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idling at 45 cmhg? is this bad?

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Old Mar 31, 2008 | 07:52 AM
  #1  
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idling at 45 cmhg? is this bad?

I read on http://www.fd3s.net/boost_test.html on the first line it says at idol you should be at 16-18hg

At idol my boost gauge says 45(ish) cmHG

I am not sure if b/c of the cmHG there is some type of conversion that needs to be done to get to HG, so that is why i am coming to the experts.

My turbos had a compression test done about 6000km ago and were both around 8-2-8.4ish (may be off by .1 or .2 i don't have the paper in front of me) so they are good.

SSSOOOooooo what do you guys think? is there a conversion that needs to be done to get from cmHG to HG or is that the same thing, if there is no conversion is it bad that i am at about 45 at idol?

thanks,
Craig
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Old Mar 31, 2008 | 08:27 AM
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Originally Posted by finneymc
I read on http://www.fd3s.net/boost_test.html on the first line it says at idol you should be at 16-18hg

At idol my boost gauge says 45(ish) cmHG

I am not sure if b/c of the cmHG there is some type of conversion that needs to be done to get to HG, so that is why i am coming to the experts.

My turbos had a compression test done about 6000km ago and were both around 8-2-8.4ish (may be off by .1 or .2 i don't have the paper in front of me) so they are good.

SSSOOOooooo what do you guys think? is there a conversion that needs to be done to get from cmHG to HG or is that the same thing, if there is no conversion is it bad that i am at about 45 at idol?

thanks,
Craig
Divide the 45 by 2.54 to get inHg = ~17.7 inHg, which is very good.
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Old Mar 31, 2008 | 08:30 AM
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2.54cm equals 1 inch, so 45 cm is 17.7 inches, your numbers are fine . What idle rpm was this at?

Also, do you mean that you had the compression tested on your engine? Again, those are very good numbers if they're in bar.
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Old Mar 31, 2008 | 09:39 AM
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Originally Posted by finneymc
My turbos had a compression test done about 6000km ago and were both around 8-2-8.4ish (may be off by .1 or .2 i don't have the paper in front of me) so they are good.


What does that mean?
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Old Mar 31, 2008 | 09:42 AM
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Originally Posted by zenofspeed


What does that mean?
Multiply bar x 14.5 to get psi. So 8.2 bar = 120 psi, which is very good.
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Old Mar 31, 2008 | 09:48 AM
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if you have a port isnt the idle lower?
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Old Mar 31, 2008 | 10:04 AM
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Originally Posted by Rx72Heaven
if you have a port isnt the idle lower?
Not necessarily the idle, but the vacuum may be lower at idle depending on the size of the port, relation to sea level, etc..
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Old Mar 31, 2008 | 05:52 PM
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Originally Posted by GoodfellaFD3S
2.54cm equals 1 inch, so 45 cm is 17.7 inches, your numbers are fine . What idle rpm was this at?

Also, do you mean that you had the compression tested on your engine? Again, those are very good numbers if they're in bar.
My idol is at about 750.

Thanks so much for this info guys i knew that I would get an educated answer here. I try to research this **** as much as i can before i post but sometimes with being out here in Japan i just can't find the answers to some of this stuff. And yes they were in bar (don't know what that means but i was told that )

thanks again guys, i am looking to get an american gauge very soon along with the 52mm steering colomn mount. I found that gauge mount here for like 50 bucks!

One more thing, i am about to get an aftermarket BOV, will that change my cmHG?
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Old Mar 31, 2008 | 07:57 PM
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Originally Posted by DaveW
Multiply bar x 14.5 to get psi. So 8.2 bar = 120 psi, which is very good.
I thought those compression tests are in K/cm^2 ? In that case, conversion is X 14.2

So 8.2 X 14.2 = 116 . Not a big difference, but bar is not exactly the same as K/cm^2 .
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Old Mar 31, 2008 | 08:04 PM
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cool thanks for the knowledge!!
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Old Mar 31, 2008 | 10:23 PM
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Right thats what i mean, thanks.


Originally Posted by Mahjik
Not necessarily the idle, but the vacuum may be lower at idle depending on the size of the port, relation to sea level, etc..
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