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Bouncy MAP

 
Old 06-24-2019, 08:59 PM
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Default Bouncy MAP

I've been seeing this bouncy, jumpy MAP and I can't figure it out. The only things I've tried is to check for boost leaks (none) and tighten up the preload on the wastegate spring.

Setup (see my signature), and 9lb spring. I believe what I'm seeing is the wastegate fluttering due to insufficient spring pressure. But want to see if anyone has actually seen this before.

I'm using a MAC valve which needs a boost duty of around 65%. One odd behavior is that it settles down. I don't really understand why that would be.

It jumps between 260 and 270kpa (about 26-27psi).



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Old 06-24-2019, 09:54 PM
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What is your VVT angle doing there?
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Old 06-24-2019, 10:06 PM
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I didn't log the vvt angle in that run. But in other datalogs it seems pretty stable.

The other piece of info is that this doesn't happen all the time. Seems like it would be pretty consistently bumpy, but I don't see it at lower kpa.
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Old 06-24-2019, 10:16 PM
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Might be worth a look, oil changes with both heat and age.
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Old 06-24-2019, 10:42 PM
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So you are saying that your EBC duty is a constant 65% during this?
If so, it looks kinda like a tiny boost leak that only leaks above 260 kpa.
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Old 06-25-2019, 09:47 PM
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Today I noticed that the MAC valve is heading up to 90% (max) to try and hold the gate shut at 260kpa (goal). That doesn't make sense because I should happily be able to hit 290-300kpa. So I'm going with my original thought, spring is too small.

5lb helper spring is going in tonight. This weapon simply does not like going slow.

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Old 06-27-2019, 12:39 AM
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Well that didn't work. So with a 15psi spring setup I'm still bouncing like crazy. Make me wonder, if this is just a MAP detection, should I average it out? Is it real?



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Old 06-27-2019, 12:45 AM
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see log.

BTW I did a boost leak test using my stethescope (just the tube) and couldn't find a leak anywhere near the ECU or it's incoming line.

Also, my MAP smoothing is set an 90 (nearly none). I could see just calling it measurement error and dropping that number to 50 or lower to smooth it out. But I don't know if that is the right path.
Attached Files

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Old 06-27-2019, 07:04 PM
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Stethoscope? So what you listed for a hiss in the passenger compartment, after you pumped all the charge pipes to 24.5 psi?
Looks like a boost leak, especially now that I can see your boost duty in the log image. Looks like it holds to 260kpa, see how nice and smooth the MAP line is below 260.
I had a similar issue last night, and the only thing I changed was my wastegate spring. Except that I was out of zip ties, forgot to add one before racing. I am pretty sure that my boost is escaping at the hose to the wastegate can above a certain pressure, going to fix that now.
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Old 06-27-2019, 07:16 PM
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Yes a really good way to detect tiny boost leaks very precisely is to use a stethoscope and cut heart-listening-thingy off. Just use the open hose and sniff around right up against every single possible escape point. Including all the way to the MS3 board.

I'm putting in 30psi and listening carefully for a leak. Nada.

So I tried putting in 50% MAP smoothing in tunerstudio and the ripple is gone. Which means I'm either ignoring something that is real or a bad measurement.

Is it possible that my throttle plate is quivering? Is it possible that this is a standing wave internal to intake manifold at high boost levels?
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Old 06-27-2019, 07:32 PM
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If it's possibly pulses internal to the manfold, maybe try moving the MAP hose to a different port? maybe one fairly central to the intake mani.

From memory I remember reading that measurements taken from just near the throttle can have turbulence, and ones from the back of the manifold can as well.
Of course, that something I think i remember reading from the internet...... so not exactly scientific.
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Old 06-28-2019, 07:08 PM
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Does this happen when EAE is turned off? The "bouncy" nature of EAE may simply be a result of the MAP bouncing, but they do correlate. As a point of reference, I have my EAE setup such that there is very little variation in adhere or sucked at high load.

Edit: I did in one instance see a rigid line going to the map sensor fix something similar to this.
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