GR Hatch: Don's 08 STI. STI Hatchback/Wagon or bust! - Page 13 - Subaru Impreza WRX STI Forums: IWSTI.com
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Don's 08 STI. STI Hatchback/Wagon or bust!
Don's 08 STI. STI Hatchback/Wagon or bust!
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Old 07-05-15, 10:12 AM   #121
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

The IAG race version with AN fittings and braided lines might achieve the form you're missing.
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Old 07-05-15, 01:35 PM   #122
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

The annoying GR stumbles have come back after driving a while on big injectors. Prior to that, I was on stock injectors and didn't have the stumble. But when I did a bigger pump, the stumble showed itself and I purchased the IAP fpr stumble fix. It disappeared after installing it and got more smooth after zeroing out the load comps. I read up on the latest findings from Cobb tuning and Injector Dynamics about intake resonance also contributing to the stumble. I decided to look into this and proceeded to go to the auto parts store and put together my own. It was unsuccessful. After following the instructions from Cobb and the Injector Dynamics video on resonance and the sound theory they had brought up, I decided to do go the complete opposite. The organ pipe theory sounded good, the shorter hose theory, also. But I got to thinking that rubber is used as a damper as its all over the car such as motor mounts, air box mount, transmission, etc and some cases the fuel line. Some folks found that adding a long 3ft fuel hose fixed their stumble. So the long hose on the fuel system dampened the resonance, it should do the same for the intake resonance that's causing the fpr to fluctuate, which causes the fpr to a lean fire condition=stumble. The hose is short already from the factory. To get an even pulse from the intake manifold, I kept the hose intended by Cobb tunings findings and cut a fpr vacuum hose to about 10-12 inches. Stumbles are gone.

Last edited by STIGR-Wagon-Dad; 07-05-15 at 04:17 PM.
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Old 07-06-15, 06:51 PM   #123
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

I got my IXIZ Concepts IxizMADblk today!





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Old 07-07-15, 02:22 PM   #124
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

I drive to work this morning and ran in in all gears in the stumble area. When I did the Cobb reference relocation, I had the stumble much worse than the stock location vacuum source. So bad that I had a CEL for #3 cylinder misfire. I noticed strong fluctuations in my boost gauge in the stumble area. I went with a long 12" vacuum hose and kept the vacuum source at the bypass valve. Stumbles are very faint, but much more smoother than the short 2-4" hose (experimented from 2" to longer) and tolerable. I then added the Ixiz Concept ixizMADblk and keeping the fpr vacuum hose 12". I drove in the stumble area again and my boost gauge once again registers smooth build in boost and no fluctuations! Stumbles gone!
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Old 07-10-15, 02:06 PM   #125
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

I replaced my Michelin Pilot Super Sport with Bridgestone S04 Pole Position. I liking these more better than the Michelin.
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Old 07-13-15, 05:11 PM   #126
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

I replaced my old scratched up lug nuts with black ones from Gorilla. I like how the wheels appear to be bigger with the 255 40 18 Bridgestone and the appearance of depth from the lug nuts.

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Old 07-16-15, 04:16 PM   #127
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

Going catless.
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Old 07-16-15, 08:26 PM   #128
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

As the car ages come the vacuum leaks. There are probably more, I'll have to look at ever intake manifold vacuum port. At least the car runs better, for now.
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Old 07-19-15, 10:38 AM   #129
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

I added some clamps and zip ties to all the 6mm vacuum hoses and noticed the a/f correction dropped down to -10 and steadily adjusted itself to zero at idle. Feels powerful again and no smoking from the tailpipe. The evap solenoid #1 was the hardest to get to so they got zip tied. Everything else is clamped. I need a retune considering it was tuned with the vacuum leaks not known at the time. I guess Subarus are prone to vacuum leaks. I also went with the Prova AOS. It was an easy 5 min install and my intercooler is clean again. It didn't cost as much as the other AOS I had and it doesn't have all the crazy vent hoses going all over the place, it works as advertised.
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Old 07-20-15, 08:42 PM   #130
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Default Re: Don's 08 STI. STI Hatchback/Wagon or bust!

Fixing vacuum leaks is a very tedious process. I had a/f learning 1 as high as 20%. I proceeded to clamp down all the vacuum ports on the intake manifold and found another leak at the vacuum hose to the bypass valve. Right now, it's at 14%, plugging up the leak at the bypass valve dropped it down to around 8%. So many vacuum leaks!

Last edited by STIGR-Wagon-Dad; 07-21-15 at 11:33 AM.
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