STROKING THE MOTOR.
A great way to fight lag or add more base hp to the motor is increasing the displacement of the motor. There is a couple routes you can take to accomplish this and will be covered below. As for power, my personal car went from rated at 180bhp and 170tq at 11psi to 172whp and 185wtq with only 8psi. That is roughly a gain of 20whp and 40wtq with 3psi less boost using 15% drivetrain loss. This is also with .25 lower in compression and a 3" dp tapered to 2.25 (should negate the decrease in boost).
USING THE STOCK 1.8T BLOCK
With using the stock 86.4mm crank, increasing bore size will give you the following:
81mm bore = 1781cc- stock displacement
81.5mm bore = 1801cc
82mm bore = 1825cc
82.5mm bore = 1847 (small 1.9L)
83mm bore = 1870cc (1.9)
83.5mm bore = 1892cc
With using a 2.0T FSI or 2.0 AEG 92.8mm crank will give you the following:
81mm bore = 1912
81.5mm = 1936
82mm = 1960
82.5mm = 1984
83mm = 2008
83.5mm = 2032
It is recommended that you do not go above 83mm on a street car. This gives you enough cyl wall to be strong and not risk blowing the block due to cyl pressure when running large amounts of boost.
CRANK INFO
the FSI cranks are forged and the AEG crank is cast. There has been much debate over the strength of the cast AEG crank but it has seen well over 500whp and has yet been broken with power. The FSI crank can be found from a couple websites or in a full kit from qedpower.com along with stroker pistons, scat rods,and all the hardware for install. You can find used AEG cranks for <$250 and a new FSI crank is ~$600. You will also need to stock 1.8t oil pump gear installed onto the new crank before it is installed.
PISTONS
You will need a custom set of "stroker" pistons when using a 92.8mm crank. These pistons have the pin (where it attaches to the rod) moved up the 6.4mm to account for the added stroke of the crank all while keeping the stock 144mm length rods. Also all these pistons come with 20mm wrist pins so 144/20mm rods from scat or IE will be needed.
You will also need to take into account the compression ratio (c/r) when ordering the pistons. Keeping the stock 9-9.5:1 is ideal for the street. This keeps plenty of power when not in boost and helps spool the turbo faster all while still being safe to run plenty of boost on pump gas. You can also choose to decrease the compression all the way down to 8-8.5:1. Bringing it down this low will allow you to run more boost on pump and also prevent timing pull. It is also safer on the motor since it decreases cly pressure considerably. This however will make running the car off boost more sluggish. This method is more for the racer (either road or drag) that will be basically in boost the entire time driving the car. Finally you can also increase the c/r. This is a less commonly done since it decreases the amount of boost on pump and makes tuning more important. It will however increase off boost response and spool up which is the plus. The highest that i have seen used is 10:1 which is about the highest one should really use on a F/I car.
When ordering your pistons you can also have the top and skirt coated. This ispretty inexpensive and offer good benefits.Having the top coated will help reduceknock and prevent some timing pull. Having the skirt coated will help reduce friction on the cyl walls and improve mpg and breaking in the motor. Both very good things to consider when orderingpistons. It will increase the cost about $75-125 but worth it to some since it will also increase the longevity of the motor while helping to produce power and reduce noise.
Piston Manufactors:
JE
Wiseco - these are actually rated for stock disp, my 9.25:1 83mm pistons come to 10.16:1 c/r when installed
Supertech
Mahle
Ross
RODS - see top of page.
MOTOR BUILD PARTS LIST - MUST HAVE
Crank bearings
Main Bearings
Main Bolts or Studs (stronger and reuseable)
Head bolts or Studs (stronger and reuseable)
Flywheel bolts
Rear main seal
Headgasket - Stock for 81-82mm or ALT (NA 20v) 82.5-83.5
Oil pan silicone sealant
Front seal
Valve cover gasket set
Timing belt kit, tensioner at the min
It is not needed, but really advised to replace the oil pump also. It is only about $100 which is cheap insurance when spending $1000's into a new motor.
USING A 2.0 AEG BLOCK.
Not going to go into this since its more work, but is an option since the crankwith block are cheap and can be built and then dropped into the car instead of using the stock engine and have more downtime. All info can be found here
http://forums.vwvortex.com/zerothread?id=2436326
USING A TDI ALH BLOCK 2.1L BUILD (95.5mm crank)
Again, not to many willing to go this route, so a link will be given.
http://forums.vwvortex.com/zerothread?id=2483044
FINALLY THE MACK DADDY, 2.2L BUILD (99mm crank)
Complete build up and then some
http://forums.vwvortex.com/zerothread?id=3335766
Also if you are a catalog kind of guy, eurospec makes engines with 2.0-2.2 with a selection of c/r's.