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Old 09-01-2003, 09:56 PM   #1
z3coupe
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Default Flat spot after 5000 rpm?

Now that I am only 70 miles away from break-in, I am starting to drive the car past 5000 rpm. And in so doing, what once felt like a bat out of hell UP TO 5000, now seems to be flat after that up to the redline. Its almost as I am just revving the engine that high but not getting anything out of it - wasted revs. Anyone else feel this? I did have the reflash done - so I wonder if that caused this?

And another thing I notice, is that the turbo boost gauge only seems to go up to .5 and a bit higher - but never seems to get to 1 bar. My old WRX always would go to to 1 bar. As much as I love the STi, now I wonder if the EVO might not have been a better choice???????
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Old 09-01-2003, 10:03 PM   #2
wgknestrick
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Get used to it or get a full turbo back. I think the STI runs out of breathing room up there with the stock downpipe. It's the same POS that is on the WRX. My full turbo back seemed to help this "flat spot", but it is still not quite as linear as I would want.
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Old 09-01-2003, 10:10 PM   #3
happasaiyan
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the STi should be hitting over about 1.0 bar. check connections, or else something else might be the problem...and your "flat spot" problem might lay there too.
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Old 09-01-2003, 10:16 PM   #4
SubaruBen
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try an ECU reset.
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Old 09-01-2003, 10:34 PM   #5
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If my car has a flat spot it is definitely under 5000rpms. When your at 5000+ rpms are you flooring the gas pedal? It should pull really hard when floored, but if it's about halfway it will be fast, but won't pull really hard. As far as the gauge goes are you sure it's functioning properly and giving proper readings? It would be the first possible problem to eliminate.
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Old 09-01-2003, 11:08 PM   #6
z3coupe
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Well, while breaking it in, I would never go over 5000 rpm. So perhaps either let the ECU relearn, or reset it might help.

Zoso, I don't feel its flat at all under 5000, but it seems that over it is just revving for the sake of revving. Maybe as above, I need to reset the ECU or let it relearn that I am going to start to shift past the 5000 mark. And yes, I have it floored (entering the highway). And only in the lower gears does it somewhat come near the 1 bar mark on the turbo gauge. Will call the dealer and ask wht is up then. I just HOPE it is not cause of the ping ECU reflash

Hmmm, of course, it being a "drive by wire" car now, and no actual cable throttle . . . . . . . sometimes technology is NOT a good thing!!!!!!!!!!!!!
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Old 09-01-2003, 11:37 PM   #7
ANZAC_1915
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I also vote for the ECU reset, could also be a bad MAF.

Definitely not normal, my car screams to redline.
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Old 09-01-2003, 11:48 PM   #8
Zoso
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I was sorta joking about the flat spot under 5000rpms. When I floor it over 5000 the car definitely moves, so it makes it seem like the flat spot to me is under 5000rpms. I guess you need to have it checked out.
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Old 09-01-2003, 11:52 PM   #9
z3coupe
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Well, one thing I forgot to mention. As the car is still quiet (everyting is stock at the moment LOL), when I get above 5000 I kind of hear some hissing noise. Don't think its the turbo, and for sure not the FACTORY popoff valve. Will have to investigate more.

As for the ECU reset - is that still the same as the old WRX? Disconnect the battery for a few minutes, then reconnect it? Its been awhile since I last had to do that.
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Old 09-02-2003, 12:03 AM   #10
sethtasy
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If I floor mine at say 2500 and leave it floored to say 6000 I can definitely feel the rate of acceleration decrease after about 4500. The car can still be accelerating, but not as quickly. In physics the rate of change of acceleration is called "jerk" and its the jerk of the STi that I love, the feeling from about 2500-4000 of being pushed harder and harder into your seat as the car accelerates harder and harder (big +jerk). But from 4000 up the force pushing you into the seat relaxes gradually (in my car) so it almost feels like you are not speeding up (-jerk) even though you most definitely are (which can lead to a common problem with me: the , I am doing XX mph! or sometimes XXX mph!)

I have never worried about it because a look at the torque curve for the motor indicates torque falls off from 4000 to the redline, so it made sense to me that the accel rate would decrease as well.

I don't have a boost gauge so I don't know what to say about that; it also sounds like not all cars are experiencing the torque dropoff that I am.

SDC
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Old 09-02-2003, 12:15 AM   #11
z3coupe
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Seth, that could be part of it - the torque dropoff. But then the HP should still be kicking in and pushing us back in our seats.
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Old 09-02-2003, 01:19 AM   #12
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Are you running 91 or 93 or 100 or 101 octane.

Bottom line: if it is crappy gas, you get crappy performance. End of story.
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Old 09-02-2003, 01:22 AM   #13
z3coupe
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I use either Union 76 or Chevron. But here in wonderful Cali, we only have 91
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Old 09-02-2003, 10:44 AM   #14
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I would think the boost only going to .5 bar (about 7psi) is the problem there. I just had that happen to me this weekend.
http://forums.nasioc.com/forums/show...hreadid=414551

I reset the ECU and the boost came back up to just over 1.0 bar. I had the same flat spot above 5k rpm with only .5 bar of boost pressure. Anyone else have this problem?
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Old 09-02-2003, 12:40 PM   #15
rallykeith
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Quote:
Originally posted by z3coupe
Well, one thing I forgot to mention. As the car is still quiet (everyting is stock at the moment LOL), when I get above 5000 I kind of hear some hissing noise. Don't think its the turbo, and for sure not the FACTORY popoff valve. Will have to investigate more.
BINGO!!!! Sounds to me like you've got an air leak somewhere. Check all the intercooler and intake hoses and clamps between the turbo and the intake manifold to make sure they are tight. If you are leaking air out of any of these joints the car will not produce full boost and will feel flat in the higher RPMs.

Keith
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Old 09-02-2003, 05:03 PM   #16
filbert
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Quote:
Originally posted by sethtasy
In physics the rate of change of acceleration is called "jerk"
wow, i haven't heard someone say that in 8 years since i took HS physics! good to know someone else was actually listening!
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Old 09-03-2003, 12:20 AM   #17
z3coupe
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Quote:
BINGO!!!! Sounds to me like you've got an air leak somewhere. Check all the intercooler and intake hoses and clamps between the turbo and the intake manifold to make sure they are tight. If you are leaking air out of any of these joints the car will not produce full boost and will feel flat in the higher RPMs.
This sounds like it could be what is wrong. Or maybe that sound is normal and I never noticed it before (my old WRX was kinda loud with the exhaust and Azenis tires LOL). Anyway, I had the ECU reset today at the dealer. It appears to be a bit better now, but watching my boost gauge, it NEVER goes to 1 bar or over. It did go to the last hash mark just before 1 bar, but mostly stays at either .5 or midway between .5 and 1. Of course, I have heard it mentioned that the stock boost gauge is not too accurate as well . . . . .

Oh, and sadly, though I LOVE Irvine Subaru . . . . . to get anything done in the service department takes an act of GOD to get an appointment. I sure do miss Anthony who used to be at South Coast Sube, but has since moved on to Timmons which is a bit far away. Now I SHOULD mention that one tech at Irvine did take the time to reset my ECU, but on the whole its impossible to get in there for other service.
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