How do we measure boost?

AlanS · Post by **AlanS** » 15 Dec 2013, 08:47

So, I read about 'turbo boost'... How does one check the 'boost' on our cars? I know that some cars come equipped with a boost gauge....

eld4au6 · Post by **eld4au6** » 15 Dec 2013, 09:55

plumb in a boost gauge.

Post by **JRL** » 15 Dec 2013, 10:12

Boost is created by vacuum
A boost gauge is a simple vacuum gauge
You buy a T connection, cut and tie it into a good vacuum line then run the hose to a gauge.
(which of course you have to snake through the firewall, wire it up and of course mount it)

Post by **jimmy57** » 15 Dec 2013, 12:40

Technically boost is pressure above atmospheric and vacuum is pressure below atmospheric. You will need a gauge capable of 15 pounds of pressure and 25 inches vacuum to be safe. Gauges like this are common and sold as manifold vacuum/fuel pump tester gauges.
On a P2 turbo there is a hose connected to inboard side of intake pointed at cylinder 5 where the turbo bypass valve hose is connected. T into that hose. You will see vacuum when you let off throttle and idling and pressure when you are into throttle to accelerate moderately or more or climbing hills.
I am assuming you just want to check boost. If you desire a mounted gauge then gauge pods that go on windshield post and a lighted boost gauge are available from a few places. IPD I believe still offers these.
If boost only is desired the place where you tap into gets a bit harder. The hose to turbo control valve from turbo outlet will work but it will cause some wilder swings of gauge and is higher pressure than what actually gets to intake manifold. A connection to tube from intercooler over to throttle is most accurate boost reading but there is no easy way to get a hose connected there.
Tell us about your car (yr, engine, etc). From the forum this is posted in I only know it is a P2 but not an S80 or XC90.

Post by **matthew1** » 15 Dec 2013, 19:19

^ What Jimmy said.

Boost Gauge Install Basics

Boost Gauge Headliner Install 850/S70/V70/XC70

Those are my writeups of installing an iPD boost gauge in my '97 850. The first is the basics of tapping into the intake manifold system with a line in order to tap into the manifold pressure. This is your sampling. You can actually drive around with nothing on the end of the tube and hear it sucking or blowing air. Boost gauges are entirely mechanical -- in my case the gauge has a dimming backlight, so I run a 12v line to it.

The second will not apply to your situation, since you have a newer Volvo. But there it is in case you're interested.

686 Sport · Post by **686 Sport** » 17 Dec 2013, 21:02

How about using an OBD2 interface device? They can send data via Bluetooth, wifi, USB, etc. Anybody had success with one of these? What software shows boost?

686Sport
2004 V70 2.5t AWD, 16t, ARD Green

Post by **precopster** » 18 Dec 2013, 12:42

686 Sport wrote:How about using an OBD2 interface device? They can send data via Bluetooth, wifi, USB, etc. Anybody had success with one of these? What software shows boost?

686Sport
2004 V70 2.5t AWD, 16t, ARD Green

Great question. Torque shows boost through the vacuum guage. You can tailor a screen to show you virtually any combination of functions. The only limit is Apple incompatability.

Post by **matthew1** » 18 Dec 2013, 12:58

Anyone know which years merely calculated boost given engine RPM, load, etc.? If it's this situation, I'd opt for the mechanical gauge. I'd opt for it anyway, actually.

Post by **precopster** » 18 Dec 2013, 13:14

The boost pressure sensor on the turbo pipe leading to the ETM or ETA on later years (to 2007) directly reads boost so it's not a calculated amount from '99 to '07. Not sure about earlier years though....

Post by **jimmy57** » 18 Dec 2013, 13:27

We haven't heard again from the OP.
What he wants to do with the gauge is important.\
The car info is important too.