Negative Boost

Meggsy · 11-02-2008, 00:41

I have just fitted a boost gauge for the first time and I just wanted to check that when I am driving at low revs (Out of the turbo) the gauge should be reading negative?

When the car is in the Turbo the boost pressure is positive as expected. (Will have a look and see what sort of boost it is hitting tomorrow!!)

fatty5000 · 11-02-2008, 00:47

In a nutshell ................Yes

If you have a re-map you should be around 15psi plus, then dropping back iirc

Babs · 11-02-2008, 00:52

No boost should be showing as 0 surely? Negative is a vacuum?

fatty5000 · 11-02-2008, 00:58

Zero is atmospheric pressure anything above is boost or something like that................. I can't remember right now to be honest. Some one how knows will be along to explain I'm sure

RobClubley · 11-02-2008, 01:16

It should defintely be showing vacuum (negative) when idling or off boost. But I don't know why!

fatty5000 · 11-02-2008, 01:18

Rob we've been here long enough to know why really. Should we be ashamed of ourselves............You especially

TKW · 11-02-2008, 05:12

Quote:

Originally Posted by RobClubley

It should defintely be showing vacuum (negative) when idling or off boost. But I don't know why!

Think about what happens when you increase the volume of the air intake system by filling a cylinder with air but have the throttle valve partially closed.

RobClubley · 11-02-2008, 05:43

Quote:

Originally Posted by fatty5000

Rob we've been here long enough to know why really. Should we be ashamed of ourselves............You especially

True!

mattbeef · 11-02-2008, 10:49

Rob cant be held responsible for not knowing why as he has the big responsibility for hosting the picture that has shown every one where to plumb in the T piece

KenONeill · 11-02-2008, 13:35

You're all correct; off-turbo, a 2-way boost gauge will read below atmospheric pressure (negative). This is because the air is flowing through a pipe, and when this happens, its pressure does drop as a result. If you want a better expn, run a web search for "gas dynamics".

auroan · 11-02-2008, 14:03

Manifold vacuum - Wikipedia, the free encyclopedia

fatty5000 · 11-02-2008, 14:43

Quote:

Originally Posted by KenONeill

You're all correct; off-turbo, a 2-way boost gauge will read below atmospheric pressure (negative). This is because the air is flowing through a pipe, and when this happens, its pressure does drop as a result. If you want a better expn, run a web search for "gas dynamics".

Had a Google............I think I'll leave that to you Ken

Quote:

Originally Posted by auroan

Manifold vacuum - Wikipedia, the free encyclopedia

Which led me to this,Turbocharger - Wikipedia, the free encyclopedia Which I find easier to understand

KenONeill · 11-02-2008, 14:52

Knowing that it happens, and that the deeper the depression, the higher the throttle setting (off turbo on naturally aspirated cars only) is about all you need for practical purposes.

fatty5000 · 11-02-2008, 14:56

Quote:

Originally Posted by KenONeill

Knowing that it happens, and that the deeper the depression, the higher the throttle setting (off turbo on naturally aspirated cars only) is about all you need for practical purposes.

I love it when you get all technical Ken...............Cheers mate

Even though sometimes I have no idea what your on about

Meggsy · 11-02-2008, 18:47

Just taken her out for a blast and I am seeing between 0.6 - 0.7bar of boost pressure...... Is this about right for an un-mapped car?

Also a big thanks to all of you for the info to allow me to fit it! (Especially Robs pictures!!)

RobClubley · 11-02-2008, 20:32

Quote:

Originally Posted by mattbeef

Rob cant be held responsible for not knowing why as he has the big responsibility for hosting the picture that has shown every one where to plumb in the T piece

Meggsy · 11-02-2008, 21:10

Also getting chatter from the Boost gauge !? Is this normal ? Can I get rid of it?

auroan · 11-02-2008, 21:31

yup, you'll need a little filter to smooth the airflow on the pipe work connecting the boost gauge

Meggsy · 11-02-2008, 21:43

Like a fuel filter?

auroan · 11-02-2008, 22:01

yeah, but a very small one. The other way is to use a small screw clamp to squash the gauge pipework a little.

fatty5000 · 11-02-2008, 22:03

Automotive Dials Gauges pods t-piece

Click on T piece resrictor

Steevie Wonder · 12-02-2008, 15:51

Quote:

Originally Posted by Meggsy

Just taken her out for a blast and I am seeing between 0.6 - 0.7bar of boost pressure...... Is this about right for an un-mapped car?

