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Old 05-17-2006, 09:36 PM   #1
hokiewrx
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Default stumble and then after or backfire - UPDATED HELP!

Hi I'm running Stage 2 (catless) + header + typhoon on my STi. I'm also running a UTEC that's been tuned by TurboXS. I've had something occur a couple of times that I'm trying to figure out if it's harmful and where to look.

What will happen is it seems like maybe around the crossover point all the sudden the car stumbles (almost like it's going to shut off) and then I get a big pop out of the exhaust and then I can continue along my merry way. I'm not getting any knock.

This has happened more when the car is warming up, but has happened when the car is perfectly warm too. It happens under lighter throttle and mid-range rpm's (I think?) It's definitely not a full throttle thing.

TIA.
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Last edited by hokiewrx; 05-22-2006 at 08:12 PM. Reason: title update
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Old 05-17-2006, 10:45 PM   #2
overdose
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that's a utec feature
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Old 05-17-2006, 10:55 PM   #3
hokiewrx
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uhh, how is a stumble and afterfire a feature persay? it's pretty violent, like i hit a brick wall for a second.
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Old 05-17-2006, 11:12 PM   #4
overdose
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cause utec sucks and nobody's ever REALLY been able to smooth the crossover, to some extent it's ALWAYS noticable

accessport ftw
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Old 05-17-2006, 11:31 PM   #5
WR^2X
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Riiiiiight. Cobb Fanboi.

Last edited by WR^2X; 08-19-2006 at 02:06 PM.
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Old 05-17-2006, 11:44 PM   #6
overdose
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Quote:
Originally Posted by WR^2X
Please... My crossover is much smoother than what he's describing.

This car has actually been tuned by TXS, or you're using a TXS OTS map?
probably so, but you can't say "100% seamless", i know you can't
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Old 05-17-2006, 11:59 PM   #7
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Quote:
Originally Posted by overdose
cause utec sucks and nobody's ever REALLY been able to smooth the crossover, to some extent it's ALWAYS noticable

accessport ftw
I once had a UTEC tuned by TurboXS... same issue.

Now I have EcuTek.
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Old 05-18-2006, 06:19 AM   #8
hokiewrx
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It's been tuned by TurboXS.

BTW overdose - I'm running firmware that has NO crossover issues, or hesitation. My car drives exactly like stock. This little fuel or whatever issue it is is my only issue.
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Old 05-18-2006, 06:28 AM   #9
WR^2X
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Really? Which firmware would that be?

Do some logging with logger #1 and post the results, then we can do a better job helping you.
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Old 05-18-2006, 09:37 AM   #10
overdose
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Quote:
Originally Posted by WR^2X
Really? Which firmware would that be?

Do some logging with logger #1 and post the results, then we can do a better job helping you.
It's vaporware firmware, every firmware release since OLF was released "fixes crossover hesitation" doesn't it
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Old 05-18-2006, 09:48 AM   #11
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Last edited by WR^2X; 08-19-2006 at 02:07 PM.
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Old 05-18-2006, 10:17 AM   #12
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In your timing table, put "ECU" into your 10% column from 0 to 3500 rpm. Seriously, try it.
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Old 05-18-2006, 11:09 AM   #13
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Quote:
Originally Posted by WR^2X
Your opinion of the UTEC has no place in this thread. hokiewrx, you might get better answers in Engine Management and Tuning.
sure it does, my point is it's never going to fully go away so while you may make it better, it's always going to be noticable or just as bad at certain psi vs. tps
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Old 05-18-2006, 01:58 PM   #14
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Dude while I appreciate your input, seriously drop the UTEC bashing thing. Just because you had a bad experience doesn't mean we need to hear about it. I started the thread to seek legit help.

My maps are at http://1dot0.itsensellc.com/sti/06-05-12_utec/. I pretty much stick with map 2 which is the same as map 1 with the exception that it lowers the boost.

I'm running v1.4. You'll find the screenshot at that same link. It's unfortunately an unreleased firmware that you can only get directly from TXS. But, it did solve all those nasty crossover issues I was having with 1.1c. I think this version may have built on the version that is coming. Data logging I will try, but it's hard because it probably happens 1 out of 7 or 8 times I'm driving and it's a PIA to hook up the laptop everytime I go somewhere ;-)

DISCLAIMER - if you choose to run any of the maps I've linked in this post you do so AT YOUR OWN RISK. Don't come crying to me when you blow your motor up.

