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Discussion Starter #1
So I installed my boost gauge last night.
It's a liquid mechanical autometer vacuum boost, -25 to 30 psi.

I spliced it to the smaller hose leading to the BOV.

During idle the gauge reads -20.
while normal driving the gauge reads 0.

EDIT: it's actually -15 or so while cruising and 0 while giving normal amount of gas.

With the stock BOV:
When I PUNCH IT @ 4-5k rpms the gauge briefly reads 12-13, then drops down to 10.

With GReddy Type-RS BOV set recirc:
When I PUNCH IT @ 4-5k rpms the gauge briefly reads 13-14, then drops down to 11-12.

Whats the deal?

Thanks!
 

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not sure man, i would say just double check your connections again. I accidently plugged into the wrong tube when i first did it. but now im reading about -20 when idle..then 15 psi when im on it and spikes up to 17-18.
 

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Discussion Starter #4
not sure man, i would say just double check your connections again. I accidently plugged into the wrong tube when i first did it. but now im reading about -20 when idle..then 15 psi when im on it and spikes up to 17-18.
[/b]
So the vacuum pressure is normal.

I wonder if my BOV spring needs to be tighter?

I dont think its the wrong line, does anyone know if I plugged it into a bad spot?
 

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Just some info. With the boost gauge if you drive it normally without any heavy foot movement, there won't be much boost pressure above the "0" reading on the boostgauge. However if you WOT or anywhere near it or really give it in a incline, it should spike it to atleast 15PSI or past this point and settle on something around 13-15PSI especially in 3rd gear onward. If not your gauge isn't reading probably.
 

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Discussion Starter #6
Just some info. With the boost gauge if you drive it normally without any heavy foot movement, there won't be much boost pressure above the "0" reading on the boostgauge. However if you WOT or anywhere near it or really give it in a incline, it should spike it to atleast 15PSI or past this point and settle on something around 13-15PSI especially in 3rd gear onward. If not your gauge isn't reading probably.
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Yeah, my tests were in 3rd gear. It's basically behaving just like you described except 1-2 psi lower.

I dont want to be loosing boost!
 

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is your boost line before or after the intercooler?
 

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I'm not sure of the order, but its just before the BOV.
[/b]
That would be after the IC. That is the same place mine is. I get the usual readings of 15-15.5 lbs of steady boost, and the usual spikes.


I'd just double check the connections and make sure there are no leaks.
 

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No that all sounds right. I have the flash and I hit 15 or so psi and it settles down to anywhere from 10-12 psi depending on the RPM.
 

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What is the elevation where you live? You may have a leak somewhere also. Idle should be around 21-22 mmHG.
 

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I'm not sure of the order, but its just before the BOV. [/b]
If it is after the IC your going to see a pressure drop, so I would not be shocked to see it settling a little lower than advertised boost.
 

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Discussion Starter #13
No that all sounds right. I have the flash and I hit 15 or so psi and it settles down to anywhere from 10-12 psi depending on the RPM.
[/b]
Reflash is not going to drop 3psi.

If it is after the IC your going to see a pressure drop, so I would not be shocked to see it settling a little lower than advertised boost.
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So if psi = 15 before IC and psi = 13 after IC. Wouldnt the actual boost pressure be 13?
I mean, its the pressure after the IC that we actually use for combustion.

So 15psi is really a lie?

Here's the boost reading from my car when I had it dyno'd at EIPRacing before I changed the BOV or installed the boost gauge.

You can see from the graph, it peaks at 16 and then levels off about 15 then 14. But thats not what I'm getting now. So either my boost gauge is reading incorrectly or I have a leak. :(
 

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The boost pressure is measured as it exits the turbo typically. This is primarily so that the wastegate can work quickly and efficiently at controlling things. I guess that thing to do would be tap into a vac line nearest the factory pressure sensor and see what you get. Have you zeroed your guage or checked its reading with an open vac line?

It is entierly possible you have a leak, I dont want you to think I am stating other wise, I was just looking at other possible causes.
 

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Reflash is not going to drop 3psi.[/b]
How do you figure? I would maintain higher boost longer before the flash, then after the flash I average 10-12psi. I have a dyno that show's the loss in power after the reflash, and it's due to less boost.
 

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I have the reflash and a boost gauge. Most of the time it is 15-16 PSI wot. Some occasions, it stays down at 14 when cold.
 

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Discussion Starter #19
Well, I guess if its a leak thats good news. The leak is most likely caused by me so it should be easy to fix.

Any chance its just the BOV not being tight enough?

I zip-tied every non-clamped place I could find (fresh out of clamps), there were a few that looked suspicious. I also tightened my BOV spring a bit more just to see. If I start to see the pressure drop too slowly after letting off the gas I'll just loosen the BOV spring a bit. So tomorrow morning If theres not too much traffic I can try it out.
 

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Umm, so you're driving normally and then punching it at 4-5K RPM's? These cars stock will taper off the boost at higher RPM's so if you're just getting to punching it at 4-5, the stock ecu program is already getting winded.

Vacuum at about -20 is right (DEPENDING ON ALTITUDE!!!!!), maybe a little off because you should be dang near sea level. Here in Vegas (a bit over 2000 feet), mine sits about -19 to -20. When I went to the Grand Canyon 6000-7000'ish feet, it dropped to only about -15 at idle.

What is your spike at boost threshold and what does it settle in at? Mine spikes to 17-18 and settles in at 15 until it tapers off past about 4K.
 
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