a bit on supercharger drive systems and the Kraftwerks kit.

[DrWill]

I am posting this thread as a bit of an experiment. I am curious to see how long it will take before this thread is spammed with unfounded, unjustified hate and then taken down as it is sure to attract the attention of some who are skeptical and have no hands on experience with what I am about to type.

Anyway, on to the purpose of this thread:

I am going to talk a bit about supercharger belt drive systems. I am going to talk a bit about the Kraftwerks drive system in particular for the majority of this post. I will also talk about Kraftwerks as a company in general, and some helpful feedback on how they may improve as a company.

First, a little background; my wife and I have been in the 86 “scene” since June 2013 when we purchased our whiteout* FRS. After a season of Autocrossing, in November of the same year we also purchased a hot lava FRS which we decided to build into a show/track car with as good a compromise between aesthetics and performance as possible. So over the past few years we have built it into what many know as “Goku, the Dragon ball themed 86”. We chose to supercharge for the linear smooth power delivery. We chose the Kraftwerks kit for the safety of an independent drive system. Now, before you get the wrong impression, this is not a plug for Kraftwerks or praise. The kit isn't perfect. There are fitment issues and Kraftwerks seems pretty inconsistent in the way they put their kits together. Two of our friends in the area have the same kit and not two out of the three were shipped all the same parts. But I digress.
Our hot lava build has become relatively well known. We have a couple of sponsors and for the most part, people seem to respect the build. As such, a fair amount of people approach us with questions or seek advice getting started with their build and ask about the Kraftwerks supercharger. One of the issues that comes up in discussion is the whole belt failure issue with the kit and the fact that there are a fair amount of posts and threads on this forum talking about the belt failure issue or denigrating Kraftwerks and their kit as being poor quality because of this issue. I'm posting this thread in an effort to dispel any misinformation on the subject and hopefully help current users of the kit better understand it and help prospective users better make an informed decision.


Cogged VS V-rib:
There are advantages and disadvantages to both options. As with most everything in life, there is a trade-off. With a cogged belt drive system, teeth on the belt fit into teeth on the cog/pulley. In this configuration, the belt (when properly tensioned) is not able to slip. This has the advantage of making sure you are getting all the boost all the time. The disadvantage to this type of setup is that it is a lot less forgiving of shock-load and places more stress on the belt. On the same token, is the poly V-rib style belt similar to your serpentine belt. In this configuration, there are ribs that run the length of the belt that fit into groves in the pulleys. With a V-rib style belt, its the friction between the pulley and belt surface area that produces the energy transfer and as such, the disadvantage to a V-rib belt is that it may slip under high load, costing you a bit of boost at certain load points. The advantage is that the same slip will cushion the system in shock-load* situations. Another thing to keep in mind is the fact the Kraftwerks utilizes a Rotrex centrifugal supercharger unit. More on that later.
“For centrifugal fans and pumps, which exhibit a strong relationship between operating speed and power, synchronous belt sprockets must be selected that take into account the absence of slippage. Operating costs could actually increase if slippage is reduced and a centrifugal load is driven at a slightly higher speed.

Synchronous belts are the most efficient choice. However, cogged belts may be a better choice when vibration damping is needed or shock loads cause abrupt torque changes that could shear a synchronous belt’s teeth. Synchronous belts also make a whirring noise that might be objectionable in some applications.”**
*'Shock Load' refers to a sudden and drastic increase of load similar to a 'hammering' effect.
From https://omnitrack.wordpress.com/2011...-loading-mean/
Note: It may seem like common knowledge to some, but explaining certain phrases and getting all the information out in the open is the purpose of this post. If you would like to read a more in-depth article about the advantages and disadvantages on different belt configurations, and to see where I cite my quote, look here:
**http://www.achrnews.com/articles/107...us-belt-drives

Tensioners; static vs dynamic:
With a static tensioner, belt tension is manually adjusted and the tensioner is then locked into place. The advantages of a static tensioner is that it won't back off too far under high load, reducing belt tension and allowing it to slip. The other advantage is packaging and cost. Static tensioners are simple and compact. Disadvantages to a static setup is that it can be a bit tricky to get the tension proper and it will need to be periodically checked and readjusted to insure proper tension and drive system operation.*With a dynamic tensioner, the pulley is mounted to an arm that pivots on a spring-loaded joint. The advantage to this is obvious (or at least it is to some), as long as the spring rate is appropriate to the belt being used, there is no tension adjustment needed. Tension is automatically set to exactly what it should be upon releasing the action of the tensioner and will never need to be checked or readjusted. The disadvantage is that under load, the spring-loaded tensioner can be pushed back by the belt, loosening the belt and allowing slippage. Another disadvantage is packaging. Dynamic tensioners are usually much larger and wont fit in the same places a static setup might. Dynamic tensioners are also more complex and tend to be expensive.

