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General => The garage => Topic started by: PIPKIN on 09 February 2011, 21:21

Title: MK2 GTI 8V idle speed drops
Post by: PIPKIN on 09 February 2011, 21:21

Hi all

Just a quick question when I remove the oil filler cap when the engine is running the revs drop.

Is this normal and if not what could be the problem.  If this is a problem how can I identify the specific concern.

Cheers

Paul

Title: Re: MK2 GTI 8V idle speed drops
Post by: Khare on 09 February 2011, 21:26

It's normal. Engines run on a pressurized system, if you let the pressure out, they don't like it  :smiley:

Title: Re: MK2 GTI 8V idle speed drops
Post by: rubjonny on 10 February 2011, 09:40

vacuumised ;)

Title: Re: MK2 GTI 8V idle speed drops
Post by: Khare on 10 February 2011, 12:05

Quote from: rubjonny on 10 February 2011, 09:40

vacuumised ;)

dam! I was going to use that rather than pressurized but I didn't know which one, so I took a gamble!  :grin:

Title: Re: MK2 GTI 8V idle speed drops
Post by: rubjonny on 10 February 2011, 12:30

if it was a turbo you would have been right  :grin:

Title: Re: MK2 GTI 8V idle speed drops
Post by: Khare on 10 February 2011, 12:39

Ahhhh, NA runs on a vacuum, turbo on a pressurized system. Got it :afro:

Title: Re: MK2 GTI 8V idle speed drops
Post by: rubjonny on 10 February 2011, 13:54

aye engine is in effect a rather big vacuum pump, as the cyls move down they suck air and fuel in so the intake is under vacuum. turbo puts the inlet under +ve pressure to cram even more air in there :)

Title: Re: MK2 GTI 8V idle speed drops
Post by: Khare on 10 February 2011, 14:20

Makes sense  :smiley:

Top man as usual RJ :afro:

Title: Re: MK2 GTI 8V idle speed drops
Post by: PIPKIN on 11 February 2011, 17:19

Cheers for the pointers and assuring me that a bill is not on the way.

Paul

Title: Re: MK2 GTI 8V idle speed drops
Post by: javalin on 14 February 2011, 16:33

worth pointing out that the crankcase on both turbo and non-turbo shouldn't be pressurised, but under a slight vacuum.  The air intake is pressurised on a turbo though (boost) and slight vacumm on a non-turbo (upto the throttle butterfly of course).

J