Local Copy - TDI Piston Info
Local copy of the TDI Club thread
1999 1999 AHU (A-3) engine # 101808 and above Cyl 1 & 2 038-107-065-AA (MAHLE) Cyl 3 & 4 038-107-065-AB (MAHLE)
1999 AHU / 1Z (A-3 & B-4) engine # 101807 and lower Cyl 1 & 2 038-107-065-D Cyl 3 & 4 038-107-065-E
1999 AHU engine # 101808 and above Cyl 1 & 2 028-107-065-BK (ALCAN) Cyl 3 & 4 028-107-065-BN (ALCAN)
1998 1998 AHU / 1Z (A-3 & B-4) engine # 101807 and lower Cyl 1 & 2 038-107-065-D Cyl 3 & 4 038-107-065-E
1998 AHU engine # 101808 and higher Cyl 1 & 2 028-107-065-BK (ALCAN) Cyl 3 & 4 028-107-065-BN (ALCAN)
1998 AHU (A-3) engine # 101808 and higher Cyl 1 & 2 038-107-065-AA (MAHLE) Cyl 3 & 4 038-107-065-AB (MAHLE)
1997 1997 1Z / AHU engine # 101807 and lower Cyl 1 & 2 038-107-065-D Cyl 3 & 4 038-107-065-E
1997 AHU (A-3) engine # 101808 and higher Cyl 1 & 2 038-107-065-AA (MAHLE) Cyl 3 & 4 038-107-065-AB (MAHLE)
1997 AHU (A-3) engine # 101808 and higher Cyl 1 & 2 028-107-065-BK (ALCAN) Cyl 3 & 4 028-107-065-BN (ALCAN)
1996 1Z engine # 101807 and lower Cyl 1 & 2 038-107-065-D Cyl 3 & 4 038-107-065-E 1996 engine # 101808 and higher Cyl 1 & 2 038-107-065-AA (MAHLE) Cyl 3 & 4 038-107-065-AB (MAHLE)
A-4 ALH engine
A-4 ALH series 1999.9 thru 2003
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)
Now here is where I'm a bit confounded: The AHU and 1Z engines both have the same block (028-100-090-TX) Both engines use the same crank (028-105-101-L) Both engines use the same rods (028-198-401-F)
The only thing I see different between these engines (1Z / AHU) are the pistons.
Early: AHU / 1Z (A-3 & B-4) engine # 101807 and lower Cyl 1 & 2 038-107-065-D Cyl 3 & 4 038-107-065-E Late: Cyl 1 & 2 038-107-065-AA Cyl 3 & 4 038-107-065-AB
The A-4 ALH engine uses the same connecting rods (028-198-401-F)
My questions are:
Ques. #1
Are these pistons the same but only different manufactures?
1998 AHU engine # 101808 and higher
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)
1998 AHU (A-3) engine # 101808 and higher Cyl 1 & 2 038-107-065-AA (MAHLE) Cyl 3 & 4 038-107-065-AB (MAHLE)
Ques. #2
Are the pistons for the higher # series (101808 & higher) the same design but different manufactures? ALCAN ~V~MAHLE ? In other words are these pistons interchangeable?
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)
Ques. #3
If you were rebuilding a 1Z or AHU of any series # (high or low) What is the reason you could not use the A-4 pistons (as long as you used all 4 of the same P/N AA & AB)? Cyl 1 & 2 038-107-065-AA (MAHLE) Cyl 3 & 4 038-107-065-AB (MAHLE)
Here are a few pics comparing a 1z piston to the Nural ASV piston. I put the Nural piston in every 1z/ahu/alh block I rebuild.
In the above photos the piston on the right is: Cyl 1 & 2 038-107-065-D Cyl 3 & 4 038-107-065-E
The piston on the left is: Cyl 1 & 2 038-107-065-AA Cyl 3 & 4 038-107-065-AB
The main differances being the placement of the top compression ring and the longer skirt on the early version.
This answers my question of interchangeablity (Thank you).
Now the question about "BK" & "BN" pistons...are these the same as the "AB & "AA" ?
But I thank you for posting the great photos.
The later AHU/1Z pistons are an improvement over the older ones, as you can see in the excellent photos above, with regards to ring placement. That is really the only difference.
So long as they are all weighed the same, just replace them in sets. And yes, ALH pistons in the older engines would be an improvement, and is why I think the ALH engines seem to generally have less oil use than its older cousins.
The ALH pistons are lighter and the ring placement is higher than in the AHU's. If you do make the swap to the ALH's, I would be sure to hone the top of the bore to make sure that you don't have any problems with a wear land. They don't usually have much wear to speak of at that mileage. Instead, there is a little burn ring. But I would hone until it's straightened out.
Also, as for the rods, they are the same in the AHU's as the ALH... no difference. However, I've found up to 3 gr of difference in a set of rods coming out of a vehicle. Same is true about pistons, to a lesser extent.
Unless you are going to put in something more exotic for rods, leave the rods with the block that were in there to begin with. There is a length issue you might run into.
Nindee-gold-tdi: that new piston you show next to a AHU is a ASV piston, not an ALH. The dead giveaway is the smaller reliefs by the wrist pin and the oil chamber holes in the bottom of the piston. The ALH has no oil chambered piston head; it is domed.
Also, the ASV is shorter from the wrist pin to the top of the piston to allow for machining the block. Your picture exaggerates the difference because the skirt is longer, but if you push the wrist pin to fit across both pistons, you'll see about an .008" variation. If building with that piston, that should be taken into account, and the block should be decked. That is SOP for oversize or replacement pistons.
Last point on the ASV's and that would include several chambered pistons... you have to re-aim the oil squirts in order for them to work correctly.
Herm: As for interchangability, although the pistons have the same numbers, you can bet the weights are different and the overall sizes can vary around .06mm (that's .0018"). I would not recommend installing pistons in anything but matched sets. If putting a replacement piston into a set, try to match the measurement on the top of the piston. For example, 79.44 or 79.46mm are common.
Some pistons are engraved with the piston size. I think most of the pistons have been laser etched with that diameter number. If you use even a Scotch Brite pad on the piston, you will erase that number. I use an acetylene torch with oxygen, lightly passing it over the widest flat area on the piston top and the number comes up like magic.
That's packing in the information...