Alright. We've talked a bit about belts and belt tensioners, lets talk a bit about why Kraftwerks went the route they did. Keep in mind, this portion is pure speculation. I don't know for sure exactly why Kraftwerks made the design decisions they did. If you want to know, I suggest emailing Kraftwerks. Perhaps they will key you in.

Cogged drive system:
Kraftwerks most likely went this route for the performance advantage of a zero-slip drive system. By opting for this type of drive system, they were able to set themselves apart and offer something a little bit unique as no other bolt on option utilized a cogged drive system at the time and to my knowledge still to date.

Double sided belt:
Its pretty obvious when you look at where the blower is located and the kit design that utilizing a double sided belt over a more traditional timing belt was the most practical way to get the belt routed to where it needed to be. This same reason likely contributed largely to the decision to go cogged rather than poly V-rib. Packaging constraints would not allow for the necessary routing to make a v rib belt work.

Tensioner:
Its also seems pretty clear that a static tensioner was chosen for this application due to packaging concerns. Additionally, this option simplified the design and kept costs down. If they had attempted to fit a dynamic tensioner into the space it would have had to go on, this application would have been overly complicated and may not have been possible at all, given the design of the mounting plate.

Independent drive system:
Kraftwerks likely chose this design for a number of reasons. First and foremost was to set themselves apart. They offer the only independent drive system. Secondly, an independent drive system allowed them to position the blower in such a way as to make piping as clean and efficient as possible. Kraftwerks claims to have the lowest IAT of any kit. I would have to examine logs from every kit to substantiate or disprove that. What I can tell you is that our tuner tells us that the Kraftwerks kit is the most thermally efficient of all the SC kits he has tuned. It should be noted that his opinion is not at all bias. Actually, he has a sour taste for Kraftwerks. The third reason for the independent drive (in my opinion, the most important), the safety and reliability of the engine. If you have a kit that utilizes the serpentine belt and there is a failure, the car is not drivable. This is more a convenience than a safety feature, but let me give you something to think about: if your serpentine belt fails I stated it would not be drivable, however, that does not mean the engine won't still run in most cases. Think about what is being driven by the serpentine belt: the alternator, the water pump, and the AC. Obviously the engine will run with no AC. Its hard for it to run with no alternator, but anyone who has ever had an alternator go bad on them knows that an engine will run for a fair distance off of just the battery. Then there's the water pump. The water pump will stop when the belt brakes. But the engine won't. So if you happen to be on the track pushing the car as hard as you are able, and your serpentine belt snaps, depending on how long it takes you to realize what happened and get off the track you may end up needing more than a replacement belt. If you are taxing your cooling system on the track and your water pump suddenly stops, this could lead to catastrophic engine damage. With an independent drive system there is still a risk as the SC drive belt can hit the serpentine belt and knock it off track but the risk is greatly reduced. Additionally, the factory tensioners on the serpentine system are not designed to hold tension under the increased load conditions seen when driving a supercharger. By going with an independent drive, Kraftwerks was able to remove the variable presented by whether or not the factory tensioners would perform as needed.

Time now for some ground truths.

Supercharger systems suffer belt failures. Any SC kit you put on this car is going to suffer failures. A friend of ours has another centrifugal SC kit that runs off the serpentine belt and has been left stranded by belt failure 4 times since owning the kit. Supercharger belt failure is a fact of life. Its another one of those trade offs I mentioned earlier. Turbo setups can be susceptible to lag and boost spikes. SC setups are slightly less efficient and suffer belt slippage/failure.

Modified cars have problems. When you modify a car, things get complicated, things go wrong, etc. No aftermarket parts company has the R&D budget or development cycle time as OEM automotive manufacturers. Automotive companies have entire teams of highly educated highly qualified automotive engineers who spend months and in some cases years designing, testing, and redesigning the parts that come on your car from the factory. It is for this reason in many cases genuine OEM parts are as expensive or more so than your average aftermarket performance replacement. The fact is, if you modify your car with aftermarket parts, it is not going to be as reliable as it was when you bought it. I don't know any one who has heavily modified a car and never had something fail on them.

Cogged belt systems are more prone to stress related failure. Again, its a trade off. If you want a drive system that wont slip you have to deal with a higher likelihood of the belt letting go when you don't want it to. In this case, a cogged drive was needed to achieve an independent drive. So if you want the peace of mind of knowing that if your belt does let go you can still drive the car you will have to accept the increased chance that the belt will let go.

