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Hey guys, Will asked me to throw up a post about the chain tensioner we're working on. I'm going to put up one of my older blog posts for now, so you understand some of the stuff I post up later. In the next few days I'll put up another lengthy post that actually covers the design process of our new tensioner along with some pics of the prototypes we're testing.

I know this was posted in another thread already; I'm just trying to condense all of the info related to our tensioner design into one thread.:up:


edit: check out my full article here: http://www.hybrid-racing.com/?cat=4&p=267
 

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Awesome guys! Looking forward to seeing what you guys came up with!

Can't wait :up:
 

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I just posted this to our blog. Either tomorrow or monday I'll take some pictures of our actual prototypes and post up some screen shots of the rendered solid model we'll be basing the production unit off of.

So now that you know how the k-series motor's chain tensioner works and what problems it has when you run aggressive cams, you're probably wondering what we intend to do about it. Well, during the last six months or so, I've devoted a lot of time to cutting up broken and new OEM k-series chain tensioners and finding out what there is to them, and how they could be improved. My first discovery was that the internals of the tensioner were great. Honda's engineers did an excellent job of controlling the pressure and oil flow through the tensioner, and there wasn't a weak link to be found there. There was no sign of excessive wear or fatigue inside the tensioner. So I wanted to mimic the construction and dynamics of the OEM internals. I then turned my attention to the design of the piston itself and the design of the ratcheting mechanism. Shown below are pictures of the teeth on a broken tensioner piston vs. the teeth on a new one and the locking tooth from a broken tensioner and the locking tooth from a new one.




As you can see, the broken (or worn out, rather) tensioner's teeth show very clear signs of wear on both the piston's teeth and the pivoting locking tooth. Some wear would be expected from a part like this, but the worn out tensioner's parts (as shown above) were so worn down that the ratcheting teeth didn't engage anymore. This allowed the piston to be pushed completely into the tensioner. When a tensioner gets worn down to this point, any force it applies to the chain is done only by the spring and hydraulic assembly, so there arises ample opportunity for the chain to push the piston into the tensioner and become slack, possibly leading to motor damage.

Now is this simply a case of poor material selection on honda's part? Some would disagree with me, but I'm going to say "no." We have not been able to find any cases of chain tensioner failure in a well maintained, unmodified engine. So in that respect, the tensioners are only failing when they are subjected to forces greater than they were designed for. That said, there is a big contributing factor to the failure of these tensioners that has less to do with material choice and more to do with the fitment between the tensioner piston and the chain guide. As I stated in my article where I dissected the OEM tensioner, there's a loose fit between the slot in the chain guide and the tip of the tensioner piston. This loose fit allows the tensioner piston to rotate several degrees. When the piston rotates (due to engine vibration, etc) and is then pushed back into the tensioner, engaging the locking tooth, the locking tooth and the teeth on the piston are not perfectly lined up (see illustration below).


This misalignment cause huge stress concentrations that fatigue the ratcheting mechanism much faster than if the teeth meshed correctly. Allow this to happen too much, and the ratcheting mechanism will be rendered completely ineffective like was seen in the worn tensioner showed earlier. Knowing all of this, I set out to design a bolt-on replacement for the OEM tensioner, that would not wear out like the OEM unit did when exposed to the increased forces (from the chain) associated with running aggressive cams and stiffer valve springs.

My first two design changes were aimed at the ratcheting mechanism and the fitment between the piston and chain guide. The piston was redesigned to make it press into the chain guide rather than loosely fit into it. This was intended to eliminate any rotation of the piston inside the tensioner. Having done this, the likeliness of wearing out the tensioner was reduced, but I wanted to make sure that you could beat the living daylights out of the tensioner and see almost no wear at all. With that goal set, I added a second ratcheting mechanism, identical to the first one. A computerized model of the tensioner (and more importantly the ratcheting mechanism) can be seen below. (Note: the image shown below is a cross section of the solid model and does not show all components).


The last (and arguably most important) step of the design phase was to select the materials for the tensioner. To avoid being overly pedantic, I'll forgo listing the alloys and heat treatments I chose for the parts on this tensioner. However, I will note that for the ratcheting mechanism, we decided to go with some more robust materials, and use steel alloys similar to those found in the ratcheting mechanisms found in impact wrenches.

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Very Nice...

any ETA on these things?
 

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Discussion Starter #10
I'll post another review once testing is complete.

peace,
russ
After thoroughly analyzing the design of the OEM K-series chain tensioner and determining the changes that needed to be implemented, it was time to fabricate some prototypes for testing. We had two units made, and are currently in the the preliminary stages of testing. The majority of testing will utilize skunk2 Stage 3 cams and pro-series valve springs. The engine will be run hard on the dyno, drag strip, and road course(s). We will also be daily driving the car, for extra measure. Like stated in my previous article on the chain tensioner, our unit uses tighter tolerances and high grade materials than the OEM tensioner, and it is these two elements, combined with a beefed up ratcheting mechanism, that will allow this tensioner to take the abuse it will see when used with the upgraded valve train we plan to run, as well as any other after market valve train meant for the k-series motor.

Developing this tensioner and sourcing the parts for it was a tremendous undertaking. Every part of it is custom manufactured to our specs. Even the springs it uses had to be custom wound to suit our application.

Shown below are some pictures of the tensioner before assembly, after assembly, and mounted to a motor.








Keep in mind that the production units will not look like the tensioner shown above. All of the features, materials, and tolerances will be identical, but the design will be a little easier on the eyes. Shown below are a few recent shots of the nearly completed production design. The body of the tensioner is 6061 aluminum that's received a T6 heat treatment and a hard anodize (clear in the case of the prototype, and most likely black on the production units).








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in your machined prototype, there is the threaded hole for a screw, couldn't there be a dowel pin there, and a machined groove in the piston to further eliminate the chance of the piston rotating in the tensioner body.
I can't wait till their done.
should contact john at hytech im sure he could do some testing with them. And they would sell good on rsx tuners website as well as k20a.
 

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Discussion Starter #12
in your machined prototype, there is the threaded hole for a screw, couldn't there be a dowel pin there, and a machined groove in the piston to further eliminate the chance of the piston rotating in the tensioner body.
I can't wait till their done.
should contact john at hytech im sure he could do some testing with them. And they would sell good on rsx tuners website as well as k20a.
It is impossible for the piston to rotate on these prototypes once they have been mated to the chain guide. The threaded hole you see is there only to allow you to insert a screw that holds the piston in place during installation, much like the thumb tack on the OEM version. Any sort of groove/dowel pin guide would be unnecessarily redundant. I say this because there is no considerable force present in the system to rotate the tensioner piston, only vibrations inherent to the motor. That said, if there is a tight fit with similar, hard metals (like the fit between the tensioner piston and the chain guide), there is no risk of wearing down the two parts, since it is merely light vibrations and not a heavy cyclic loading condition.

Good call on the rsx tuner market; we were thinking the same thing. :up:

peace,
russ
 

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Nice idea. Any ETA on this?
 

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Nice idea. Any ETA on this?
Thanks. These will be available 2 months from now at the soonest. We still have a lot of testing we want to do, and we haven't decided which of our manufacturers should make the production run just yet.
 

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now to conquer the oil pump issue, billet oil pump that has s2000 internals that fits in stock cast pan. Fix all the problems at once, the cavitation issues, fitment, pan choice, ect
keep the great designs coming. on your way to the complete k series market.
 

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You guys never cease to amaze me! :)
 
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