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Old 09-16-2012, 12:42 PM   #1
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Exclamation PLEASE READ: Once and for all, why did this happen?

So as some of you may remember, my turbo blew up like 3 weeks ago after boosting in the ballpark of 28psi. I want to find out why this happened once and for all because the boost has been erratic for a long time.

Here's how it usually goes:

1. Start car. Smooth idle, drives around smoothly.

2. Get on highway. Third gear pull. Even boost at 20-21psi (JZW stg. 4 tune and supporting hardware (B205R with stock td04, full exhaust, ETS intercooler, 3.5 bar FPR). Runs like a top.

3. Cruise a bit, then slow down to about 60mph for another 3rd gear pull. Same. Totally fine.

4. Repeat. This time, higher boost. 24psi or so. Car is actually slower as ECU apparently detects too much air flow and tries to reduce it- boost drops to like 18 psi really quickly.

5. Repeat. Car boosts to like 26 psi and holds it. Flies like a fucking rocket ship but is clearly running very lean. Boost creeps down to the 21psi area and holds. Air mass reading on open SID is generally between 1500 and 1600. Yeah, it's that high. Request is steady at 1300.

6. Repeat. Hits well over 26psi, sometimes the needle hits 30 (the max on my gauge) and it probably goes higher than that. Hits fuel cut or whatever you want to technically call that- it's like a misfire.

7. At this point, it's going to do either #5 or #6 every time, but it's impossible to predict which one.

THINGS I HAVE TRIED:

MAF is newly replaced with a used one. I actually have 3 different working MAFs and all have been tested both at idle and under load by the shop I go to. All are said to be FINE.

DIC was brand new (OEM from GS) last fall- has about 10k miles on it.

Fuel pump was new this summer, has <1500mi on it.

The shop SAYS the BPC is fine, but I'm thinking it might be worth trying another one? The thing that throws me is that after the car sits for a bit, it always has TWO normal pulls before acting weird. It apparently adapts boost upward as it goes.

Also, I've been running the same tune for just over a year and haven't had this problem before, so I really don't think it's an issue with the tune. Lot's of other people have John's stage 4 with no issues.

I know this was a lot to read, but it's a big deal. I really don't need to be blowing up another turbo any time soon. Please help- anything you can contribute would be greatly appreciated.
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Last edited by miker92; 09-16-2012 at 12:46 PM. Reason: added info
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Old 09-16-2012, 01:26 PM   #2
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Temperature related? Does #1 begin with a fully warm engine or ate you actually getting to temp later in the process?

After all the stuff your thrown at it, makes sense to at least try a BPC.
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Old 09-16-2012, 03:33 PM   #3
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Check the hoses goign to the bpc for cracks as well. My 9k had a cracked fitting on the hose that goes to the inlet of the turbo. It did some funky things.
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Old 09-16-2012, 08:36 PM   #4
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The short hose that goes from the BPC to the wastegate actuator is 100% fine. Will definitely try a new BPC.

I'm really interested in the temp thing. The numbered list in my first post always starts with a cold engine. Starts acting up when it gets up to temp. Never overheats though- temp gauge is always right in the middle where it always has been. I did have a coolant hose crack over the summer and ended up replacing it. Is there some kind of sensor I could have messed up doing that? More info down this alley would be helpful.
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Old 09-16-2012, 08:47 PM   #5
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There are three temperature sensors on the engine.
Intake air temperature
Coolant temperature sensor
Coolant temperature sender

I have read many a posts that explain funky thinks happening to people's cars. Many of them were solved by replacing one of those sensors.

Have you replaced any?
Have you replaced your cps?
How many miles on the engine?
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Old 09-16-2012, 08:57 PM   #6
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Your running 26psi on a stock turbo, turn that shit down.
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Old 09-16-2012, 09:04 PM   #7
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There are three temperature sensors on the engine.
Intake air temperature
Coolant temperature sensor
Coolant temperature sender

I have read many a posts that explain funky thinks happening to people's cars. Many of them were solved by replacing one of those sensors.

