My Car's Pulling 20 Vacuum at Idle

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Feb 17, 2002 | 06:08 PM

mightyslash

Thread Starter

Will Work for Ferrari

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From: West Coast

My Car's Pulling 20 Vacuum at Idle

So, what does that tell me? Is it good or not?

Feb 17, 2002 | 06:10 PM

pweizman

Senior Member

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From: The 'Nati, Ohio

If the idle is at 750 rpm...that is really good.

Patrick

Feb 17, 2002 | 06:15 PM

mightyslash

Thread Starter

Will Work for Ferrari

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From: West Coast

Yeah, between 750-800 rpm

Feb 17, 2002 | 06:37 PM

Tim Benton

FD title holder since 94

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From: Cedartown, Ga

mines around -470 mmhg on the PFC, gauge shows a little more than 17. Is your gauge off any when the car is off? I'll bump up my idle to 800 with the PFC and see what vacuum I pull then, it should be more.

Tim Benton

Feb 17, 2002 | 06:41 PM

JBC

Full Member

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From: earth

Mine shows about 450-500 mmHg at idle 850 rpms. That is on a stock motor with no mods and 66,000 miles.

Feb 17, 2002 | 06:47 PM

to_slow

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From: michigan

Mine`s at 15 -16 at 800rpm.. is that good ?

Feb 17, 2002 | 06:59 PM

Rx7aholic

Rotary Freak

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From: Morris Plains, NJ USA

According to Mazda shop manual {what the dealer use} if I remember correctly anything above 14 is good on stock motor not ported.

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Feb 17, 2002 | 07:01 PM

Cetchup

The Cursed FD

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From: CA

Im boosting 10lbs and i pull 15 vaccum...at around 1000 idle..?

Feb 17, 2002 | 07:02 PM

Johnny

Joined: Feb 2001

Posts: 1,291

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From: Pleasanton,California

it's usually a good sign to pull 15-16 at idle (750ish)...but porting ..airpump and other mods can change the vac. Nothing replaced a compression test...

I for instance pull 490 on the PFC sometimes 510...sometimes 450...
depending on I dont know what...car always pull hard and strong

Feb 17, 2002 | 07:28 PM

#10

to_slow

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From: michigan

Well at 1000rpm i have like 19-20 around that ..

Feb 18, 2002 | 08:20 AM

#11

Hyperite

Vagina Junction

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From: Seattle, WA

Also it depends what your mods are. Air flow mods (intake, IC and exhaust) will drop the idle vacuum down. With intake, IC, DP,MP,CB, i see about 13 psi at 740 idle. Runs like a champ.
~Tom

Feb 18, 2002 | 08:52 AM

#12

ivanuscg

Full Member

Joined: May 2001

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From: Clearwater, FL, USA

My car was just ported and at around 800 rpm i'm pulling like 17 or 18lbs of vacuum.

Feb 18, 2002 | 09:06 AM

#13

Scott Olsen

Junior Member

Joined: Dec 2001

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From: Snellville, GA

Probably not a very aggressive port. My street ported motor has always pulled 14-15inHg@750rpm from the beginning.

Feb 18, 2002 | 11:54 AM

#14

BlackR1

Meesto Spakaro

Joined: May 2001

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From: Redondo Beach, CA

I have a ported motor as well and I pull ~15 @ 800 rpm.. at first I was concerned that I was getting low vacuum, but since im ported and have some intake and exhaust mods, i think it is normal?

Feb 21, 2003 | 05:46 AM

#15

Wankel7

Haven't we ALL heard this

Joined: Mar 2001

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From: Indiana

I also think that atmospheric pressure will affect your readings to some slight degree.

Not that I care....but an engine at idle produces a vacuum. Not pressure. So, any idle vacuum reading is just that (Vacuum being messured as Inches of Mercury (HG). Not PSI (pounds per square inch).

James

Feb 21, 2003 | 05:53 AM

#16

maxcooper

WWFSMD

Joined: Jun 2001

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From: SoCal

Altitude affects the idle vacuum, too. With that, RPM, gauge accuracy, porting, mods, etc., I don't think it is very useful for comparing between cars. If you notice a distinct drop in idle vaccum, that might tell you something about your engine. Or if it starts jumping around a lot, that might tell you something as well. But comparing car to car doesn't tell you much, in my opinion.

-Max

Feb 21, 2003 | 06:41 AM

#17

teamstealth

Ozone Depleter

Joined: Jul 2002

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From: StL

im pulling 19-20 on vaccum.....but i idle around 1k-1150. What does that tell me? I also have a intake and CB

Feb 21, 2003 | 11:42 AM

#18

Johnny

Joined: Feb 2001

Posts: 1,291

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From: Pleasanton,California

you know you bumped a thread over a year old...

dont you ?

Feb 21, 2003 | 11:49 AM

#19

R Xplicit

Senior Member

Joined: May 2001

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From: Mississippi

i pull around 17-19 at idle @ 1100~ rpm, and have full open exhaust and a street port...

Feb 21, 2003 | 03:40 PM

#20

Wankel7

Haven't we ALL heard this

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From: Indiana

Wow, post whoring from the past!!!!!

James

Feb 21, 2003 | 04:48 PM

#21

yzf-r1

Banned. I got OWNED!!!

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From: Charlotte

vacuum at idle = lazy person's excuse for not running a compression check

in other words, meaningless

Feb 21, 2003 | 09:15 PM

#22

SleepR1

Lives on the Forum

Joined: Sep 2001

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From: IN

480 to 510 mm Mercury from the Power FC Commander display @ 750 rpm idle. Converting to inches Mercury that's 19 to 20 inches Mercury. FWIW my Autometer shows 17 inches Mercury. I tend to believe the Power FC readout over the Autometer, at least for accuracy's sake.