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Old 06-19-2008, 11:53 PM   #1
n2oiroc
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Default laying down on the top end! (vid added pg 2!)

my car is fine in 2nd gear, but 3rd gear on up it falls flat on its face above 6,500 rpm or so. i logged it and didnt see anything except a little timing (-2.8*) being pulled right before it happens. no misfire being picked up either. it didnt do it on the dyno either. the only thing that was changed since the dyno runs was the plug gap, i closed it up from .030 to .026 because the tuner logged a slight misfire at 7,300 rpm. it almost feels like its running out of fuel or hitting the rev limiter, but it shouldnt be.

so far i checked the crank sensor gap and its tight. idc's are in the upper 70% range. i added a 12gauge ground from the block to the battery and unless im imagining things, it seems a little better. any ideas?

07 sti
new 9.5:1 built block
T3/T04S u.r. turbo kit (65 lb/hr compressor .82 a/r turbine)
stock heads and cams
12mm jdm oil pump shimmed .040"
one step colder ngk iridium ix plugs gapped to .026"
tgv deletes
deatschwerks 1,150cc injectors
walbro 255
perrin fmic
blow thru maf
tial 44 ewg
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Last edited by n2oiroc; 06-27-2008 at 12:40 AM.
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Old 06-19-2008, 11:57 PM   #2
HOLLYW00D
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what's your maf voltage at the point where it falls on its face?
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Old 06-20-2008, 12:05 AM   #3
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Quote:
Originally Posted by HOLLYW00D View Post
what's your maf voltage at the point where it falls on its face?
4.3 ish then obviously it drops.
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Old 06-20-2008, 12:40 AM   #4
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Tuned with?
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Old 06-20-2008, 12:43 AM   #5
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Quote:
Originally Posted by reddevil View Post
Tuned with?
cobb ap 2, tuned by jorge. the turbo was a very late spooler, so we called it quits after 2 hours, so its not the final tune, but its tuned. i want to track this down before i dig into the turbo.
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Old 06-20-2008, 01:58 AM   #6
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Does the MAF voltage drop before or after the boost pressure?
If before then aftermarket intake hose collapsing?
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Old 06-20-2008, 02:04 AM   #7
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Quote:
Originally Posted by ciper View Post
Does the MAF voltage drop before or after the boost pressure?
If before then aftermarket intake hose collapsing?
boost drops first. and there is no inlet hose. i have a big filter clamped right to the turbo.
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Old 06-20-2008, 07:31 AM   #8
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is boost just tapering and the car doesn't pull as hard?
or are we talking it just instantly plummets?
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Old 06-20-2008, 11:39 AM   #9
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Maybe too much backpressure?
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Old 06-20-2008, 03:13 PM   #10
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Quote:
Originally Posted by Homemade WRX View Post
is boost just tapering and the car doesn't pull as hard?
or are we talking it just instantly plummets?
it doesnt feel like a boost and power drop off, it feels like a rev limiter kicking in or the spark getting blown out. no misfire though. weird.
boost - rpm - maf voltage - fine learning knock correction
22.85 @ 5,914 rpm 4.4v -2.8*
21.09 @ 6,184 rpm 4.4v -2.8*
18.69 @ 6,447 rpm 4.5v -2.8*
13.71 @ 6,690 rpm 4.36v 0*
-10.73 @ 5,636 rpm 1.26v 0*
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Old 06-20-2008, 03:15 PM   #11
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Quote:
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Maybe too much backpressure?
its a .82 a/r turbine, atmospheric dump ewg and the catback is a full 3" that worked fine at 390 whp with an internal gate last year.
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Old 06-20-2008, 07:23 PM   #12
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What spring is in the ewg?
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Old 06-20-2008, 07:27 PM   #13
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What spring is in the ewg?
.9 bar. per the tuners recommendation, im going to try running it off of spring pressure and see if it changes.
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Old 06-20-2008, 08:35 PM   #14
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alright, on wastegate spring pressure its fine, revs cleanly up to 7,500 rpm. i guess ill ask him whats next. it looks like the plugs cant keep it lit, but i dont know why it wouldnt show up as a misfire. i guess its time for a tighter gap, different plugs, etc.?
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Old 06-20-2008, 10:28 PM   #15
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I really doubt its the plugs.

Are you using the stock boost control setup?
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Old 06-20-2008, 10:34 PM   #16
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Quote:
Originally Posted by LiquidForce View Post
I really doubt its the plugs.

