Typrus
Veteran Member
Whats the difference??? Aren't they both wastegated setups? What else is changed?
1Z vs. AHU
- Thread starter Typrus
- Start date
compu_85
Gadget Guy
The AHU has higher pop pressure injectors, a different make turbo, and slightly cleaner emissions. The ECU is slightly different between them too. They are virtually identical.
-Jason
-Jason
ninedee_golf_tdi
Vendor
I missed this at first, but a European AHU has a different intake manifold as well. The egr valve is closer to the head.
Typrus
Veteran Member
I thought I heard someone say they have different pistons?
paramedick
TDIClub Enthusiast, Vendor
Different pistons, IIRC.
Lug_Nut
TDIClub Enthusiast, Pre-Forum Veteran Member
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Different valve seats, different valve guides and seals, too. Some of these were incorporated as running changes in the 1Z, thus the 97 Passat (1Z) and 97 Jetta (AHU) have different engine codes, but likely have the same internal components.
paramedick
TDIClub Enthusiast, Vendor
Jon, remember some 97 Jettas had the 1Z. Mine did.
dieselgrandad
Veteran Member
The 1Z preceded the AHU. Here is an ancient thread that may help:
http://forums.tdiclub.com/showthread.php?t=48444
The engines are interchangeable. I have an AHU in my '97, thanks to a stealership screw-up and subsequent TB failure. I did not change the ECU.
I can't attest to the interchangeability of specific parts (i.e. fuel pumps, etc.). However the intake manifolds from both engines are identical.
12MPGHWY
Veteran Member
please be specific which cars have which engine code?
What engine would a 98 jetta have
What engine would a 98 jetta have
paramedick
TDIClub Enthusiast, Vendor
AHU..12MPGHWY said:
IndigoBlueWagon
TDIClub Enthusiast, Principal IDParts, Vendor , w/
Some '97 Jettas have (mine included) have 1Z engines. All B4 Passat TDIs were 1Zs, I'm pretty sure. Later '97 Jettas and all '98s are AHUs.
tomo366
TDI Lifer, Member #68
My newly aquired 1996 B4 Passat has the best of both worlds.......
QC ECU and a European AHU engine
QC ECU and a European AHU engine
bikeprof
Veteran Member
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- 1996 Passat B4 Variant white, 1996 Town & Country 3.8 LXI
Is jelous OK. to mention...,
I am.
My 1996 B4 has the old clunker, the 1Z with the GQ ECU.
Wish I had the better AHU/ALH pistons and MORE power !
I am.
My 1996 B4 has the old clunker, the 1Z with the GQ ECU.
Wish I had the better AHU/ALH pistons and MORE power
!a350z4me
Well-known member
My 98 has a 1Z. I'll get a picture of the build sheet later if you want.IndigoBlueWagon said:
IndigoBlueWagon
TDIClub Enthusiast, Principal IDParts, Vendor , w/
Sometimes the build sheets are incorrect. I'm not doubting you, but the engine number is the most reliable way to tell.
a350z4me
Well-known member
Where is that located?IndigoBlueWagon said:
IndigoBlueWagon
TDIClub Enthusiast, Principal IDParts, Vendor , w/
On the front of the engine, above the oil filter flange, usually covered with crud.
a350z4me
Well-known member
You are correct. My build sheet is wrong, it is an AHU.IndigoBlueWagon said:
bikeprof
Veteran Member
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I have wished many a time that my build sheet was wrong. 1Z is what mines got...
heere AHU, heere AHU..., where is that AHU?
heere AHU, heere AHU..., where is that AHU?
bikeprof
Veteran Member
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Trimmy, yours is probably an AHU since it was built in 1998.
"we" have never seen an '98 with a 1Z engine(so luck seems to be in YOUR favor !).
The AHU/ALH pistons are lighter therefore more boost/compression can be had in the AHU before blowing a head gasket.(means more HP/TQ ).
"we" have never seen an '98 with a 1Z engine(so luck seems to be in YOUR favor !).
The AHU/ALH pistons are lighter therefore more boost/compression can be had in the AHU before blowing a head gasket.(means more HP/TQ
).
Jetter_Sprinta
Veteran Member - TDIClub Contributor
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Another way to tell is the 1Z does not have the liquid cooled EGR(look for the ribbed aluminum tube on the back side of the intake manifold). Or, in the interim year (`97) are some of those mixed as well? My `97 B4 sedan has the AHU,. Both `96 B4 Wagons have the 1Z. I don't see a big difference. Unless you're modding to extremes, they'll both get you 400K+ miles
Last edited:
RIP TDI
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All '97 1Zs had water-cooled EGRs.Jetter_Sprinta said:
BigVWman
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I thought the difference in pistons was actual a production run change in the 1z and all blocks after #450001 came with the updated ahu pistons?
well mine has a liquid cooled EGR but I would still like to know where the stamp is on the block lol it's bugging me now that I started looking for it. Can anyone point me in a directions other than above the oil filter flange?
Thanks a lot
Justin
Thanks a lot
Justin
Franko6
Vendor , w/Business number
For me, the biggest difference is internal. The 1Z has an 8mm valve stem. It's a lot beefier and quite typically will last longer, at the expense of a bit of horsepower. The stem does take up some of the port...more than you think.
The 8mm valves are nearly unobtainable, or if you can get them, they are priced out of line.
I have a small collection of 1Z valves. If more than 3 valves need replaced in a head, it's cheaper to knock out the guides and replace all the 8mm valves and guides with 7mm. It's a direct exchange.
The 8mm valves are nearly unobtainable, or if you can get them, they are priced out of line.
I have a small collection of 1Z valves. If more than 3 valves need replaced in a head, it's cheaper to knock out the guides and replace all the 8mm valves and guides with 7mm. It's a direct exchange.
ARCJr
Veteran Member
Brought that one back from the dead, Frank...
oilhammer
Certified Volkswagen Nut & Vendor
LOL.... way to go Frank!
FWIW, my 1998 Jetta had an AHU engine, and said 1Z on the trunk tag.
FWIW, my 1998 Jetta had an AHU engine, and said 1Z on the trunk tag.
Lug_Nut
TDIClub Enthusiast, Pre-Forum Veteran Member
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Some 1Z have 8 mm valves, others have 7 mm. It depends on the engine serial number. The improved (thicker) valve guides were introduced during the 1Z production run.
In steps...
There are actually THREE combinations of 1Z valve, guide, springs used from the factory during the 1Z run. As Frank points out, going to full AHU valve componentry makes sense in many situations.
Ashes to ashes. May this thread rest in peace.
In steps...
There are actually THREE combinations of 1Z valve, guide, springs used from the factory during the 1Z run. As Frank points out, going to full AHU valve componentry makes sense in many situations.
Ashes to ashes. May this thread rest in peace.