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Old 10-13-2005, 02:26 AM   #1
woody77
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Default Stock (?) MY04 WRX pulling 12psi+ in 1st gear.. that's not good, right?

We picked up our WRX used with 35K miles. Due to the pattern of missing plastic rivets, it's definitely been modified, and "placed back to stock" before sale.

In diagnosing some roughness in the way it builds boost (especially when hot), I hooked up a cheap vacuum/boost test gauge, and WOT in 1st I was pulling well over 10psi (hard to pay a lot of attention while driving).

I was informed that an MY04 limits boost to 7psi in 1st, 10psi in second, and 14? in the rest of the gears.

I did a couple test runs today with an OBD2 logger, and they confirmed the results of the test gauge:

1st: 12.6psi (~5200rpm)
2nd: 13.5psi (~5200rpm)
3rd: 13.9psi (~3000rpm) <- shortly aborted right after I my 2->3 shift as I ran out of even remotely straight road for the speed I'd hit.

And in case I've done the conversion from inHg absolute to psi relative, those are (obd software claims 0inHg is absolute vacuum, I converted from inHg to psi (*.4912), and then subtracted off an atmosphere (-14.695595)

55.7inHg
57.4inHg
58.3inHg

From this, either the "boost limits" aren't limits but "expected" values for level driving (this was an uphill run), or something's not right with the car.

I've also noticed that it seems to spike boost a bit on throttle tip-in, especially over 50% throttle in 3rd or 4th gear. Quickly running up to full boost, dropping to 10ish, and then with a hair more, back to full boost.

Logs agree with that, 65% throttle and 12+ psi built up, then dropping and back to 12+ again as the revs go up.

Idle appears to be 12.2% throttle, and WOT 78% throttle. With the logger in real-time display, I can hold the throttle at the 78% mark, and put the pedal another inch to the floor, and lift it again, and no change from the 78% mark. It's odd.

At this point, I'm trying to figure out if the car is stock or not. Either way is fine, so long as I know WHAT was done to it, so that when I get detonation again (like I did monday) I'll have a better idea as to the cause aside from assuming it's OL/CL delay.

Nothing in the engine bay LOOKS modified, but if it was a non-flashy part, I'd not be able to tell in the first place.
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Old 10-13-2005, 02:33 AM   #2
eric94501
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The first gear seem alittle high but still in stock range to me.
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Old 10-13-2005, 02:56 AM   #3
hondaeater69
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boost levels look fine to me
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Old 10-13-2005, 06:32 AM   #4
ChrisWRB
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Yeah they look fine to me, too.
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Old 10-13-2005, 06:36 AM   #5
spoolinsuby
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My friends 03 wouldnt make more than 8 psi in first and the dealer said that was normal to help save the tranny from the 1-2 shift.
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Old 10-13-2005, 09:24 AM   #6
02subadrew
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one thing you might want to look into is the 3/16s mod...he/she may have done that and left it in there. big long debates about that mod, but the general consensus is bad. i tried it a year ago and got spikey boost so im back to the stock restrictor.

http://forums.nasioc.com/forums/show...ght=3%2F16+mod
http://forums.nasioc.com/forums/show...ght=3%2F16+mod
http://forums.nasioc.com/forums/show...ght=3%2F16+mod
http://forums.nasioc.com/forums/show...ght=3%2F16+mod

just something to check for
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Old 10-13-2005, 09:24 AM   #7
Celly
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Quote:
Originally Posted by woody77
We picked up our WRX used with 35K miles. Due to the pattern of missing plastic rivets, it's definitely been modified, and "placed back to stock" before sale.
The boost numbers look normal for an 04. If there is a bit of jittery boost, or over boosting, check to see if the 3/16th mod was done to this car. [Search, there is TONS of info on this..] 3/16th + 04/05 = Bad. Bad. God forbid if they had a MBC on there before you bought it...

Lower boost in 1st is normal. if you look at any EM, one of their FIRST selling points is "Full Boost in 1st gear". IIRC 10-11 is normal on a stock 04.

Also, Make sure you read up on the 04/05 OL/CL [Openloop Closed Loop] Issues with the ECU. Ok, they are not issues, but make the car act a little "Funny" to where you think you have a problem.. i.e. There are 1000 posts in this forum that say "04 WRX! POWER SURGE @ 4500RPM!!!!!!"

