Blanked Vacum Hose

[Dave G 0]

noticed today that my vacum hose from the circular item under the dizzy has a bolt in it and the other end that goes to the throttle pot just goes to atmosphere. any ideas why this may be?

[CosKev 16]

Perhaps cause the vacuum unit is shagged????

 

Suck on the pipe goin to it and see if you get a vacuum

 

Should really be fitted,will be affecting your performance cause you won't be getting any advance on your timing

[Dave G 0]

ok will do. going to put gearbox back in tomorrow and proving ive got that side of it sorted thats next

[CosKev 16]

How did the car go with it off?????

 

Also you want to blank off the pipe going to bottom of throttle body in the mean time if your running the car round

[Dave G 0]

really well to be fair, this is my 4th gti and i my brother has the best of the other three still and i pulled slightly on him on a 20-100 mph sprint ( on a private road of course).

 

would rather have it working right and set up though, it does how ever sound very spluttery at idle. Just waiting to get my 4 branch etc on there as it sounds more down pipe than engine

[CosKev 16]

When I had mine set-up at Skip Brown Cars he even noted the few BHP that I was losing just cause of the age related wear in my dizzy timing advance parts

So I would have thought running with no advance at all as you have been would have made a big difference

The pipe being open to atmosphere on bottom of throt body probably hasn't helped your rough idle

[Dave G 0]

yeah. going to check it straight away when its running. thanks for the help

[sutol 0]

Yer disconected vacuum advance will not affect performance as long as the manifold pipe is blanked.

The only thing that will be affected is part throttle running when the dizzy will not advance far enough to burn the leaner mixture which will in turn cause the engine to use more fuel when cruising.

Full throttle power will not be affected as the vacuum will not be operating at full throttle anyway.

[Dave G 0]

got one on order, its obviously fubared or it wouldnt be blanked. bodging gits before though could take the time to blank the advance unit but not the hose from the throttle pot

[CosKev 16]

Yer disconected vacuum advance will not affect performance as long as the manifold pipe is blanked.

The only thing that will be affected is part throttle running when the dizzy will not advance far enough to burn the leaner mixture which will in turn cause the engine to use more fuel when cruising.

Full throttle power will not be affected as the vacuum will not be operating at full throttle anyway.

 

I thought it worked the opposite to that goin from what Skip Brown's said

 

Full throttle should be getting the max advance in timing,and the higher up the revs the engine goes the more it sucks on the vacuum advance unit and advances the timing???????

 

Anyone explain it please?????

Edited September 4, 2009 by CosKev

[jackherer 543]

Are you sure they weren't talking about the mechanical advance in the distributor as opposed to the vacuum advance?

[CosKev 16]

Are you sure they weren't talking about the mechanical advance in the distributor as opposed to the vacuum advance?

 

Ah,could of been

 

Hows that work then???????

 

All I know is he said there was age related wear in the timing advance part of dizzy,resulting in a few degrees of advance bein lost at full advance.

Apparently common wear on these Pug dizzys.

[sutol 0]

Ah,could of been

 

Hows that work then???????

 

All I know is he said there was age related wear in the timing advance part of dizzy,resulting in a few degrees of advance bein lost at full advance.

Apparently common wear on these Pug dizzys.

The mechanical advance does wear and can be fixed by opening the dizzy up and bending the posts slightly that hold the springs to take up the wear. The springs wear a groove in the posts that hold them and become a bit slack.

The mechanical advance advances the timing as the engine revs increase.

The vac advance advances the timing when the throttle is lifted or at idle and gives most advance when the throttle is shut. The vac advance gives no advance when the throttle is wide open, the engine then relies on the mechanical advance which works on centrafugal force spinning weights and springs in the dizzy body.

Mechanical advance can be slowed by using stronger springs, this is when you need a lot of advance at low revs (with a hairy cam for instance) you then start with a lot of advance and so do not want much more so it has to be pegged/stopped at for instance 32degrees after 4000rpm depending on the engine spec.

It is quite easy to alter the max advance and advance rates to suit your engine by swapping springs and soldering up the stops in the dizzy.

You need as much advance as the engine will take without pinking to produce good power, get as much info as you can and you will soon undrstand it.

[richsmells 2]

http://forum.205gtidrivers.com/index.php?showtopic=102663

 

Pics of distributor internals

[CosKev 16]

The mechanical advance does wear and can be fixed by opening the dizzy up and bending the posts slightly that hold the springs to take up the wear. The springs wear a groove in the posts that hold them and become a bit slack.

The mechanical advance advances the timing as the engine revs increase.

The vac advance advances the timing when the throttle is lifted or at idle and gives most advance when the throttle is shut. The vac advance gives no advance when the throttle is wide open, the engine then relies on the mechanical advance which works on centrafugal force spinning weights and springs in the dizzy body.

Mechanical advance can be slowed by using stronger springs, this is when you need a lot of advance at low revs (with a hairy cam for instance) you then start with a lot of advance and so do not want much more so it has to be pegged/stopped at for instance 32degrees after 4000rpm depending on the engine spec.

It is quite easy to alter the max advance and advance rates to suit your engine by swapping springs and soldering up the stops in the dizzy.

You need as much advance as the engine will take without pinking to produce good power, get as much info as you can and you will soon undrstand it.

 

Nice one,cheers

 

 

http://forum.205gtidrivers.com/index.php?showtopic=102663

 

Pics of distributor internals

 

Good thread that,excellent info cheers