Author Topic: 95 WRX STi, only 6 pounds of boost. Help? (Read 9984 times)

blessthekellen · « **on:** August 13, 2011, 03:07:35 pm »

Hey guys, been driving the car around for a little over a month now, loving every bit of it.

Finally got around to installing a few gauges today, electric boost gauge & EGT.
After all said and done I was excited to go out and take a quick rip and see what PSI I am actually making with the car.
To my surprise...6 pounds. Pulls hard to redline, no hesitation, no bogging, but really? only 6 pounds?
Whats the stock PSI on these vehicles, I would have thought it would have been more around the 12 PSI mark.

Vehicle has 3" catback, stock downpipe, original coilpacks (conversion has not been done), Apexi intake.

Is there something I should be looking at here? The car pulls the same since I have had it day one, but I am really stunned at the low stock boost this car is making.

Fuel filter? Spark plugs? Any input would be greatly appreciated.

-Kellen.

blessthekellen · « **Reply #1 on:** August 13, 2011, 04:14:05 pm »

The more reading I do, the more I am thinking something is wrong. Boost leak, faulty boost solenoid?
If my coilpacks are cracked is this going to cause a huge decrease in PSI? I have not checked them, but just wondering. Like I stated I don't get any hesitation, I just really need to figure out what the hay is going on here now. I should be expecting more out of this car since I guess its only running half of its potential at best.

cmyles · « **Reply #2 on:** August 13, 2011, 09:25:45 pm »

Factory boost should be 12.9psi if your running a Z4 ECU i believe, in and around there.

You have an manual boost controller? If its shut off, that sounds like wastegate pressure, at least that's what mine is.

farva · « **Reply #3 on:** August 13, 2011, 10:14:29 pm »

Check the cheap option first. Check to make sure there is no pinch or kink in the vacum line to the gauge.

blessthekellen · « **Reply #4 on:** August 13, 2011, 10:18:23 pm »

No MBC. What should these cars be sitting at in vac? I tapped into the BPV for my reading.
Went for a quick drive tonight, when the car first warmed up to operating temp, same thing, 6 PSI, then on the way home.
Reached up to 9.5 pounds.

Initial vac was 24, initial boost 6 pounds.
on way home, vac was 21, boost 9.5 pounds.

Ive read a few threads saying that someone had this problem as well, ended up doing the coil conversion then shot right back up to 14 PSI. I guess I should take a look and see if there is any cracking on these coils as this may be my problem as well.

Kind of a headache now, I just want this car running to its full potential $:-\$

farva, actually now that you mention it, I think the BPV line I tapped into may need a little trimming, that might be my problem, I'll be sure to check that out when I swap over my clear hoses that came with the gauge over to black ones tomorrow. Thanks for the suggestion!

cmyles · « **Reply #5 on:** August 14, 2011, 12:18:07 am »

Quote from: TEAMFaint on August 13, 2011, 10:18:23 pm

No MBC. What should these cars be sitting at in vac? I tapped into the BPV for my reading.
Went for a quick drive tonight, when the car first warmed up to operating temp, same thing, 6 PSI, then on the way home.
Reached up to 9.5 pounds.

Initial vac was 24, initial boost 6 pounds.
on way home, vac was 21, boost 9.5 pounds.

Ive read a few threads saying that someone had this problem as well, ended up doing the coil conversion then shot right back up to 14 PSI. I guess I should take a look and see if there is any cracking on these coils as this may be my problem as well.

Kind of a headache now, I just want this car running to its full potential $:-\$

farva, actually now that you mention it, I think the BPV line I tapped into may need a little trimming, that might be my problem, I'll be sure to check that out when I swap over my clear hoses that came with the gauge over to black ones tomorrow. Thanks for the suggestion!

Damn, thats really low, mine is usually 18 at idle and 20 a deceleration, boosting 8.6psi.

bejamin · « **Reply #6 on:** August 14, 2011, 11:17:38 am »

Before you crap yourself, are you sure your boost gauge isn't faulty? I mean if it drives nice and hasn't changed since you bought it you might wanna check that gauge before you go spending money on other stuff.
What brand are the gauges?

blessthekellen · « **Reply #7 on:** August 14, 2011, 11:25:43 am »

prosport premium series. i know they dont tend to be the most reliable, both mechanicals i used in my previous toyotas worked great, this is the first electric i have ever used and i know people have talked about the sending units on these occasionally being piled up straight out of the box.

went for a late night drive last night again, and as soon as the car warmed up i hammered on it again to see where it was at, and the car seemed to pull way harder than previously during the day, and was reaching 10 PSI consistently in every gear. Vac still ranged from -21 to -24.

