Ok, this isn't exactly the way that I wanted to introduce this, but oh well. I recently had the Kraftwerks SC kit installed with the C38-91 blower and an 85mm pulley installed. I picked the car up Saturday, drove it gingerly to the dyno, and then had it tuned. The car made 462/281 at 19si on a Dynojet dyno. However, this was short lived. On the 4th pull the tuner stopped and said the car wasn't making boost anymore. We looked under the hood thinking maybe a vacuum line blew off, nope, the pulley was just sitting there off of the back of the supercharger. The bolt that holds the plate that the 85mm pulley attaches to wound up breaking in half. Sorry for my lack of mechanical terminology as I'm not exactly sure what these pieces I'm referring to are called. Things are in the works between the installer and Kraftwerks to fix this issue, so there is no need for bashing of any kind.

Now this is where I need everyone's help. How could this have possibly happened? Has anyone seen anything like this happen before? How or what can I do to prevent this from happening again?

The Good:

SC5 by gccgoalie33, on Flickr

SC3 by gccgoalie33, on Flickr

SC6 by gccgoalie33, on Flickr

SC2 by gccgoalie33, on Flickr

SC4 by gccgoalie33, on Flickr

SC1 by gccgoalie33, on Flickr

https://www.youtube.com/watch?v=hBJjMY7r-dM



The Bad:

The bolt that broke is circled in the middle, part 11

 

Wow! Interested in seeing what caused this! Very sorry to hear/see this.

Maybe just over torquing the bolt...not too sure... Here is the Rotrex technical hand book for reference. See 4-1 and 6-1.
http://www.rotrex.com/media/5fd67e23...20Handbook_pdf

 

Thanks man, I was actually reading that the other night trying to find an answer there.

I was actually commenting back and forth with a person on IG and he mentioned stiffer engine mounts. Which honestly makes perfect sense to me. If the engine was flexing too much, that could put a lot of pressure on the pulley. So if a tight belt is pulling down on that pulley as the engine lifts, that one single bolt in the middle is then taking the brunt of pressure, so I could see it possibly snapping in half like this one did.

 

I would call KW and send them the blower. That bolt is installed by rotrex if I read their documentation properly.

Also the whole belt system is mounted to the motor and mount very solid too. I don't see how motor mounts would account for any additional stress on any of the drive belt pulleys.

 

Is this on pump gas? And yeah motor mounts shouldnt affect that, since the blower is attached straight to the block. If motor moves the sc moves withit. Only thing i can think of are the charge pipes but the have rubber couplings that shoyld bend anyway.

 

Only a guess, but belt tension could have been too tight. That bolt is indeed installed by Rotrex. The installer only installs the 6 perimeter bolts holding the pulley to that mounting plate.

 

Yes...as others above mentioned, that is not possible as the system is mounted directly to the engine. All of the factory pulleys would have this problem if this was the case. It could just be a bad bolt or simply a case of over torquing that bolt. I do agree that over tensioning of the drive belt could be possible as well. Let's see what KW has to say.

 

Thanks for the advice guys. The installer is in contact with KW trying to sort out the issue. I'm just trying to lend a hand in figuring out how this happened in the first place. So if/when a new blower is received we can make the necessary adjustments so this doesn't happen again.

And yes this tune was on 93oct.

 

I'm hoping to get my C38-91 installed next week, so this excites me very much! (the numbers, not the broken piece).

As for the bolt, as far as I'm reading the instructions and looking at the same kit sitting in my living room. That is definitely the bolt that's installed by rotrex on the blower.

 

i tihink is overtiting the belt bro! but lets see what KW says...

NICE! mods in that intake custom... also what blow off valve is that? why you decide to go with? thanks!