Now that we've got that out of the way lets talk a bit about how you can avoid belt failure.

Installation:
In the early 90s a study was conducted by a group of independent engineers in conjunction with the gates rubber company.

https://www.google.com/url?sa=t&rct=...efGFWkuQjjXvjg

The subject of this study was premature belt failure on top fuel drag cars. In this study, one of the key contributing factors in premature belt failure was pulley pitch tolerance (AKA runout). Most everyone is familiar with the task of changing a set of brake rotors. Before you install the new rotors, you have to clean the hub face to make sure excess corrosion doesn't cause runout in the new rotors. The Kraftwerks drive pulley bolts directly to the face of the OEM crank pulley. Similar to a brake rotor, if there is a bunch of crud between the drive pulley bracket and the crank pulley this may cause runout which will make the system more prone to premature failure. Clean the face of the crank pulley thoroughly with some type of solvent and preferably a wire wheel or at least a wire brush. If you really want to be absolutely sure, put a dial indicator on the face of the pulley after installation and check for runout. We checked ours with a dial indicator and found less than one thousandth of an inch of runout which is well within tolerance.

Proper belt tension.
Unless you have a stethoscope that reads sonic frequency, its very difficult for me to say exactly what you need to do to tension your belt properly. Kraftwerks gives a measurement of how far out the tensioner position screw should be for proper tension but this was given for the last revision and no longer applies to the latest pulley sizes and belt size. To my knowledge, this has not been updated and probably should be. I could give the measurement for our position screw(12.5mm from the bottom of the head to the mounting bracket) but that is only good for anyone who is running the 90mm pulley vice the 95mm pulley that comes standard with the kit on the most current revision and even this would only give a ball park for what is right. I scoffed at Kraftwerks when we first got the latest revision and all they could tell me for belt tension was that it should be “ not to loose, but not too tight.”. However, after having experienced trying to properly tension this kit, honestly there really isn't a better way to put it into words. The best way to learn proper tension is to feel it for yourself on a properly tensioned kit and have a friend who knows how help you learn. I will do my best to help you figure it out:
If the belt is too lose, it will flap excessively at idle and make a sort of rattle, flapping, or purring noise. You will also be able to see it flapping back and forth. If it is too tight, the blower will be a lot more noisy and have a higher pitched whine than would be considered normal. You need to get to know your blower. Loosen the belt a bit until it flaps at idle. Do not load the system with it that loose (don't rev the engine). Listen to the sound of the blower when its set loose like that. Shut the car off before adding more tension to the belt. Add tension until the flapping at idle stops. You may have to turn the car on and off to check a few times. If you've got it right, the blower noise should be pretty close to the same as it was when the belt was loose, just without the flapping noise. Some movement in the belt is normal. If you can't hear it flap at idle, take the car out for a short test drive. If you hear it flap a bit when the engine boggs taking off from a stop, its a touch too lose, so add just a tiny bit of tension but be careful not to add to much (less than a quarter turn of the screw should do). An important note to remember when tensioning your belt; when the bolt on the back side of the tensioner pulley is tightened, it will add additional tension to the belt. If you set the tension with the position screw to where you feel it should be, then tighten down the tensioner pulley and walk away, it will be tighter than you wanted it to be. Set the tension slightly looser than you want it to ultimately end up with the position screw, then tighten the pulley and check it again to ensure its where you feel it should be. There is a Y shaped bracket coming off of the lower idler pulley where the bottom of the SC mounting plate attaches to the block on the left hand side viewed facing the engine. When feeling belt tension by hand, if you are not able to stretch the belt with a reasonable amount of force until it touches that bracket it is much too tight. This may seem counter intuitive to some, but as long as the belt is not so loose that it makes the flapping noise at idle, it won't contact the bracket or damage the belt. Check belt tension often. As I stated earlier, this is a static tensioner drive system. The engine block, mounting brackets, and pulleys are all aluminum. Aluminum expands and contracts quite a bit with temperature variation and heat cycling. Belt tension needs to be checked and reset every so often. It is worth noting that drastic ambient temperature changes may require you to retension it more frequently, such as seasonal changes. This is not a “set-it-and-forget-it” system. Any time we notice that the blower pitch or belt system sounds unusual, we check the belt tension and usually find it off by a little bit. Once we reset the tension everything goes back to normal.

Spoiler alert!:

This next part is likely to offend some people:

Learn. To. Drive.

