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Old 10th September 2017, 11:07 AM
ajax1976 ajax1976 is offline
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Join Date: Oct 2016
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Default AHC/ABZ help req'd?

Hi, new member looking for some help/advice on the the 4.2 AHC lump.

I'm in the middle of putting a 4.2 AHC into my B4 Audi Coupe quattro, The motors in, converted to manual, oil system sorted, cooling nearly done now starting to struggle with some of the final stages.

The car in question,




I'm slowly working my way through the various vacuum systems but really struggling to get my head around them. On the throttle body there's a strange mess of pipes that comes off the top of the throttle, loops around a couple of times through a couple of valve things(?) before heading back into the throttle.



I think one of the loose tails coming off it used to go to the brake vacuum? My car doesn't have vacuum brakes but the hydraulic booster set up so would I be right in saying I can just plug that pipe as I've done in the picture(bolt instead of plug)?



Or as I don't require the vacuum feed for the brakes can I simplify it more but removing most of the pipes and just plug the two take offs off the throttle? Or should I just run one pipe to join the top and bottom outlets on the throttle?

Got loads of other probably silly questions that hopefully someone will be able to help me with?

Thanks Alan
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Old 10th September 2017, 07:22 PM
MikkiJayne MikkiJayne is offline
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Join Date: Jan 2012
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Gorgeous!

I'm fairly sure that chunk of stuff is just for the brake servo. The plastic piece is a suction jet pump which just helps pull a vacuum. If you've got no other vacuum powered stuff then you should be able to just blank off both ports.

The manifold changeover valve obviously uses vacuum, but iirc that takes its vac feed from the front of the manifold. The 40V does anyway. Not 100% on the 32V though.
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Pecuariam felis
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Old 12th September 2017, 01:53 AM
ajax1976 ajax1976 is offline
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Join Date: Oct 2016
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Quote:
Originally Posted by MikkiJayne View Post
Gorgeous!

I'm fairly sure that chunk of stuff is just for the brake servo. The plastic piece is a suction jet pump which just helps pull a vacuum. If you've got no other vacuum powered stuff then you should be able to just blank off both ports.

The manifold changeover valve obviously uses vacuum, but iirc that takes its vac feed from the front of the manifold. The 40V does anyway. Not 100% on the 32V though.
Perfect, Thanks for your reply.

That's more or less what I was thinking, a few of the hoses are quite badly split so think I'll try blanking them off first. Once I get it running I'll probably just play about with it and see how it runs with it blanked off.
Yeah 32v seems the same, smaller vac line straight off the front so that should be ok.

Thanks again Alan
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