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Old 12-08-2017, 09:52 AM   #1
wrx_b666st
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Default 2015 WRX stumbling on accel

Alright guys, my first post here and I've been searching and can't seem to find an answer. I just got my car back after a year long rebuild to an IAG stage 3 short block. When the motor blew pretty much all of my oil was in the exhaust. It took my tuner and his guys a while to get the oil out and to stop smoking but during the process my turbo took a crap. I got it replaced and all was great. I picked the car up and noticed almost instantly that it didn't seem to have the power that it showed on the dyno. I thought this was just the limp tune it had so I wouldn't go over 4000 rpms and not use a lot of boost. It's out of the break in and my new tune is installed and I noticed that it stumble and almost starve for fuel during any hard or moderately hard acceleration. I swapped the fuel pump to a DW65c and it seemed to run a lot better last night but still not great at 100% throttle. This morning it's back to stumbling. I'm at a loss so any insight would be really helpful guys.
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Old 12-08-2017, 10:07 AM   #2
boxterWRX
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sounds like the tune
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Old 12-08-2017, 10:10 AM   #3
sth36
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Sorry about your motor man. Considering you have a built block, I'm assuming you know all this already but I'll try to answer anyway. It could be tune related in which case talk to whomever tuned your car. There are quite a few mechanical things that could cause stumbling--maybe start by cleaning your MAF and checking for any leaks specifically around the intercooler. Could you post all your mods and a log of the stumbling?
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Old 12-08-2017, 11:29 AM   #4
wrx_b666st
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I can log it in a few. It's no so much stumbling now, but it's like a flat spot in the power band. It feels really good down low and then mid it falls. Anytime I get off throttle and back on it takes so long to get power again. My car is stock other than a drop in air filter and custom axle back deletes.
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Old 12-08-2017, 11:46 AM   #5
sth36
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Logs will help. Make sure you're logging Cobb default parameters plus Comm Fuel Final AFR.

So this piqued my curiosity so I have to ask--how did you managed to blow a block with no real mods? Are you planning on building a racecar, otherwise why go built block?
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Old 12-08-2017, 12:33 PM   #6
wrx_b666st
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I had a spun rod bearing and my tuner who built the car said that it was a cascading effect lol. That happened and then slowly it went down hill and cylinder one had a ring land failure. I will log all of that here in a second, I gotta make a store run so perfect time to log it
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Old 12-08-2017, 12:34 PM   #7
uofime
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Quote:
Originally Posted by wrx_b666st View Post
Alright guys, my first post here and I've been searching and can't seem to find an answer. I just got my car back after a year long rebuild to an IAG stage 3 short block. When the motor blew pretty much all of my oil was in the exhaust. It took my tuner and his guys a while to get the oil out and to stop smoking but during the process my turbo took a crap. I got it replaced and all was great. I picked the car up and noticed almost instantly that it didn't seem to have the power that it showed on the dyno. I thought this was just the limp tune it had so I wouldn't go over 4000 rpms and not use a lot of boost. It's out of the break in and my new tune is installed and I noticed that it stumble and almost starve for fuel during any hard or moderately hard acceleration. I swapped the fuel pump to a DW65c and it seemed to run a lot better last night but still not great at 100% throttle. This morning it's back to stumbling. I'm at a loss so any insight would be really helpful guys.
so you connected the turbo and accessories from a blown up motor to a fresh motor....?

If you didn't clean all of them out very carefully, you now have trash from your blown up motor all over the inside of your new motor, wrecking all the bearings and god knows what else.
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Old 12-08-2017, 12:48 PM   #8
wrx_b666st
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No, after my original turbo took a crap I replaced it. All the lines and everything from the old was replaced when the new motor was installed. We didn't want to chance anything getting into it.
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Old 12-08-2017, 09:35 PM   #9
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So the problem was learned timing. I reset my ECU and all is good. A small stumble down low and crushing but plenty of power while in boost now and accelerating hard.
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Old 12-08-2017, 11:34 PM   #10
GlarryHoodDIT
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Quote:
Originally Posted by wrx_b666st View Post
So the problem was learned timing. I reset my ECU and all is good. A small stumble down low and crushing but plenty of power while in boost now and accelerating hard.
You're going to have to elaborate what you mean by "the problem was learned timing." On its face that statement doesn't make a lot of sense.
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Old 12-09-2017, 11:06 AM   #11
gn4rwhals
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You mean Fine Knock Learn was pulling timing in the range and it felt like it was falling on its face.

