Mercedes M113k Supercharger Belt failure fixed over sized crank & pulley issues explained E55 SL55

hey everyone i'm just doing a video today to try and help explain a few things about uh crank pinning uh crank pulleys and then i'm gonna go on to uh belt wrap kits and why um large crank pulleys and small fixed pulleys can destroy belts and cause problems nothing in this video is going to be about why you shouldn't do it any modification comes with risks and yeah i'm not not against modifications i'm just trying to explain to a few people that have problems and um hopefully this video helps i've had a customer that has probably contacted me maybe 50 times actually he's not even my customer hasn't bought anything but i'm just trying to help a guy out and it seems like this is a maybe a bit of a common thing and hopefully this video helps explain it so the first thing i'm going to go over is the customer or this guy he has a problem with his uh his larger crank pulley so this is an oversized pulley this is a 1 72 i believe this is what you call a welded pulley so basically what happens is it's an original mercedes center and then they cut it off and then they make this new section here at a larger diameter and then weld it on so that's what these tabs are there's a few different ways they do it but basically it's because they still want to use the standard harmonic balancer that's inside this and it's basically it's a rubber mounted uh unit inside there doesn't look like it you'll see some people have pulley failures where this whole section comes off or they have a pulley that wobbles now what the this guy was thought the problem was was he thought that it was wobbling here and the attachment point pretty much next to no chance that that's happening if that was the case you would find that the pulley itself would be slipping on the whole crank and it wouldn't be turning at all so these two pulleys here can actually detach from each other and the inside dampener with all the mass and the first set of pulleys and the second set can be running independent to each other so this pulley here might be wobbling it might actually be wobbling from factory it's a chance of that there's probably only one pulley i've seen on the market that is really high end and that's innovators west and all the rest are basically a version of this so stock mercedes cut the outside pulley off put a new one on hope for the best see how it goes so he was basically inquiring about a crank pin kit which is what this is it's just a it's a fancy jig basically and what it does is it allows you to line up with the end of the crank and put extra dowels in halfway between the pulley and the end of the crank so basically that's what it does it slides inside here with a bolt like this bang and allows you to drill uh two extra dowels halfway in the crank pulley and halfway in the crank so on to the oem setup so from factory uh this is a sl55 crank and this is the bottom chain gear mechanism so basically this slides on there and you'll see there's a heart there's a half moon here and this is what is referred to as a woodruff key and you'll find that the top half of the moon is flat and it is shared between halfway between this and halfway between the pulley so if you look at this it's probably shared you know somewhere here now looking at the size of this you don't actually get a lot on the end of the crank and you can see it inside here exactly that's how far try and get it to focus that's how far it hangs on so you're attaching this big weight off the end of the crank and then off that you've got all the belts and all the supercharger and it's hanging on by probably about that much now the reason for that is uh it's basically a somewhat of a sacrificial design that if you do have a problem it will smash the wood drift key and hopefully not break the crank you're thinking oh why don't they just key the whole way across here and put a huge key in it and then all you know from st from factory you'll find that some of the diesels do that um but with the petrols it's not really a big issue and they actually want it to break if you made it in such a way that it was so strong it's a let's put a huge 5ml key or six mil key through there and put the whole length across here and we'll make it so it never comes off if you do have a problem with this pulley and you are pushing it to the limits it will destroy the crank it will absolutely just tear it to shreds so the idea is the sacrificial part is the woodruff key in the case of running oversized pulleys it is a benefit to put these extra dowels in it and they basically go in the end of the crank here uh for stability because the factory wood drift key will not be enough to keep them together and um under higher load um you know more ratio on the pulley you will end up smashing the wood drift key spinning the end of the crank and if you're not lucky you'll be putting a new crank in the car okay guys on the second part of the video i'm just going to go over a few ratios and talk about the relationship between the crank pulley and the top pulley um now i'm sure i'm going to be inboxed by all these people say oh it's not actually 23 oh it's not actually 168 oh it's actually this it's i don't really care this is just for illustration reasons to uh to show people what's going on so this is uh again for those who are running a larger crank pulley the standard crank pulley is 152 mil i believe and uh especially a fixed pulley at the top so uh the person uh that messaged me and is having problems he's running a 168 millimeter crank pulley and a 68 top pulley and a belt wrap kit so i'm going to go around i'm going to explain it all and i'll as well start with the belt wrap kit so basically what the belt wrap kit does is adds another pulley in here and it increases the wrap over the top this is because the smaller you make the top pulley the more problems you're going to have with belt slip so the bottom pulley is quite large it probably is not going to slip so the smaller the diameter of the top pulley the less surface area it's got on the belt uh especially when it's going