MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: xxx_mojo_xxx on March 11, 2010, 07:19:28 pm
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What's the vacuum pressure being shown during idle?
Thanks,
Mo
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iirc should be around -20 but don't quote me on it...
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yep around 20mmHg vacuum at idle :happy2:
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Is it a good or bad thing if it's below 20? Should I be expecting imminent failure?
What intercoolers do you have?
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Is it a good or bad thing if it's below 20? Should I be expecting imminent failure?
If it deviates much from -20 then I would look for a vacuum leak.
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I'm running the defi boost gauge with apr hpfp and forge fmic
When I first turn on the engine I have noticed boost sits a little higher than 22hg around 15hg the revs also sit a liitle higher c1100rpm rather than usual 8krpm
It soon settles down once warmed up and boost will then sit at 22hg
I have suspected a vacuum leak but holds boost well, so just put up with it :happy2:
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agree not seen a gti yet thats below 20mmHg when warm ...
first place to check are the boost guage connections, which guage and how have you fitted it (t piece etc?)
if the revs are above idle then itll naturally be less of a vaccuum, mines the same during the warm up phase its normal
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Is it a good or bad thing if it's below 20? Should I be expecting imminent failure?
If it deviates much from -20 then I would look for a vacuum leak.
Where would I start checking for a vacuum leak?
Am I correct to think the turbo boost pipe and intercooler pipes only carry positive boost?
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I think most find that the issue lies where you tap off the vacuum for the boost gauge so I would check that first.
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I think most find that the issue lies where you tap off the vacuum for the boost gauge so I would check that first.
Sorry to be really ignorant...but does anyone have a pic?
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the way in which a boost/vacuum signal has been taken depends on the make/type and parts you have fitted to your car.
normally there will be a T piece fitted under the engine cover RHS as looking from front and a small bore pipe running into the cabin then into boost gauge.
(or if its a DEFI electrical gauge then the small bore pipe runs to a sensor usually in the engine bay then an electrical cable to the cabin/gauge)
if you have a forge DV fitted then theres also a 'takeoff' point there which can be used negating the need for a t piece.
Id look for
1. broken plastic t piece with a hariline crack , put a metal one in there ...
2. check all fittings that have been touched during install, inc the one on the back of the boost guage
another thing you can try is spraying some fairy liquid water around connections and listening/checking gauge.
you may get a momentary inc in vacuum or change in sounds if it temporarily stops the leak.
or with some throttle get bubbles .....
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once warm mine sits at 22hg
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once warm mine sits at 22hg
Same as mine when warm. Read using a Defi boost gauge. :happy2:
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once warm mine sits at 22hg
Same as mine when warm. Read using a Defi boost gauge. :happy2:
sorry forgot to add mine is a newsouth boost gauge :)
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Thanks for the tips guys especially around isolating a potential vacuum leak.
I was using a Forge DV and running the 'vacuum' pipe directly from it. I figure if everyone has a reading of 22 then there might not be a problem after all!!!
I guess the intercooler and HPFP must have increased the vacuum pressure. As a test I removed my Forge DV and went back to the OEM one (rev. D) and the read outs are the same.
I must say I'm missing the "whoosh" noise from the Forge DV.... not sure if I should fit that one back again. Open to opinions?
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mine sits at 22-24, i have i/c, twintake, forge dv, tbe. :smiley:
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someone may correct me, but from my understanding the ability to draw a vaccuum to a maximum value
would defintely not be influenced by HPFP (it just delivers fuel and has nothing to do with the intake tract)
and prob not an I/C directly....
but if your idle speed/engine parameters have changed, your 'closed throttle' variables may have changed improving the vaccuum
other considerations are that adding parts has sealed something that previously had a minor leak
evening having air con on/off effects the value...
you say 'was' reading from DV, have you now changed where the boost signal is coming from?
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I haven't changed where my vacuum pressure is being read from...the DEFI gauge is connected at the same place.
What I was trying to determine was whether the increase in vacuum pressure was something to get concerned over, or if it was a positive effect influenced by the intercooler. I suspect with an upgraded intercooler with it's increased mass/air flow, etc. this has caused my previous value of 20 to change to 22-24.
I can't remember where, but somewhere on this forum, it was suggested that if vacuum pressure was to increase from 20 then there could be a potential problem....hence the question to see if the change was expected/normal after the addition of a intercooler and HPFP.
By the sounds of it...looks like my car is behaving normally if the consensus is that the readings are in the region of 22-24.