Can I use a ahu downpipe on a 1z?

Joshua4507

Member
Joined
Mar 13, 2019
Location
Santa rosa
TDI
1998 jetta tdi
So I have in my garage a down pipe and cat from an AHU engine in my garage. I just bought a 1996 b4 passat wagon glx tdi.
So far I'm very happy with the car but I need to replace the flex pipe on the down pipe my local muffler shop said only problem is it would cost me way too much for what I'm looking to Spend. I have in my garage an extra motor and harness and down pipe with cat for an AHU in the only thing I could see that is different is the flex pipe itself is longer I was wondering if anyone on here has swapped out 1z down pipe with the short flex pipe for the ahu version? It seems like it would be better as they don't grenade as much.

My question is has this been done before? And can it be done that way? Will it bolt up to the turbo just the same?

I've been searching and haven't found anything definitive
I don't see why it wouldn't work? It'll work right? right?
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
I’m guessing the AHU dp is from a Jetta? There should be some exhaust mount points that would attach it to the subframe. The B4 dp doesn’t have this. Other than that, it should bolt up.

Your muffler shop won’t cut out and weld in a new flex section?

-Todd
 

Joshua4507

Member
Joined
Mar 13, 2019
Location
Santa rosa
TDI
1998 jetta tdi
Yes the down pipe is from an a3 Jetta aka 98 Jetta tdi. The guy at the muffler shop said he would have to unbolt and drop the dp to weld in the new flex pipe because of where it is located. can't get to it with the welder he also pointed out a number of welds that made it look like someone has hackjobed this back together a few times before. Then pointed out how rusty the nuts and threads are that hold the dp on and said if one of my guys breaks one of those off it means you're gonna have to drop the turbo to put new studs in and order parts and pretty quickly it would cost more than I paid for the car.

He basically said if it wasn't for the rust it would be 2/3 hours max but if a stud broke its gonna get real expensive real quick.

If it's the same I'm gonna use the dp from the ahu Jetta and hope and pray I don't break any exhaust studs. I don't really want to drop the turbo if it's not necessary.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Fingers crossed, but getting those nuts off is murder. There isn’t a lot of space to work.

Last time I did it, at least 1 stud snapped and I ended to dropping the turbo. Start soaking it down with penetrating oil.

-Todd
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
I'm using the Mk3 DP (sans cat) on an AHU installed in a B3 (same as B4) chassis and it fits fine. There won't be any mounting for the lower DP fork that the Mk3 uses but you can have that cut off no problem.

The flange at the turbo is the same so it should be a direct swap I would think.

As others have said it's good to start soaking those nuts now...

Steve
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
TT also sells a larger diameter DP but it's $355 and I never liked the location of the flex joint TBH.

Steve
 
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