Have you replaced any?
Have you replaced your cps?
How many miles on the engine?
Have not replaced any of those sensors or the CPS. Will look into that. Thanks. 119k on the engine.


lms, did you read the OP? This entire thread is about me trying to figure out why it's boosting so high and how to make it stop.
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Old 09-17-2012, 06:20 AM   #8
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What kind of psi does the stock TD04 15t run on average? What does a stage 3/4 tune run?
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Old 09-17-2012, 06:46 AM   #9
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Your running 26psi on a stock turbo, turn that shit down.
i kinda agree... pretty sure they arent designed to run that kind of boost for any extended period. at least not in used form
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Old 09-17-2012, 06:48 AM   #10
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Quote:
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i kinda agree... pretty sure they arent designed to run that kind of boost for any extended period. at least not in used form
He knows that, he's trying to figure out why it's boosting so high.

OP, Have you reached out to John and asked about your tune. I'm sure he would be more then happy to give you some advice on what to look at.
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Old 09-17-2012, 06:53 AM   #11
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Have not replaced any of those sensors or the CPS. Will look into that. Thanks. 119k on the engine.


lms, did you read the OP? This entire thread is about me trying to figure out why it's boosting so high and how to make it stop.
Ok, did it do this before, in other words, has this tune by John always boosted so high? I know some of his old tunes were like this? If so, call John.

A stock tdo4 at sea level will around 9-12 psi on a T7. Stage 3/4, it should run up to 20 max, anything after that is out of its efficiency range, 18psi is just right. Sure it can hit 25 psi, but will not sustain it.
Be very careful, as you know, because this is how you melt pistons.
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Old 09-17-2012, 08:14 AM   #12
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How do you know it is lean? I'd check if the wastegate is getting jammed. Sometimes when they get really hot they get sticky, that is, the actual flapper has binding points in the housing. Perhaps the the duty cycle of the BPC is too high? Do you have a BOV? I know T7 should NOT have one, but some people have 'em.
I call BS on lean, and if instruments tell you otherwise they are prolly wrong. Ya see, a tiny turbo moving tons of air outside its pressure-flow efficiency realm is going to be pumping heat--massively. Yes, the ETS is good, but, for all that back pressure on the choked Td04 #5, you are going to get soaring EGT's as well. If it were *actually* lean you'd have A) The ECU pulling boost, dumping fuel, and killing timing. B) A toasted engine.
You'd notice if the ECU intervened, which means that it is probably not knocking and thus not lean.
I'd wager it is something mechanical or something to do with the software not meeting requests somewhere else and compensating by over-cycling the BPC. Since JZW is a tuning demigod, I'd imagine it is the former.
Experiment: Unplug the BPC and do your pulls.If you notice boost increasing this means that your WG is sticking. If not we'll try something else.
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Old 09-17-2012, 09:55 AM   #13
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How do you know it is lean? I'd check if the wastegate is getting jammed. Sometimes when they get really hot they get sticky, that is, the actual flapper has binding points in the housing. Perhaps the the duty cycle of the BPC is too high? Do you have a BOV? I know T7 should NOT have one, but some people have 'em.
I call BS on lean, and if instruments tell you otherwise they are prolly wrong. Ya see, a tiny turbo moving tons of air outside its pressure-flow efficiency realm is going to be pumping heat--massively. Yes, the ETS is good, but, for all that back pressure on the choked Td04 #5, you are going to get soaring EGT's as well. If it were *actually* lean you'd have A) The ECU pulling boost, dumping fuel, and killing timing. B) A toasted engine.
You'd notice if the ECU intervened, which means that it is probably not knocking and thus not lean.
I'd wager it is something mechanical or something to do with the software not meeting requests somewhere else and compensating by over-cycling the BPC. Since JZW is a tuning demigod, I'd imagine it is the former.
Experiment: Unplug the BPC and do your pulls.If you notice boost increasing this means that your WG is sticking. If not we'll try something else.
-Cm
When it hits higher boost levels, it stutters and doesn't accelerate smoothly. It's as if the engine is gagging. Sometimes, but not always, boost drops off almost instantly from ~26psi to about 15psi. If it stays at the higher level, the revving of the engine sounds strained. It's hard to describe, but it's sort of higher pitched and quieter, not as throaty sounding. When it boosts really super high, like 28 or so, the entire car bucks in what essentially feels like a violent misfire. This stuff, combined with the idea that my fuel system, which is stock except for the 3.5 bar FPR, can't possibly supply enough fuel to balance out that much air flow, is why I thought it would be running super lean under high boost.
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Old 09-17-2012, 07:31 PM   #14
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If it were knocking, the ECU would seamlessly do these things and it would make a lot of noise but feel slow, which my car will do with poorer quality gas. The stuttering is spark quench, that is, when the internal atmosphere of the cylinder is too great for the DIC to overcome. This is either from too much gap/wrong plugs or a weak DIC or both. Now, the phantom boost loss is prolly from knocking.
Lastly, I just thought of this; what it seems like you suffer from is boost creep( strange for a turbo of this size) mixed with too little fuel mixed with too high EGT. Basically, the "normal pulls" are the ECU upping the ante; if you hit knock it drops its attack. However, if you hit no knock, then what the ECU does is try again, except this time once the inertia of the wheel has been pushed to a point, your wastegate isn't bypassing sufficient gasses and the turbo keeps spooling until the engine knocks or it misfires. Go out and wiggle the wastegate, see if it opens and how far. If it only opens a crack then that answers it.
I'd also gap the plugs and maybe put new ones in. Do you need an upgraded MAF? I know on T5 you need an upgrade MAP.
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Old 09-19-2012, 12:31 PM   #15
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I'd also gap the plugs and maybe put new ones in. Do you need an upgraded MAF? I know on T5 you need an upgrade MAP.
-Cm
Plugs were brand new and properly gapped a week before the turbo blew.
Stock t7 MAF should be fine.


