Vacuum On Idle - Whats your number????

[Hyper_Mike]

Hey guys,


Just wondering what vacuum you are getting on idle and if a bigger turbo would effect it at all?


Cheers, Mike

 

[elnevio]

About 18-20 inHg (around -0.6 to -0.7 bar). The turbo shouldn't make any difference, AFAIK.

 

[EV0300]

Bigger cams can change it because of overlap but i dont think turbo size matters iii have 14-16 with 268 cams

 

[VIN18M]

I get 18-19, on a 93 with a 20g.

Big cams will affect vacuum, as when I had 290s in mine the vac went down to about 10 :blink:

 

[Hyper_Mike]

Awesome, cheers guys. I'm getting around 10 with 272 cams

 

[evo-gsr]

About 18-20 inHg (around -0.6 to -0.7 bar). The turbo shouldn't make any difference, AFAIK.

Mines roughly the same...I have big turbo too.

 

[White Knight]

18-20 on stock cans here mike.

 

[Parabola]

-376

 

[evo-gsr]

You cars well and truly fucked then ↑

 

[Parabola]

You cars well and truly fucked then ↑

I disagree.
Perhaps I should of stated I measuring the vacuum in mmhg.
So by my calculations -376mmhg is the equivalent of about -7 or -8psi.
While I'm at it, if your measuring your vacuum in mmhg and it is reading 18-20, don't you think that your car might be fucked? As 18-20mmhg is actually around 1psi. Therefore there is actually no vacuum and you are making boost (albeit small)

 

[evo-gsr]

:lol: ↑

 

[MDK87]

217.6493 inches of water at mean sea level... :lol:

 

[evo-gsr]

I disagree.
Perhaps I should of stated I measuring the vacuum in mmhg.
So by my calculations -376mmhg is the equivalent of about -7 or -8psi.
While I'm at it, if your measuring your vacuum in mmhg and it is reading 18-20, don't you think that your car might be fucked? As 18-20mmhg is actually around 1psi. Therefore there is actually no vacuum and you are making boost (albeit small)

I can assure you my car is not fucked.....anytime you want to line it up, I can show you ?
You might want to read the post I qouted in my reply as it tells you what the measurement used was.

 

[SIKWPN]

280's

 

[penngwyne]

I'm getting about 18 to 20 and sometimes with a bit of engine braking up to 23 inHg (If I believe my gauge)
Stock HSGR Auto with (i think) all of the leaks fixed including the throttle body seals
If I was only getting 11 inHg I would be worried that something was wrong although I suppose a different cam would affect the valve timing yes???

http://www.freeasestudyguides.com/engine-vacuum-test.html

According to http://www.unitarium.com/pressure

508 mmHg is 20.0 inHg is .6773 bar
457 mmHg is 18.0 inHg
376 mmHg is 14.8 inHg
285 mmHg is 11.2 inHg

 

[EVO-00X]

Its good to see some numbers with bigger cams because Ive looked at pics and videos of my AVCR readings and its been anywhere from around -150mmHg @ 1,000rpm with the old Crower 280 cams, to last tune at -230 to -280mmHg @ 1100-1200rpm with the 11mm lift Kelford TX272's (which was my last tune at Micks Motorsport as per my signature). We thought there must have been a vac leak to produce the low number at idle but after running a smoke machine into the intake system there was no vac leak. Checked cam gears at zero zorst and 4 advance on the inlet. Different setups will show different numbers. Was a bit of a pig braking at low rpm due to the low vac but I put that down to the tune. Not much time was spent tuning in a good idle. With the new ECU and setup I hope that will all change.

 

[EVO-00X]

Found this old pic from a couple of years back. I cant remember what I had taken it for so I cant comment on the state of tune at the time other than it was actually idling and after taking it for a bit of a drive (I know I drove the car before taking the pic because it shows the highest readings recorded since engine start up as 1.8 bar boost (26psi) and 8216 rpm lol). The cams back then were the old Crower 280 cams. It shows -322mmHg

 

[4piknup]

I think idle vacuum is a pretty good indicator of fuel economy and driveability. I think the more vacuum is from more low down torque, and the better that is the better it is at cruise.

 

[khubner1]

-12 to -14 inmg drops to around -10 inmg under the load of ac

-30 inmg is perfect vacuum for the record -30inmg is practically impossible on the planets surface

i'm making about the same as rob 322mmmg is 12.6 inmg or -6.2 psi
and sik wpn has around 11.2inmg