Ti vs. Stainless Valves?


8 replies to this topic
  • danstorm801

Posted November 29, 2004 - 02:03 PM

#1

Does anyone know the advantages/disadvantages of Titanium vs Stainless valves? Thanks.

  • NAFLASH

Posted November 29, 2004 - 04:02 PM

#2

titanium valves are lighter that steel valves
lighter =faster

  • grayracer513

Posted November 29, 2004 - 05:21 PM

#3

Titanium has a very high strength to weight value, and is as strong as many steels are at a much lower weight. This allows higher engine speeds to be reached before loosing control of the valve train (valve float). When you realize that at 11,500, the rev limit of a YZ450, the valves open and close 95 times a second, it's easy to see how important that is.

Lighter valves also require less spring pressure, which in turn reduces the operating load on the entire valve train, and results in longer wear life and less internal power loss.

So, like he said, lighter = faster. :cry:

  • Rich_Rohrich

Posted November 29, 2004 - 06:52 PM

#4

Lighter valves also require less spring pressure, which in turn reduces the operating load on the entire valve train, and results in longer wear life and less internal power loss.

So, like he said, lighter = faster. :cry:



There is no question that is true in theory, but I think the difference is regularly overstated. In practice I've yet to see a dyno test that can show a loss of power running stainless valves on any of the YZFs (or CRF450s for that matter).

One engine guy I know of ran 113 different tests on 250Fs before he declared no measureable performance change between the OEM and the higher pressure aftermarket springs used with stainless steel valves.

We've put a whole lot of stainless steel valves out there with heavier springs and I've yet to have a customer comeback and complain about a lack of performance as a result. Although I do get a lot of nice e-mails telling me how happy they are not having to deal with valve train issues any longer.

If you change the valve springs regularly the Yamaha OEM valves hold up really well, much better than Honda valves, but for the money a good set of stainless valves and quality springs seems to me to be a better long term value. We build them both ways all the time, but in my own 52 HP YZF444 I have stainless steel valves and high end springs (same goes for my CRF450). :cry:

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  • Beef

Posted November 29, 2004 - 06:55 PM

#5

What they said is completely true. However, stainless is more resistant to wear, and (I think) is less ductile. Less wear means longer valve life, and less ductile means it will take longer to stretch the valve stem.

Every time the valve slams shut, the stem streches a little. VERY little, but over time, it adds up. In conjunction with valve seat wear, it results in the tightening of your valves against either the cam or the rocker, depending on the head design.

  • yz426onNOS

Posted November 29, 2004 - 07:34 PM

#6

Titanium valves are lighter and stronger. The bad part is they beat the living hell out of the valve seats. Which meens you need new valve seats more offen. Stainless steel valves if one piece are far better. They weigh a little more and the valve seats will last longer with them and there plenty strong to handle what you need.

When you build a hi performance motor you want single piece stainless valves, not titanium.

The reason yamaha went to titanium is because of the two piece steel valves breaking (like mine at 8000 RPM's plus in 4th WFO) and to get higer RPM's.

Get the stainless 1 piece, they are the best!

  • danstorm801

Posted November 30, 2004 - 11:13 AM

#7

Thanks for the info guys. I was thinking along the same lines - that Ti valves meant lower mass and therefore a faster opening/closing valvetrain. I was also recently talking to a machinist friend and he told me that in a lot of cases, Ti is more brittle than stainless, which would make them more susceptible to breaking when used with high lift cams and heavy springs. Have any of you experienced this?
Anyone know of a company that is making oversized stainless valves? I know Ron Wood is selling oversized Ti valves, but I haven't found anyone making oversized stainless? would it even be worth spending all of the money on big valves, or would a good port job be enough?

  • FFRacing79

Posted November 30, 2004 - 11:26 AM

#8

There is no question that is true in theory, but I think the difference is regularly overstated. In practice I've yet to see a dyno test that can show a loss of power running stainless valves on any of the YZFs (or CRF450s for that matter).

One engine guy I know of ran 113 different tests on 250Fs before he declared no measureable performance change between the OEM and the higher pressure aftermarket springs used with stainless steel valves.

We've put a whole lot of stainless steel valves out there with heavier springs and I've yet to have a customer comeback and complain about a lack of performance as a result. Although I do get a lot of nice e-mails telling me how happy they are not having to deal with valve train issues any longer.

If you change the valve springs regularly the Yamaha OEM valves hold up really well, much better than Honda valves, but for the money a good set of stainless valves and quality springs seems to me to be a better long term value. We build them both ways all the time, but in my own 52 HP YZF444 I have stainless steel valves and high end springs (same goes for my CRF450). :cry:


So Rich, what is your take on the reasoning behind the factories using Ti?? Tryce

  • beezer

Posted November 30, 2004 - 11:30 AM

#9

There are a bazzillion different grades of titanium and stainless.

To understand the difference between them you need to be a metallurgist.

I think the TI valves might be there for marketing reasons.





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