New idea: see question in my post (last post of thread) here:
https://www.saablink.net/forum/perfor...htm#post914492
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Old 09-19-2012, 06:25 PM   #16
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That means they are now covered in whatever crap the Turbo dumped into the engine when it let go. Forget the Turbo letting go; this happens for a load of reasons. If you have good oil flow and your EGT's aren't too high you should be fine. Your ECU is calling for the same amount of air each time, correct? Yet it is high. MAF is possibly problem but you say it's good.
I'd say MAF or mechanical again. Do you know your boost gauge is correct? Most mechanical gauges are off--especially with high pressures.
The difficult thing here, is that we all have to shoot from the hip because you have nothing to assess the ECU and what data it's getting and what it is doing with it. In essence, you need to systematically go through all your shit and take some recommendations and apply them.You aren't going to get a clear answer because thus far there isn't one.
What plugs do you have? Maybe they're too hot for this boost range...
Go out and DO THIS: Loosen your wastegate arm by turning it such that it takes less force to hook on the wastegate flapper arm near the DP flange. Go out, with premium gas, and beat the snot out of it. Report back. You are not going to make the boost you want. Period. You will save your turbo if your mechanicals are in good shape though and that is the point of this thread. In the mean time, check everything and get JZW on the horn if he did in fact do your tune. T5 is more a reactive system than T7, so more wizardry is involved.
Good luck,
Cm
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Old 09-19-2012, 06:26 PM   #17
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Plugs were brand new and properly gapped a week before the turbo blew.
Stock t7 MAF should be fine.


New idea: see question in my post (last post of thread) here:
https://www.saablink.net/forum/perfor...htm#post914492
Maybe, but unless you messed it up all it does is crisp up response.
-Cm
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Old 09-19-2012, 06:58 PM   #18
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It's not that mod like I said. If ou did that mod right your bpv is now running off a true vac source from the manifold like every other turbo car that doesn't have rediculous ecu intervention.



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Old 09-20-2012, 12:59 PM   #19
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Talked to JZW. Looks like base boost is too high? I'm 3 hours away from the car so I gave my dad specific instructions for loosening the actuator arm a bit. Hopefully that does it. Going home this weekend to check it out and hopefully drive it back.
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