I'm not an expert in this area but I know there are many different "grades" of stainless steel. While stainless steel IS generally softer than carbon steel, it is still much stronger than most grades of aluminum. Experience in the field has revealed that most (or possibly all) pulleys that have failed have been the aluminum pulleys. Also remember that the Karmen pulleys were designed using a smaller bearing (smaller than other reduced diameter pulley designs) allowing for a thicker wall between the outer bearing and the gooved area. I personally have no concern about the stainless steel grooved part on the Karmen 62mm pulleys ever breaking apart.

 

What he said.

 

Hmm.. all those years in sheet metal.. wasted.. Oh wait.. drill a stainless plate and drill a carbon steel plate and get back with me on which is softer..

 

Well I DID start out saying I'm not an expert in this area . . .

 

LOL.. YEARS of cnc punching.. I hated stainless steel with a passion.. they finally came out with titanium coated punches that a least made it easier to deal with..

 

thanks for info REDDOG. i will contact Khang to see what version I got.

 

I like the fact that Bob took the time to research this. I already knew mine was stainless steel, and anyone who thinks stainless is soft should do as suggested and that is try to drill thru a piece. It's hard, and it's strong. I would never put anything less on either of my cars. I just wanted to understand what the problem was. Thanks to Bob, I now know, and that is that. I will still monitor my pulley as I still do the Code 3 I run on the roadster. Any guess what that metal is? Stainless is used quite a bit, especially in the trucking industry. I have a lot of polished stainless on my new rig. I feel a little better now. As I stated earlier, I voluntarily left the facebook page, as I did not feel at all welcome there. A few people got under my skin very quickly. Best to move on in that case, as you know from my posts here, I don't last long taken crap from someone who hasn't been there and done that. With that said, I think we are done here. A big thanks to Bob, and others who contributed reliable information here. Thanks for posting a photo of all three Lenin. Maybe that will help others keep the names straight. Thank you Rudy for you quality control. Later gentlemen.

 

Thank you to Dave-180 for posting this issue. I was not aware of the other failures since I don't do Flakebook. Also to Bob - RedDog for his very thorough reporting of the pulleys, pics and causes. Great work.

 

Unfortunately, after the research I did on the Karmen 62mm pulleys, I'm pretty sure your pulley had to have been one of those from the original production. I believe all of the pulleys from the "improved" production batch were sent to Rudy and distributed directly by him (except possibly one that Khang Vo kept for himself and installed on his own car). Accordingly, any of the "extra / leftover" pulleys that you, LENIN and I purchased directly from Khang Vo must have come from the original production batch. I suspect that also has to include the "replacement" pulley that was sent to LENIN. Personally while I hate to be the bearer of bad news . . . I would think all of those pulleys from the original production batch are subject to failure.

Here is why I've come to that conclusion . . .

The photo below is from post #164 in the original group buy thread started by Rudy . . .

https://www.crossfireforum.org/forum...tml#post703406

Rudy was showing that the assembly of the (improved) Karmen 62mm pulleys was underway. Note there are 20 backing plates pictured. Accordingly, I presume there are only 20 "improved" pulleys in existence and I believe (can't find proof but strongly suspect) that after assembly, all 20 (or maybe 19 as noted above) were sent to Rudy. If that is true then if you didn't get your pulley directly from Rudy you probably didn't get one from the "improved" production batch.

 

Bob, just got back from inspecting mine and while there, installed my pulley saver kit on the roadster. Mine appears to be doing just fine. No evidence of anything failing at this point. I hope you are correct. I haven't heard back from Rudy on this matter and that is fine. What I have discovered and this applies to all crossfires. My factory original crank pulley is showing signs of failure. She isn't turning true. It's never been off the car. I have a call in to Rob to send me a new one. I am going to replace it. Once I have it off, I will report back what the problem was....thanks again for those doing the investigative work.

 

Hey Doc . . . Good information about the crank pulley and good advice to check it. I will take a look at mine. Looking forward to what you find when you get it removed . . .

 

So I'm trying to understand...forgive me if I'm a little slow on the uptake.
What is the cause of failure?....heat?
Why is heat a problem? Because it can make the backing plate brittle?
Where is the heat being generated from? Sliding on the magnet?
Why is it sliding? Too much gap?
Why is there too much gap? 1) Rivets not recessed?, 2) incorrect shims/setup?
What evidence is there that heat/sliding is a problem? - Burnishing on the rivets and backing plate (ultimately)

Please fill in any missing or wrong details/statements. And we'll come to a consensus.

