MAP take-off location

General Megajolt Questions and Answers

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rmaddock
Posts: 6
Joined: Thu Dec 15, 2005 12:57 pm

MAP take-off location

Post by rmaddock »

Hello...another question about Series LandRovers.

Correct me if my assumptions are wrong but...the MJLJ unit has the actual manifold pressure sensor built into it. All that is required from the engine is a vacuum tube from some suitable point.

The question is what this suitable point is? Can it be before the carb'? The Zenith carb' on my LandRover is connected to the air cleaner via (amongst vaious bits) a 90 degree metal tube which is secured to the top of the carb with rubber hose and jubilee clips. This metal elbow already has a short take off pipe which is currently crimped and sealed....I've no idea what it might be for. Can I just open this up and slip a pipe over it?
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brentp
Site Admin
Posts: 6284
Joined: Wed Jan 24, 2007 6:36 am

It should be an "un-ported"

Post by brentp »

It should be an "un-ported" vacuum take-off location. Meaning, it should have constant access to the manifold vacuum source. Some ports open and close depending on the position of the throttle plate, etc.

If your car has vacuum-assisted brakes then that port would be best since it always sees manifold vacuum.

Regards,
Brent

Brent Picasso
CEO and Founder, Autosport Labs
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greypride
Posts: 2
Joined: Wed Feb 09, 2005 5:33 pm

..

Post by greypride »

it needs to be on the engine side of the carb so that it can sense the pressure of the engine, where i think your talkinbg about is just on the air filter side

try and find somewhere on the inlet manifold to take it from, or drill and tap it and fit a take off pipe, on my mini ive used the take off that used to supply the vacuum advance

is that on the carb on the landrover? presumably it will be fine in this case too

rmaddock
Posts: 6
Joined: Thu Dec 15, 2005 12:57 pm

Thanks Brent. I have both

Post by rmaddock »

Thanks Brent.

I have both vacuum assisted brakes (cutting edge on a series III) and a vacuum advance on the dizzy........now that you point them out and I think about it.

Would the brake vacuum be better then? It's certainly a much larger diameter pipe than the advance. I guess though that the advance pipe is, by its nature, providing exactly the information required too.

I am correct though in that no other electro mechanical sensor part is required?
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