Author Topic: wtb tdi piston 1Z or AHU (Read 6992 times)

jimfoo · « **on:** November 27, 2007, 02:27:55 pm »

Well, I'd prefer free. It doesn't matter what shape it is in as long as there is enough to take some measurements off of. I am just wanting to see exactly what the difference is between a TDI and AAZ piston.

jimfoo · « **Reply #1 on:** November 29, 2007, 08:11:03 am »

So no one has a crappy worn out piston? Well at least it says something about reliability.

Vincent Waldon · « **Reply #2 on:** November 29, 2007, 09:09:49 am »

Are you just looking for the physical dimensions ??

Pretty sure my A3 Bentley lists them... could look them up if that will help ?

jimfoo · « **Reply #3 on:** November 29, 2007, 10:26:01 am »

That would be sweet!

burn_your_money · « **Reply #4 on:** November 29, 2007, 11:05:54 am »

AHU Piston Diameter

standard 79.448
1st 79.72
2nd 79.98

Thats all I can find in my Bentley

jimfoo · « **Reply #5 on:** November 29, 2007, 11:25:14 am »

Bummer as I need info about the pin diameter, top of pin to top of piston, and bottom of pin to bottom of piston info. Looks like someone in the TDI forum has a bum AHU, so maybe I'll hit him up for one of his pistons.

burn_your_money · « **Reply #6 on:** November 29, 2007, 12:44:31 pm »

I can't see the bentley listing those specs, they aren't critical to a rebuild other then pin diameter which I was surprised wasn't there.

jimfoo · « **Reply #7 on:** November 29, 2007, 03:12:22 pm »

But they are critical to putting TDI pistons in an IDI block.

QuickTD · « **Reply #8 on:** November 29, 2007, 03:28:19 pm »

All the piston/rod dimensions are the same from a 1Z/AHU to an AAZ. I can't speak for the new style ALH except that the rod length and pin diameter are the same, not sure about pin/deck height.

One question that feeds on my mind though, why convert something as rare in the US as an AAZ, wouldn't a real TDI block be more common?

jimfoo · « **Reply #9 on:** November 29, 2007, 04:11:28 pm »

I have an AAZ which will need to be bored, need a new head, need rings, pistons and bearings. It would be cheaper to convert it to a TDI than buy one. But I was told the TDI pistons are a different height, so I'd like to compare them and see by how much, and if they could be made to work or not.

jtanguay · « **Reply #10 on:** November 29, 2007, 04:20:33 pm »

the height difference is probably due to the fact that there is a big chamber inside the piston itself. although on the 1.9's and 1.6's there isn't really much room to spare anyways.

if the 1Z block is the same as the AAZ (size wise) then it should work. those internal piston domes are what lower the CR.

the only way i can see the 1Z TDI pistons being taller, is if the block was taller, which i dont think it is, except for maybe a few mm's??? and if the pistons are shorter, why not just shave a bit off the deck of the block???

jimfoo · « **Reply #11 on:** November 29, 2007, 05:35:54 pm »

Maybe I figured the solution out. If they are taller, I could just have the crank ground to sort of un-stroke it as this would lower the piston height.

MacGyver · « **Reply #12 on:** November 29, 2007, 10:16:11 pm »

I have one sitting here with a valve stuck in the top of it :lol:

Tell me what exactly you want measurements for & I'll fire up the vernier.

jimfoo · « **Reply #13 on:** November 29, 2007, 10:21:43 pm »

basically the height from the top of the pin hole to the top of the piston, and from the bottom of the pin hole to the bottom of the piston

MacGyver · « **Reply #14 on:** November 29, 2007, 11:04:51 pm »

There is a brass insert in the pin holes, I'll assume that's standard since I don't have any others in front of me.

Top of pin hole to top of piston: 32.70mm.

Bottom of pin hole to bottom of piston directly below hole: 7.98mm

However, the skirts are longer front & back than on the sides where the pin is, so it appears to be ~13.15mm from the bottom of the pin hole to the lowest part of the skirt.

Taken as approximates, that should tell you whether it's within the margin of error or unworkable.

Let me know if you'd like anything else