benefits of titanium valves in the engine

[uamir]

Is there any significant advantage of using titanium valves on a Yamaha YZR6 engine? as the valves are expensive. Well it is obvious that it is going to reduce wait, but do we get better acceleration or better valve timing?

[uamir]

Is there any significant advantage of using titanium valves on a Yamaha YZR6 engine? as the valves are expensive. Well it is obvious that it is going to reduce wait, but do we get better acceleration or better valve timing?

[Luniz]

Less weight, therefore less inertia, and therefore more accurate valve timing in higher revs would be my guess...

[Wesley]

Real advantages - reduced valve float due to lower sprung mass, lower exhaust valve temps due to thermal properties, thus less detonation.

Sort-of advantages - less weight to drag around, but it's a tiny difference, less thermal expansion> less valve lash change.

Disadvantages - ridiculously expensive.

[Superfast Matt McCoy]

The big advantage of Ti is that you can spin the engine faster without getting the kind of valve loft that results in excessive bounce or piston-valve intimacy (note that loft itself is not a bad thing). But a restricted 600 already redlines waaay past the point where the restrictor chokes and your power decreases from added mechanical losses.

You're only going to get better acceleration or better valve timing if you have new camshafts made. Ti valves will allow you to use cams with more acceleration, but since you're not using the top 4000RPMs (you shouldn't be) you could just rev limit it to 12k and do the same thing with the stock valves. But you're airflow choked anyways, so what do you gain? Peak horsepower at a slightly less RPM, possibly resulting in some negligible increase in power and fuel mileage from the small decrease in mechanical losses. Maybe, and only if you do all the computer analysis and testing to get the camshaft profile correct.

Even if you didn't have to pay for the valves, the hassle and cost of pressing in new seats, having them re-cut, grinding them smooth with the port, not to mention all the analysis and testing... I think it would be hard to justify.

[Erich Ohlde]

titanium valves require lower EGT's. you cant run TI exhaust valves unless you have a really good coating or you don't care if you tulip a valve. TI valves generally loose strength at about 1250*F where stainless valves are good to a much higher temp.

[VFR750R]

i don't agree with the egt comment. they can withstand much higher.

agreed on all other points. it would take several team members to work on camshaft design and springs to take advantage of a ti valve. otherwise it's money down the drain. maybe a good long term project, but i'm not about to predict the gains you might be able to make from the stock valvetrain with a restrictor.

[Wesley]

A quick look at some property tables confirms VFR's statement - high temperature creep strength of titanium is higher than austenitic stainless steels.

http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Homemade WRX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VFR750R: several team members to work on camshaft design and springs to take advantage of a ti valve. otherwise it's money down the drain. </div></BLOCKQUOTE>

well, with a 600 engine now redlining well before what its springs can control with a steel valve, the titanium change and just changing to much lighter springs would free up some power in itself. While utilizing a cam to take advantage of the lower mass would be best, I think dropping spring rates would have a noticeable increase in power.
Just look at a spintron test to see the kind of power just the valvetrain eats up.

(VFR750R, I have no doubt you know this.)

[Wesley]

Noticeable as in how much? 1HP?

Do you have spintron test data available for a 600cc motor?

[VFR750R]

We can't measure it on a spintron so i doubt you'd measure the hp gain on the dyno. What you would measure is a cam with 20 deg less duration but the same or more total lift area.

i think the fact that a 600cc 4 cylinder makes more peak torque then a 600cc single points to friction losses in the engine being more then offset by VE improvements those extra valves provide.

[Wesley]

Right, I concur that the only reason to go with Ti valves would be in conjunction with a more aggressively ramped cam.

By just switching to the valves, however, you won't notice the horsepower difference.

[Matt N]

Also, keep in mind that ti valves or not, you cannot run super-steep opening and closing ramps nor can you run inverse flank lobes with bucket actuation. Unless you were going to figure out how to put finger followers or roller finger followers under the cams (major head redesign work) you wouldn't be able to run super crazy cam profiles anyway.

Matt

[VFR750R]

There is no need for finger followers even if they are ideal. Stock camshafts are incredibly weak in aggresiveness, and the flat bucket limits speed but not acceleration so there is alot of room with stock components.

beyond that, pinned buckets (to keep them from spinning) with unidirectional crowns can dramatically improve valve speed with minimal 'head work'.

[Wesley]

VFR, I was under the impression bucket rotation was necessary for proper wear, and the rotation was induced by the crown?

[cipivts]

Hi to all,

I'm servicing my 2007 R6 which i use for race only and after 2 full seasons i found out that i have to replace all the titanium valves as they are mostly damaged and out of spec. Compression is low bellow 12 on all cylinders and the mechanic suggests a new set is required.

My engine is standard, i only tend to increase the compression by adding a thinner gasket; a head job will be performed and the rest will remain standard. I don;t plan to increase the revlimit of the engine.

I checked the prices and the titanium valves are very expensive.
A UK company suggested that they have a direct fit stainless steel valve replacement valves for this engine.
Should i go for it as the price is significant lower and these are more reliable on the long term.
what else should i change? Springs would be my first guess

Please advise!

[Kevin Dunn]

Nice thread hi-jack cipivts...As of right now, your post is just above this one.

[Drew Price]

If you're keeping the rest of the hardware stock, and aim to save a little money on future rebuilds you may want to opt for stainless valves, but like you said, some changes to make up for the additional reciprocating mass in the valvetrain wouldn't be a bad idea, and might offset the lower cost of the valves.

How often are you having to do rebuilds? Every two seasons isn't bad at all, and you might be able to get a whole low mile cyl head for a reasonable price and keep swapping in partially used ones.

If it were me, I'd stick with the Ti valves, it's what everything is set for.

Are you using stock software, stock rev-limit, all that stuff? You could always try it out and see if you are having valve float issues, but if you do then it'll have to come apart again, and offset the cost again.

Best,
Drew

[VFR750R]

maybe you could get aftermarket Ti valves, or have stock valves coated to improve life.