RLNY

Got a 76mm pulley on my s55 and was told I need a bwk but I do not feel any slip. Will getting a bwk indeed give me 1-2psi extra boost or is it if your slipping you get that boost back. I do have black crud on top of my gates 496 HD belt. It does fit really tight too.

maw1124

Poke around on the E55 board and on YouTube to make sure you have the right belt. I have 83mm, no BWK, and found the belt from Tavarish on YouTube. He's enough of a scientist that he'll catch the detail of the correct sized belt. Obviously a smaller pulley requires a smaller belt and I always felt the BWK was for people who missed that detail. That said, I'm no expert and I didn't deviate so far from stock. Faster is not what this car needs IMO so I have no thoughts about another 2psi of boost (although the attached chart might hold some interest for you
-- I don't think 17psi of boost is good for anyone here).




maw

RLNY

I think I got the correct belt. It fits perfectly and it’s very snug. I hear you on the speed thing but I got this car so I can have a fun daily that I can whip around and mod for more power. It’s an m113k motor so I know it’s super reliable and loves mods. I guess to each is own.
The reason I started this thread was because I wanted to know does this bwk make extra power at all and is it something I may need. I greatly appreciate your advice though maw for sure. You seem very knowledgeable on this platform.

maw1124

Yeah I've owned the car long enough to see people come and go running power experiments. The VRP chart is about as helpful as I've seen. People don't often blow the motor but they certainly lose superchargers and crank pulleys which is why I tell people to do their supercharger fluid first. People have talked for years about supercharger chirp and belt slip (for which the BWK was apparently designed), but I never had those issues so I can't answer your precise question. I have to believe the belts will expand a bit with heat cycling as they wear in though. But again since I'm not all over more power I can't tell you I pay much attention to it. If I had to guess I'd probably spend the money on headers first. YMMV.

GL

maw

PS... the actual experience of owning and driving a fully modded S55k might have a word with you about whether the cars love mods as much as people love to mod them.

maw1124

BTW, before the BWK came out, people used to pair the smaller S/C pulley with larger crank pulleys to keep the belt size the same (and reduce slip or chirp), and with predictable results... 2 non-factory components instead of one (double the risk -- MB are MB because of the components), and more boost than intended, the cars would lean out, etc, etc (which is why VRP now have a handy chart). You see we've gotten to the same point with looped fuel rails, larger throttle bodies, cooler plugs, larger injectors; all different solutions to the same problems (more boost without the car leaning out). Not to mention BWK are cheaper to produce and sell than crank pulleys of all different sizes.

So hopefully that gives you some context for the various claims (2psi at high rpm, protecting the factory idlers, increasing belt surface area with the supercharger pulley, yadaX3).

Bottom line, 76mm with a stock crank pulley is safely in the green on the VRP chart, and if you notice the belt slipping you can always add the BWK later. They're plenty cheap. For my money, at this age, spend that money on (1) new factory pulleys that haven't been changed yet -- crank and idlers; (2) supercharger fluid change and (3) headers. This assumes you've already upgraded your intercooler pump, which I think you have.

The car will be plenty fast but not the fastest. The fastest are the "sell on Monday" builds which I've never seen anyone actually be happy with when they're done, if they ever actually get done LOL. Those cars are endless Frankenstein science projects.

maw

RLNY

Yeah I did all the fluids in the car with the exception of coolant which I with ink was replaced with radiation about 2 years ago and brake fluid. I did the supercharger fluid yesterday.
not looking to be the fastest I have another car for that lol. Just want a fast m113k. I had this same exact car in 2018 but it had a bunch of issues at the time. Had to sell it cause of some family issues. So through the universes great glory I happened to buy the same car color and everything with a big folder of receipts from when it had 40k miles. Plan on putting this car in the lifetime collection. I have a clk55 too that I’m working to fix up. Want to get a cl65 next.

So I’m not gonna do that bwk since no slip for me. Don’t plan on doing anything else to the car other then maintenance until next spring. Well got an Mk Ultra tcu tune last night but that’s it until next spring lol.

maw1124

Same re lifetime collection. You see the fleet in my signature.

I’ve had this one for almost 15 years, and only decided to tune it a year or so ago. I also have the MK Ultra TCU and a spare RaceIQ TCU. Both are fine although I’ll likely revert to stock there. I trust MB most for transmission management. The pulley and tune (76, 80 or 83) are all a no brainer, which is why I settled on it. BUT, I also have a new crank pulley and have done the idlers multiple times so I don’t have any worries about those. At this age, if your crank pulley hasn’t been replaced you might be on borrowed time. My guys wouldn’t let me tune mine until that had been done. Every time I mentioned tune, “Are you still on the factory crank?” was the question that came back. So I took the lesson.

Also, double clicking on this just in case you overlooked it… all extra power is useless until you upgrade your intercooler pump. The supercharger will just shut off sooner due to heat soaking from more power.

maw