Boost Fluctuations - Subaru Enthusiasts Car Club of the Sierras

bluestreak · 2009-12-01, 01:30 PM

Coming back from Thanksgiving in Cali on Saturday over the 80 my car started to have some strange boost fluctuations. It was in 4th and 5 gear - it could hold steady boost to about 7 psi and then after that it would vary rapidly from about 6 to about 18 psi when at partial throttle. At WOT, it varied from about 14 to 18 psi. I was near Squaw and put some gas in (taking it from below 1/4 tank to a bit over 1/2 of a tank); after I added the gas, the problem nearly went away. It was still not holding completely stable boost, but it was much better.

I had a similar problem before when my original turbo went out, but having a more full tank did not help it...

I was thinking fuel filter or pump, but before I start replacing things I wanted to see if anyone had some advise.

As for the car's setup: Cobb stage 2 (ACN 91 OTC map), catless uppipe/dp, Borla Hush exhaust, stock turbo, intercooler, and injectors - and a cobb intake (I know, I know... the whole intake deal, but I haven't gotten around to piecing together a stock snorkus setup since I ditched my FMIC setup)

sperry · 2009-12-01, 01:44 PM

I don't know how a clogged fuel filter would effect boost unless the car was bucking all over the place because the fuel was cutting in and out. I also don't know how topping off the tank would help the issue if it were a fuel filter or pump.

I would guess the problem is that your map doesn't match your mods, exacerbated by driving at high elevation.

cody · 2009-12-01, 02:45 PM

What doesn't match? I thought Cobb says you can use their intake on their canned maps?

03wrxwagon · 2009-12-01, 02:51 PM

your ap map is fine for your mods I have the same thing but CAI.My car started running funny coming to SLT but id say do a boost leak test if your boost is jumping like that...Elevation does play a big part in our cars,everytime i go to so cal at 0 elevation my cars runs like shit and takes a few hours for it to fix itself..

03wrxwagon · 2009-12-01, 02:52 PM

Quote:

Originally Posted by cody

What doesn't match? I thought Cobb says you can use their intake on their canned maps?

you can use any intake on there maps and yeah yeah i know some of you are like no thats wrong but im correct I asked cobb when i saw them at subiefest

cody · 2009-12-01, 02:57 PM

Quote:

Originally Posted by 03wrxwagon

your ap map is fine for your mods I have the same thing but CAI.My car started running funny coming to SLT but id say do a boost leak test if your boost is jumping like that...Elevation does play a big part in our cars,everytime i go to so cal at 0 elevation my cars runs like shit and takes a few hours for it to fix itself..

Sucks. My car runs perfect at every elevation. It's been documented with data logging including AFR. I guess that's the difference between a custom map and a canned one.

bluestreak · 2009-12-01, 03:07 PM

Yeah, I checked their site and on the map notes it says specifically that the SF intake and an uppipe are "still within acceptable parameters of this mapping."

How exactly would I go about doing a boost leak test?

Thanks

03wrxwagon · 2009-12-01, 03:32 PM

http://www.vfaq.com/mods/ICtester.html

2009-12-01, 01:30 PM	#1
bluestreak EJ22 Join Date: Feb 2009 Location: NW Reno Posts: 111 Car: 2003 WRX Sedan - Blue	Boost Fluctuations Coming back from Thanksgiving in Cali on Saturday over the 80 my car started to have some strange boost fluctuations. It was in 4th and 5 gear - it could hold steady boost to about 7 psi and then after that it would vary rapidly from about 6 to about 18 psi when at partial throttle. At WOT, it varied from about 14 to 18 psi. I was near Squaw and put some gas in (taking it from below 1/4 tank to a bit over 1/2 of a tank); after I added the gas, the problem nearly went away. It was still not holding completely stable boost, but it was much better. I had a similar problem before when my original turbo went out, but having a more full tank did not help it... I was thinking fuel filter or pump, but before I start replacing things I wanted to see if anyone had some advise. As for the car's setup: Cobb stage 2 (ACN 91 OTC map), catless uppipe/dp, Borla Hush exhaust, stock turbo, intercooler, and injectors - and a cobb intake (I know, I know... the whole intake deal, but I haven't gotten around to piecing together a stock snorkus setup since I ditched my FMIC setup)

2009-12-01, 01:44 PM	#2
sperry The Doink Real Name: Scott Join Date: Nov 2002 Location: Portland, OR Posts: 20,335 Car: '09 OBXT, '02 WRX, '96 Miata Class: PDX/TT-6 The way out is through	I don't know how a clogged fuel filter would effect boost unless the car was bucking all over the place because the fuel was cutting in and out. I also don't know how topping off the tank would help the issue if it were a fuel filter or pump. I would guess the problem is that your map doesn't match your mods, exacerbated by driving at high elevation. __________________ Is you is, or is you ain't, my con-stit-u-ints?

2009-12-01, 02:45 PM	#3
cody Candy Mountain Real Name: Cody Join Date: May 2005 Location: Californication Posts: 7,751 Car: 03 Pussy Wagon, now with more pink! Class: TESP OMG Internet!	What doesn't match? I thought Cobb says you can use their intake on their canned maps? __________________ Slow and low, that is the tempo.

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2009-12-01, 02:51 PM	#4
03wrxwagon EJ22 Join Date: May 2009 Posts: 188	your ap map is fine for your mods I have the same thing but CAI.My car started running funny coming to SLT but id say do a boost leak test if your boost is jumping like that...Elevation does play a big part in our cars,everytime i go to so cal at 0 elevation my cars runs like shit and takes a few hours for it to fix itself..

2009-12-01, 03:07 PM	#7
bluestreak EJ22 Join Date: Feb 2009 Location: NW Reno Posts: 111 Car: 2003 WRX Sedan - Blue	Yeah, I checked their site and on the map notes it says specifically that the SF intake and an uppipe are "still within acceptable parameters of this mapping." How exactly would I go about doing a boost leak test? Thanks

2009-12-01, 03:32 PM	#8
03wrxwagon EJ22 Join Date: May 2009 Posts: 188	http://www.vfaq.com/mods/ICtester.html