D-Jet vacuum hose question, Which hose, or Both? Options

[Olympic 914]

Just finished up installing all the FI wiring harness and the vacuum hoses and now the engine compartment looks like a bowl of Spaghetti.

This engine started out as a 73 1.7 with the stock FI and I converted everything to a 2.0 system. I did use some of the original 1.7 parts as they were the same for both engines. But all the 2.0 FI parts ( throttle body, plenum, air filter housing ,etc.) where cobbled together from fleabay purchases and I am not sure what years those parts were from. Also used the original 73 1.7 FI wiring harness and ECU and had to make a couple extensions to get everything to hook up. Not much problem there, (except for trying to connect those ground wires under the plenum. )

Now to the question, I was using Bowlsby's vacuum diagram that is for a late 74 2.0 system and while hooking up the vacuum lines to the dizzy it seem that one line is no longer used.



in the diagram above I have the green vacuum hose connected from the throttle body to the dizzy as shown by the Orange circles. I also have another vacuum port on my dizzy that I have connected to the second vacuum port on my throttle body shown by Blue circles.

Should I have both of these hooked up? or do I disconnect the Black vacuum line as shown in Bowlsby's diagram and just plug the second port on the throttle body.
This is what I have hooked up now.



Is there a reason that the later versions did not have this second port hooked up?
What benefits are there to using the second line to the dizzy vacuum canister?

in picture below the green line from the throttle body is routed differently

[mgphoto]

German's didn't think of everything. If the clamping device in the mps had the edge radiused the diaphrams might not crack as easily.If the German's were worried about the vaccum signal to the mps they would not have placed the ports in the plenum the way they did. This is not intended to be an argument, just some facts do what you will.

The de acel valve adds air into the mixture reducing hydrocarbons, so the engines would pass US emissions, only 2.0l euros have the valve, none of the 1.7 or 1.8 have it. This is sort of the same thing the Audi / VW engineers did to fool the emissions inspection.

You built a bitchin motor why gimp it to worry about a replacable part, I have a couple of spare mps's on my shelf ready to go if I run into a problem.

The vaccum retard is not your friend with a set up like yours, get Racer Chris's mps tuning kit and a spare diapham.
Again my 2 cents.
Mike

[Dave_Darling]

The de acel valve adds air into the mixture reducing hydrocarbons, so the engines would pass US emissions, only 2.0l euros have the valve, none of the 1.7 or 1.8 have it.

This is incorrect. Most of the 1.7s, all US-spec 1.8s, as well as US-spec 2.0s, have decel valves. I believe the early 1.7s did not have them.

--DD