Crazy boost levels

[95TSiNewbie]

I have a FWD Tsi basically stock except for:
Injen Intake with cone; Buscher UICP and TB Elbow; 1g BOV ; Denso IR Plugs and 8.5mm wires.
Im currently runnign at the stock boost level(no controller yet..) and i have a boost gauge the i installed over a month ago. At idle, its reading about 10 VAC....hard on the throttle i get anywhere from a 17-19psi boost spike and it levels off about 10-12 psi when on the throttle. To me, these reading sound a little high?? I have a dual stage MBC coming from Dejon Tool and didnt know if i should chance blowing a turbo by turing up the boost. Could i be getting false reading from my boost gauge?? Any imput would be great, thanks.

 

[nine5raptor]

1. Where did you tap the guage?

2. What does the guage read when the car is off?

 

[flinguist]

I had a similar problem when I installed a new UICP and 1G BOV. I installed a manual boost controller, and it got my boost spike under control. The boost spikes caused some detonation and wasted my spark plugs. You should get a boost controller before you end up with more problems.

 

[Keaka26]

Umm, either theres probably something wrong with your car or your boost guage is not installed properly.

Ten inches of mercury (vacuum) is NOT a good thing. Should be reading closer to 20.

 

[DeezNutsForYou]

why is it that our cars only pull 20 in/hg and not closer to 30. Because 29.9 in/hg is about 1atm.

 

[Keaka26]

Im not being a jerk, just asking:

How is 29.9 in/hg = to 1 atmosphere? 1 atmosphere is = 14.7 psi, psi is a measure of pressure. Atmosphere would be short for the term atmospheric pressure. How could vacuum even relate to a measure of pressure? Let alone 30 inHG...

Enlighten me

 

[nine5raptor]

Keaka: It is simply convention. 30 in. Hg is -14.7 psi.

Deeznuts: If you had 30 in Hg in the mani, it would be completely airtight and the motor would stop turning from the suction. Plus it is nearly impossible to pull a vaccuum that strong. You need exceptional seals.

 

[Keaka26]

Rite! ~30inHg = -14.7 psi. -14.7 is not 1 atmosphere, its -1 atmosphere.

 

[nine5raptor]

Some things get lost in translation on the net...

 

[Keaka26]

, Alritey then.

 

[DSMJim]

And to take away an atmosphere would create a black hole like in outerspace and your motor would get sucked into it. I have seen it, guys driving down the street, then all the sudden silence. They look at the boost gauge and see it way past 30 inches of vac then goes to 0 and they pull over. Poof the motor is just gone, empty engine bay.

Becareful!

 

[95TSiNewbie]

I fallowed the install on this site actually, I spliced the line right out of the Throttle body. I put teflon on all hte threads. Maybe my -T- is leaking. Maybe ill try and use a different -T- in its place.

 

[Keaka26]

Originally posted by DSMJim
And to take away an atmosphere would create a black hole like in outerspace and your motor would get sucked into it. I have seen it, guys driving down the street, then all the sudden silence. They look at the boost gauge and see it way past 30 inches of vac then goes to 0 and they pull over. Poof the motor is just gone, empty engine bay.

Becareful!

I KNEW thats what happened to my motor...I just couldnt figure it out for the life of me! Thanks man, I owe you one

 

[DeezNutsForYou]

You can NEVER have negative pressure. Here is a chart straight out of my physics book. Hope this clears things up for you.
1atm=1.013bar
1atm=14.7ib/in^2
1atm=760mm-Hg

Originally posted by Keaka26
Rite! ~30inHg = -14.7 psi. -14.7 is not 1 atmosphere, its -1 atmosphere.

 

[Keaka26]

By your #'s 29.921 inHg is equal to 1 atmosphere. How can 14.7 psi be the same thing as 29.921inHg of VACUUM?

Not being a jerk, I just want to know the answer. (Hard to tell on the internet, as we all know.)

 

[95TSiNewbie]

Not to interupt all of your fueding but i still have my question here.
Gauge reads 5 psi when car is off. When in park at idle, reads 10 vac. At full throttle i get anywhere from 16-19 psi boost, then levels off to 10-12psi. Is this right on a stock t25???

 

[nine5raptor]

Originally posted by 95TSiNewbie
Not to interupt all of your fueding but i still have my question here.
Gauge reads 5 psi when car is off. When in park at idle, reads 10 vac. At full throttle i get anywhere from 16-19 psi boost, then levels off to 10-12psi. Is this right on a stock t25???

Your guage is fu(ked. It should read 0 to 2 in hg with the car off, to take all your readings and subtract 5 psi. Your vac it around 20 in hg (where it should be). Boost is 11-14 (normal) and it drops to 5-7 (pretty low). Problem solved.

 

[nine5raptor]

Originally posted by DeezNutsForYou
You can NEVER have negative pressure.

Depends on who you are/what field you are in.

We engineer types have no respect for rules like this We just use the numbers how we want.

BTW Force (which lbs is a unit of) has a direction, so by definition (#/sq. in.) would also have a direction and therefore would be positive/negative.

 

[DeezNutsForYou]

wrong!
Pressure is the same in every direction in a fluid at a given depth, if it weren't the fluid would start to move.
Your correct FORCE, is a vector quantity, but not pressure. The force due to fluid pressure ALWAYS acts perpendicular to any surface it is in contact with.
Where did you go to school anyway

 

[nine5raptor]

Originally posted by nine5raptor

We engineer types have no respect for rules like this

Details, details... :laugh:

Im a student at the University of Missouri - KC

 

[nine5raptor]

Originally posted by DeezNutsForYou
wrong!
Pressure is the same in every direction in a fluid at a given depth, if it weren't the fluid would start to move.
Your correct FORCE, is a vector quantity, but not pressure. The force due to fluid pressure ALWAYS acts perpendicular to any surface it is in contact with.
Where did you go to school anyway

ok, I'll give you that hydrostatic pressure can't be negative, but pressure can be

Main Entry: 1pres·sure
Pronunciation: 'pre-sh&r
Function: noun
Etymology: Middle English, from Late Latin pressura, from Latin, action of pressing, pressure, from pressus, past participle of premere
1 a : the burden of physical or mental distress b : the constraint of circumstance : the weight of social or economic imposition
2 : the application of force to something by something else in direct contact with it : COMPRESSION
3 archaic : IMPRESSION, STAMP
4 a : the action of a force against an opposing force b : the force or thrust exerted over a surface divided by its area c : ELECTROMOTIVE FORCE
5 : the stress or urgency of matters demanding attention : EXIGENCY <people who work well under pressure>
6 : the force of selection that results from one or more agents and tends to reduce a population of organisms <population pressure> <predation pressure>
7 : atmospheric pressure
8 : a sensation aroused by moderate compression of a body part or surface
- pres·sure·less adjective

 

[DeezNutsForYou]

cool
I'm a student at Oregon State Univ. I'm going for ME, what's your discipline.

 

[nine5raptor]

Same. Im in my 3rd year of ME. I did a year of Biology before that and decided it wasn't for me. I should finish up next year, assuming all goes to plan. How far along are you?