Vacuum/MAP feed?

spandit · Post by **spandit** » Fri Jan 21, 2011 11:37 am

My engine doesn't appear to have a vacuum system - the distributor is mechanically advanced. However, the brake servo has a vacuum feed - can I tap off this to go to my MAP sensor?

Failing that, there is a manifold that connects the air filter assembly to the two carburettors (which, being Zenith models, apparently don't have a vacuum feed) - can I just drill a fitting into that?

On a vehicle-specific forum, someone who is installing full EFI wrote:

"The pinz engine has INSANE manifold pressure at higher RPM on deceleration and at idle... 24-27MP" - is this a problem for the MJLJ?

Funky Diver · Post by **Funky Diver** » Fri Jan 21, 2011 4:13 pm

You need to take a feed off the inlet manifold, and if you have servo assist braking, this would work.

VW's (Mk1/2 Golfs) use vac assist on pretty much anything outside the engine block... dizzy advance, carb operation, brake assist.

spandit · Post by **spandit** » Fri Jan 21, 2011 7:13 pm

Turns out I didn't know what an inlet manifold was (despite having built a kit car in the past!)

. Just need to work out how to tap into it. The line that feeds the brake cylinder is 14mm diameter, I think. I'll have a look tomorrow if I have time

spandit · Post by **spandit** » Fri Jan 21, 2011 7:45 pm

Here's a dreadful vignette-style (thanks, iPhone "flash") picture of the brake servo fitting (it's the braided hose going to the banjo fitting in the bottom left of the picture):

Any thoughts on how to add a fitting onto this. It's an M16 hollow screw? There's a 12mm pipe linking the two inlet manifolds (4-cylinder engine with 2 carbs) - I presume to balance things.

spandit · Post by **spandit** » Fri Jan 21, 2011 8:57 pm

OK, I'm thinking if I cut the braided pipe I can install a piece of copper tubing with some copper brake pipe soldered into it to act as my vacuum pipe. Any problems with this?

NITROPIXIE · Post by **NITROPIXIE** » Sat Jan 22, 2011 5:50 pm

Go to a scrapyard and find an old mk2 golf, they have the proper adaptors for just this so you don't need to make up your own.

spandit · Post by **spandit** » Sat Jan 22, 2011 7:01 pm

Thanks - any chance of a picture/description of what you mean? I've been told on certain Pinzgauer engines they have the vacuum attached here but don't know how

A better picture here (with hose and engine cover removed):

NITROPIXIE · Post by **NITROPIXIE** » Sat Jan 22, 2011 7:38 pm

Something like this. This is the CIS injection model. The carb models have a similar one on the right hand side of the manifold. This T piece is also a valve to store vacuum escaping from the Vacuum reservoir of the brake servo when in low vacuum MAP (possibly engine stall) and requiring to still brake.

You may find similar ones on most models of VW's (petrol).

spandit · Post by **spandit** » Sun Jan 23, 2011 11:12 am

Thanks for that - the one I'll make will be very similar to that. There's already a valve in the vacuum line for the purpose you mention

spandit · Post by **spandit** » Wed Mar 16, 2011 4:55 pm

Just thought I'd update this post with what I eventually came up with. The copper pipe you can see in the picture is a scrap piece that is soldered shut and can be easily replaced with a longer section once I come to install the MJLJ