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Old 10-18-2009, 11:37 PM   #1
slates74
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Default Dead spot under boost, near 4k RPM?

Hi guys I recently picked up an 08 wrx with 22k miles. Loving the car but under acceleration there seems to be a point around 4000rpms where the car seems to cut out for a moment, maybe about 500 rpms or so. After that it seems to pull as usual through the rest of the rev range. Is this usual and could it be remedied with something such as stage one map from cobb or perrin?

I tried to use the search for the forum but couldn't find anything relating to it.

Thanks in advance for your help,

Sean
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Old 10-19-2009, 04:49 AM   #2
aberg12012
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This is normal. I also have an 08 sedan, mine has about 9k on it thus far. Before I went with a stage 1 open source tune I noticed it too, mostly when logging. I would start a pull around 2K rpm, it would hit boost and pull hard, then back off very noticeably shortly after usually around 2.8 or 3K. Then immediately pick back up and pull hard again.

I think it's really a combo of 3 or 4 things that tend to add up to it being more pronounced on the stock mapping.

#1 it seemed to occur about the same time it would transition from closed to open loop. So it didn't always happen at "x" rpm.

#2 our tiny turbos have a "tiny turbo" boost curve, in that the boost spikes way up when it first spools, and then suddenly drops back down. (At least mine does this, guess I shouldn't assume this means they all do...) For my car, it makes it feel like it surges real hard when it spools, and then settles down. For my car this tended to occur around the same time as the car would transition to open loop fueling, adding to the affect.

#3 Stock drive by wire mapping sucks. Plain and simple. It goes 100% requested torque at exactly 25% pedal angle. This makes it feel like "woah!!! hold on betty!!!" at first, but then seems to "flat line" as you give it more pedal angle, because your brain says you're giving it more gas, when really you aren't. This is probably the easiest thing to tune with a tactrix cable, btw.

#4 Surely there's reasons other than I've mentioned. (Some one else feel free to add anything I've missed, or correct anything I'm wrong about...)

Anyways, I'd suggest picking up the tractrix cable and downloading the open source programs to flash with. Then visit xpt and consider their stage 1 map. It's what I use, and it works very well for me. It's a much better option than going with AP or something else, since you can take it to any tuner you like to tune it, or you can simply use off the shelf maps to start with. Just make sure any off the shelf maps you use are highly rated by many users. This is why I suggest XPT, as their map for our car seems to be proven safe by many, many others.

EDIT: Nice color choice! Also, you'll probably figure this out, (if you haven't already) but don't bother ever exceeding 5K rpm. There's no power up there anyways. I use anything over 5K as over-rev only if I have to, (usually at the track) but it's kinda useless up there otherwise.

Last edited by aberg12012; 10-19-2009 at 05:11 AM.
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Old 10-19-2009, 10:21 AM   #3
slates74
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Thanks for the tips! I'm dropping off the car on wednesday to wayne subaru to have the oil piping recall done and they said they'll double check everything a do a stock reflash if needed. I have an incling that whoever had the car before me had some goodies on it so that may have something to do with it as well. It's so weird getting used to the power curve in this car as I just came out of an s2000 lol, couldn't be more opposite. Is there anyway to get a bit more top end pull out of this car?
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Old 10-19-2009, 02:41 PM   #4
slates74
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Old 10-19-2009, 09:14 PM   #5
torinalth
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New turbo... Only way to more top end
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Old 10-20-2009, 01:26 AM   #6
aberg12012
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If they re-flash to ensure the stock map is loaded, that's a good idea but what you're describing sounds like oem map behavior in my experience anyways. I wouldn't worry too much about it, provided you're experiencing what I think you are. When I noticed mine doing it and started looking for answers, I quickly discovered many others reporting the same issue with the stock map. The oem map is pretty ugly when you really start looking at the values that are in there, since it has to be "safe" for all conditions for all parts of the country high and low. If you do nothing else, I highly recommend finding some one with a tactrix cable simply to smooth out the dbw map. You'll be amazed at how much easier to drive it is, honest.

Yea, as for having no power up top, first is that our turbo (which I think is a TD04?) is very small. If you do any logging, you'll very quickly see that it doesn't flow enough air to produce much more than 9 or 10 psi after 5k, as it simply can't keep up with the amount of air the motor is breathing. The 09 WRX has a larger turbo (I think a VF52?) which I'm sure helps. But I also think the turbo is only part of the equation. I'm sure the cams are also cut more for low end power and smooth running, rather than massive valve overlap for high rpm performance.
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