Magnuson SC Kit Idles Like Garbage - HELP!
 

Hi All,

I've been dealing with a Magnuson SC issue for 6-months with no resolution. The installer and Magnsuon have worked together to replace all sorts of parts and they just can't get the kit to idle on my 2016 Limited.

Anyone else had issues with idle or warranty issues?

The issue I'm having is with the belt drive system. The tensioner can't keep the belt stable and there is belt flutter and resonance at idle. It's prematurely wearing the belt and when it is warm the belt is so loose you can pop it off with your fingers.

Now, Magnuson is saying this is normal and the belt is supposed to flap around and make noise. In 20-years as a motorsports hobbyist, I've never seen a working sc drive belt flap around, lol.

Not sure how to share a video on this site, but you can download a quick clip here if you want to see the belt issue. Link

So far, Magnuson has tried several different belts, multiple tensioners, inspected the SC and the intsaller replaced the facotry crank pulley JIC. Nothing works and now that I want it fixed or to get my money back the installer and Magnuson are trying to say this is "normal" after trying to fix it four times. They have totally flipped their stance now that their is skin in the game.

Any feedback would be appreciated on how to deal with this issue.

I know nothing about your specific situation. Generally if it's not a bad belt - a flapping belt is a result of a belt being too long, tension spring not being strong enough, or the pulleys being out of alignment. A pulley with a machining error could cause an issue if it's eccentric on the axis it rotates on.

I'd check your supercharger shaft for any play in the bearings of the shaft that the pulley is attached to as well. And make sure the pulleys appear to be aligned visually.

Thanks! They did say the original bet was too long. However, they did replace the belt. They said the new one was within their spec BUT it still has flutter. :doh:

Sorry to hear about your issue. I have a Magnuson SC on my 2016 Trail since April of 2018 and haven't had one issue. The tensioner has always worked correctly and the belt has been tight. I hope you get your issue resolved soon so you can enjoy the SC.

Looks like one of the pulleys are out of round or not centered correctly.

Agreed - I saw a friends Mustang this year ( after a charger bolt on kit with underdrive pulleys ) doing the same thing ( tension arm wobbling away like that ) The resolution was indeed one of the aftermarket pulleys out of round. Seemed quite obvious to the mechanic who installed the kit but didn't affect operation initially so he was able to drive it until they could replace the pulleys again. After another set things were just fine, no more tension arm movement or belt flutter.

Thanks! After they replaced the belt and tensioner those are the only things that make sense, pulleys, and idlers, maybe even the bracket that holds them isn't true.

I did notice that some of the earlier kits have nice machined AL pulleys and mine has much cheaper looking plastic parts that might be the culprit.

I appreciate all the feedback. Magnuson's techs and the local dealer are trying to gaslight me into thinking belt flutter and vibration in the drive belt is normal. It's not normal. This is not my first experience with an aftermarket supercharger, not even my first boosted application. I've been around the block a few times.

That's the experience I expected.

So, at idle your belt is nice and smooth like the factory serpentine belt? It doesn't flap around or vibrate randomly? If you could share some video I'd love to compare.

Thanks!

I installed mine Jan 30 2020, myself, took a trip and run the odometer up about 3K miles so far.

It's running smooth and no belt wobbling anywhere, at idle or with gas. From your VDO the tensioner wobble, probably something not true or round to cause the tensioner to wobble.
Sorry..
I will take a VDO later and show you.

Thanks, I really appreciate you taking the time to look at the video.

I watched the video. Hadn't before my last comment. It sure looks like some type of surging problem to me. Now my guess is that it's not a belt problem. It's a cyclical supercharger resistance problem is my bet.

Do you have the ability take the belt off yourself? If you do - take it off and rotate the supercharger input shaft by hand. Feel whether it has a spot of high resistance as it goes around or whether it spins with roughly the same resistance throughout a few rotations of the pulley.

The next place you should consider looking, and I'd bet this is where you find a problem, is for a leak in the vacuum bypass or a problem at the vacuum bypass valve (like a sticky butterfly valve - which is my armchair quarterback diagnosis #1). If you have a vacuum leak or a problem with the diaphragm in the vacuum bypass solenoid mechanism it could cause something like what you're experiencing if there's condition where the vacuum causes it to close the bypass ->engine surges from extra air from the supercharger -> ECU closes throttle body slightly more to stabilize rpm -> manifold vacuum increases -> supercharger bypass opens -> rpms drop -> ECU opens throttle body -> manifold vacuum drops -> bypass closes some-> and the cyclical balancing keeps going round and round. Just spitballing here on the cycle that would happen - but suffice it to say that a vacuum leak somewhere could very well cause a problem and this may be a symptom of that. I'd place my bet on it being a vacuum leak somewhere.

Tell Magnusson they can send me a free one for diagnosing the problem from a 10 second video. :)

Good luck!

Awesome feedback. Note, it does have bigger belt fluttering when there's any load at idle, such as in gear but stopped or when the ac or power steering is causing load.

Another friend of mine, a mechanical engineer, said to look for the same thing you said. I can poke around a bit but can't open it up to check anything myself as not to void the warranty.

I'd love to have Magnuson send you anything! Unfortunately, the dealer nor Magnuson will reply to any communications from me since I told them to fix it or take it off! We'll see where this goes :playball:

mine has been fantastic since day one, apart from the coolant hose rubbing against the belt and getting cut, but the dealer fixed that. Hopefully they'll figure it out.

It's too bad there's not a Magnuson rep on the site to address this. Frankly, its the type of problem and customer service that would result in the loss of sales. I'm certainly re-thinking it for the future.

The problem may be rare, as evidenced by loads of different positive things I've read about the system, but you're not just judged by what goes right. You're judged by how you deal with someone having a problem, and this doesn't sound like proper customer service to me. Had it been my company, I would have put one of my engineers on a plane to come have a look at it. And if he couldn't figure it out, I'd have him install a brand new one on my dime.

This "it's not our fault and its normal" response is unacceptable. Anyone who knows anything about forced induction knows that's not normal.

I posted the vdo on BAJA4RN IG
My belt seemtighter than yours that why less wobble on my. I would take the belt out and check each pulley for play or anything.
Hope that help.