it's not the chip.

- It's heat related as it started this spring, as temps have risen above 40F, and it doesn't do it on the 1st full throttle run when the car has just reached ***8216;operating temp'. It is very consistent and repeatable. I finished the swap in the late fall/early winter so this is the car's 1st exposure to warmer weather.

- It doesn't sputter or miss, and no CEL when the boost drop occurs.

- If I let off the gas and then floor it again, it repeats the process - accelerates to 5K and boost drops to 0.

- If I left off the gas, but only go to ½-3/4 throttle it'll continue to accelerate and boost stays solid @ about 16psi, and pulls to 6K before shifting to the next gear.

- AFR readings:

o With Stage 2 chip/480cc's/JECS MAF I'm getting from 10.95-11.11 AFR in 2nd gear full throttle. There is one 'dip' where it drops to 9.94 when the boost drop hits. It then goes up to 12.2-12.6 @ full throttle when the boost drops to 0.


What I've replaced:

- 4 different BPV's - 3 stock; 1 Bosch

- 3 different BCS - 2 stock and 1 GM (also occurs w/an MBC)


- 2 different ECUs

- 2 different TCUs

- IAC

- 2 TPS -the whole throttle body

- Coil pack - diamond and stock

- New plugs - tried gap @ .025 and .030 (smaller gap suggested/required by Revtronix for chip)

- Ignitor

- Wastegate actuator - both were the newer WRX ones. Tested @ 10psi.



What I've tested: (all tests done @ Off or Idle - not while issue occurs)

- TPS - some values marginal, but still occurs w/separate TPS harness so we ruled out a TPS/wiring issue.

- IAC

- Press. Exch. Sensor

- BCS



Thanks for any input.
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Last edited by wtdash; 06-18-2015 at 12:12 PM.
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