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I just installed mine tonight. Took about 1.5 hours 'cause all I had available to trim the housing was a file :(.
 

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Did you end up resolving your hesitation issue? Did you also do an injector install at the same time?

Unfortunately, i'm also seeing bad hestitation at 2800-3000rpm under light-medium throttle :( Ocurrs at same range in any gear.

Note: WOT is fine. No hestitation or leaning under full throttle.

AFR's are spiking as high as 20:1 momentarily whilst the hestitation occurs. At the same time the IDC reading are steady and consistant.

The Walbro install seemed very solid, but i removed the Walbro and re-installed the stock pump as i was sure it was a problem with the Walbro install. But the stock pump hasn't fixed the issue!

I installed some new DW850cc injectors at the same time, so i'm guessing the issue is with the injector install. The injectors are flow tested from new so it seems unlikely that they will be faulty.

I filled the manifold with around 16psi of air pressure today and it didn't leak at all. So i can assume that the injectors are sealed properly in the manifold.

Could it be the injector latency values? Can anyone confirm the latency values for DW850's? Would it be worth re-installing the stock injectors to rule that out?



Hmmm, maybe I shouldn't have grinded those down then...they really didn't yield me too much clearance. However, my problems haven't changed--just did some street pulls tonight with my tuner, and the car spikes far too lean when I hit peak boost.

I've tried it all, dremmeling the housing, the pump, the 2nd o-ring, and lastly, the CJ-Motorsports clamp--problem still persists.

I'll be returning to the stock fuel pump until I (if I ever do) purchase the AVO--but money is tight at the moment, and there are higher priorities--like credit card bills :\ and snow tires.

Best of luck in doing this mod, and congrats to everyone who did this, but I just advise you to watch your AFRs--go on a dyno, or use a wideband, and make sure you don't go too lean.

Chris
 

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Did you end up resolving your hesitation issue? Did you also do an injector install at the same time?

Unfortunately, i'm also seeing bad hestitation at 2800-3000rpm under light-medium throttle :( Ocurrs at same range in any gear.

Note: WOT is fine. No hestitation or leaning under full throttle.

AFR's are spiking as high as 20:1 momentarily whilst the hestitation occurs. At the same time the IDC reading are steady and consistant.

The Walbro install seemed very solid, but i removed the Walbro and re-installed the stock pump as i was sure it was a problem with the Walbro install. But the stock pump hasn't fixed the issue!

I installed some new DW850cc injectors at the same time, so i'm guessing the issue is with the injector install. The injectors are flow tested from new so it seems unlikely that they will be faulty.

I filled the manifold with around 16psi of air pressure today and it didn't leak at all. So i can assume that the injectors are sealed properly in the manifold.

Could it be the injector latency values? Can anyone confirm the latency values for DW850's? Would it be worth re-installing the stock injectors to rule that out?
I assume that you had the injectors tuned for. There is a load compensation table for RPM and MAP that needs to be adjusted for new injectors or intake. I am in the process of addressing this same issue on my car with modded stock injectors (about 1000 cc/min). Very lean around 2800-3200 when coming into boost. No knock though.
 

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Thanks for letting me know! I managed to find the thread on RomRaider that outlines how to adjust that compensation table you mentioned.


Problem solved !! :D thanks mate!

In case anyone could use some background on solving the hestitation issue:

I read the thread on RomRaider titled 'How To Fix The 08 STI 2400-3200rpm stumbles', then went for a long drive and logged the following parameters using RomRaider with cruise control engaged to keep it in closed-loop with a steady throttle to avoid tip-in enrichment:

Engine Speed
Manifold Pressure
Throttle Opening Angle
A/F Correction #1
A/F Learning #1
A/F Sensor #1

Cruised along for 30mins at light throttle between 2600-3200 whilst the hesitation was occuring. Went over the logs and got a rough idea of how much compensation was required for each Manifold Pressure/RPM combination by looking at the A/F Correction #1 value.

I then added those values to the 'Engine Load Compensation A & B' tables as described in the thread (my compensation tables were all zero'd out to start with). Then I checked the results were in line with what others had posted on the thread mensioned.

Flashed the new image and there's no longer any hesitation at all. I'll have to work on it some more as the initial values were only rough estimates based on a relatively small amount of data. But it worked a treat.

I have a stage-2 08 STI with a 3in turbo-back, DW850 injectors and a Walbro. I've attached the rough compensation values that did the trick for me.

Cheers




I assume that you had the injectors tuned for. There is a load compensation table for RPM and MAP that needs to be adjusted for new injectors or intake. I am in the process of addressing this same issue on my car with modded stock injectors (about 1000 cc/min). Very lean around 2800-3200 when coming into boost. No knock though.
 

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Thanks for letting me know! I managed to find the thread on RomRaider that outlines how to adjust that compensation table you mentioned.