Are you using the stock boost control setup?
yes, with a perrin ebcs. wgdc is in the 70% range at peak. how could it be a boost control problem?
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Old 06-21-2008, 12:25 AM   #17
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Quote:
Originally Posted by n2oiroc View Post
alright, on wastegate spring pressure its fine, revs cleanly up to 7,500 rpm. i guess ill ask him whats next. it looks like the plugs cant keep it lit, but i dont know why it wouldnt show up as a misfire. i guess its time for a tighter gap, different plugs, etc.?
I know it's going to sound crazy, but try tightening up the gap MORE, like .025 and then see. Clearly, lowering cylinder pressure (which you have a LOT of with that compression) fixes the problem.

If we can't find the right gap, then there are only two real options, Less boost and/or timing (which ultimately limits you on your octane, or an increase in ignition energy (something like an HKS twin power).

I ran into this problem on a built motor running an AEM on a 35R. That was more so the older black coils used by the bug-eyes. When I increased the dwell in the AEM it worked perfectly.

If tightening up the gap doesn't do much, then the next step will be to simply turn down the boost for now.

That's ultimately cheaper then buying a twin power.

-J
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Old 06-21-2008, 01:00 AM   #18
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Quote:
Originally Posted by RiftsWRX View Post
I know it's going to sound crazy, but try tightening up the gap MORE, like .025 and then see. Clearly, lowering cylinder pressure (which you have a LOT of with that compression) fixes the problem.

If we can't find the right gap, then there are only two real options, Less boost and/or timing (which ultimately limits you on your octane, or an increase in ignition energy (something like an HKS twin power).

I ran into this problem on a built motor running an AEM on a 35R. That was more so the older black coils used by the bug-eyes. When I increased the dwell in the AEM it worked perfectly.

If tightening up the gap doesn't do much, then the next step will be to simply turn down the boost for now.

That's ultimately cheaper then buying a twin power.

-J
i'll tighten them up a little more and see what it does. after i solve this its time to chase the lag monster.
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Old 06-21-2008, 01:15 AM   #19
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i would prefer to fix it without tossing more parts at it, but i wonder how this compares to the twin power. http://www.msdignition.com/ignition_28_7010.htm
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Old 06-21-2008, 10:38 AM   #20
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Quote:
Originally Posted by n2oiroc View Post
yes, with a perrin ebcs. wgdc is in the 70% range at peak. how could it be a boost control problem?

My thinking was that if your wastegate was opening up as the boost was plummeting it would be a boost control problem. If your target boost is > 20 then the gate shouldn't be open at all at 13 psi. If it is opening its not the turbo or the plugs. It is more likely to be the spring or some other component of the boost control systsem.


I run a high compression motor with the same turbo but with a .63 exhaust housing. I run the stock gap on the one step colder Iridiums for a wrx which I believe is .040 and have no issues running 30lbs on c16.


Is it possible that the plugs were damaged when they were gapped?
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Old 06-21-2008, 01:59 PM   #21
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it is without a boubt you stock heads and cams. u can make HUGE power up top with your setup but having 208 duration cams is NOT helping you... its hurting you pretty bad. get soem head work done. 272s are amazing
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Old 06-21-2008, 04:48 PM   #22
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Quote:
Originally Posted by LiquidForce View Post
My thinking was that if your wastegate was opening up as the boost was plummeting it would be a boost control problem. If your target boost is > 20 then the gate shouldn't be open at all at 13 psi. If it is opening its not the turbo or the plugs. It is more likely to be the spring or some other component of the boost control systsem.


I run a high compression motor with the same turbo but with a .63 exhaust housing. I run the stock gap on the one step colder Iridiums for a wrx which I believe is .040 and have no issues running 30lbs on c16.


Is it possible that the plugs were damaged when they were gapped?
it holds set boost fine, it only drops when the spark goes out. its possible the plugs got damaged, but very unlikely. im very careful installing them. i'll check them over real good and try another gap.
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Old 06-22-2008, 02:29 AM   #23
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what's the afr?
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Old 06-22-2008, 07:48 AM   #24
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Quote:
Originally Posted by Dom'sGurl View Post
what's the afr?
i dont have a wideband, but according to the dynojet probe, definatly not rich!

you can also see how laggy it is, thats my next mission. we are thinking its a defective turbo.

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Old 06-24-2008, 07:41 AM   #25
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update: i tried it at 20 psi and its better, but still there. it was previously at 22-23 psi. plugs are at .025".
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