Its purpose is to slow down the water pump at higher RPM. The reason for doing this is simple. We have seen with high HP high revving setups over spinning the water pump actually creates coolant pressure to increase, also adding a good amount of resistance on the rotating assembly including the water pump its self.
The new under drive pulley reduces back pressure on the pump, cavitation at higher rpm, lower coolant pressure, and also slows the coolant momentum speed down allowing better cooling time as the coolant passes threw the radiator. These are also lighter then OEM and anything rotational weights savings is always a bonus.
On the Evo 7 threw X we have dropped 5psi at 7000+ rpm of coolant pressure and average of 5 degrees of coolant temp during a WOT pull. and on the DSM we have dropped about 3psi of coolant pressure. All setups DSM/EVO as shown zero effects on street driving, long periods of idle while gaining better cooling efficiency for road racing, drag racing, and just every day normal use. 1/2 filled blocks, full wet blocks and even 1/2 radiator cooling setups have all shown great results.
These will come in 3 versions for the DSM 1G/ 2G Evo 1 to 3.
V1 will be WITH OEM power steering pumps
V2 will be properly offset for those who DELETED OEM power steering. No more spacer needed.
V3 will be for those who deleted OEM power steering and use ONLY 1 serpentine belt for the crank, water pump, and alternator. This pulley is offset additionally to use only 1 belt. (Some engine bracket trimming is required)
These will include 4 light weight titanium bolts.
Pricing is as follows.
V1 & 2 raw 130.00
V1 & 2 anodized 165.00
V3 raw 145.00
V3 anodized 180.00
You will need to get a new belt. Below is a chart with your setup and new belt part number you will need. Its just to many for me to stock at this time.
Please be advised
1g = no modification required to the mount.
2g/evo 1-3 = slight shaving on motor mount to clear the belt path. Very minor amount.