Vacuum at idle

e82m_van · 01-11-2016, 06:16 PM

Can anyone with a boost gauge verify the vacuum at idle for me?
Mine reads around 17.6 psi and was wondering if I have a leak.
I did a quick search and couldn't find anything.
I read someone with 135 with vacuum of 20psi....

Thanks in advance!

MightyMouseTech · 01-11-2016, 06:24 PM

Quote:

Originally Posted by e82m_van

Can anyone with a boost gauge verify the vacuum at idle for me?
Mine reads around 17.6 psi and was wondering if I have a leak.
I did a quick search and couldn't find anything.
I read someone with 135 with vacuum of 20psi....

Thanks in advance!

What engine?

e82m_van · 01-11-2016, 10:58 PM

Quote:

Originally Posted by MightyMouseTech

What engine?

N54!

Pig Farmer · 01-12-2016, 06:10 AM

I'm seeing a vaccum of ~18 psi at idle when the engine is warm (~600 RPMs).

I could be wrong, but I don't think the pressure at idle will tell you if you have a vaccum leak. The throttle body is nearly closed at idle.

e82m_van · 01-12-2016, 10:42 AM

Quote:

Originally Posted by Pig Farmer

I'm seeing a vaccum of ~18 psi at idle when the engine is warm (~600 RPMs).

I could be wrong, but I don't think the pressure at idle will tell you if you have a vaccum leak. The throttle body is nearly closed at idle.

Thank you!
You might be right, as I'm not super experienced when it comes to boost/vacuum pressure.
But for now, I'm satisfied with the fact that we have similar vacuum of around 18psi.

1swift1 · 01-12-2016, 07:57 PM

I'm using a P3 gauge in my 1M. I'm not sure how often you're supposed to calibrate it, but I did calibrate it at one point. However, today when at a cold idle, the PSI was -19.6. After warming up, the idle was -20.6 psi. I tried playing with M mode on/off (at idle), but that made no difference (I wasn't sure it would have an effect, but I figured I'd experiment).

e82m_van · 01-13-2016, 12:22 AM

Quote:

Originally Posted by 1swift1

I'm using a P3 gauge in my 1M. I'm not sure how often you're supposed to calibrate it, but I did calibrate it at one point. However, today when at a cold idle, the PSI was -19.6. After warming up, the idle was -20.6 psi. I tried playing with M mode on/off (at idle), but that made no difference (I wasn't sure it would have an effect, but I figured I'd experiment).

Thanks for checking

I'll check again in my car (with P3 gauge) soon.
Just waiting for some parts to arrive so I can put my car back together before I can start it up.

Dackelone · 01-13-2016, 01:34 AM

I saw this posted before and saved the info.

N54 335i - 17 mbar
N54T 335is - 14 mbar
N55 - 38mbar

e82m_van · 01-13-2016, 01:52 AM

Quote:

Originally Posted by Dackelone

I saw this posted before and saved the info.

N54 335i - 17 mbar
N54T 335is - 14 mbar
N55 - 38mbar

So for 1m (N54T), it should be around 20.31psi..

Thanks!

Dackelone · 01-13-2016, 02:23 AM

Quote:

Originally Posted by e82m_van

So for 1m (N54T), it should be around 20.31psi..

Thanks!

Vacuum isn't measured in psi, its measured in inches of mercury(normally).

Use an online converter for 14 mbar

http://www.anver.com/document/compan...es/vacuum.html

Dackelone · 01-13-2016, 02:48 PM

So... you got me thinking... why do you want to know the vacuum values? Do you have an issue at idle ?

Dackel

e82m_van · 01-13-2016, 03:30 PM

Quote:

Originally Posted by Dackelone

So... you got me thinking... why do you want to know the vacuum values? Do you have an issue at idle ?

Dackel

I recently got a Tial bov and charge pipe for a fairly cheap price so I decided to give it a try.
After installation, I noticed a occasional BOV flutter sound on lower gears. So before I go back to stock charge pipe and diverter valves, I decided to figure out if there is a way to fix the BOV flutter.