straight down so basically you increase the wrap on the belt go around and then add this pulley down the bottom here so a lot of people are very fond of larger crank pulleys because it has such so much surface area that um you don't have belt slip and people talk about oh there's more torque there's better benefits other than the fact that a larger crank pulley can strip the wood drift key and damage your crank so on top of that people stack pulleys they get a larger crank pulley and a smaller top pulley so just to go over some rough numbers uh standard gear change when you're flogging the car 65 100 rpm so by the time it gets up to the top and has used the 2.47 ratio difference between the two pulleys you're at sixteen thousand rpm so basically what i was explaining to this customer was there is a good chance that your pulley that you think is wobbly and is throwing a belt it might actually not be the case so what's happening is as you're racing down the road and you hit 6500 rpm and it changes gears the supercharger at the top on the input is doing 16 000 rpm on the inside of the pulley inside the snout of the supercharger here is an extra step up gear of about 30 so your supercharger rotors are doing nearly 21 000 rpm at the point when you race along and it comes up to 6500 rpm and changes gears basically this is what's happening with your belt speed it's going from 21 000 odd back down to 16 000 because it's about the same 30 percent change between 6500 and let's say 5000 rpm it does this very quickly i'm going to say one second it's not but it's just easy to say that so basically what's happening and this happens a lot with fixed pulleys is there is no slip in it it is a one-to-one ratio basically the clutch is designed to allow for some slip acceleration and de-acceleration when you fix that there is no slip whatsoever so your crank pulley is uh sending the belt up to you at this rpm change gears bang down again up again so a lot of people find that they throw a belt around this area because what's happening is your supercharger turbines all the weight all the cogs everything involved is doing 21 000 rpm and all of a sudden it's being told no you've got to do 16 000 rpm now so it's a big change quite quickly and what happens is when you have a belt wrap kit on there it's got so much grip that something's got to give so it's probably not going to break the crank it's probably not going to break the top pulley it's probably not going to break these because they're just really to keep the belt on track what it's going to do is it's going to destroy the belt it's going to throw it off because it's got nowhere to go so one thing i did tell this this certain person is that he should potentially try a longer belt and the reason is the tighter the belt the higher up your tensioner is now under load if it's already super tight it's got nowhere to go if you have a longer belt the tensioner can actually sit down lower and it has more movement when it needs it so when the belt's under extreme stress and the engine loads it up and it flicks up and it's going to try and throw it off the top pulley you might have more luck now it might not be the solution then my solution might be to get rid of the belt wrap kit so a lot of the guys that run the uh the n a compression monsters whatever you want to call them what they end up doing is they end up running a larger crank pulley a stock top pulley and no belt wrap kit so they can still get the boost they want you know it's 13 14 15 psi but it stops throwing belts now in saying that i did say before the best crank pulleys i've seen are innovators west hello dan from innovators west um that's what pretty much all of the big um high compression builds run and it's the best bet you have sure if you want to run a build wrap kit you're also going to run into more problems it's not the pulley it's not this bottom pulley it's the fact that when you've got nowhere to go and it's a fixed pulley here and a fixed bully there something's got to give and it ends up being the belt now on top of that i've just put down here 500 horsepower so most of these you know modified mercedes 500 horsepower at the crank that is a lot of power and it's not going to be slowed down or decrease in speed it's not really going to be affected at all by this supercharger even though it has a lot of rotational mass it is an enormous amount of power so to give you an idea some of the bigger cnc machines they run a 15 or um you know 20 maybe possibly like a 25 horsepower engine and they absolutely rip shreds out of steel they throw metal everywhere you amaze the amount of power they have so this has got 500 horsepower to spin the crank and it's not going to stop it basically and the weakest link even the best belt you buy the best system is going to be the belt so i hope this video helps explain a few things um again i'm not against modifying cars i've modified my car a lot i'm not saying don't do it but what i'm saying is just be aware that every cause has an effect and especially when you're running a fixed pulley you may end up destroying belts i'll go on to noises and other things about fix pool is later that'll be another video and i'm sure people will harass me and and talk about but this one is basically just saying if you're running a large pulley on the crank a small pulley on the top and it's a fixed pulley and you're having belt issues it's probably because of the change in rpm when you change gears you can possibly test this by just revving the car if you haven't changed the ecu setup it won't let you rev it past 3 500 rpm but a slow increase in gear basically if you were just cruising along the second gear and you get the rpm right up 6500 and you back off slowly to me that would tell you that the only time it's throwing your belt is during rapid de-acceleration when you're changing gears so best of luck to everyone out there hopefully this explains a bit and yeah keep modifying

Channel: Benz Performance Parts

Views: 2,652

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Id: l-hwPZiP-7g

Length: 14min 35sec (875 seconds)

Published: Mon Oct 26 2020