Pressure and Vacuum

[sean sherry]

Perhaps for Patrick...... thinking about fitting a Turbo Boost Gauge .....
Is Pressure and Vacuum actually the same thing in the inlet manifold ?? and or the inlet tube before the Air Flow Meter ? Instructions are to tap into the line running from the inlet intake tube, before the AFM, which runs to the Turbo to control the Waste Gate. ( Lower Vacuum delays the Waste Gate opening) Via a boost Controller in the line to the Turbo.
On our standard C Class CGI Engines, 19 PSI is the safe maximum.
Atmospheric plus about 4 PSI Boost...Hence a Gauge to keep it in the Safe Range

??????????? Sean

 

[Patrick_R]

A really good question Sean.

I’ve been contemplating how to answer.
However, there is only one way to answer your specific question.
The answer is no.

Simple explanation

Vacuum is the absence of pressure
Pressure is the absence of vacuum.

However, I really do understand what you are saying.
The force created of atmospheric pressure pushing into an inlet manifold on the intake stroke can feel like pressure for sure.

Remember
It’s atmospheric pressure pushing in, its not being sucked in.

Think of drinking out of a straw in a glass.
The drinker is simply creating a negative pressure or a vacuum within the straw.
The drink isn’t being sucked up the straw, the atmospher (14.7lb / sq inch) is working on the surface area of the drink and forcing or pushing it up the straw.

 

[sean sherry]

I new I could rely on you Patrick ..... Both labels are Air Flow. I also now understand the continuous Loop system in a Vacuum controlled Turbo Charger.
The Boost Control Valves, now on both our 2010 C Class CGI Cars have made a significant difference to the Torque and driveability of them.
Mercedes along with the others set a conservative boost levels. So a 3/4 lbs extra boos is very safe setting.

 

[Patrick_R]

Just don’t push it too far Sean.

Engines that run low boost are typically designed for low boost only, and there could be hundreds of parts and factors as to why it shouldn’t be run at a higher boost.
However I am sure there would be a good amount of buffer engineered in.

Air flow is still correct Sean, as the air that flows past, regardless of how it is produced will create a reading.

When doing experiments at work with air pressure or vacuum, I have to admit vacuum is far more dangerous, than air pressure as it can form silently and have catastrophic consequences if not monitored correctly.
It is all based on the surface area that vacuum is produced in, thus atmospheric pressure doing its job on the other side.

The biggest issues I have seen in the truck engineering world is where people use an air tank as a vacuum tank, or worse still a vacuum tank used as an air tank for storing compressed air.
Both tanks appear very solid, but are made to either contain pressure within (air tank) or resist pressure from the outside (vacuum tank), and use them for the opposite reason they were designed for, look out!

 

[sean sherry]

The Australian GFB Boost Controllers ( reputed to be the best quality) are marketed by "Tornado Tuning".... a major supplier of tuning equipment. They have run a GFB controller on their own C 250 for 18 months with no issues. Set at 2 turns out (set from fully in( giving a Max. Boost of 19 psi. I am running both our C Class Cars set at one and a Half turns out just to be sure. They seem to perform just as well as when I tried 2 turns out on the settings. Tomorrow I will fit a Boost Gauge to check both Cars... c200 & c250 both 2010 low k Models ..... W204.

 

[Patrick_R]

Looking forward to the results Sean.

 

[sean sherry]

Boost Gauge fitted and tried on both the C 250 and the C200.. Max reading is 10 PSI both Cars... I can't achieve the 19 Psi achieved on the USA C250
They have emission testing .. we don't. I have double checked everything. The Gauge tests ok. With the Boost Controller turned right down I don't get any Boost Reading at all. So maybe my 10 PSI reading is ok.... the Cars drive well.
I have contacted the suppliers and am waiting for a reply.

 

[Patrick_R]

Keep a record of fuel economy Sean, and please update us to the results.

 

[sean sherry]

I notice that the Engine is running about 3% hotter on the open Road maybe 87/88 % More heat .. more pressure in the combustion Chamber to push the Pistons down. the Fuel consumption is down from around 8.5 to 7.7 Lp100 Ks.
So I guess it is producing more Power ..
Just a light touch on the throttle is all that is now needed.