Hopefully you can figure out what caused the learned timing in the first place.
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Old 12-09-2017, 11:08 AM   #12
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The fact that my car was stumbling on accel and just had a real lack of power for making 260 awhp. I sent a log to my tuner and he said for some reason my cars learning for timing was way off. So he advised to reset ECU learning and that seemed to fix it but last night when I was driving again it seemed to be reverting back.
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Old 12-10-2017, 09:36 PM   #13
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I changed the name of this thread because it seems that my issue is I cab reset ECU learning and everything is going great with my DAM when I running the piss out of the car but as soon as I'm cruising around the city and around 2.5k rpms and decide to give it some throttle my DAM drops. The lowest it got today was .562. I reset and cruised again and it dropped to around .8 but then after running a civic it went back up to .952. All of this is within 15 minutes of reset. Should I just drive the car and keep an eye on it?
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Old 12-11-2017, 11:36 AM   #14
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Your DAM is dropping because your engine's knocking. Most likely causes are that your tune has too much timing, is running lean due to MAF or air leak problems, or your fuel quality is bad. Post some logs of 3rd gear pulls, and be sure to include DAM, FBK, FKL, AF Sens 1, and Comm Fuel Final. Assuming your tuner is competent, it's likely that something has changed mechanically for there to be such a big drop in DAM. Are you using the same fuel the car was tuned on?

You should be fine to keep driving the car, but don't reset the ECU learning often, or you'll end up getting more knock while your car learns to drop DAM and FKL. You want your final tune to have a DAM of 1 with no FKL. Drops in these values should be reserved for unusual conditions like bad fuel quality or MAF problems.
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Old 12-12-2017, 01:24 PM   #15
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I've got an IAG stage 3 short block and I read that it will "produce" FKL even when there isn't actually any knock occurring. I've got my tuner looking into it and I'm at work right now, but I do have 3 logs that I can post later.
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Old 12-12-2017, 02:42 PM   #16
X49
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Quote:
Originally Posted by wrx_b666st View Post
I've got an IAG stage 3 short block and I read that it will "produce" FKL even when there isn't actually any knock occurring. I've got my tuner looking into it and I'm at work right now, but I do have 3 logs that I can post later.
I've had this occur on my Stage 1 car, where I got FKL and DAM reduction with no feedback knock, even though I was datalogging continuously since a reflash. I'm not sure what causes it, but it's only happened after I try running more aggressive timing so I assume it's associated with actual knock that just doesn't show up in the log. I'm interested in what your tuner has to say.
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Old 12-12-2017, 04:29 PM   #17
ericdet
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Default 2015 WRX stumbling on accel

Quote:
Originally Posted by X49 View Post
I've had this occur on my Stage 1 car, where I got FKL and DAM reduction with no feedback knock, even though I was datalogging continuously since a reflash. I'm not sure what causes it, but it's only happened after I try running more aggressive timing so I assume it's associated with actual knock that just doesn't show up in the log. I'm interested in what your tuner has to say.


Depending on which knock correction mode is active when the knock occurs it will register in different ways. FBK is really only used in certain situations. Load changes, throttle swings, etc. FKLC is used more in the upper rev range. This is knock itís just not knocking in the FBKC windows. Most steady WOT pulls above 4800 will only see FKLC.

The poster above is likely referring to the louder chatter of a built engine artificially triggering knock readings. Which is common.

Wild DAM swings arenít really uncommon on these cars. Mostly gas/maf motivated.
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Old 12-12-2017, 10:14 PM   #18
wrx_b666st
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The knock swings aren't even all that annoying, but for some reason mine keeps pulling the DAM down. I've swapped the gas now and I'm running it to see if it changes and my tuner has yet to get back to me. Hopefully he's able to fix it on the tune
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