We were once asked by Mike at Counter Space Garage if we were confident enough to let him take our car on a track and test the belts reliability. The answer? Yes Mike, we are. We are fully confident that you are a good enough driver to properly rev match and achieve smooth downshifts and upshifts as well as smooth brake and throttle inputs, and we trust you not to be bias and intentionally beat the shit out of it to make the kit look bad. Everyone wants to be like Mike right? Unfortunately, if you aren't like Mike, and you aren't able to properly drive a car fast, you are going to brake some belts before you learn. Driver mod is the first mod you should ever consider with this platform. If you bang the hell out of every gear change, jab the brake like a mustang driver about to hit the crowd and stomp the throttle like the same guy about to take out the crowd (sorry, couldn't resist sliding that joke in) then yeah, you will most certainly brake a belt on the track or leaving cars and coffee. We have been running this kit for almost 3 years now and have never broken a belt while driving.

Another important bit about the Kraftwerks kit: make sure you have the correct pulleys installed. While we have never broken a belt while driving, we have had a belt failure on the dyno. The failure we had was due to the fact that we had the wrong pulley revision on the car. In retrospect, this explains the comment I received from Kraftwerks when complaining about the failure:
“We have had less than 1% of failure since the latest revision.”
Neither myself or Kraftwerks at the time were aware that the pulleys on our car were NOT the latest revision. Since the new revision, we have had not had any issue other than one dyno related failure due to improper tension as we learned the tension settings for the new pulley and belt size. If you are running a 100mm crank/drive pulley and a 75mm – 70mm nose pulley, YOU ARE RUNNING THE WRONG PULLEYS. Contact Kraftwerks for the latest revision. If you are running smooth idler and tensioner pulleys, YOU ARE RUNNING THE WRONG PULLEYS. Contact Kraftwerks for the latest revision. I cannot stress this enough. Measuring from the tips of the teeth down the center, the crank/drive pulley should measure 128mm and the standard nose pulley should measure 95mm. The high boost pulley is 90mm and if you are running the larger C-38 with the lower drive ratio you can run an 85mm nose pulley which is also available from Kraftwerks. We had actually ordered the 85mm nose pulley and were shipped the 90mm pulley, but its too late to complain about it or have it exchanged now...

Finally, if you are absolutely positive that you have the belt tension mastered and you believe without a doubt that your failures aren't due to bad driving, you have made sure you have all the correct pulleys installed, and you're the 86 stig, break out the laser level and check for misalignment between the drive pulley and the nose pulley (the pulley on the back of the supercharger itself and the one that attaches to the crank pulley). In the earlier mentioned study, it was found that the largest contributing factor to belt failure was misalignment between drive and nose pulley. What this means is if the two pulleys are at a slight angle to one another there will be an uneven stress load across the width of the belt which will cause premature failure. The easiest way to determine if your kit suffers from this misalignment is to look at the wear on the pulley. If your pulley is more worn on one side than the other, there is a misalignment. We have checked ours and no apparent misalignment is present with our kit but that doesn't mean it won't happen. No manufacturing process is 100% perfect. That is why OEM tolerance specs are given in a range, not a dead nuts specific number. No two parts are ever exactly the same. Just the same as no two engines are the same. It is possible you may have got hold of an engine block and a set of mounting brackets that both happen to fall on the same side of the tolerance range in the same spot and a pulley misalignment was the result. Get a laser level. Set it up so that it can be rotated to cast the beam on both the drive pulley and the nose pulley without effecting its alignment with the pulley axis. You may need to remove the SC idler pulleys to do this. Line the beam up with a tooth on the drive pulley. Rotate the level until the beam is cast on a tooth of the nose pulley. If there is a misalignment, shim until they are as close to perfect as possible. The easiest way to do this would be to shim/file at the points where the mounting brackets coming off the block meet the SC mounting plate. Only do this if you have checked both pulleys for runout and corrected that issue first. As for correcting pulley runout, you can try to contact Kraftwerks for a replacement. You can try to find tapered shims that will fit behind the pulleys or see about having a machine shop true the pulleys/adapters. As stated before, we found no runout or misalignment, we have also never observed any misalignment or runout issues on the multiple kits run by friends of ours locally. Its not very likely that you will find misalignment or runout but it is possible.

