eurocars
5/17/15 - Never forget
- Location
- Indianapolis
- Car(s)
- 2006 GTI
The MK4 1.8T (06A) block has many advantages over the MK5 2.0T (06F) block. Most high horsepower builds tend to convert the front oil filter housing to the MK4 metal style with an adapter plate and remove the MK5 balance shaft assembly in favor of the 1.8t oil pump. With a MK4 block, no adapters are needed as they come standard. There is also no need to drill and tap an M7 hole for the oil chain drive tensioner. MK5 rods and pistons come with 20mm wrist pins as opposed to the MK4’s 19mm. The FSI crank has a longer stroke, making the FSI crank popular for 1.8 stroker builds, and it is also forged vs the 1.8 crank is cast. The 1.8 block will need to be bored out to accept FSI pistons as the bore is too small. There are two style MK4 blocks, 058 and 06A. The 058 has an internal balance shaft assembly, external water pump and 11mm head studs and cannot be used for hybrid builds. The block type and part number is cast into the backside of the block. Any engine code can be used (AEB, AWW, AXW etc) as long as it is 06A. I have noticed that blocks have either Mexico or Germany cast into them. I cannot find any difference between the two as far as construction but I went with a German block.
Block specific parts needed for the conversion:
1.8t oil pump drive gear (must be swapped onto FSI crank)
1.8T thrust bearings as they are specific to the 1.8 block. FSI only uses two thrust bearings and they are too wide for the 1.8 block. If using aftermarket main caps, they must match the block type.
FSI timing belt
FSI head gasket
FSI front crank flange plate. The FSI cover has a mounting area for a roller bearing for the timing belt. The 1.8t timing belt tensioner is prone to failure so many people convert to a manual roller (IE offers a conversion kit if you don’t have the FSI front cover or can’t use it). FSI part number is 06D 103 153.
FSI oil pan – You can really use either pan, but the FSI pan has mounting points on the belt drive side for the charge pipe. If you are not using the factory mounting locations, either pan can be used.
MK4 J-plug – There is a hole next to the thermostat area where a thermostat bypass hose connects, or it can be blocked off. Using a j-plug blocks the hole. ECS offers a billet version. Part number 06B 103 033. If using the j-plug ,the knock sensor nearest the thermostat moves to the flat boss to the left of where the J-plug bolts up. It uses an M7 bolt.
MK5 thermostat. This bolts directly up to the MK4 block. I have converted mine to a MK4 style flange and extended the pipe to use an FSI coolant hose (custom part).
Turbo oil feed line – The MK5 block has a port on the rear of the block for oil feed to the turbo. The MK4 block uses a port on the oil filter housing to supply oil to the turbo. A custom line must be made to supply oil to the turbo since there is no provision for rear feed on the MK4 block.
MK4 main cap bolts – MK4 and MK5 main bolts/studs are different. If you have upgraded to ARP main studs in the past on your FSI, they cannot be reused on the MK4 block and you will need to purchase MK4 specific studs.
Let me know if you have any questions or information to add. I will modify this post as needed.
Block specific parts needed for the conversion:
1.8t oil pump drive gear (must be swapped onto FSI crank)
1.8T thrust bearings as they are specific to the 1.8 block. FSI only uses two thrust bearings and they are too wide for the 1.8 block. If using aftermarket main caps, they must match the block type.
FSI timing belt
FSI head gasket
FSI front crank flange plate. The FSI cover has a mounting area for a roller bearing for the timing belt. The 1.8t timing belt tensioner is prone to failure so many people convert to a manual roller (IE offers a conversion kit if you don’t have the FSI front cover or can’t use it). FSI part number is 06D 103 153.
FSI oil pan – You can really use either pan, but the FSI pan has mounting points on the belt drive side for the charge pipe. If you are not using the factory mounting locations, either pan can be used.
MK4 J-plug – There is a hole next to the thermostat area where a thermostat bypass hose connects, or it can be blocked off. Using a j-plug blocks the hole. ECS offers a billet version. Part number 06B 103 033. If using the j-plug ,the knock sensor nearest the thermostat moves to the flat boss to the left of where the J-plug bolts up. It uses an M7 bolt.
MK5 thermostat. This bolts directly up to the MK4 block. I have converted mine to a MK4 style flange and extended the pipe to use an FSI coolant hose (custom part).
Turbo oil feed line – The MK5 block has a port on the rear of the block for oil feed to the turbo. The MK4 block uses a port on the oil filter housing to supply oil to the turbo. A custom line must be made to supply oil to the turbo since there is no provision for rear feed on the MK4 block.
MK4 main cap bolts – MK4 and MK5 main bolts/studs are different. If you have upgraded to ARP main studs in the past on your FSI, they cannot be reused on the MK4 block and you will need to purchase MK4 specific studs.
Let me know if you have any questions or information to add. I will modify this post as needed.
