-7 psi at idle? - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 11-08-2008, 05:02 AM   #1
Registered Member
 
Join Date: Jun 2007
Posts: 146
Country: United States
Send a message via AIM to GasSavers_Dust
-7 psi at idle?

I just got my boost vac gauge installed in the car, and I noticed that I was getting -7 psi for idle. That is about 14.25 inches of mercury, and I was wondering if this was normal, of if I need to be checking for leaks.
__________________

GasSavers_Dust is offline   Reply With Quote
Old 11-08-2008, 05:50 AM   #2
Registered Member
 
GasSavers_Erik's Avatar
 
Join Date: Nov 2006
Posts: 1,027
Country: United States
That's a little low, it should be 18-20" of mercury. Is that at a hot idle- such as 7-800rpms?

Wait, I see that your car is only 600cc- is it a 2 cylinder? If so, maybe 14" is acceptable.
__________________

GasSavers_Erik is offline   Reply With Quote
Old 11-08-2008, 06:02 AM   #3
Registered Member
 
Join Date: Jun 2007
Posts: 146
Country: United States
Send a message via AIM to GasSavers_Dust
it's a 650cc 4 cylinder turbo. it's about the same at warm idle
GasSavers_Dust is offline   Reply With Quote
Old 11-08-2008, 06:06 AM   #4
Registered Member
 
GasSavers_Erik's Avatar
 
Join Date: Nov 2006
Posts: 1,027
Country: United States
Is it idling smooth? Ignition timing that is retarded can cause low vacuum at idle. Or maybe your boost gauge's needle isn't calibrated correctly with the numbers on the dial.
GasSavers_Erik is offline   Reply With Quote
Old 11-08-2008, 12:41 PM   #5
Registered Member
 
Join Date: Apr 2008
Posts: 689
Country: United States
My '88 Escort holds about 20-21 inches vacuum at idle hot or cold.
__________________
Hipermiler
#47 on my way to #1
Ford Man is offline   Reply With Quote
Old 11-08-2008, 02:04 PM   #6
Registered Member
 
kamesama980's Avatar
 
Join Date: Nov 2007
Posts: 742
Country: United States
Location: Columbus, IN, USA
Send a message via AIM to kamesama980 Send a message via Yahoo to kamesama980
that's pretty low for idle. things like vacuum don't change much for engine size. briefly I thought it might be the turbo but it shouldn't be doing anyhting at idle. I'd start by checking for vacuum leaks and that the throttle plate is closing fully.
__________________
-Russell
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
kamesama980 is offline   Reply With Quote
Old 11-08-2008, 04:08 PM   #7
Registered Member
 
JanGeo's Avatar
 
Join Date: Jan 2006
Posts: 2,442
Country: United States
Send a message via Yahoo to JanGeo
Try reving it up and see if the vacuum increases. An engine that small doesn't generate a lot of vacuum at idle because of all the losses moving four small pistons but reving it up should make a little more vacuum.
JanGeo is offline   Reply With Quote
Old 11-09-2008, 01:45 AM   #8
Registered Member
 
Join Date: Jun 2007
Posts: 146
Country: United States
Send a message via AIM to GasSavers_Dust
vacuum increasedto -9 psi, and goes to -10 on a hill.
GasSavers_Dust is offline   Reply With Quote
Old 11-09-2008, 08:35 PM   #9
Registered Member
 
suspendedhatch's Avatar
 
Join Date: Apr 2008
Posts: 445
Country: United States
Send a message via AIM to suspendedhatch
Is it a cheap brand of gauge? Find something you can check it against. Like a vacuum diagnostic tool.
__________________

Civic VX, D15Z7, 5 Speed LSD, AEM EMS, AEM UEGO, AEM Twin Fire, Distributor-less, Waste Spark
suspendedhatch is offline   Reply With Quote
Old 11-10-2008, 08:43 AM   #10
Registered Member
 
JanGeo's Avatar
 
Join Date: Jan 2006
Posts: 2,442
Country: United States
Send a message via Yahoo to JanGeo
Not sure if that is correct because usually vacuum is measured in inches of mercury except in Turbo gauges.

for the inches of vacuum multiply by 2.0293855020699732121113726763536

so 10spi is about 20.2 inches of vacuum sounds about right.

500mm vacuum = 9.7 psi

Atmospheric pressure is about 15psi and that is about 30-32 inches of mercury about 2 to 1
__________________

JanGeo is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ruses to stop tailgaiters ArtFox General Fuel Topics 41 06-16-2008 05:52 AM
Am I calculating this right? stumeston General Fuel Topics 8 12-15-2007 08:56 AM
Timing chain and FE bowtieguy Experiments, Modifications and DIY 22 11-11-2007 09:48 AM
Hello everyone cubajean10 Introduce Yourself - New member Welcome 7 09-12-2007 10:13 AM
Make the page lengths 30 posts again, please SVOboy Fuelly Web Support and Community News 4 05-18-2006 01:43 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 06:25 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.