Story time: About six months ago, my wife had the oil changed at the Toyota dealership she worked for at the time. Her buddy who did the change forgot to tighten the pass through bolt that holds the sandwich plate to the oil filter mounting point. The next day the car spat all of its oil out from under the sandwich plate and all over the engine bay and the freeway. I know what you're thinking. Surely this is irrelevant? Not so. I mention this because when this happened the SC drive belt and serpentine belt were both completely saturated with hot engine oil. For those of you who don't know, when a belt gets soaked in oil it weakens it, making it more prone to failure. We have since changed the serpentine belt out of concern for engine safety. The SC drive belt however is still the same belt we have had on the car for about a year now. If the design of the kit were intrinsically prone to premature belt failure, I would think that a year-old belt that was weakened by its hot engine oil bath 6 months ago would have failed by now. This car is driven hard on a regular basis. Its not that we baby it. One comment I have heard is “I wonder how many 20 to 60 to 20 pulls I could do before it failed.” We recently installed our R1 Concepts big brake kit and took the car out to bed them in. We took the car from 65mph to 5 mph back to 65mph as hard and as fast as possible 8 times without any issue. This was on the same year-old,oil bathed, weakened belt. It didn't brake. Its still on the car going strong. Now that I'm no longer stationed on a ship and am no longer out to sea every time there is a track event, we hope to get the car on the track as much as possible this summer. I will be sure to let you guys know if the belt brakes on the track. Don't worry. We always carry a spare. Because as I mentioned earlier, superchargers brake belts. Its going to happen at some point. That is a drawback that must be accepted when running any supercharger. The kit performs beautifully in its current configuration on our car and we absolutely love the way the car drives so it is a drawback we are more than happy to accept.

Now lets dispel some of the BS. My favorite comment on this kit is “Kraftwerks didn't read the F***ing manual!” This was a reference to the technical manual for the C series rotrex SC. This is absurd. Individuals touting this claim are selectively omitting details from the very same manual they reference and attempt to shift focus to something largely irrelevant. While the manual in questions does state that Rotrex recommends the use of Rotrex pulleys, the manual also states that the blower can be ordered with a nose adapter for those who wish to utilize other pulley types such as a cogged pulley setup. Now why would they offer an adapter facilitating the use of other pulley types if they didn't want other pulley types used? Furthermore, Rotrex themselves have responded directly to this comment, stating that they are not against a cogged configuration and many of their customers have used cogged pulleys with good results. The fact of the matter is Kraftwerks is an authorized distributor of Rotrex products and Rotrex will warranty the blower for the same amount of time if you purchase it from kraftwerks as part of this kit, as they will if you came by it as part of any other kit or any other means. It doesn't take an incredible feat of logic to discern that if Kraftwerks were running the blower completely outside the envelope of its intended use this would not be the case.

I could go on about threads that complain about all the failures, but the posters have the wrong pulley setup on their car. Not saying its the OP of those threads fault. Kraftwerks could have done a better job getting the revisions out to the customers. However the fact is the design has been revised and the belt failure issue has been largely resolved. Any post on failure where the car in question had an older version of the drive system should be ignored. Further failures after the last revision are likely due to improper tension and/or failing to maintain proper tension throughout the life of the belt. As stated earlier, we have been running this kit going on 3 years and have never had a belt fail while driving. Several of our friends also run the same kit and have also had no failures while driving.

This has turned out pretty long so I'm going to wrap it up by stating a few things that in my humble opinion Kraftwerks could do to improve the kit and its reputation.

Fitment:

If you have the C-30 kit, your silicone hot side IC pipe probably fits ok. If you got the C-38 kit, it doesn't fit at all. Not even a little bit. I'm not really sure but it seams to me as though all they did was widen the diameter of the original charge pipe design so it would fit over the larger outlet of the C-38. It doesn't seem like the overall shape or dimensions were changed between the two to compensate for the larger blower, placing the outlet significantly farther forward than the C30. We had to have all new hot side IC piping custom fabricated in order to get the kit installed properly because the charge pipe fit so poorly that we had to jam it in between the frame rail and the headlight to get it to fit over the blower outlet so much so, that it was kinked in the middle. It's possible this issue has been addressed already, I'm not really sure. The cold side piping fits more or less, but still rubs the radiator hose, the headlight, and the frame. If the lowest angle joint on the cold side were extended by a few inches, this would alleviate this issue.

Consistency:

We have helped two other local friends of ours install this kit and no two kits were the same. Each intercooler was different from the other two in some way. The latest kit to be installed somehow found its way out the door with the older oil reservoir mounting brackets that mount it between the engine and the radiator rather than the mount next to the battery that the previous two kits had. Our kit didn't get the check valve for the PCV line while the others did. And so on. That amount of inconsistency is a bit unprofessional. You should work on that.