(I'm sure the following information is something you probably already know

)
Tial requires you to have the proper spring inside the BOV depending on your vacuum at idle as well as a direct connection to the manifold.
Before I mess around with the manifold, I decided to check the spring first.

http://www.tialsport.com/documents/w3_tial_qqr_sp.pdf

When I checked the vacuum at idle on my p3 gauge, it read around -17.6 to -17.8 (in/hg).
With this information and according to the chart provided by Tial, I require a plain spring.

So I opened up the Tial BOV to check what kind of spring I have inside, as well as give it a good clean, and I found out I do have the plain spring inside.

While I have the BOV taken apart, I also made sure the hole on the banjo for the vacuum hose at the BOV end was lined up with the hole on the inside cylinder (air bolt).

http://www.tialsport.com/documents/explodedq.pdf

This is when I lost the bolt for the V band clamp....

I'm waiting on the replacement to arrive via mail.

Also, I do have a line tapped on the vacuum line for the P3 gauge.. So maybe that is another problem?
I've also read somewhere that the vacuum hose provided by Tial is too soft.. So that could be another issue as well..

For solution, I've read people cutting down the plain spring or going down to a softer spring.. But I rather not mess around too much with it.

But for now, I can't do anything until the new bolt for the V band clamp arrives.
If all fails, I'll be returning to stock cp and diverter valves

martymil · 02-02-2016, 03:44 AM

The problem with the manifold the vacuum port is too small for the tial to work properly.

Its well documented.

You basically have to drill and tap the manifold with a bigger outlet to match the tials
input, currently the tial barb is twice the size of the manifolds outlet.

Best thing to use is turbosmart dv or stock ones on an aftermarket charge pipe.

The tial will work but its not opening fast enough as the manifold cant supply enough
vacuum to the BOV to work efficiently.

HP Autosport · 02-04-2016, 05:07 PM

While vacuum pressure can be affected by the size, the affect is very nominal in this case. If this was the case, the factory diverter valves would not work right either there are two DV that are feed by the same port. What effects the vacuum pressure is the distance vacuum has to travel. Typically don’t want to run a long hose unless you need to. By putting a T connection you increase the travel of the vacuum. The original poster has his boost gauge tapped to the manifold port. Probably has a line running to the gauge in the cabin so that could be a reason. This is why we I typically recommend not to T the DV/BOV port. The distance between the BOV and intake manifold is pretty small so even though the port on the TIAL is bigger, it does not affect the vacuum pressure it sees.

lightning · 02-04-2016, 10:20 PM

hmmm.. i'm on the tial BOV with ER charge pipe for 3 years and no issues.

as it came from ER, i have not taken it apart to clean. seems ok to me, i have travelled 130,000km so far.

martymil · 02-04-2016, 10:47 PM

They work but not quick enough especially at high hp levels

On gear changes on a automatic car they tend to over boost, we are talking fraction of a
sec, when you give it a bigger vacuum source they work really well

Just what I observed on two 400+ rwk cars

On a stock turbo car this doesn't happen as most stockers are out of puff already
at high rpm

