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06-18-2014, 09:35 AM | #5 |
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The throttle opening back up makes sense after the injectors stop spraying fuel in a 0% accelerator situation. It will reduce lag the next time you press the accelerator down as it allows the turbo to keep spinning with less resistance.
Not sure I'd consider it a problem. The stock diverter valves were certainly designed with this in mind, so if your HKS setup has symptoms perhaps it's not the best DV/BOV solution.
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06-18-2014, 10:19 AM | #6 |
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My guess would be there is a possible vacuum leak. Maybe a line leading to one of your wastegates. What spring are you running in your bov?
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06-18-2014, 08:06 PM | #7 | ||
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My theories: -The car will hold 5 PSI every time I let off at HI LOAD/HI RPM...its always 5 PSI, Sometimes it reminds me of a NO LIFT SHIFT setup....Initially it'll blow off anything over 5psi, when it hits 5psi, the throttle body opens for what seems like a preset time frame(in milli second I guess) causing the BOV to seal for fractions of a second, and then blow off everything....Maybe BMW internationally coded this so that when you engage the next gear (6mt) the system is already in positive pressure, instead of having to start from vacum, yielding faster boost buildup. -Some type of PCV gass recirculation technique by BMW...which doesn't really make sense given the symptoms. The HKS bov is replicating exactly what the stock BOV's did down to the milli second...I am 100% sure it is not the HKS bov or it's current calibration...BTW I am using the stock 11psi springs, I get no fluttering, and the valve does not open during idle...the calibration is perfect. Ive read a lot of members on here have this "hi load/hi RPM double blow off" using all types off diff BOV...its the ECU trying to control boost pressure during overrun.. To me it's a huge issue, almost a make it or break it type issue Has anyone tried fixing this thru a cobb tune? iirc, cobb gives you access to absolutely all ECU reference tables ? |
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06-18-2014, 09:03 PM | #9 | ||||
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The accelerator pedal in this car is not so much controlling the throttle plate as it is defining a target load. Then the ECU decides how to get the load through changing the throttle plate angle and wastegate control, and at least to some extent even timing.
The idea that your foot controls the throttle plate has been broken for years as just about every modern car has an electronic throttle. Even in naturally aspirated cars there is a fair amount of decoupling. Quote:
Your statement is like saying VANOS's purpose is to manipulate oil flow rate through the oil filter. While they are attached functionally, your line-drawing between the two is nonsensical. Quote:
Particularly for turbocharged cars, keeping the throttle closed when you are coasting in gear is just wasting energy, both from a performance and fuel economy perspective. Quote:
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Last edited by Freon; 06-18-2014 at 09:28 PM.. |
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06-18-2014, 11:22 PM | #11 |
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Drives: 90' s54 325i ; 93' carrera 2
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I had a similar affect - was a failed DME. No mean to get paranoid, but just letting you know.
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06-22-2014, 10:07 PM | #12 | |||||||
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I am here because the DME is internationally creating a 5PSI spike letting off at HI LOAD/HI RPM...and I am concerned that the turbo's are surging during this event, it also introduces a bunch of drivability problems that i'm not even gonna get to.... huge drivability issue for me. Quote:
With that said, The DME has very smart logic, I am sure that the DME knows there are mechanical pressure relief valves in place, and knows that it does not have DIRECT control over them...and I'm sure that it is written in its logic that if it needed to control the pressure relief valve for whatever reason, it would by manipulating intake manifold pressure using throttle body angle...its literally the only tie the DME has to the mechanical pressure relief valve...right or wrong?...according to you, that's actually exactly what the DME is doing right? spiking the throttle body open after letting off the accelerator so that the pressure relief valve seals and holds 5 PSI between gear changes?...I understand, I just need to get rid of this for the sake of drivability Quote:
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06-22-2014, 10:11 PM | #13 |
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Could be, but, would that explain the spike in throttle body angle after letting off the accelerator?...I think the spike in throttle body angle is exactly what's causing the car to hold 5psi between gear changes...I think Freon is right about it being being a built in feature of the DME...with stock software anyway...
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06-22-2014, 10:13 PM | #14 |
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06-22-2014, 10:14 PM | #15 |
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I think bmw released a software update for these cars as a recall a while after they first came out....could this be a feature that was added in the update? to reduce lag between shifts?
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06-23-2014, 01:45 PM | #16 |
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I believe this is to "pre boost" during the shift. Logic dictates if you go that high in a gear you want to move fast. So throttle close to give you some boost so next shift don't have lag, at least less. I was confused by this when I put my bov. After some logs and thinking, made sense. So I timed the throttle closure and shifted before opens again and got a nice pull.
Besides, bovs are to release surges and prevent turbo back spin. When the throttle opens and the bov closes. The air flow goes in to the engine, so won't harm the engine. |
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06-23-2014, 07:30 PM | #17 | ||
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Further, there's nothing happening with the throttle that you couldn't reproduce with your right foot. If the car is surging when the throttle blips (which it should not and is not), then the BPV system is the problem (valve design/flow insufficient, valve sticking, valve preload too high, lines too big, lines clogged, lines collapsing), not the throttle behavior. It doesn't make sense to point the finger at the ETC behavior as the problem causing your BPV to not work. It's not a line of reasoning that adds up. And again, you're not surging. Quote:
Your statement with regards being "sure" the DME "knows" about the BPV would make sense if there was a BPV position sensor, but there isn't. You are unnecessarily fixated on the BPV behavior as some sort of goal criteria for the throttle behavior. The BPV is just there to open when the throttle is not so the turbo doesn't get damaged, and that's a simple pneumatic connection. I think you need to start back on step #1 and explain your problem. Now you're pushing it as a drivability issue, so perhaps add more details on that. There's no surge, so let's move on to the symptom that really matters.
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