I understand making the crank pulley from Ali, smaller turning mass, but what is the advantage of an under drive pulley and turning the water pump slower.

 

Paul

Same thing really, turning the other pulleys slower means less force is required so more left for the wheels.

More low end torque, it does make a noticable difference. I don't think that the water pump will turn much slower if it does at all. The underdrive pully i put on mine was a smaller radius and in theory (i think) should in fact turn the water pump quicker.

 

HTH

 

Alex.

Making the crank pulley lighter and smaller reduces the drag on the crank thereby releasing a few more HP's. However, installing a so-called Under-Drive crank pulley will run the water pump slower which could be detrimental to engine cooling under extreme load (ie, track) conditions. To counter that you can purchase a so-called Over-Drive water pump pulley which will return the rotational speed of the water pump back to normal when used in conjunction with an under-drive crank pulley.

 

If you're interested in purchasing any lightened pulleys please let me know as I sell the lot:

 

Unorthodox lightened under-drive crank pulley

H.I. overdrive water pump pulley

Unorthodox lightened pulley set (4-pcs)

 

Also sell STOCK sized but LIGHTENED crank pulley

 

HTH

 

Dan

ok, cheers guys.

The UK and Jap models have different size stock water pulleys.

 

The UK Pulley is much larger than the Jap Pulley (I imagine this it to prevent water cativation at high speed on European roads).

 

I do not believe there are any problems with an undersize crank pulley on a Jap model. However fitting an undersize pulley on a UK model could potentially cause more of a risk to overheating issues than a Jap Model.

The UK and Jap models have different size stock water pulleys.

 

The UK Pulley is much larger than the Jap Pulley (I imagine this it to prevent water cativation at high speed on European roads).

 

I do not believe there are any problems with an undersize crank pulley on a Jap model. However fitting an undersize pulley on a UK model could potentially cause more of a risk to overheating issues than a Jap Model.

 

Might be an idea to confirm this with Mike feeney, as I have compared some and they were the same?

Ah, perhaps its only certain years then. I swapped the larger UK pulley that came on my engine (from a 93 UK) for a smaller jap pulley.

Dan - these overdrive water pump pulleys - I take it theyre not necessarily heavier than stock (i.e. counteracting the weight saved from the crank pulley)? Also do you need to use different belts when installing an overdrive one? Price?

Ah, perhaps its only certain years then. I swapped the larger UK pulley that came on my engine (from a 93 UK) for a smaller jap pulley.

Got an underdrive pulley on my 93 UK and its seems fine mate. Runs at 83 degrees no matter how hard i drive it. I do have a koyo radiator though which might make a difference and I also noticed a drop in a couple of degrees when i fitted the bonnet vent.

Got an underdrive pulley on my 93 UK and its seems fine mate. Runs at 83 degrees no matter how hard i drive it. I do have a koyo radiator though which might make a difference and I also noticed a drop in a couple of degrees when i fitted the bonnet vent.

 

my temp sits nice and low while driving, but when stationary it starts to creep up a little too much for my liking - this is probably due to a) my numberplate used to cover pretty much the whole of the front bumper, and b) since i installed a twin intake kit, it runs quite lumpy and at about 600rpm. i think this is likely giving the cooling system a hard time. i need to blip the throttle, or even hold it down slightly, just to bring the temp down. now that my number plate is smaller and i have a vent cut into the bonnet, no doubt this well help, but im hoping that getting the rough idle sorted (maybe going back to a single filter), and possibly installing one of these overdrive water pulleys should do the trick.

I would also be interested. in prices for the full kit belts etc