Vacuum take off(s)

pollymog · Post by **pollymog** » Fri Jun 08, 2012 10:09 pm

Hi all - I've installed a 2 litre zetec engine into my Reliant Scimitar SS1 (which originally had a 1600 CVH engine in it). I'm using a Megajot Lite jr/EDIS along with single Weber 32/36 DGV carb mounted on an aluminium banger inlet manifold. The MLjr/EDIS is all wired in & I've actually had the car runing albeit roughly. Originally I thought I could use the vacuum take off on the carb (that would originally have been connected to the distributor) however, having done a bit of research, it turns out that this connection isn't really suitable. So I've bought a couple of vauum connectors to tap into the manifold & this is where my problem lies:

Do I need to tap & fit one of these connectors into each of the 4 branches of the inlet manifold & fit a plenum chamber? If so which layout - 1 pipe connecting all 4 connectors & then into the plenum (so 1 pipe into the plenum) or a seperate pipe from each of the 4 connectors with each one going to the plenum (so 4 pipes into the plenum)?
Or can I just tap & fit one connector into one of the branches of the manifold - if so which branch (cylinder 1, 2, 3 & 4) & where on the branch (nearer the engine or nearer the carb)?
Or should I tap & fit one of the connectors into another part of the inlet manifold - near the brake servo take off for example?

Sorry for all the questions

& I hope someone can help

toenee · Post by **toenee** » Fri Jun 08, 2012 11:22 pm

http://www.autosportlabs.net/MJLJ_V4_ve ... _.28TPS.29

cng1 · Post by **cng1** » Sat Jun 09, 2012 6:59 am

You can simply take a t-piece and insert that into an existing vacuum line - no need to drill and tap the manifold.

pollymog · Post by **pollymog** » Sat Jun 09, 2012 7:54 am

Many thanks for the replies toenee & cng1 - I'd seen the diagram linked to & it was that that prompted my questions. The only other vacuum line is the one for the brake servo & I was under the impression that if I put a T piece into that then the running of the car would be affected every time I braked. It would certainly be easier than tapping & drilling the manifold though.

Sorry to ask again but can anyone give me a definitive answer or is it just a case of trying the various options & seeing which works best?

Thanks again

cng1 · Post by **cng1** » Sat Jun 09, 2012 8:02 am

The servo doesn't consume air, it just uses the pressure differential so shouldn't make any difference to the MAP signal. In any case the whole inlet manifold is linked so if the pressure in the hose changes it means it is also changing in the manifold and thus what the engine is seeing.