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Author Topic: N75 leaking during pressure test  (Read 336 times)
KasperH
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« on: August 17, 2017, 09:41:33 AM »

I noticed something strange while pressure testing.
N75 was leaking into the TIP.
But only if I exceeded 1 bar, everything below that,
and it can hold pressure all day.
But when I exceed 1 bar it would begin to leak,
and leak all the way down until the system was empty.

Tried with 3 different N75 valves and all exert the same "failure"  Undecided

I think it is bleeding more air than the duty cycle is telling me?
And would cause unpredictable boost control.

Is this a feature of the valve or am I just unlucky
and have 3 faulty valves that failed the exact same way?
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KasperH
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« Reply #1 on: August 20, 2017, 05:14:53 AM »

Can't really find anything useful on this problem.
All I found was some technical documentation from pierburg.
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nyet
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« Reply #2 on: August 20, 2017, 11:12:20 AM »

N75 should be able to hold just fine. You sure you have it oriented right?
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KasperH
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« Reply #3 on: August 20, 2017, 12:29:02 PM »

Yes.
Long leg->TIP
Bottom leg->charge pipe
Short leg on side->wastegate

The N75 operates fine.

But maybe this is just a thing it does when static? (As in "spring pressure" in N75 is 1 bar)
as it would begin venting when request is higher than spring pressure and/or during spool up.
The wastegate would actually never see 1 bar, because it would be vented in the N75.
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nyet
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« Reply #4 on: August 20, 2017, 12:33:05 PM »

yea. wgs don't need 1 bar to crack. As long as the n75 is holding enough pressure to open the WG when needed it shouldn't matter. Under boost the N75 should be dumping pressure away from the WG anyway.
« Last Edit: August 20, 2017, 01:13:11 PM by nyet » Logged

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KasperH
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« Reply #5 on: August 20, 2017, 12:54:04 PM »

So this is just me chasing a solution to a problem I created myself(that really isn't a problem)

Apparently Cheesy

Edit: but I can see this could be a potential problem if someone is using a wastegate
with 1 bar spring pressure or greater.
That could result In some interesting overboost, or boost control issues?
« Last Edit: August 20, 2017, 12:59:04 PM by KasperH » Logged
nyet
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« Reply #6 on: August 20, 2017, 01:09:19 PM »

So this is just me chasing a solution to a problem I created myself(that really isn't a problem)

Apparently Cheesy

Edit: but I can see this could be a potential problem if someone is using a wastegate
with 1 bar spring pressure or greater.
That could result In some interesting overboost, or boost control issues?

IMO any waste gate system that needs 1 bar over ambient to crack the wgs is probably going to be uncontrollable.

Dual port wgs are generally used if you need a very strong wastegate holding pressure
« Last Edit: August 20, 2017, 01:29:04 PM by nyet » Logged

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KasperH
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« Reply #7 on: August 20, 2017, 01:19:10 PM »

IMO any waste gate system that needs 1 bar over ambient to crack the wgs is probably going to be uncontrollable.

Dual port wgs are generally used if you need a very strong wastegate spring.

True, but I have seen people mention running 1 bar springs a couple of times.
Maybe they just run it straight to pressure and delete the N75 completely?
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nyet
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« Reply #8 on: August 20, 2017, 01:28:04 PM »

True, but I have seen people mention running 1 bar springs a couple of times.
Maybe they just run it straight to pressure and delete the N75 completely?


Dunno. No experience in the matter.

[edit]: BTW I corrected an earlier post: dual port wastegates if you need more holding pressure *without* using a stronger spring.
« Last Edit: August 20, 2017, 01:31:26 PM by nyet » Logged

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nyet
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« Reply #9 on: August 20, 2017, 01:32:27 PM »

BTW did you try pressurizing an n75 all by itself? I would not surprise me if it couldn't hold more than 1bar
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Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
KasperH
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« Reply #10 on: August 20, 2017, 02:52:43 PM »

BTW did you try pressurizing an n75 all by itself? I would not surprise me if it couldn't hold more than 1bar

Nope, just turned the red silicone hose up and plugged in the pressure tester(PVC pipe end with tire valve)
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