Titanium Wrist Pin

here is a quote from https://www.highpowermedia.com/blog/3342/piston-pins-material-choices

"Steel is not the only choice for piston pins though; a number of companies offer titanium pins. Titanium has a much lower density than that of steel, although its elastic modulus (a measure of stiffness) is also low compared with steel. Titanium Ti-6Al-4V is often used, although pins made from Ti-17 (Ti-5Al-2Sn-4Mo-2Zr-4Cr) are also commercially available.
We should not, however, expect to replace an optimised steel piston pin with one of the same dimensions made from titanium, and expect to find success. Titanium has particularly poor wear behaviour in sliding contacts, so titanium pins would need to be coated to achieve an acceptable level of durability. Again DLC is often used here, but pins are also marketed which have a titanium nitride coating."

from http://amt-advanced-materials-technology.com/app/download/.../Ti-Auto2.pdf
"Connecting rods require strength, fatigue performance, stiffness (particularly the big end)
and wear resistance. The strength and fatigue performance of titanium are more than
sufficient for this component, however stiffness and wear resistance need enhancement
via reinforcement particles and coating. Novel concepts such as bimetallic steel
(lower part of the big end) – titanium components allow a shifting of the connecting rod’s
center of gravity towards the crankshaft, giving a positive effect on piston guidance.
Reduced weight connecting rods, in combination with lighter weight pistons and
wrist pins lead to significantly reduced NVH (noise, vibration and harshness) and
improved engine performance including fuel economy.
Piston assemblies (piston, piston pin and the connecting rods discussed above) account
for a large amount of the friction losses in an engine over the full speed range.
Reduced mass here leads to improved fuel economy and reduced emissions. Titanium
use in these components could increase as the operating temperatures in the engine
exceeds the capabilities of aluminum alloys. For piston pins where strength, wear
resistance, high stiffness and high temperature capabilities are required the titanium
aluminides appear to be a good choice. "
 
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butre, 10:1 is very high, way too high for these engines.
a '98 KDX200 has a 9.4:1 ratio and its cranking pressure is 155 so yours would of been around 165 if the rings were sealing good.
I recommend never going above 135psi.
and it is unknown if muddy rain water was splashed onto your air filter and sucked in which provides enough abrasive material to wear down bearings and their surfaces. That happened to me on my KDX200 and it was the same parts that suffered the most.

Unless all the owners of the titanium pin from Juice are experiencing the same problem then I can only deduct that premature wear is due to too-high cranking pressure (which almost all of the aftermarket high compression heads create) and/or ingested muddy water (or dust in the case of cheap paper filters or a tear in the filter)
 
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my steel pin survived 1000 miles and showed no signs of wear at the end of it at that compression. titanium was the problem.

I also use a prefilter so sucking up dirt is unlikely
 
yeah but until I hear from people who have standard compression and don't get rain splashed by cars I won't believe that titanium is never a good choice. It's probably just not a good choice for the high stress situation of high compression. Going up from the standard 90 psi to 165 psi creates a huge peak pressure difference in the cylinder which is pushing down on the piston/bearing/wrist-pin.

I don't care what super duper filter you have, if you don't have a splash guard on your filter then muddy water can be sucked right through it.
 
there are literally hundreds of people running much higher compression than I am and are having no problems with their steel pins. I don't believe for a second that compression makes an incredible difference on wrist pin life if the wrist pin is good quality.

Titanium may be fine, but the pins juice moto parts are selling (and that your signature link advocates) are complete junk. That's not the only questionable part juice is selling either, the aluminum top end bushings being a particularly outstanding example.
 
I don't believe for a second that compression makes an incredible difference on wrist pin life if the wrist pin is good quality.

I would think that combustion pressure is far greater than compression pressure, regardless of it's number, so i agree with your logic.


the pins juice moto parts are selling (and that your signature link advocates) are complete junk.

That may be the case because i have a 32" GB Titanium chainsaw bar and it lasted no longer than a standard Oregon bar.
When reading the fine print, the GB Titanium bar uses only 2% titanium, but costs double the price of an Oregon bar of the same size.


That's not the only questionable part juice is selling either, the aluminum top end bushings being a particularly outstanding example.

For a racing application where every gram counts, and for when the engine only needs to last one single race, the aluminium bushing may be an advantage, but for general day to day use, an aluminium small end bushing is a foolish idea to consider; with premature failure being the likely outcome, which doesn't add anything to the concept of reliability.
 
I would think that combustion pressure is far greater than compression pressure, regardless of it's number.




That may be the case because i have a 32" GB Titanium chainsaw bar and it lasted no longer than a standard Oregon bar.
When reading the fine print, the GB Titanium bar uses only 2% titanium, but costs double the price of an Oregon bar of the same size.




For a racing application where every gram counts, and for when the engine only needs to last one single race, the aluminium bushing may be an advantage, but for general day to day use, an aluminium small end bushing is a foolish idea to consider; with premature failure being the likely outcome.

those aluminum bushings are designed to slip in place like you would a standard bearing, not press fit like it should be. it's an incredibly half-baked part
 
it's an incredibly half-baked part

If the aluminium bushing is a slip-in part, then i am in complete agreement with you.
On that basis, the aluminium bush has the liberty of sliding out of the small end which will dramatically reduce it's load bearing capacity; having the thing chewing itself to pieces in short time.
 
"I don't believe for a second that compression has an incredible difference on wrist pin life if the wrist pin is good quality."
yeah but obviously the titanium pin is not as good as the steel pin which is why I just changed the recommendation on my page concerning it and high compression.
It is probably fine to use for people who don't exceed my recommended 135psi.
165 is way too high for these engines. I hope you will lower it.
 
But could it not be argued that combustion pressure gives far greater cylinder pressure than 165 PSI, so in effect, the compression pressure which is a function of the compression ratio, will be of negligible consequence to wrist pin life, even if it were placed at diesel compression ratio.
 
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