01-11-2016, 06:16 PM	#1
e82m_van First Lieutenant 100 Rep 339 Posts Drives: AW 1m Join Date: Mar 2012 Location: Vancouver iTrader: (3)	Vacuum at idle Can anyone with a boost gauge verify the vacuum at idle for me? Mine reads around 17.6 psi and was wondering if I have a leak. I did a quick search and couldn't find anything. I read someone with 135 with vacuum of 20psi.... Thanks in advance!
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01-12-2016, 06:10 AM	#4
Pig Farmer Major 340 Rep 1,293 Posts Drives: E92M Join Date: May 2010 Location: Florida iTrader: (0)	I'm seeing a vaccum of ~18 psi at idle when the engine is warm (~600 RPMs). I could be wrong, but I don't think the pressure at idle will tell you if you have a vaccum leak. The throttle body is nearly closed at idle. Last edited by Pig Farmer; 01-12-2016 at 06:20 AM..
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01-12-2016, 07:57 PM	#6
1swift1 I pass gas for a living. 10 Rep 98 Posts Drives: 2011 VO 1M Join Date: Nov 2010 Location: Northern California iTrader: (1)	I'm using a P3 gauge in my 1M. I'm not sure how often you're supposed to calibrate it, but I did calibrate it at one point. However, today when at a cold idle, the PSI was -19.6. After warming up, the idle was -20.6 psi. I tried playing with M mode on/off (at idle), but that made no difference (I wasn't sure it would have an effect, but I figured I'd experiment). Last edited by 1swift1; 01-12-2016 at 07:57 PM.. Reason: correction
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01-13-2016, 01:34 AM	#8
Dackelone European Editor 10528 Rep 22,992 Posts Drives: N54 e82 Join Date: Feb 2010 Location: Bayern, Germany iTrader: (1)	I saw this posted before and saved the info. N54 335i - 17 mbar N54T 335is - 14 mbar N55 - 38mbar __________________ Dackel's European Delivery Museum Guide
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01-13-2016, 02:48 PM	#11
Dackelone European Editor 10528 Rep 22,992 Posts Drives: N54 e82 Join Date: Feb 2010 Location: Bayern, Germany iTrader: (1)	So... you got me thinking... why do you want to know the vacuum values? Do you have an issue at idle ? Dackel __________________ Dackel's European Delivery Museum Guide
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02-02-2016, 03:44 AM	#13
martymil Banned 389 Rep 2,186 Posts Drives: Garage is to big to list. Join Date: Jun 2013 Location: Sydney iTrader: (8)	The problem with the manifold the vacuum port is too small for the tial to work properly. Its well documented. You basically have to drill and tap the manifold with a bigger outlet to match the tials input, currently the tial barb is twice the size of the manifolds outlet. Best thing to use is turbosmart dv or stock ones on an aftermarket charge pipe. The tial will work but its not opening fast enough as the manifold cant supply enough vacuum to the BOV to work efficiently.
	Appreciate 0 Quote

02-04-2016, 05:07 PM	#14
HP Autosport Supreme Allied Commander 3815 Rep 54,307 Posts Drives: F80 M3 Join Date: Mar 2007 Location: Santa Barbara, AP, Brembo, GIAC, Koni, Ohlins, Performance Friction, www.hpautosport.com iTrader: (36)	While vacuum pressure can be affected by the size, the affect is very nominal in this case. If this was the case, the factory diverter valves would not work right either there are two DV that are feed by the same port. What effects the vacuum pressure is the distance vacuum has to travel. Typically don’t want to run a long hose unless you need to. By putting a T connection you increase the travel of the vacuum. The original poster has his boost gauge tapped to the manifold port. Probably has a line running to the gauge in the cabin so that could be a reason. This is why we I typically recommend not to T the DV/BOV port. The distance between the BOV and intake manifold is pretty small so even though the port on the TIAL is bigger, it does not affect the vacuum pressure it sees.
	Appreciate 0 Quote

02-04-2016, 10:20 PM	#15
lightning First Lieutenant 69 Rep 359 Posts Drives: 1M Pure S2 Join Date: Sep 2009 Location: Singapore iTrader: (0)	hmmm.. i'm on the tial BOV with ER charge pipe for 3 years and no issues. as it came from ER, i have not taken it apart to clean. seems ok to me, i have travelled 130,000km so far.
	Appreciate 0 Quote

02-04-2016, 10:47 PM	#16
martymil Banned 389 Rep 2,186 Posts Drives: Garage is to big to list. Join Date: Jun 2013 Location: Sydney iTrader: (8)	They work but not quick enough especially at high hp levels On gear changes on a automatic car they tend to over boost, we are talking fraction of a sec, when you give it a bigger vacuum source they work really well Just what I observed on two 400+ rwk cars On a stock turbo car this doesn't happen as most stockers are out of puff already at high rpm
	Appreciate 0 Quote