Recirc valve:

If you are going to offer an optional larger recirc valve, offer a charge pipe it will fit into. My friend who got his kit about a year or so ago, ordered it with the larger BOV but didn't get a charge pipe with a larger opening to accommodate it. When he called to get the right charge pipe to fit his BOV, he was told there wasn't one. That doesn't make a lot of sense. If you are going to offer an option that requires custom fabrication to use it, it should be made known beforehand. And honestly, if someone were going to go the custom route, they would do what we did and fit a nice turbosmart or GFB or something, so no offense, but I don't really see the point to be honest.

Ship what is asked for:

When we received our revision, we were supposed to receive the high boost pulley as we had purchased it for the prior revision. We were shipped the standard 95mm by mistake. When we discovered this, we contacted Kraftwerks to exchange it and asked for the 85mm pulley. We received the 90mm pulley. At that point we said screw it, I'm sick of messing with it, we will mess with getting the smaller one later once we see how it runs on the 90mm. When you ship someone the wrong parts twice in a row that's not cool. You should work on that.

Product support:

When we called to see if we had been shipped the wrong charge pipe because the one we had didn't fit, we were told that there wasn't a different pipe for the C-38 kit, that it was the same part for both kits. Obviously, that is not the case. If it was, no one would be able to install the C-38 because the charge pipe wouldn't fit on the blower outlet. Half the time when myself or someone I know talks to someone at Kraftwerks about the kit, the person on the line gives wrong information or doesn't seem to know much about the product. Support representatives should know the products they are attempting to support. Train the people who answer the phones.

Documentation:

The documentation is pretty great actually. But it should be updated to reflect the tensioner position screw measurement for the latest revision if it hasn't been already.

Well folks I'm done ranting for now. I hope this article has been informative and helpful. Hopefully it will help prospective users of this kit to make a more informed decision. And maybe it will help a few who run this kit already with proper belt maintenance.


If you have legitimate questions or concerns, ask away. This isn't a supercharger vs turbo thread, so take that shit elsewhere. This is not the thread you are looking for.
Spamming this thread with BS won't be tolerated, and spam will be reported. This is meant as an informative post, so let's keep the BS out please.

Inb4 TL;DR
LRN 2 TENSION, LRN2 DRV

[ATL BRZ]

This is like the perfect intro to a Jackson Racing supercharger info-merical.

[boredom.is.me]

Oh you're already here.

[wbradley]

Kraftwerks got lucky, scored a free communications person here. Informative post!

[Calum]

What's the difference between a synchronous belt and a cogged belt? To my knowledge they are the same thing.

Ways to tension a belt properly that could be included in the instructions given by Kraftwerks:

You can use the Gates app.
https://play.google.com/store/apps/d...lculator&hl=en
https://itunes.apple.com/us/app/carb...438346486?mt=8

You can use one of many designs of belt tension gauges.
https://www.amazon.ca/OTC-6673-Unive.../dp/B000I198J0

Or you can use a ruler to measure delfection.
http://www.pfeiferindustries.com/ins...ensioning.html

Here's a link to an automatic tensioner that takes up less space than the manual tensioner. There's many other varitions of this design that could have worked.
http://www.rockauto.com/en/moreinfo....284230&jsn=383

Using the stock crank pulley's face as a flat mounting surface is an inherent design flaw. It's one with limited risk as the OEM does a decent job, but that surface was never meant to be a mounting surface.

Why do you say that cogged belts are prone to failure during high load transitions? I've read some documentation that refers to them as "high torque drive belts." Surely driving a camshaft has a larger number and increased amplitude of load variations than the supercharger. And then there's the motor bikes that use cogged belts instead of a chain and many other industrial applications.

[go_a_way1]

Holy fuck!! I thanked your post based on the number of words alone. I only got the first paragraph hahaha!! Thanks for the TL;DR

[Apoc]

This post is very informative and clears up much of the misinformation or incomplete info that has been tossed around on these forums since the kit came out.

[DrWill]

Originally Posted by Calum

What's the difference between a synchronous belt and a cogged belt? To my knowledge they are the same thing.

Ways to tension a belt properly that could be included in the instructions given by Kraftwerks:

You can use the Gates app.
https://play.google.com/store/apps/d...lculator&hl=en
https://itunes.apple.com/us/app/carb...438346486?mt=8

You can use one of many designs of belt tension gauges.
https://www.amazon.ca/OTC-6673-Unive.../dp/B000I198J0

Or you can use a ruler to measure delfection.
http://www.pfeiferindustries.com/ins...ensioning.html

Here's a link to an automatic tensioner that takes up less space than the manual tensioner. There's many other varitions of this design that could have worked.
http://www.rockauto.com/en/moreinfo....284230&jsn=383

Using the stock crank pulley's face as a flat mounting surface is an inherent design flaw. It's one with limited risk as the OEM does a decent job, but that surface was never meant to be a mounting surface.

