Bar to PSI conversion
10-24-2005, 03:06 AM
#1
Rennlist Member
Thread Starter
Join Date: Oct 2005
Location: Up High in the Colorado Rockies
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
Bar to PSI conversion
OK, I’ll admit it. I’m a newbie at this turbo stuff so please bear with me.
The conversion info I got is 1 bar = 14.5 psi.
The factory manual reads: “maximum boost pressure of 1.75 bar (absolute value) is reached at approx. 3k rpm…” It also states that the “charging pressure indicator in the vehicle tachometer shows charging pressure in bar absolute pressure”
So does that mean that when the boost gauge reads approx 1.75 bar it is actually indicating around 25 pounds of boost???
Even to a non-cognoscenti such as myself that seems like a heck of a lot of boost.
Will someone please explain where I’m going wrong.
Thanks
The conversion info I got is 1 bar = 14.5 psi.
The factory manual reads: “maximum boost pressure of 1.75 bar (absolute value) is reached at approx. 3k rpm…” It also states that the “charging pressure indicator in the vehicle tachometer shows charging pressure in bar absolute pressure”
So does that mean that when the boost gauge reads approx 1.75 bar it is actually indicating around 25 pounds of boost???
Even to a non-cognoscenti such as myself that seems like a heck of a lot of boost.
Will someone please explain where I’m going wrong.
Thanks
10-24-2005, 03:32 AM
#2
Nope! The factory gauge reads vacuum, then boost. So at 1bar you are at atmospheric.
Get the right gas and tuning and you could run 25psi, just as Special Tool
Where abouts in CO are you?
Get the right gas and tuning and you could run 25psi, just as Special Tool
Where abouts in CO are you?
10-24-2005, 03:37 AM
#3
Rennlist Member
Thread Starter
Join Date: Oct 2005
Location: Up High in the Colorado Rockies
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
So then: at 3k rpms = .75 bar = 10.875 psi
Meaning that up to 1 bar is vacuum, 1 bar is atmos. and past 1 bar there is boost pressure?.
Leadville, very little atmos up here.
Meaning that up to 1 bar is vacuum, 1 bar is atmos. and past 1 bar there is boost pressure?.
Leadville, very little atmos up here.
10-24-2005, 03:57 AM
#5
Banned
Join Date: Feb 2004
Location: In self-imposed exile.
Posts: 14,072
Likes: 0
Received 8 Likes
on
7 Posts
Your conversion factor is correct but the pressure you're referring to is total, not in excess of atmospheric. The factory spec. for boost level is 1.75 bar +/- 0.05. You need to subtract atmospheric pressure from the 1.75 bar to obtain the boost level - this varies by area, elevation and temperature.
10-24-2005, 04:01 AM
#6
Race Car
Join Date: May 2005
Location: Being censored by a Moderator
Posts: 4,074
Likes: 0
Received 1 Like
on
1 Post
2 bar boost
so what boost is being ran @ 2 bar? I bought my car from someone who did a lot of in house mods, and the turbo is putting down 2 bar with stock turbo, stock exhaust, minor head work, air box removed and replaced with k&n type filter (like I said...in house i.e. garage mods) and a chip set ( unknow chips - just replaced with Lindsey but switching to Vitesse as soon as I get feedback about how the lindsey chips run). So at 2 bar what boost was I running?
10-24-2005, 04:09 AM
#7
Banned
Join Date: Feb 2004
Location: In self-imposed exile.
Posts: 14,072
Likes: 0
Received 8 Likes
on
7 Posts
At 2 bar you're running 14.5 x 2 = 29 psi minus whatever atmospheric pressure is in your area at that time (usually about one bar), so assuming a "perfect" situation where atmospheric pressure is 14.7 psi you'd be running 29 - 14.7 or 14.3 psi of boostage.
Trending Topics
10-24-2005, 04:11 AM
#8
Rennlist Member
Thread Starter
Join Date: Oct 2005
Location: Up High in the Colorado Rockies
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
Well I'm going out on a limb here since I'm still trying to understant all this (others please correct me) but I would have to say 2 bar = 14.5 psi?(absolute pressure, what a gauge would read?)(at sea level?)
10-24-2005, 06:49 PM
#11
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
So lemme see if i'm getting this. TheoreticallySpecial tools 25 psi is actually about 10 psi above atmosphere? or am I getting this wrong? I HATE math
10-24-2005, 06:59 PM
#12
Rennlist Member
Thread Starter
Join Date: Oct 2005
Location: Up High in the Colorado Rockies
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
Well the way I'm understanding it 
, yes. 14.7psi of what the gauge reads is atmospheric pressure (at sea level) the rest is boost. So I'm guessing that is why you get lower psi rattings when doing a compression test at 5K feet as opposed to doing it at sea level. Corrections pleaaaaaze????
, yes. 14.7psi of what the gauge reads is atmospheric pressure (at sea level) the rest is boost. So I'm guessing that is why you get lower psi rattings when doing a compression test at 5K feet as opposed to doing it at sea level. Corrections pleaaaaaze????
10-24-2005, 07:47 PM
#15
Rennlist Member
Thread Starter
Join Date: Oct 2005
Location: Up High in the Colorado Rockies
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
Aaaaarg Ok then, so if you have an aftermarket boost gauge installed on your car and its reading 25psi it is basically ignoring the atmospheric pressure? It is just meassuring additional pressure above atmos???
Ok then, so if you have an aftermarket boost gauge installed on your car and its reading 25psi it is basically ignoring the atmospheric pressure? It is just meassuring additional pressure above atmos???