NST Crank pulley specs

Paging any owner of the NST crank pulley for the TRD supercharger.

Bust out your tape measure if you would for me real quick please and measure the overall diameter of the pulley (OD). I'm trying to figure out how large they were but I can't seem to find the mm specs for it, or even overall inches. If you can get me a relatively rough idea of how large they are based on what your tape measure read then that would be great.

Yes I realize NST doesn't make pulley's for them anymore, but humor me please.

 

Nevermind,

175mm or 6.89 inches

Max size you can go on the crank pulley for those wondering if you ever want to swap out to a lightweight billet crank pulley on your TRD blowers and not touch the supercharger pulley.

 

So does this mean you are getting a custom made overdrive S/C pulley?

Not exactly sure what you mean by the that is the max size? Why do you say that?

 

Because any larger and you will run into tensioner interference. Unless you relocate the tensioner which would be a total headache. That's why I say max size. I really cant see the pulley being any larger than that. Stock size cuts it within what appears to be mm as it is.

 

Taken by @XeddeX the stock pulley size is in between 6 5/8 and 6 11/16 or 168.275mm and 169.86mm.



Like I was saying, the pulley can't be much larger than the stock one as it's OD pretty large as it is.

 

It is in a sense. Unless you can score a larger crank pulley for fairly cheap, or get one custom created by a machine shop. I do have the drawings to the larger crank pulley both front and side profiles in CAD, so getting one created without ever having to send a machine shop the pulley is a possibility.

 

^^^ That is true.

When NST made the O.D. kit, the purchaser had to have the Water pump pulley. As it was slightly smaller than the OEM. This gave enough clearance to allow the larger S/C pulley to fit. As well, smaller idler pulleys were needed for the s/c belt.

Where that kit immediately failed, was the cheap Chinese bearings used in the idler pulleys. To save on cost, that is the route which was taken. Those bearings would wear out in a few months. Shredding the s/c as a result. Owners could then either send in the idler pulleys and have new bew rings installed, of the same brand, or purchase their own bearings. Many opted to upgrade them to Micro Blue steel bearings.

There is a member with a stock engine, running the NST O.D. kit (I believe from another post of his) as well as the 2.55" URD pulley. He's also using meth injection and a 7th injector.

 

His list is pretty damn good considering his year model.

 

Do you absolutely have to run a water pump pulley in order to run the 3-4mm larger OD overdrive crank pulley? I would figure the tensioner would be the main are of concern before the WP pulley

More options, less downtime of the supercharger. Pull the belt off, remove pulley, install new pulley, retighten bolt, done.

No kidding. Very extensive list of mods!

 

Additionally, I have heard the new Corvette Z06 supercharged vehicles are having overheating issues. Apparently what they are doing to alleviate that issue is draining out the coolant and running 80/20 water/antifreeze mix. Water is supposedly better for the cooling system and keeping temps down. I am wondering what sort of effectiveness that would have if we did something similar in our system. Maybe less heat soak?

 

I remember them talking about it. It could have just been one of his selling points though.... A tape measure or calipers would let it be known very quickly though. Smaller idler pulleys might be necessary to keep the same belt though. Then just press out the bearings and move them over. Or buy new good bearings. Cross that bridge one step at a time.

 

Water does run cooler than antifreeze. However, it also freezes. That is what the antifreeze is for.

Just use the Toyota premix pink stuff. It is VERY good coolant. Just pink. Yuck.

 

I noticed that was a selling point of theirs as well. However, if the concern is belt slippage, that issue should ideally be non existant if you are increasing the size of the pulley as it will apply further tension on the belt due to it being slightly larger. Remember. You overdrive the crank pulley in order to up the boost, the reverse is true for the supercharger pulley.

Right, hence the fact they still run antifreeze, they just dilute 80% of it with water instead. So the non freeze properties are still there to prevent it, but the benefits of better water cooling.

 

Belt slippage wasn't the concern. Only making sure that the same belt could still be utilized instead of having to find another size. Thus the smaller idler pulleys, to compensate for the increased circumference.

 

The NST water pump pulley is slightly underdrive.

 

Oh crap. So they had to replace the pulley tensioner to a slightly smaller one. I see what you are saying now. I didn't even think of that. Was that pulley plastic like the stock one or was it billet as well? As long as it isn't much smaller it shouldn't be a huge issue. The range of movement in tension that they supercharger idler tensioner has is quite impressive.

 

I'll see if I could get a hold of a digital caliper or some sort of caliper to measure the air gap distance between the current stock crank pulley and idler pulley. As long as you match them up to the next larger setup you should be good to go.

 

How many pulleys are on the belt bracket? Including tensioner?

I don't remember if the tensioner was replaced. I do remember the idler pulleys were.

 

I don't see what the reasoning behind underdriving the WP pulley, is there close distance to interference with that as well?

 

If I remember correctly there is only 5. The crank, the tensioner, the bracket right below the SC which house two small pulleys and the supercharger pulley itself. I don't see why any other pulley including the water pump, idler, power steering, etc. Would be any kind of issue as they are all driven behind the supercharger drive.