Freon - So let the ECU handle timing from 0-3500rpm in the 10% load column? You think that has something to do with it?

Thanks!!

DISCLAIMER - if you choose to run any of the maps I've linked in this post you do so AT YOUR OWN RISK. Don't come crying to me when you blow your motor up.

Last edited by hokiewrx; 08-19-2006 at 02:52 PM. Reason: Adding disclaimer
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Old 05-18-2006, 03:38 PM   #15
overdose
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you can let ecu control it or try to "mimmick" what the ecu wants to run in those lower load zones so it's nice and smooth
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Old 05-18-2006, 03:47 PM   #16
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The problem is the 10% load column has to cover from who knows how much vacuum up to 1-2psi. The 20% column covers a very narrow range, just 1-2psi up to 3-5psi. Same is true for the remaining columns. So you cannot put a meaningful timing number in the 10% column like you can 20-100.

10% takes over as soon as TPS is met. It does NOT wait until you hit 0psi! That's why it transitions like crap. A good timing number for 10% load could be anywhere from +46 to +26 or so. But a good timing number for, say, 20% is probably a narrow range, say, +26 to +23, or whatever depending on the RPM, etc. Either way, the window of a good number is much narrower. Basically, you cannot mimmick the ECU in the 10% column since there is just too much variance in airflow to cover. You'll see the ECU running anywhere from +46 deg to about +26, since that is all the way from lots of vacuum to about 1-2psi.

Doing this got rid of over half the transition issues I ever had. I have no idea why the TXS base stage 1 and stage 2 maps do not do this right out of the box. It should be in the canned maps, IMNSHO.
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Old 05-18-2006, 03:56 PM   #17
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Ok, so what is the worst case scenario? Obviously letting the ECU run timing as it see fits doesn't seem to really pose any big risk other than loss of low end power potentially?
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Old 05-18-2006, 04:22 PM   #18
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Quote:
Originally Posted by Freon
The problem is the 10% load column has to cover from who knows how much vacuum up to 1-2psi. The 20% column covers a very narrow range, just 1-2psi up to 3-5psi. Same is true for the remaining columns. So you cannot put a meaningful timing number in the 10% column like you can 20-100.

10% takes over as soon as TPS is met. It does NOT wait until you hit 0psi! That's why it transitions like crap. A good timing number for 10% load could be anywhere from +46 to +26 or so. But a good timing number for, say, 20% is probably a narrow range, say, +26 to +23, or whatever depending on the RPM, etc. Either way, the window of a good number is much narrower. Basically, you cannot mimmick the ECU in the 10% column since there is just too much variance in airflow to cover. You'll see the ECU running anywhere from +46 deg to about +26, since that is all the way from lots of vacuum to about 1-2psi.

Doing this got rid of over half the transition issues I ever had. I have no idea why the TXS base stage 1 and stage 2 maps do not do this right out of the box. It should be in the canned maps, IMNSHO.
Exactly. How can timing be exactly the same for -520 mm all the way to 1 psi? Let the ECU mimic itself.
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Old 05-18-2006, 05:51 PM   #19
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Is that 3500rpm inclusive or exclusive?
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Old 05-18-2006, 05:54 PM   #20
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Well I hope TXS releases this 1.4 firmware soon. We've been waiting for quite awhile.
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Old 05-18-2006, 06:06 PM   #21
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I'd try inclusive, but I'm just learning this UTEC stuff. Coming from a Hydra it's soooo convoluted.
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Old 05-18-2006, 06:10 PM   #22
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Unfortunately the 1.4 firmware is a dead end release from what I understand. But TXS is cooking up something new and hot too so I think patience will reap huge rewards!
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Old 05-19-2006, 09:47 AM   #23
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So far so good on the timing changes... actually, the car drives a lot better I must say!
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Old 05-19-2006, 01:42 PM   #24
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Quote:
Originally Posted by hokiewrx
Is that 3500rpm inclusive or exclusive?
3500rpm is somewhat arbitrary. Use whatever works for you but I suggest trying around 3500, give or take.
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Old 05-19-2006, 03:50 PM   #25
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you did something dude... turbo xs would'nt have let that car go like that. my utec never does that.
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