Replacing the crappy plastic T connector today as well as the clear hoses with black ones today, will see what happens after this, i think that my problem may be vac leak related.

thanks for the input benjamin, your new STi looks flawless with the new JDM lights/fogs combo.

farva · « **Reply #8 on:** August 14, 2011, 01:39:39 pm »

I'm willing to bet its an issue with the gauge. They will show odd things when you mess with the refrence line.

blessthekellen · « **Reply #9 on:** August 14, 2011, 09:33:20 pm »

Well I went for a first real good cruise with the car today and here is the verdict.

Replaced the crappy clear vac hoses and t-connector.
Trimmed down the BPV line to ensure no kinks in the hose.

1st gear 9 psi.
2nd gear 9 psi.
3rd gear...6 psi.
4th gear...6 psi.
5th gear...6 psi

Changing out the line helped the Vac. consistently staying at 21 vac.

I can definitely feel that the car is actually having less power. Occasionally in 2nd gear the car would bog and only hit 6 psi as well. Happened randomly during the hour of driving. This was with the A/C off as well.

Ideas?

Jarrod · « **Reply #10 on:** August 15, 2011, 10:35:11 am »

If it feels the same since day one then I don't see how this could be a gauge issue. Your car has been sucking since day one haha.
I'd look at vacuum lines I guess, specifically around the boost controller. Take them off and inspect, reseat them tighter. What do people do with a leak, spray carb cleaner on the hoses or something to see if it gets sucked in and changes the idle?

Maybe get an MBC, they're $25 or borrow someone's. Also borrow someone's gauge or something. Any new JDM car, you should be checking spark plugs and all that normal stuff. Usually people are stuck at 10psi and it's because of a bad boost controller but you're only at 6 so it's a tad odd.

Grasp · « **Reply #11 on:** August 15, 2011, 10:50:10 am »

Also wondering, are you in a Wagon or a Sedan?

blessthekellen · « **Reply #12 on:** August 15, 2011, 06:07:59 pm »

Vehicle is a sedan version.

Tried out a different mechanical boost gauge, vehicle readings are still the same 23 - 21 VAC and car is feeling like it is hitting a wall now and only going 6 PSI through all gears for most of the time.

I have been reading that the factory boost solenoid tend to be iffy on these vehicles, but also read that coilpacks have caused this problem for someone as well, so here is how it looks what I need to do on this thing:

coilpack conversion
fuel filter
spark plugs
MBC and bypass the factory boost solenoid.

blessthekellen · « **Reply #13 on:** August 16, 2011, 10:23:53 am »

Reset ECU using dianostic connectors under the dash. After reset took the car out for a drive.
Feels so much better hitting 10 PSI in all gears

Still not hitting what people say it should be (14 psi) but I am not consistently hitting 10 pounds in every gear so I am satisfied. I think I may have gone through a bad tank of gas, or the gas went from running 94 octane from the previous owner with using octane booster to 91 octane v-power and adjusted the timing a little too intensly. Quick reset and now all is well.

Still any ideas on why I wouldnt be hitting 14 psi though? Quick MBC fix this set up?

sniper512 · « **Reply #14 on:** August 16, 2011, 10:31:54 am »

What ECU are you running? 10-11psi is stock psi on most early EJ20G's. Hitting 6psi in the upper gears sounds like limp mode to me. The car will go to wastegate pressure if there is a problem. It could have been an earlier issue that was solved and you clearing the code with the ECU reset satisfied the ECU to not be running in limp mode. If your looking to run more boost I would recommend a tuned ECU. I was blown away at the difference running 14psi(MBC untuned) compared to running a new tune from Rob at 14psi.

blessthekellen · « **Reply #15 on:** August 16, 2011, 01:09:34 pm »

Not sure what ECU exactly, but the car is a 95 WRX STi and read somewhere that stock PSI is supposed to be around 14?

LegacySTI · « **Reply #16 on:** August 16, 2011, 03:42:55 pm »

I thought I was the only one

For what its worth. My first gen EJ20G runs 10 PSI stock. In limp mode, I hit ~5 PSI. Coil conversion did nothing for my boost levels. Neither did fuel filter or new plugs.

I suspect I may have a vac leak that forces me into limp mode occasionally. If your car runs 9PSI in 1st and 2nd, it may have switched to limp mode after throwing a fault during the shift to 3rd.