Why do you say that cogged belts are prone to failure during high load transitions? I've read some documentation that refers to them as "high torque drive belts." Surely driving a camshaft has a larger number and increased amplitude of load variations than the supercharger. And then there's the motor bikes that use cogged belts instead of a chain and many other industrial applications.

Synchronous and cogged belts are both terms used to refer to the same type of belt however there are some differences between subcategories of that same type which I am assuming is what is being referenced in the article that suggests cogged over synchronous. Blowers and other centrifugal fan drive systems typically utilize a polly chain type cogged belt as opposed to a mor traditional synchronous timing belt. The differences are in tooth shape/design and overall belt construction.

As for the differences in load on a cam timing belt vs a blower belt that question is addressed in the engineering study on belt failure linked in this post. In that study they found that due to the higher rotational speeds of blower belts a blower belt on an engine being spun at 7500 rpm can be subjected to as much as 600 lbs of additional centrifugal load or more. The tortional vibration loads and centrifugal loads are amplified in a blower belt configuration which is why it was found that even at optimal conditions blower belts suffered fatigue failure in real world applications much sooner than in a lab.

[DrWill]

As far as cogged being more prone to failure. Yes they are a high torque load belt. This means they are capable of carrying a higher load than a rib style belt as they will not slip. Sense they don't slip however they will be subjected to higher shock load stress than a rib belt and suffer fatigue failure sooner than a v rib belt would.

[vgi]

Originally Posted by DrWill

Proper belt tension.
Unless you have a stethoscope that reads sonic frequency, its very difficult for me to say exactly what you need to do to tension your belt properly. Kraftwerks gives a measurement of how far out the tensioner position screw should be for proper tension but this was given for the last revision and no longer applies to the latest pulley sizes and belt size. To my knowledge, this has not been updated and probably should be. I could give the measurement for our position screw(12.5mm from the bottom of the head to the mounting bracket) but that is only good for anyone who is running the 90mm pulley vice the 95mm pulley that comes standard with the kit on the most current revision and even this would only give a ball park for what is right. I scoffed at Kraftwerks when we first got the latest revision and all they could tell me for belt tension was that it should be “ not to loose, but not too tight.”. However, after having experienced trying to properly tension this kit, honestly there really isn't a better way to put it into words. The best way to learn proper tension is to feel it for yourself on a properly tensioned kit and have a friend who knows how help you learn. I will do my best to help you figure it out:
If the belt is too lose, it will flap excessively at idle and make a sort of rattle, flapping, or purring noise. You will also be able to see it flapping back and forth. If it is too tight, the blower will be a lot more noisy and have a higher pitched whine than would be considered normal. You need to get to know your blower. Loosen the belt a bit until it flaps at idle. Do not load the system with it that loose (don't rev the engine). Listen to the sound of the blower when its set loose like that. Shut the car off before adding more tension to the belt. Add tension until the flapping at idle stops. You may have to turn the car on and off to check a few times. If you've got it right, the blower noise should be pretty close to the same as it was when the belt was loose, just without the flapping noise. Some movement in the belt is normal. If you can't hear it flap at idle, take the car out for a short test drive. If you hear it flap a bit when the engine boggs taking off from a stop, its a touch too lose, so add just a tiny bit of tension but be careful not to add to much (less than a quarter turn of the screw should do). An important note to remember when tensioning your belt; when the bolt on the back side of the tensioner pulley is tightened, it will add additional tension to the belt. If you set the tension with the position screw to where you feel it should be, then tighten down the tensioner pulley and walk away, it will be tighter than you wanted it to be. Set the tension slightly looser than you want it to ultimately end up with the position screw, then tighten the pulley and check it again to ensure its where you feel it should be. There is a Y shaped bracket coming off of the lower idler pulley where the bottom of the SC mounting plate attaches to the block on the left hand side viewed facing the engine. When feeling belt tension by hand, if you are not able to stretch the belt with a reasonable amount of force until it touches that bracket it is much too tight. This may seem counter intuitive to some, but as long as the belt is not so loose that it makes the flapping noise at idle, it won't contact the bracket or damage the belt. Check belt tension often. As I stated earlier, this is a static tensioner drive system. The engine block, mounting brackets, and pulleys are all aluminum. Aluminum expands and contracts quite a bit with temperature variation and heat cycling. Belt tension needs to be checked and reset every so often. It is worth noting that drastic ambient temperature changes may require you to retension it more frequently, such as seasonal changes. This is not a “set-it-and-forget-it” system. Any time we notice that the blower pitch or belt system sounds unusual, we check the belt tension and usually find it off by a little bit. Once we reset the tension everything goes back to normal.

this ^^^ is going to confuse a hell lot of people IMO kinda like advise given by Kraftwerks - “ not to loose, but not too tight.” - go be "feeling" the belt

one piece of missing info - according to Kraftwerks, belt tension should be done when engine is cold!

