Dethred

Hey guys,. I'm finally getting some time in to work on the installation. Before I install the blower and bracket, I wanted to check and see if the default included pulley is ideal or if there is a smaller (?) Pulley available to make more power/boost. I don't want to end up disappointed with a low 400whp number and later realize I could have used a different pulley to make more power. Thanks in advance!

outeiroj

the common theme from kw is that they do offer a 90mm pulley but it starts to overspin the blower at high rpm. If someone had a gun to my head and i had to redo it i would probably not go to a smaller pulley but run id1300 injectors and get a ballade ported intake manifold and 70mm throttle body... some s/c guys have been seeing major increases from the added flow. I may make an attempt to get to 500 on pump gas this year with those additions

Dethred

I wonder if simply spinning the motor up to 8500rpm will bridge the larger pulley vs over revving the blower... I just don't want to continue, and then realize that a $90 pulley would have gotten me an extra bump in power. Really don't want to do this twice, it has been hard enough to find time to do it once.

outeiroj

if i remember correctly the 90mm pulley wouldnt start overspinning the blower at 8-8200 rpms

S2DALOO

With the 90mm pulley, I believe the RPM max is 8450 before overspinning the blower.

Code

Last piece arrives today,..........

kumar75150

This chart was correct to a tee in my case. https://www.s2ki.com/forums/s2000-fo.../#post23517831

I have an AP1. I made 405whp with the 12.5psi pulley and 460whp with the 16.5psi pulley.

Kyle

To me the sweet spot would be the 95mm pulley for an 8900 redline. I'd gladly sacrifice 200 rpm for 2 more pounds of boost. If anything I highly doubt exceeding the maximum speed limit by such a small margin would be of any detriment.

Formula for the C38 calculation is as follows:

Max impeller speed = 90,000 RPM

RPM calculation = ( crank pulley diameter (128mm) / blower pulley diameter (90-100mm) x drive ratio (7.5) x engine RPM)

So in the case of the AP1 standard 100mm pulley it would be 128 / 95 * 7.5 * 8900 = 89,937 RPM


I REALLLLLLY couldn't see the blower grenading from keeping the fuel cut RPM redline at 9200 with the 95mm pulley. That would put your max impeller speed at 92,968 which is only 3.3% over the maximum limit....

Conversely, if you keep fuel cut rpm on the 90mm pulley that puts you at 98,133 RPM which is 9% over...at that point I'd definitely be weary. I know the Paxton Novis can handle being overspun like that all day, but the Rotrex blowers have been known to be much more sensitive to overspinning. 3% though? I'm willing to roll the dice on that one.

LHT just did an AP1 with the C38-92 and the standard drive pulley (100mm) and it made 430ish whp on 93. I'm sure you'd be looking at over 450 with the 95mm pulley and close to 500 with the 90mm.

outeiroj

this makes me sad that I didn’t follow my gut and do the 90mm pulley. I could have hit 500hp on pump gas =(

kw talked me out of it on the phone and my redline is 8200 so I would have been fine with the 90mm

leov36

Started my car up for the first time! I was pretty nervous but everyone went surprisingly well. The banjo bolt on top of the oil reservoir wasn’t seated correctly so oil spewed everywhere but that was an easy fix. I did the whole priming procedure by myself which wasn’t a big deal. I let the car idle for quite a bit after reving it several times and checked the oil level several times. Once I turned the car off I did loosen then re tightened the belt according to the kw Facebook group procedure. The car sounded great. The supercharger sounded perfect with no weird or concerning noises (something I was worried about). The belt and pullys all seamed straight with no wobble. The car seemed to rev and idle quite nicely on the base tune. I didn’t get a chance to drive it yet as it’s still up on jack stands and missing headlights till tomorrow(that has been a whole project in itself) and I just don’t have the time today. That will be the true test