Have you pulled the ECU codes? Is the check engine light on or did it flicker after 2nd gear?

blessthekellen · « **Reply #17 on:** August 16, 2011, 04:17:27 pm »

two codes.

code 51, neutral safety switch (dont have to have clutch pedal pressed in to start car, no biggie to me)
code 52, park brake switch.

neither engine related. but the car is no longer limping to only 5-6 PSI. It is now pulling hard and so much smoother hitting 10 psi at all times now.I honestly think the car has been in limp mode since day 1 of me owning the vehicle as it feels like a completely different car now. we will see how long this keeps up, if it lasts longer than a week im going to suspect the problem is fixed.

cannot wait for a 550 tune and 18 pounds of boost, these cars must be absolute rockets with those tunes!

sniper512 · « **Reply #18 on:** August 16, 2011, 05:56:31 pm »

Well my 04 STi I traded for is slower than my GC8 for sure. My STi has a TBE, Cobb Stg 2 93 hitting 17psi and a modded air box. My old GC8 would make short work off it......well for now anyways. Bang for your buck the early GC8 WRX is hard to beat.

blessthekellen · « **Reply #19 on:** August 18, 2011, 09:21:39 am »

Okay so after digging deeper I am convinced that the stock PSI on these is supposed to be around 14.

Car is running way better than previously and still hitting 10 PSI through every gear but I still think there is more to be uncovered.

Read a thread on nasioc. and someone else is having the same problem. He unplugged the line going to the wastegate and the car pulled to 15 PSI. I tried this. Hey. Same thing. This definitely feels like THIS is how the car is supposed to be. Now here is my question:

With the wastegate line unplugged on the factory boost solenoid does this mean my boost solenoid is clogged/dead/useless? Going to try and spray some cleaner inside of it. All connections are in good shape, hoses not cracked or anything, I just know there is something else to work out here and trying to determine what it is.

Jarrod · « **Reply #20 on:** August 18, 2011, 02:53:53 pm »

My reply on NASIOC

"By unplugging the line going to the wastegate, you theoretically get infinite boost right?
It is possible that your wastegate actuator is opening too soon but I would tend to say boost controller more (the wastegates rarely fail right?). And even if your wastegate is opening too soon, if you put in the MBC, the wastegate won't see any pressure until the MBC hits its point (unless it's one of those bypass ones)."

cmyles · « **Reply #21 on:** August 18, 2011, 09:01:55 pm »

Quote from: Jarrod on August 18, 2011, 02:53:53 pm

My reply on NASIOC
"By unplugging the line going to the wastegate, you theoretically get infinite boost right?
It is possible that your wastegate actuator is opening too soon but I would tend to say boost controller more (the wastegates rarely fail right?). And even if your wastegate is opening too soon, if you put in the MBC, the wastegate won't see any pressure until the MBC hits its point (unless it's one of those bypass ones)."

Need a new wastegate?

cmyles · « **Reply #22 on:** August 20, 2011, 11:31:27 am »

U8, 2C - 1993/1994 WRX 11.47psi
W6 - 1993 WRX RA 11.47psi
W9 - 1994 WRX RA 11.47psi
V7, 7D, 6D - 1993 to 1996 UK/Euro 11.47psi
SA (STi chipped) - 1993/1994 STi 13.64psi
SB (STi chipped) - 1993/1994 STi RA 13.64psi
SC (STi chipped) - SAME AS Z4 - 1995/6 STi Ver2 Wagon 12.7psi
Z4 - 1995/1996 WRX 12.7psi
Z5 - 1995/1996 WRX RA 12.7psi
6K (STi mapped, but not Chipped) - 1995/1996 STi 13.64psi
7K (STi mapped, but not Chipped) - 1995/1996 STi RA13.64psi
Prodrive UK ECU (Prodrive Chipped) -- SAME AS 6K - 1994 to 1996 13.64psi
1C, 3B, V9, V5 - All WRX Wagons 10psi, dropping to 6.8psi

GC8REX · « **Reply #23 on:** August 22, 2011, 09:59:10 pm »

Stock boost in my WRX (Z4 ECU) was 12.8 PSI. I would try changing up your gas. I was running at 7PSI for a long time before I tried some octance booster/94 octane gas. Instantly I had my full power again. Turned out to be off and on though and Rob's tune fixed the knock problem permanently

running 16PSI now with no issues.

Otherwise, like everyone is saying, I would check all vac connections and give your boost solenoid a good cleaning (take it off, spray inside with brake cleaner, put back)

Also, and MBC is a very cheap and very effective mod

blessthekellen · « **Reply #24 on:** August 22, 2011, 10:09:55 pm »

Just picked up a Turbosmart Boost Tee MBC here in town second hand. Unused. Minty. Best $30 mod I have purchased I must say.

Have it set at 13 pounds, its amazing how much of a difference 3 PSI makes on these cars.
Robs 440 tune is next, thanks for all the help you guys