Within the past few thousand miles, my supercharger has started rattling at high rpms. (5000+). Recently I've also noticed a lack of power at higher rpms. It's not a huge difference but it does not feel like it pulls as hard as it used to.

Wondering if this is normal as the supercharger slowly dies? Or should I look elsewhere for the missing power?

Also, I know the bypass valve going bad can cause these cars to loose boost. I replaced mine 80k miles ago with a DT BPV. The original was worn after 75k miles. Do these also wear out like the stock ones? Should I replace mine?

 

would start with basics - spark / fuel / air

Spark - how old are the plugs and coil pack? Have read here and elsewhere a new set of plugs can make quite a noticeable difference, in the seat of the pants as well as dyno
Fuel - injectors, pump, regulator, especially if you're starving at high rpms
Air - not sure how long a BPV lasts, but 80K seems like you definitely got your money's worth. Also, maybe check throttle body for full range of movement, any hangups near WOT, a good cleaning etc. Double check all pulleys / tensioner / belt for signs of binding or slippage under load

As for the blower, if it's rattling, not sure how many more >5K RPM pulls it will last. Maybe bite the bullet for a rebuild or look for a better condition salvage yard unit to pull?

 

Spark plugs were replaced 25,000 miles ago. The coilpack was replaced 65,000 miles ago, looks good with no corrosion.

The fuel filter has never been replaced and the car has 150k miles on it, so I think it's well about time. Not sure if it would really cause a lack of power though?

I've heard the stock BPVs wear out after 75k miles or so, but the DT ones are supposed to be more durable. Don't know if I should just replace it anyways.

Belt looks great, still have almost a whole hole on the tensioner, the idler pulley is new and everything spins smoothly.

As for the supercharger, I'm planning on getting it rebuilt. Just hoping it'll hang on another month or so till I have the time to tear the car apart and ship it off. Will the worn gears cause a lack of boost though?

 

Just changed mine at about 68K, seventeen years since leaving the factory. Long overdue. At higher demand in theory it very well could if clogged up enough. At that mileage you may also be pushing your luck with the fuel pump. Usually those fail suddenly with a crank / no start which can sometimes be addressed with a mallet or fist on top of the access cover i.e. the "Fonzi method."

As for that BPV not sure; hopefully someone will weigh in who had one (or more) DT models actually fail on them. The typiical OEM failure mode is broken spring and/lor compromised diaphragm. If they've addressed those weaknesses with their product would think they would last a lot longer than factory. Loss of higher end power on a BPV failure is more dramatic with the sluggishness supposedly starting at 3K or so. There's also a code thrown when they do fail, believe Mod MINI covers that in his BPV video.

Depending on what's wrong with the supercharger - bearings, gears, blades etc any manner of things could reduce its efficiency. Since you're getting it rebuilt, you soon should know for sure. Would be interested to hear what it was if you'd care to share it.

 

Will definitely post an update. Hmm.. yeah I might just do the fuel pump with the filter for peace of mind. I make way too many roadtrips I'd hate to get stranded somewhere. Hopefully someone else can chime in on the BPV.

 

Daftlad, any performance differences after you replaced your fuel filter? Just curious.

 

Oh, 15 HP right out of the box. Just kidding. None noticed from my end, other than about a 12% reduction in general anxiety. I don't push the car (or my luck) too hard, as it is my daily.

As for replacing the fuel pump, it would be peace of mind, although you may or may not notice a difference in performance especially at the high end. You'll just as soon hear someone tell you to measure the pressure at the rail, and 55psi = good to go. That's fine but motors don't last forever, especially if at any time in the pump's history the tank was run to empty or nearly so [pro tip: never go below 1/4, the warning light is there for a reason, if you run the pump dry even momentarily it can be damaged and you may also burn up the relay]. It is ~$160-200 (get a Continental / VDO, never a cheapie no-name knock off) and like everything else "YMMV." Can always shelve the old one (still working) as a ready service spare to add to the pile of other ready service spares you naturally had going for this car.

 

Back to your question... Supercharger, IF the bearings are worn, out of oil, the rotors can touch and make noise and you could lose boost. However, I would first start with a cylinder pressure test, and leak down test. Checking your spark plugs as you pull them to check their condition (if one or more are wet with oil) Until that is done everything is a guess, but with guesses in mind I would guess either a possible minor head gasket issue or worse case burnt valve. Regardless, if you start looking into it and the Supercharger is good you might as well service it (drain and refill the oil). As for the BPV, I don't remember ever replacing any of mine (four cars = 3 R53 and 1 R52) Also double check you airbox filter element, just to make sure you haven't had a critter make a nest in it, or you sucked up a shop rag.

 

Oh the blower is 100% worn. It sounds like a bunch of rocks tumbling around in there above 5k rpm off throttle. I'd hope its not the headgasket or valves since I recently had those replaced on this car.

I think for now, I'll get the supercharger rebuilt and see if that fixes the issue since I definitely have to have it done anyways. It's honestly not a significant difference in power. Just noticed at highway speeds passing does take a little longer.