JeffinMd

Could someone clear up what makes the compression different between these two? I'm assuming that the head of the 225 has more volume since the bore & stroke are the same. This seems misleading to me since they're both called the same 1.8L.
Am I clueless here?

Thanks, Jeff.

Taner Halicioglu

I think the innards are the same, no? I don't know for sure...

ask on the TT forum? :-)

CharlieGSanD

IIRC the 225 TT has forged internals

Agent911

they are all forged. 225 and 180 as far as i know.

xr4tic

is to add a thicker head gasket. I'm not sure what the two compression ratios are, but you can drop quite a bit, depending on the chamber volume and piston dish.

xr4tic

and the stock 1.8T rods from my 97 1.8T were forged, most connecting rods are.

The following 4 things will affect the compression ratio:
1. displacement (volume)
2. piston dish/dome volume
3. combustion chamber volume
4. head gasket volume

any change in those four areas, will change the compression ratio.

Žob

I can't remember exactly why, but I do recall in Maximum Boost he did not recommend that.

Tron (///M)

I was told by some of the Automotive enigneers that this wasn't such a good idea on the 1.8T. I'll try to find the thread.

WYSIWYG

well? go get the book! =P

4kq

There is no engineering reason not to do it. It is done all the time by factories and racing teams. The advantage is that you don't irretrievably mill off head material and it gives you a safety margin if you overdo the boost.