Problem solved !! :D thanks mate!

In case anyone could use some background on solving the hestitation issue:

I read the thread on RomRaider titled 'How To Fix The 08 STI 2400-3200rpm stumbles', then went for a long drive and logged the following parameters using RomRaider with cruise control engaged to keep it in closed-loop with a steady throttle to avoid tip-in enrichment:

Engine Speed
Manifold Pressure
Throttle Opening Angle
A/F Correction #1
A/F Learning #1
A/F Sensor #1

Cruised along for 30mins at light throttle between 2600-3200 whilst the hesitation was occuring. Went over the logs and got a rough idea of how much compensation was required for each Manifold Pressure/RPM combination by looking at the A/F Correction #1 value.

I then added those values to the 'Engine Load Compensation A & B' tables as described in the thread (my compensation tables were all zero'd out to start with). Then I checked the results were in line with what others had posted on the thread mensioned.

Flashed the new image and there's no longer any hesitation at all. I'll have to work on it some more as the initial values were only rough estimates based on a relatively small amount of data. But it worked a treat.

I have a stage-2 08 STI with a 3in turbo-back, DW850 injectors and a Walbro. I've attached the rough compensation values that did the trick for me.

Cheers
Glad to hear you fixed it! Part of my lean issues were also caused by the valve cover vent hose being off from when I last installed the IC. Oops. Fixed and now I am retuning the load comp table to cure all hesitation.
 

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I've had no problem with mine. As long as the pump 'clicks' in, you should be ok. Been a few months now, no problems, no codes. AFRs were great when I got it retuned.
 

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If DENSO has a fuel pump that flows 62% more then the walbro 255 and is similar to the stock pump in size, fitment and requires no cage modifications would you guys buy it?
 

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Thinking of trying to tackle this job tomorrow. Just want to get something strait here. If I use 2 o-rings, it should seal up much better? Should I just use one of the Vitron 203's in addition to the OE o-ring? Or just put 2 brand new ones on there? Also, could someone post a picture of exactly what part of the fuel pump you are trimming?
Thanks.
 

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Nevermind! I got it installed and it works perfect. I bought a set of fuel injector o-rings from NAPA for $2.80. Perfect fit. This thread was great help!
 

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I just wanted to put in my 2 cents worth on this tread.

I installed my Walbro yesterday. I was very mathodical in approach and evaluated every means possible for mounting the pump, the double o ring trick, and the bulg in the bottom of the house that have all been mentioned here.

  • 2009 models have a black clip that needs to be pulled forward to release your back seat on the right and left sides--the middle doesn't.
  • You will have a bulg. Unless you physically alter your pick up tube on the pre filter as some have done.
  • I don't believe that the prefilter will collapse causing flow issues due to its design.
  • The pump has no way of coming out of the housing--the hanger clips are not necessary for the Walbro to stay in place. The bottom of the prefilter is agaist the inside of the housing.
  • A single o ring on the pump seems to be fine
  • The tank seal must be installed properly--there are three teets on the rubber that MUST line up with the correct holes on the metal plate.
I wonder if some of the issues caused on WRBear's unit was due to the tank seal not being properly reinstalled. The three teets on the tank seal MUST line up with the holes in the metal ring that holds it down. If they don't it could cause the extra force to seal the tank possibly resulting in a broken stud and/or an evap leak.

I hope this helps for anyone else who may take this on.
 

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Hey guys,

I got my Walbro today and is installing on my 08 wrx tomorrow morning. I've pretty much prepared the car as far as gas goes(little less than 1/4) I had ordered the kit from IAG and also bought the install kit. After reading all 8 pages I didn't see anyone posting about also getting an install kit and was wondering... where the hell these pieces go lol. Are there any more tips I should follow other than the first post? I'll take pictures as I go too.

-John
 

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You will not be able to use the install kit. I think the filer will go on it but it doesn't go as easily as the factory one.

Good luck and let us know if you have a bulg in the bottom of your housing.
 

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I did not get to take pictures.. only because I was so frustrated with the dremeling part of the install lol. Taking the pump apart was actually quite easy and almost too simple. The dremeling though was a headache and took most of the the whole install part. After having it "click" in twice I doubted myself and almost after 30 minutes of trying to get that "click" again I gave up and said eff it and put everything back together. It's been two days and I haven't come across any problems yet so I'm pretty happy.
 

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I had the same problem, the pump wasn't maintaining pressure, hard to start, etc.. and I took the pump out and then took off the collect black spacer on the discharge that keeps the oring up in the plastic housing and stacked the whole nipple with the napa orings. It took 6 iirc. I was going to leave the stock oring for last but in my case it was loose and nasty compaired to the new napa rings so I just put on all napa rings and it fit a lot better and was really snug too. I didn't have any more problems either.
 
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