Also a big thanks to all of you for the info to allow me to fit it! (Especially Robs pictures!!)

Yes this is correct for an un-mapped car (roughly 8-9 psi).
As for negative boost, mine used to be around 1 bar or -15psi when running the standard turbo on tickover/off boost.

Hope this helps.

Steve

richm · 12-02-2008, 22:50

Quote:

Originally Posted by Meggsy

Also getting chatter from the Boost gauge !? Is this normal ? Can I get rid of it?

You need to make a restriction in the pipe feeding the gauge, the further down the pipe away from the gauge the better. You only need a 0.5mm hole or so.

11-02-2008, 00:41	#1
Meggsy Briskodian Join Date: Jun 2007 Location: Derby / Exeter Posts: 147 Thanks: 15 Thanked 3 Times in 3 Posts	Negative Boost I have just fitted a boost gauge for the first time and I just wanted to check that when I am driving at low revs (Out of the turbo) the gauge should be reading negative? When the car is in the Turbo the boost pressure is positive as expected. (Will have a look and see what sort of boost it is hitting tomorrow!!) __________________ 2003 Black Magic Octy VRS Current Mods - Milltek Exhaust, Forge Recirculating DV, Pipercross panel filter, Fast rd Pads and Discs, Coilover kit, Front mounted intercooler, 18" Alloys, Forge TIP, a few stickers and plenty of ICE Planned Mods - Highflow Cat, Custom Re-map

11-02-2008, 00:47	#2
fatty5000 Why So Serious Join Date: Jan 2006 Location: "What" ...What ain't no god damn country Posts: 5,529 Thanks: 271 Thanked 199 Times in 180 Posts	Re: Negative Boost In a nutshell ................Yes If you have a re-map you should be around 15psi plus, then dropping back iirc __________________

11-02-2008, 00:52	#3
Babs Briskodian Join Date: Jul 2006 Location: Newport/Preston Posts: 4,163 Thanks: 215 Thanked 138 Times in 122 Posts	Re: Negative Boost No boost should be showing as 0 surely? Negative is a vacuum? __________________ - Andrew Octavia vRS For Sale / Bosch Rotary Polisher For Sale

11-02-2008, 00:58	#4
fatty5000 Why So Serious Join Date: Jan 2006 Location: "What" ...What ain't no god damn country Posts: 5,529 Thanks: 271 Thanked 199 Times in 180 Posts	Re: Negative Boost Zero is atmospheric pressure anything above is boost or something like that................. I can't remember right now to be honest. Some one how knows will be along to explain I'm sure __________________

11-02-2008, 01:16	#5
RobClubley Ta moko! Join Date: Jun 2004 Location: Aotearoa - land of the long white cloud Posts: 6,904 Thanks: 149 Thanked 155 Times in 129 Posts	Re: Negative Boost It should defintely be showing vacuum (negative) when idling or off boost. But I don't know why! __________________ Corrida Red 2004 Octavia vRS Estate - It's the bestest Skoda in New Zealand! Whaia te mātauranga, whaia te māramatanga - Pursue knowledge, pursue the wisdom of knowledge www.pimpmyskoda.co.uk www.clubley.org Facebook

11-02-2008, 01:18	#6
fatty5000 Why So Serious Join Date: Jan 2006 Location: "What" ...What ain't no god damn country Posts: 5,529 Thanks: 271 Thanked 199 Times in 180 Posts	Re: Negative Boost Rob we've been here long enough to know why really. Should we be ashamed of ourselves............You especially __________________

11-02-2008, 10:49	#9
mattbeef Briskodian Join Date: Apr 2006 Location: Sheffield Posts: 3,368 Thanks: 36 Thanked 116 Times in 115 Posts	Re: Negative Boost Rob cant be held responsible for not knowing why as he has the big responsibility for hosting the picture that has shown every one where to plumb in the T piece __________________ I few bits here and there but im happy to Performance Torque Go on click me you know you want to

11-02-2008, 13:35	#10
KenONeill Briskodian Join Date: May 2006 Location: Normally somewhere in Scotland! Posts: 11,043 Thanks: 63 Thanked 548 Times in 536 Posts	Re: Negative Boost You're all correct; off-turbo, a 2-way boost gauge will read below atmospheric pressure (negative). This is because the air is flowing through a pipe, and when this happens, its pressure does drop as a result. If you want a better expn, run a web search for "gas dynamics".