Another thought....
Trying to understand the pulley itself......

When the magnet engages - the backing plate gets magnetized and lock step with the main magnet/rotors.
Of course the backing plate can't move - so this locking is purely magnetic...or is there movement and you get friction "grip"?
Now - all the force/resistance provided by the rotors in compressing the air - is fed back through the pulley to the belt.
This is transferred through the rivets and the attached arms....into the pulley.
The force required to pump at 74mm pulley is much less than a 65 or a 62mm pulley. We are talking something like a change from 25 to maybe 45-55kW of required energy in the Sc.
So - is this increase accounted for in the design? - is it reaching the limit of the material strength?...
Is all this I've said bull$hit?

 

Not BS.........
You've pretty much hit the nail on the head to my mind.
There obviously has to be some slip at the initial hook up, any slippage after that is not wanted at all.

 

Well, not to open another can of worms..... At this point, I think a batch was produced that did not recess the rivets far enough into the plate. Once the plate started to wear, which it shouldn't have in my opinion, it started to heat up and wear on the rivets until a failure occurred. Just my take on it. Mine are recessed into the plate.... Plate isn't showing a lot of wear on mine either. Some of the failures you are seeing here had NOTHING to do with the Karmann pulley. But were the aluminum EC pulley. Lets not get them confused again. That is all I have to say... on it for now. WE will see what the builder has to say with actual facts about the failure.

 

Is our electromagnet clamping force adequate for the added forces? Is there a big difference in the magnetic properties of the different metals used for the different backing plates on the different pulleys?

 

Different irons and steels have different magnetic qualities, iron is the most attracted to a magnet. Carbon steel alloys are very attracted to magnets. The various stainless steel alloys vary in their attraction to a magnet, from highly attracted to not noticeably attracted, some are attracted prior to hardening and not after.

A malleable iron would be best as a clutch plate as it is ductile, a cast iron is brittle and will crack.

The rivet head being flush or under the surface is really no concern, the clutch plate is not like a brake pad and subject to a lot of wear. Let's face it if there was a lot of wear we would be replacing SC clutch plates quite often so as they do not wear then a flush mounted rivet will not wear either, they get scratched a bit and so would you be if you were practically stationary and then grabbed hold of a rotating SC pulley.

A clutch driving the SC at higher revs sees forces that increase exponentially. A SC driven at higher speeds will fail faster than the ones at OEM speeds. Those are givens and cannot be avoided. Bearings in the SC will fail sooner, if the bearings fail catastrophically then the rotors may touch and will be ruined.

Your replacement SC may be worth more than the car the way prices are going.

 

Old thread - sorry, but I want to add some observations, now that I too am a member of the Xfire SC Grenadiers club. With both pieces of the aluminum pulley now removed,(it split) I inspected the shaft to which the pulley attaches closely and found numbers that had been hand scratched into the shaft, for what reason, I have no idea. As the shaft turns, a dry sound is heard from the rear of the SC. So I put on my stethoscope to confirm and yes, the noise is from one or both of the rear bearings of the SC screw shafts and I feel like it is best at this point not to continue the failed dogbone /pulley replacement until I can feel secure about the SC and its future longevity. I feel that this SC needs to come off and be rebuilt or restored before putting it back in service. Is it possible that a vibration was set up by the failed screw bearings which led to the failure of the dogbone and subsequently the pulley split? or, would one guess that failed casting of the aluminum pulley caused the pulley to first split resulting in the dogbone failure? Either way, whats done is done and what now has to be done is change out the SC I feel. I was going to try to get by with changing out the SC oil, but those noisy bearings are sealed type and the SC oil does not lubricate them I see. Is it true that only one place in the US can rebuild these? A link would be helpful and some tips on crating the SC for shipping please....Thanks in advance...Peace

 

It is not too hard to replace the bearings yourself. There are photos here that show the SC apart and you can see the individual parts. The bearings can easily be found, there is nothing much to be done except to replace the bearings.

 

From the Chrysler Crossfire Owners group on facebook..

Deborah Marrone Zerillo just sent an email asking for a price to rebuild the SC - a place out of oklahoma called PSE superchargers. anyone deal with them before? i'm not ready to let this car go!

And a follow up post...

Deborah Marrone Zerillo it's not 8k - that was for a new SC - it's $1,700 to get a re-manufactured one from PSE out of oklahoma - having my mechanic remove the SC (very specific instructions), shipping it out (again with the instructions) - it'll take 4-6 weeks to be shipped ...See More