Board logo

Locost Vacuum Plenum
RazMan - 10/12/10 at 06:01 PM

You know the feeling when you make something that's really cheap, simple and just as good as expensive shop-bought items? Well I was thinking about how I am going take the vacuum feeds from my throttle bodies and bring them together so that I have a common vacuum source for the fuel regulator, idle valve etc etc. The cheapest I could find was about £35 and seemed huge for fitting in the engine bay. Looking around in my odds & ends box I found an old fuel filter like this one.

Description
Description

I think I paid about £2.50 for it a while back. So I got my drill and taps out, found some suitable air fittings and an hour later came up with this..

Description
Description

To get the size needed, I had to make the fittings by soldering two halves of different adaptors together

Description
Description

I can now take all 6 vacuum lines (4mm hose) and merge them into an 8mm hose - perfect!

I just wanted to share


[Edited on 10-12-10 by RazMan]

blakep82 - 10/12/10 at 06:10 PM

pictures don't seem to work. not even in your archive

v8kid - 10/12/10 at 06:16 PM

Looks OK to me!

blakep82 - 10/12/10 at 06:17 PM

hmm, that is strange then., all other photos seem to be working for me...

ashg - 10/12/10 at 06:23 PM

looks too small to me.

the problem with joining all of them together with small pipes is that you get a pulse effect which will play havoc with the fuel regulator map sensor etc. the ideal size of a vacuum pulse smoothing chamber without affecting the vacuum response is about the size of a 330ml coke can.

Confused but excited. - 10/12/10 at 06:48 PM

Poo! Pics won't open for me either.
Archive pics open OK but not these, strange.

stevec - 10/12/10 at 07:01 PM

I thought a plenum was the opposite of a vacuum
Steve

MikeR - 10/12/10 at 07:02 PM

quote:
Originally posted by ashg
looks too small to me.

the problem with joining all of them together with small pipes is that you get a pulse effect which will play havoc with the fuel regulator map sensor etc. the ideal size of a vacuum pulse smoothing chamber without affecting the vacuum response is about the size of a 330ml coke can.


I was wondering if you'd get the pulsing, talking to a dutch bloke at Stoneleigh this year and he was talking about this exact issue, he thought the best solution was an electronic damper circuit. IrvineD knows the bloke who I was talking too.

dhutch - 10/12/10 at 07:02 PM

I can see the pics...

loggyboy - 10/12/10 at 07:07 PM

Pics are red Xs for me, both on here and in your gallery/archive.

RazMan - 10/12/10 at 09:24 PM

Strange that some are having problems with the pics - I haven't a clue why that should be

Regarding the pulsing issue, I have not detected any problems so far, but it might be the fact I have six cylinders which may be smoother than a four-pot? If anything I would have expected the small bore hose (4mm) and 3mm i/d connectors to damp out any pulses - it certainly sounds very smooth if I disconnect the pipe and listen to the hiss.

rusty nuts - 11/12/10 at 11:22 AM

If you do have problems with pulsing it might be worth fitting a vacuum reservoir from something like a Mk2 golf that uses a Pieburg carb?

britishtrident - 11/12/10 at 11:37 AM

Just Tee together then pass them through a small bore restrictor then a plenum volume then another restrictor

The volume dosen't need to be that large provided you use restrictors.