Having the day off today, and doing some reading and researching I figured, why not? I ran up to the shop and prop the tool box open and started with the VGS mod. In theory it makes great sense, my old turbo cars were setup similarly. Use a post-intercooler boost signal source for the wastegate so it gets the most accurate reading to whats entering the intake manifold.

Anyways, I perform the VGS mod per instructions and popular writeups of the internet and common sense. Took our shop scan tool out and entered a live data mode to see the MAP sensor readings. I registered 41.93inHg on the map sensor at WOT and about 5500 RPM.

After doing some simple math, I came up with 41.93inHg = 20.5 psiA which is not including the subtraction of atmospheric pressure (14.7psi) to come up with a WHOPPING 5.8 psiG! Thats 5.8psi on a boost gauge! Bone stock 02 MCS, no pulley nothing! Ambient temperatures were about 46 degrees Fahrenheit. THERE ARE NO VACUUM/BOOST LEAKS AT THIS TIME! ALL LINES SECURED WITH ZIPTIES!


Does that not sound extremely low even for a stock pulley MCS? What could cause it to drop from the stock measurement of around 8-10psi?

 

some time the VGS mod does not wok for our cars, i feel its hit or miss. so air slips by the bypass valve.

also maybe your belt is slipping that's why you see low boost.

 

lol well I actually just replaced the belt the day before I did the VGS, I am gonna flip it back to stock and see what the MAP reads.

 

 

Seen too many people try the VGS and it not work. I don't recommend it. Just put it back to stock and it will run fine.

 

Update on VGS testing.

4th gear WOT pull to ~115mph, 32 degrees ambient temps, elevation is 897ft above sea level.

Scan tool readings were as follows,

IAT = 52-58 degrees during 4th gear pull to redline.
inHg = 51.09 which is what I used to convert to kPa (172.5256) = 25.02psiA minus 14.7 psi for atmospheric to calculate 10.3psiG. Yes I do not have a boost gauge in the car which would have made this a lot quicker. I wanted to use the scan tool's reading of the MAP sensor for most accurate numbers I could get.

ZERO mods on this car, 111k miles.

 

Please tell us you did this test on a track before you get pounded by the speed police. lol

 

Tested at VIR back straight on South Course

lol good lookin' out!

 

So with your results, what are your plans now?

 

Ravage the brain over the math of how an extra 1200 RPM gave me another 5psi? haha