Good Luck, Enjoy!
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Old 10-13-2005, 09:29 AM   #8
TurbojonLS
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I made full boost in 1st when I was stock, as did other people I know w/ 04s. Nothing to worry about.
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Old 10-13-2005, 12:40 PM   #9
el_banano_wrx
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the boost is secuencial you will reach full boost in 4th gear
thats where the car needs the most tork
thats wy you should set your boost control in that gear
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Old 10-13-2005, 01:38 PM   #10
StealthfishWRX
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i get the same when it was stock.
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Old 10-13-2005, 01:39 PM   #11
timmah
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Quote:
Originally Posted by el_banano_wrx
the boost is secuencial you will reach full boost in 4th gear
thats where the car needs the most tork
thats wy you should set your boost control in that gear


umm..

you are dead wrong.

that is all.
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Old 10-13-2005, 01:51 PM   #12
woody77
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Thanks for the replies.

I'll check the hose for the 3/16th mod (I know where to go looking for it), and am also familiar with the OL/CL issue (spotted that in some of the logging as well), and am currently thinking that the det issue is OL/CL delay (I was romping on it from a light, and pulling hard in 2nd, heard the gravel..

This is good, I'll not be worrying about it much then, and continue to save up for the EM that I plan on putting in soon (if nothing else than to smoothen out the power).

So the boost limits in 1st/2nd aren't super hard, but can spike over those levels due to lag in the control loop for the wastegate? Or is it supposed to be a hard line somewhere? 1st goes by in a mighty hurry...
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Old 10-13-2005, 06:53 PM   #13
EagleRockWrex
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my 05 has no differential in boost from certain gears, it hits almost 14 in each gear, obviously in 1st, not as long but mine is an 05 with only a TBE.
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Old 10-13-2005, 07:24 PM   #14
waktasz
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Maybe I'm way off but I don't think they are limited. It is just a by product of engine load and the amount of time you are in 1st gear...not enough time to build full boost...the car isn't holding back in boost on purpose.

Quote:
Originally Posted by woody77
Thanks for the replies.

I'll check the hose for the 3/16th mod (I know where to go looking for it), and am also familiar with the OL/CL issue (spotted that in some of the logging as well), and am currently thinking that the det issue is OL/CL delay (I was romping on it from a light, and pulling hard in 2nd, heard the gravel..

This is good, I'll not be worrying about it much then, and continue to save up for the EM that I plan on putting in soon (if nothing else than to smoothen out the power).

So the boost limits in 1st/2nd aren't super hard, but can spike over those levels due to lag in the control loop for the wastegate? Or is it supposed to be a hard line somewhere? 1st goes by in a mighty hurry...
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Old 10-13-2005, 07:31 PM   #15
SlideWRX
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Quote:
Originally Posted by waktasz
Maybe I'm way off but I don't think they are limited. It is just a by product of engine load and the amount of time you are in 1st gear...not enough time to build full boost...the car isn't holding back in boost on purpose.
Exactly. The car isn't limited to any boost by gear. Find a steep hill and you can get full boost easily in first.

My suspicion is that he adjusted the wastgate actuator to hold tighter, which helps in lower gears.

Tom
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Old 10-13-2005, 07:32 PM   #16
woody77
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Quote:
Originally Posted by waktasz
Maybe I'm way off but I don't think they are limited. It is just a by product of engine load and the amount of time you are in 1st gear...not enough time to build full boost...the car isn't holding back in boost on purpose.
That makes sense, I just thought that part of what the Cobb AP did was remove the low gear limits on boost... maybe just the retune from the flash makes it hit higher boost in the low gears due to a faster spool-up...?
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Old 10-13-2005, 07:33 PM   #17
woody77
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Quote:
Originally Posted by SlideWRX
Exactly. The car isn't limited to any boost by gear. Find a steep hill and you can get full boost easily in first.

My suspicion is that he adjusted the wastgate actuator to hold tighter, which helps in lower gears.

Tom
0 wiggle on that when the engine's off. Tight enough that I can't move it with fingers...
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Old 10-14-2005, 09:15 AM   #18
ride5000
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Quote:
Originally Posted by SlideWRX
Exactly. The car isn't limited to any boost by gear. Find a steep hill and you can get full boost easily in first.

My suspicion is that he adjusted the wastgate actuator to hold tighter, which helps in lower gears.

Tom

^^^ 2nded.
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Old 10-21-2005, 09:47 PM   #19
woody77
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Quote:
Originally Posted by ride5000
^^^ 2nded.
This going to cause any problems, or is ok?
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Old 10-22-2005, 08:42 AM   #20
ride5000
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it's fine, woody. enjoy the extra torque in the lower gears.

just be sure to shift out of 1st quick enough so that you don't hit the revlimit!
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