Author Topic: 1Z/AHU differences (Read 14597 times)

vwmike · « **on:** June 02, 2006, 05:03:07 am »

Can anyone tell me what (if any) differences there are in the 1Z and AHU longblocks? The only thing I can think of is that the compression ratio may be a bit different but otherwise they should be interchangeable though I've had limited experience messing with them. Can anyone comment? Thanks.

Piper106 · « **Reply #1 on:** June 03, 2006, 09:51:40 pm »

Agree, as far as I know, the 1Z and AHU long block are identical, difference was the turbo fitted. TDIClub.com would be the place to get definite data.

Piper106

Bookerdog · « **Reply #2 on:** June 05, 2006, 10:30:02 am »

Piper pretty much has it. Very small differences. Garrett Turbo on the 1Z and a KKK on the AHU. Different ECU's and the 1Z had a wierd 5th injector that was subsequently disabled through a recall process. Mechanically though, the longblock was exactly the same.

RabbitGTDguy · « **Reply #3 on:** June 05, 2006, 06:56:31 pm »

One more difference between the 1z and the AHU... The AHU uses different pistons with thicker ring lands and ALOT more "beef" in general compared to the 1z pistons. When I built my 1z motor here I tossed the 1z units in favor for the AHU/ALH style units...

Joe

A2TD · « **Reply #4 on:** June 10, 2006, 11:05:24 am »

IIRC the 1Z piston's had lower ring lands than the AHU/ALH(the comp rings were further away from the piton crowne). This would subject the comp rings to less heat, I don know on the other hand that the ALh pistons came with brass trunions that are supposed to make them more robust, but then again I've never heard of any 1Z pistons going south.

RabbitGTDguy · « **Reply #5 on:** June 11, 2006, 08:09:27 pm »

Guess pics are worth a thousand words...
1z Units... there are stories on other boards (namely Fred's) of those stretching the legs of their MK3/B4 units with 1z's and cracking the 1z pistons... The AHU introduced a newer, beefier style. They are prone to cracking on the crown, mainly starting in the area of the bowl lip for the combustion chamber and going from there. I don't have a good shot of the 1z's from the side it looks like, but I do of the later units. They are def. stronger

Here are a couple shots of my modified ALH pistons... I had the lip of the bowl removed to lower CR so I could run more fuel/boost here with the setup. I also had the ceramic coated.... its a fairly good shot though as you can see the thickness of the ring lands as well as the brass truions

and after ceramic coating at SwainTech... (TBC for top, PC 9 on skirts)

Supposedly the 1z units are good to about 140/150hp or so... I can't confirm this but have read it in digging through the threads on Fred's prior to my build. Cracking happened to a number of people, namely across the pond.

Joe

vwmike · « **Reply #6 on:** June 12, 2006, 03:45:32 am »

Well, 1Z's were also much more common there as they came in Golfs, Jettas, Audis, etc. We only got the 1Z in the Passat.

A2TD · « **Reply #7 on:** June 12, 2006, 12:44:26 pm »

I talked to one of parts guys at our local VW dealerships, and we referenced part#'s of piston's used in the 1Z/AHU's. Now heres something ineteresting. The 1Z/AHU use the same piston up to a certain serial #. Basicly to make it simple, the 99 MK3 Jettas TDI's had different pistons, than the 97-98 mk3 Jetta. I was also assured that both pistons used were forged aluminum. So I guess its a crap shoot when your sourcing used pistons.

A2TD · « **Reply #8 on:** June 12, 2006, 01:38:54 pm »

Found a pic of a 1Z piston from the side......................I'm having a hard time spotting the differences in the ring lands.

http://forums.tdiclub.com/showthread.php?p=702096

scopefrfd · « **Reply #9 on:** July 04, 2006, 01:56:11 pm »

I disagree in regards to the 1z being a weaker piston...the 1z piston the top ring land is much thicker than an AHU piston...the 1z piston also is much more robust on the skirts...full 360 skirt. The 1z piston resembles both the 2.5 5cyl tdi piston and the 150hp tdi piston. THe ahu piston seems to be prone to scuffing much easier than the 1z. I do not know if this is caused by the skirt design. I have the 1z, AHU, ALH, audi 2.5 piston types on the shelf. I do not have a 150hp piston but I have seen pics of it

A2TD · « **Reply #10 on:** July 04, 2006, 03:12:38 pm »

This whole story comes from one person on TDICLUB (Dieseldes), who claims claims to have cracked multiple sets of 1Z pistons, until finally he swapped in a set of MK4 pistons and they never cracked again.

Simon aka TDI RS ran a 1Z up to almost 200whp, before finally bending all 4 rods, and lunching one piston. According to him the damage that happened to his piston was a result of the bending rod, not from cracking of the piston crowne.

I wonder if the pistons out of a 1Z in europe/UK, are the same part # as the 1Z piston in Northamerica.

vwmike · « **Reply #11 on:** July 04, 2006, 05:23:39 pm »

European '96 Golf TDI - 1Z -

Cylinders 1,2 - 028 107 065 L

Cylinders 3,4 - 028 107 065 M

US '96 Passat TDI - 1Z

Cylinders 1,2 - Mahle 038 107 065 AA
Alcan 038 107 065 BK

Cylinders 3,4 - Mahle 038 107 065 AB
Alcan 038 107 065 BN

That's out of Etka 6...it's hard to say really if there is in fact any big differences.

A2TD · « **Reply #12 on:** July 07, 2006, 02:58:40 pm »

Quote from: vwmike

European '96 Golf TDI - 1Z -

Cylinders 1,2 - 028 107 065 L

Cylinders 3,4 - 028 107 065 M

US '96 Passat TDI - 1Z

Cylinders 1,2 - Mahle 038 107 065 AA
Alcan 038 107 065 BK

Cylinders 3,4 - Mahle 038 107 065 AB
Alcan 038 107 065 BN

That's out of Etka 6...it's hard to say really if there is in fact any big differences.

Hmmmm one # can make all the difference. I have a feeling they may have upgraded for the NA engine.

lord_verminaard · « **Reply #13 on:** July 07, 2006, 09:20:03 pm »

Quote from: A2TD

Hmmmm one # can make all the difference. I have a feeling they may have upgraded for the NA engine.

I bet you are right. Maybe due to the lower quality fuel in North America? Also strange I list the same ring set for all of the AAZ, 1Z, AHU, and AFN.

Brendan
84 Scirocco 8v
00 Camaro L36 M49

caddy · « **Reply #14 on:** July 12, 2006, 06:14:49 am »

head of 1z and ahu are different , valves axle are in 8mm on 1z and 7mm on ahu.
some 1z tdi engine come with single stane injectors.