11-02-2008, 14:03	#11
auroan Why me ? Join Date: Oct 2005 Location: North Yorkshire Posts: 2,840 Thanks: 205 Thanked 108 Times in 95 Posts	Re: Negative Boost Manifold vacuum - Wikipedia, the free encyclopedia __________________ '05 Audi A4 2.0 Tdi SE - no mods until the warrenty expires '00 Audi A4 2.8 Quattro - Gone.... (bleeding money pit ) Audi A4 2.6 Avant (Breaking - Check out http://shop.ebay.co.uk/merchant/auroan)

11-02-2008, 14:52	#13
KenONeill Briskodian Join Date: May 2006 Location: Normally somewhere in Scotland! Posts: 11,043 Thanks: 63 Thanked 548 Times in 536 Posts	Re: Negative Boost Knowing that it happens, and that the deeper the depression, the higher the throttle setting (off turbo on naturally aspirated cars only) is about all you need for practical purposes.

11-02-2008, 18:47	#15
Meggsy Briskodian Join Date: Jun 2007 Location: Derby / Exeter Posts: 147 Thanks: 15 Thanked 3 Times in 3 Posts	Re: Negative Boost Just taken her out for a blast and I am seeing between 0.6 - 0.7bar of boost pressure...... Is this about right for an un-mapped car? Also a big thanks to all of you for the info to allow me to fit it! (Especially Robs pictures!!) __________________ 2003 Black Magic Octy VRS Current Mods - Milltek Exhaust, Forge Recirculating DV, Pipercross panel filter, Fast rd Pads and Discs, Coilover kit, Front mounted intercooler, 18" Alloys, Forge TIP, a few stickers and plenty of ICE Planned Mods - Highflow Cat, Custom Re-map

11-02-2008, 21:10	#17
Meggsy Briskodian Join Date: Jun 2007 Location: Derby / Exeter Posts: 147 Thanks: 15 Thanked 3 Times in 3 Posts	Re: Negative Boost Also getting chatter from the Boost gauge !? Is this normal ? Can I get rid of it? __________________ 2003 Black Magic Octy VRS Current Mods - Milltek Exhaust, Forge Recirculating DV, Pipercross panel filter, Fast rd Pads and Discs, Coilover kit, Front mounted intercooler, 18" Alloys, Forge TIP, a few stickers and plenty of ICE Planned Mods - Highflow Cat, Custom Re-map

11-02-2008, 21:31	#18
auroan Why me ? Join Date: Oct 2005 Location: North Yorkshire Posts: 2,840 Thanks: 205 Thanked 108 Times in 95 Posts	Re: Negative Boost yup, you'll need a little filter to smooth the airflow on the pipe work connecting the boost gauge __________________ '05 Audi A4 2.0 Tdi SE - no mods until the warrenty expires '00 Audi A4 2.8 Quattro - Gone.... (bleeding money pit ) Audi A4 2.6 Avant (Breaking - Check out http://shop.ebay.co.uk/merchant/auroan)

11-02-2008, 21:43	#19
Meggsy Briskodian Join Date: Jun 2007 Location: Derby / Exeter Posts: 147 Thanks: 15 Thanked 3 Times in 3 Posts	Re: Negative Boost Like a fuel filter? __________________ 2003 Black Magic Octy VRS Current Mods - Milltek Exhaust, Forge Recirculating DV, Pipercross panel filter, Fast rd Pads and Discs, Coilover kit, Front mounted intercooler, 18" Alloys, Forge TIP, a few stickers and plenty of ICE Planned Mods - Highflow Cat, Custom Re-map

11-02-2008, 22:01	#20
auroan Why me ? Join Date: Oct 2005 Location: North Yorkshire Posts: 2,840 Thanks: 205 Thanked 108 Times in 95 Posts	Re: Negative Boost yeah, but a very small one. The other way is to use a small screw clamp to squash the gauge pipework a little. __________________ '05 Audi A4 2.0 Tdi SE - no mods until the warrenty expires '00 Audi A4 2.8 Quattro - Gone.... (bleeding money pit ) Audi A4 2.6 Avant (Breaking - Check out http://shop.ebay.co.uk/merchant/auroan)

11-02-2008, 22:03	#21
fatty5000 Why So Serious Join Date: Jan 2006 Location: "What" ...What ain't no god damn country Posts: 5,529 Thanks: 271 Thanked 199 Times in 180 Posts	Re: Negative Boost Automotive Dials Gauges pods t-piece Click on T piece resrictor __________________

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