Using "measurement for the position screw" is a bad idea IMO as according the Gates sound frequency app a minor variation causes rather large change in frequency.

The design should encounter (belt should handle extra tension when hot) for expansion/contraction of the pulleys and if it doesn't - it's a major flow and there is nothing one can do. I'm not convinced they did. The loaded dynamic tensioner would address this issue. The new pulleys, I guess due to larger diameter, do cause larger play in belt when engine is cold/hot.

I personally do not check belt tension often and basically set-it-and-forget-it after I did tension recheck about a month after I installed new pulleys and belt. Maybe I'm wrong, my thinking however is that pulleys operational temp, after about 10-20 mins, should be roughly consistent and affected more so by engine temp and especially friction. The seasonal change does affect the belt while the car is still cold so I take it easy and don't do hard pulls until it warms up. I also have been running on new pulleys and belt for over 1 yr and 10k miles but do not consider it to be an achievement.

[DrWill]

As stated in the initial post. My listed reasons for why Kraftwerks may have done certain things is mostly speculation. While the tensioner you list might fit it is a smooth tensioner and wouldn't be optimal for this setup which is why kraftwerks switched from smooth idler and tensioner pulleys to cogged that would keep the load on the belt more even and not risk damaging the teeth. There is also the question of weather or not a tensioner like that would be up to the load requirements. Given how close the belt runs to some of the mounting brackets if a spring tensioner backed off under load and the belt were allowed to deflect to much it would hit the bracket potentially damaging the belt. As far as using a phone app to tension the belt. Idk if I would trust that. As for using a tension gage that would be the best way if kraftwerks listed a tension measurement in their documentation. I may measure ours and post the results here if there is enough interest.

[DrWill]

Originally Posted by vgi

this ^^^ is going to confuse a hell lot of people IMO kinda like advise given by Kraftwerks - “ not to loose, but not too tight.” - go be "feeling" the belt

one piece of missing info - according to Kraftwerks, belt tension should be done when engine is cold!

Using "measurement for the position screw" is a bad idea IMO as according the Gates sound frequency app a minor variation causes rather large change in frequency.

The design should encounter (belt should handle extra tension when hot) for expansion/contraction of the pulleys and if it doesn't - it's a major flow and there is nothing one can do. I'm not convinced they did. The loaded dynamic tensioner would address this issue. The new pulleys, I guess due to larger diameter, do cause larger play in belt when engine is cold/hot.

I personally do not check belt tension often and basically set-it-and-forget-it after I did tension recheck about a month after I installed new pulleys and belt. Maybe I'm wrong, my thinking however is that pulleys operational temp, after about 10-20 mins, should be roughly consistent and affected more so by engine temp and especially friction. The seasonal change does affect the belt while the car is still cold so I take it easy and don't do hard pulls until it warms up. I also have been running on new pulleys and belt for over 1 yr and 10k miles but do not consider it to be an achievement.

You're probably right. It will likely confuse some people but like I said I was trying to explain it as best I could in the absence of any real data from kraftwerks. I don't recommend setting it py position screw either. Like I said that will only get you in the ball park. I wouldn't say we recheck it especially often but every couple months or so we notice a change in blower pitch or in the sound of the belt at idle/low load and check the belt tension. If you tension the belt just tight enough that it doesn't flutter at idle it should be loos enough that it won't be over tensioned once everything warmes up but we usually re check after driving it for a bit to make sure it's not to tight. While I agree a dynamic tensioner would be a huge bonus. I'm not convinced it would be able to hold enough tension under load transition to keep the belt off the lower mounting bracket as it runs pretty close.

[Vinnito1]

So I have access to a Gates ultrasonic tension meter. Anyone in the Dallas/Fort Worth area willing to find out what their belt tension is actually set too? That's assuming there is actually a spec, belt span to measure, and i can get information about the belt.

[ZionsWrath]

So the TL;DR is there is a ton of margin for error to get the proper install?

That's enough to steer away customers even if the kit is amazing when "perfectly" installed.