Oversize pistons, Increasing Displacement

I want to increase the size of my TDI via bore only. Has anyone done this or know where to get pistons? I would like to go as big as I can and not effect reliability. Any info would be great. Thanks, Ian Hoover

VW has over size pistons but I forget how much over it is. They only offer one over size.

Greg

Probably not a worthwhile modification unless you were rebuilding an engine anyway. Even still, I’d just hang with the thicker wall if boring was not needed, but just a good hone. If a 350 cid Chevy only gets 5 cubic inches from a .30 overbore on a 4-inch bore, and 8 cylinders, there probably isn’t more than a couple cubic inches to be gained. And since the Jetta doesn’t make more than one hp per cubic inch stock, you are looking at less than 2 hp. I didn’t do any math, so I could be of by 1 or 2 hp/images/graemlins/grin.gif

Ive bored mine out to 81mm to 1968cc, id only recommend it if you block needs boring out but at least it save a block from being scrapped.

[ QUOTE ]
tdi rs said:
Ive bored mine out to 81mm to 1968cc, id only recommend it if you block needs boring out but at least it save a block from being scrapped.

[/ QUOTE ]
You`re using 2.5 pistons, right?

I am doing a rebuild (bought a motor with piston to valve damage) and since I'm doing serious work, i wanted a serious upgrade, especially if i have to pay to get the block machined anyway. I saw that VW offers slightly enlarged pistons for stock type rebuilds, and i may have to do that, but i was hoping for something bigger. I have heard rumors of 2.2l TDIs and was thinking about something in that range, although that may be a bit extreme. With the very large TDIs, dothey go to a longer stroke as well?

You just use 2.5 tdi pistons and have the block bored out 1.5mm extra,as for the head gasket just use a g60 gasket.There steel and have a bigger bore size.

Is there anything bigger than the 2.5L pistons? And do you know the actual size of the 2.5 pistons? What do they do for compression?

VW releases each engine with 3 standard piston sizes, and 3 oversizes. The oversizes are available in increasing sizes of .25mm ... So says the Factory manual.

The pistons are 81mm and there isnt any oversize versions available of the pistons i use,there is of the lower powered up to 1mm oversize.

Hi i have some piston questions for you. You told me the biggest pistons avaliable were the 2.5l pistons and that they are 81mm, you also talked about a lower power piston that's avaliable in a 1mm oversize? Could you tell me more about these pistons vs. your pistons? Are the lower power pistons you speak of a different compression ratio? Is the 1mm over bore an 82mm piston? Do you know of any aftermarket pistons? What i have is a TDI that i swapped into a vanagon and i need all the power i can get. I bought a bloack that had a timing belt failure and i want to rebuild it for maximum reliable torque and power. My plan was to go with as big of a displacement as possible with bigger injectors and a mild boost increase with stock compression ratio. Any help you can offer would be great. Thank you, Ian Hoover.