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Discussion Starter · #1 ·
I haven't seen this information posted anywhere, but it's so simple that I imagine someone out there has already discovered this and just hasn't shared the goods.

The story of this discovery goes like this. My friend Sam (shadowMD) has a k20a2 swapped ep3. In this Ep3 he has installed skunk2 stage I cams with the skunk2 pro series valve springs and Ti retainers. Since he put the cams in, he's burned through the original tensioner, a replacement used a3 tensioner, and a brand new k20a2 tensioner. The last tensioner, the new k20a2 tensioner, was shot in less than a week. The original tensioner lasted for quite some time, maybe a few months, and the a3 tensioner lasted a week or so. As a last resort, Sam went ahead and ordered the Toda Timing Chain Tensioner. Since he invested the $180 in the Toda tensioner, I was able to inspect it and observe a few key differences that could EASILY be implemented in the stock tensioner.

Below is the disassembled stock tensioner from an a3. I disassembled an a3 and a2 tensioner and found them to be constructed identically. The spring within seems to be of similar stiffness, but I don't have a proper means of testing the spring rate.

body - spring - piston


The Toda tensioner supposedly has a stiffer spring. The spring itself could be replaced quite easily with a replacement unit from McMaster-Carr. However, The Toda tensioner's spring did not feel any stiffer than the stock unit. I always disputed the value of simply having a stiffer spring since even a small amount of oil pressure would easily provide more support than the spring within the tensioner. I soon observed another feature of the Toda that seems likely to be far more important modification. More on that after I detail what exactly is failing on the tensioner.



Note the middle section of the piston where the teeth are worn down. What has been happening on the tensioner is that the ratchet mechanism is getting worn down to the point where the two teeth on the catch no longer engage the teeth on the piston of the tensioner.



It's hard to see here, but there are two teeth on the catch of the ratchet mechanism and both of them are worn down. Also notice the oil inlet at the bottom of the tensioner body.



There is a view of the inside of the piston.

Now, in the way that Moses parted the Red Sea, I shall part the sea of confusion surrounding timing chain tensioner failures.

One thing most of you have probably noticed about the stock tensioner is that the piston can be compressed all the way into the body of the tensioner.



Sorry for the blurry pic, but I was compressing the tensioner with one hand and trying to take a macro shot with my camera in the other. Now, the Toda tensioner does NOT allow the piston to compress fully into the tensioner body.



The significance? Let me detail the function of the ratchet. The ratchet exists to STOP movement of the piston into the body of the tensioner when the tension in the chain exerts a compression force on the piston. When the ratchet fails, the piston can compress fully with the stock tensioner when there is low oil pressure. If you have enough oil pressure, then the ratchet is not necessary.

The Toda tensioner can not be fully compressed. In fact, it is engineered such that it compresses only enough to allow installation. When you install the tensioner, you have to compress it that last .5mm, which raises the lever allowing the pin to fall out, to get the tensioner bolts in. This means that when the chain exerts a compression force on the piston of the tensioner, it hits a hard mechanical stop instead of relying on the ratchet as the safety stop. This theoretically makes it much more reliable in low oil pressure situations (low rpm and oil pump cavitation).

Given the internal construction of the tensioner, it should be obvious what modifications are necessary to impart this behavior to a stock tensioner.

1) get a longer spring that coil binds at the point where the piston is compressed just enough to permit installation.

2) using washers, shim the stock spring so that it coil binds at the specific point where the piston is compressed just enough to permit installation.

3) install a sleeve inside the tensioner that limits the compression of the piston to a point that is just enough to allow installation.

There are many ways to get this job done, there is no right or wrong way. You could even get a ultra stiff spring and use that so that even with no oil pressure the tensioner does not permit excessive movement of the chain. I observed no differences in the ratcheting mechanism of the Toda tensioner versus the stock tensioner. I did not disassemble the Toda tensioner as I wasn't the one that had just paid $180 to purchase it. :p

As for how to disassemble the tensioner? It's easy. Let it extend fully, twist the piston so that the teeth are facing the lever side of the tensioner, and work it out by turning it back and forth gently. It helps to have the tensioner oiled and to wrap the piston in rubber and grip with pliers. It takes 2 seconds to disassemble it.

I'm not going to post up any specific measurements or spring/washer part numbers just yet. I haven't actually tried this out, but I'll be doing so in my car very shortly as I have upgraded valve train of the sort that seems to warrant the need for a backup to the stock ratchet mechanism. I will mention that I have an a3 block with an a2 oil pump. I don't have oil squirters so oil pressure in that region of the block should be higher/more stable than on a k20a2 block with the squirters installed. As of yet, I have not experienced timing chain tensioner problems, but I will be inspecting everything very soon.

Anyhow, hope you enjoyed the read. Use the information at your own risk! :p
 

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Ive always wanted to see the differences between the oem and toda tensioners. Good job bro.
 

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Discussion Starter · #8 ·
PapiTuyo326 said:
Ive always wanted to see the differences between the oem and toda tensioners. Good job bro.
Hehe. It's annoying how the Toda unit ends up being a 200% markup over the cost of a stock tensioner. I'm all for quality parts, and I feel overall Toda makes quality parts, but this is just highway robbery. Hopefully I'll have a more detailed write up on a specific path for modding the tensioner soon.
 

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chunky` said:
Hehe. It's annoying how the Toda unit ends up being a 200% markup over the cost of a stock tensioner. I'm all for quality parts, and I feel overall Toda makes quality parts, but this is just highway robbery. Hopefully I'll have a more detailed write up on a specific path for modding the tensioner soon.
so is there a way to change the stock one to work like a toda? Any one have a CNC machine lol.
 

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TransformedBG said:
so is there a way to change the stock one to work like a toda? Any one have a CNC machine lol.
Chunky,

I have access to a Mill and a Lathe... if you need help let me know! I am gonna play w/ this as well. Thanks for the great write-up and out of the box thinking :up: most importantly... sharing!!!

Robert
 

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Discussion Starter · #15 ·
nikos said:
I want to place an order for 10 chunky tensioners. Let me know how much :p
LOL. I wish I had time to do all that. Since I'm not affiliated with any race teams nor am I trying to get rich (yet :p) might as well just share.

I've got a new tensioner coming that I will mod. Then i'll put it in my car and hopefully never worry about the tensioner. :)
 

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Discussion Starter · #16 ·
Oh, I'll add that there are actually 2 springs in the tensioner. One is the main spring that is pictured above. The other is the small spring that applies pressure to the ratchet's catch. Not sure if there's any benefit to be derived from upgrading that smaller spring, but I thought I'd mention it.
 

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I did this awhile ago..easiest way is to replace the spring with a little bit longer/stronger spring then get a solid steel rod that fits inside of the spring and cut it to length (and round off both ends, but, the side with the oil port needs a little slot cut in it to let oil in) with the spring out then re-install it all and you have a toda..
 
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