haha i was a freshman in high school

 

Isn't it me of doesn't titanium have a very low melting point?

If so sticking it on something as hot as a turbo or as hot as a rotary engine bay would have disastrous results to me.

Alex

 

Just for reference:
Here is some discussion of boosted rotary EGTs. They spend a lot of time talking about if you want to tune for a particular EGT, but they all agree that temps up to and temporarily above 1000C occur regularly. Here is another discussion mentioning normal EGTs for an FD.

I dug around a little, and it looks like 850-900C is about what the WRX and Evo folks preach as their limit. And I didn't come across any advice specific to using the Titanium Aluminide turbo, which might be tuned for even lower EGTs.

The Gamma TiAl turbo testing in the Mitsubishi paper stopped at 900C, and was only tested for 600hours and without variation in load. As well, you can see in the graph that the strength of the TiAl is falling steadily above 750C, and so at 1000 or 1100 it could be literally falling apart. It might pay to call the vendor of the turbo unit and see if they have any EGT recommendations for it.

Unless there is a way to reliably keep EGTs under 900C at all times, or data suggesting that the Gamma TiAl can handle higher temps, or simply a willingness to cook one for the sake of experimentation, I would not expect this material to work on the rotary as it is now. I'm getting tired and I have work to do, otherwise I'd try to do some research on how much (and how reliably) CO2 or water injection can keep down EGTs, and if it presents disadvantages that outweigh any performance improvements.

It would be interesting to pose this question again in the Single Turbo section and see what they say. (Many of them don't cross over here often). Just keep the question focused on the Titanium Aluminide material and away from titanium metals, lest sloppy readers like me get off-track

Dave

 

dave,
thanks for the info your a good guy, maybe i'll see you around one day. englishtown is opening up a road course here in jersey. If you know of any in E. PA let me know.

josh

 

Doug, are you always this incredibly off topic?

Umm...isn't how much air the motor can flow a pretty big consideration as well? Ie, even if you have super lightweight titanium wheels, if you throw on a huge single on a stock ported motor, I doubt the motor would flow enough to spool the turbo at any decent rpm, if at all...

Hey Dave...slightly off-topic, but can you clarify something for me? To my knowledge, a ceramic is generally any inorganic, nonmetallic solid processed or used in high temp applications. So how can a ceramic (a non-metal) be titanium (ie metal) based? Is the term "ceramics" used more widely than that, and not limited exclusively to non-metallics, or is it simply used to denote the majority of the material being a non-metal?

Thanks
~Ramy

 

Titanium is an element just like any other, and can be used in metals (e.g. pure titanium metal or titanium alloys), or it can be found in more mundane covalent materials like Titanium Oxide (a white pigment).

It turns out, this titanium aluminide is not a ceramic, but an "intermetallic" - something slightly in between that I haven't studied before. It's somewhere in between a covalent structure like a ceramic and a metallic alloy. They do mix it in proportions like an alloyed metal, so it's definitely not a ceramic. When I have more time I'll research it myself.

Dave

 

so is it possible to change out a turbo's wheel for a tiAl or not? just have to find a way for it to not melt?????

 

Melting is not an issue. It would probably get whittled away at the blade edges by iron particles in the exhaust flow.

So yes, my opinion is that you'd need to find out 1) if it can withstand higher temps than 900C, and if not, how to reduce the EGTs to a suitable level. You'll have to talk to a turbo builder (BNR Supercars, for example) to see if the wheel can be swapped or to adapt the whole housing.

I have to wonder though - the Evo IX is not using that material already - they are using Titanium-Magnesium, which I presume is a similar intermetallic. I can't find any information about it.

Dave

 

well, it would cost an incredible amount, but why not use the materials for regular turbines and split it 50/50 with Ti. Bond the Ti and your other metal together, then pour it into the casting. Obviously you will need to become a chemist and do this properly but you will lighten the wheel while still holding more strength then pure Ti.

You could also form a smaller wheel with Ti then have it "wrapped" in a stronger material. It would do the same as above except the core would be pure Ti. You would still need to bond the Ti with whatever else you would use.

Cryo treat both of them, and in theory they should work.

 

You'd have to do more than spend a bunch and "do this properly" - you'd have to do it better than anyone in history has done it. Researchers have tried bazillions of combinations of materials for thousands of years. (Since the bronze age, really, when man discovered that Copper and Tin made something better called Bronze). When research develops something new, the resulting marketing talk makes it sound nice and simple, but the reality is that most advances were developed at a detailed level and offer their advantages only in a narrow range of environments.

If you've not studied materials, it wouldn't be obvious that you can't just mix 50% of one material and 50% of another and get something with properties somewhere in between. But that's the reality of it. The science that allows a mixture of iron and carbon to make a material with superior properties over the pure ingredients are the same rules that dictate that if you change the mixture in some materials it all goes to pot.

To give an analogy, your approach resembles "I like cake, and I like beer, so let's take all the ingredients of both and cook them together". It just doesn't work like that.

Materials that we call Titanium, Titanium Aluminide, Inconel, Aluminum, etc are already finely tuned mixtures. Nobody uses pure elements for these applications - they use alloys. Alloys contain very specific amounts of elements "cooked" a very specific way. In case you're wondering what I mean, the most common form of Titanium is actually 89% Titanium, 6% Vanadium, and 4% Aluminum. Inconel 751 is a mixture of 70% Nickel, 15% Chromium, 6% Iron, 2.3% Titanium, 1.2% Aluminum, and 1% Niobium. How you mix, cool, and "cook" these metals also has a major effect on the result.

Feel free to dig around yourself: http://www.matweb.com/ is a neat materials resource - just type in the name of a material into the search that you see at the middle of the page. You'll get a lot of hits, but many of them have good descriptions.

That's an interesting concept - but it would be crazy expensive to pull off. As well, a turbine is actually a spidery-thin structure that doesn't lend itself to a layered construction.
Haha, yeah cryo fixes everything - even the common cold. And there is no theory here to support the possibility.

Cryo works for some things, and not for others. It does not help these high temperature alloys and intermetallics, otherwise it would already be in use. It does work in wringing some extra performance out of mass-produced hardened steels. If the manufacturers believed they needed the extra performance out of the material, they would spend the extra money and get it.

Dave

 

Niobium, huh Dave? LOL. That's one of the elements I had to look up. I was like whaa? That's not a real element...then I saw the "Nb," was like "OH YEAAA...that's one of those ones I saw but we never EVER had to look up or use And trust me, by the time I finished few YEARS of Chem courses, I thought I knew the Periodic Table like the back of my hand... but in reality, there's a ton of transition metals none of us bio guys have ever looked at twice

~Ramy

 

Well Ramy I will completly concur with you on that one. I am studying for the School of Pharmacy (applying next year to VCU). All this chem crap is killing me. I understand about 68.943% of it.

The other crap my instructor sucks *** at teaching, so hes like do you understand it and no matter how long he yaps with me, his crap still doesnt make sense. Its one thing to know the subject, its another to teach it.


Dave, yes I do realize all that has to go into my first claim. Hence the reason it would cost an incredible amount

However, wrapping the TI might just work. If you had certain holes drilled through the fins so the outer coating could hold a stronger inner bond it might work properly. Kinda like bonding fiberglass to stock bumpers(cant think of what they are made of at the moment).

 

Well, yes, incredible is an appropriate word. People spend careers, and companies have spent countless millions just to develop more affordable, lightweight, ultra-high temperature, high strength materials. The fact that we even have a turbocharger that lasts 100k miles is solely due to these folks. They deserve plenty of credit.

Dave