Did I mention that Cryo can extend the life of turbos by 20X.
Titanium is just friggin expensive. That's my brilliant input.

 

Better tell Mitsubishi that, the EVO 6.5 RS TME (Tomi Makkinen) used a Titanium Aluminide turbine wheel, and that would be circa 2001.

 

Two reasons why Titanium Aluminides hadn't come up before now:
1) The OP asked about "titanium". That means, in my industry experience, pure metallic titanium or titanium metal alloy.

2) I hadn't heard of it before today. In conducting searches and other research about using titanium in high temp applications, Titanium Aluminides were not mentioned. It is possible that the poster might have meant to ask about these new TiAls and mistakenly asked about titanium. Mitsu literature refers to it only as "Titanium Aluminide", which supports point 1. If the poster had asked about TiAl, it would have been a different conversation.

What Mitsubishi has done with TiAl to adapt it to turbochargers is interesting and promising. But it is very new, and if the aftermarket can replicate it and manufacture it with the HIP process, the material will probably be very expensive, and relatively untested. Without the HIP to improve its strength, The TiAl actually shows no advantage over Inconel 713C. So I agree, we should be watching for TiAl to come down to be available to us regular Joes.

Dave

 

Dgeesman, I do believe your writeup for vacuum hoses is the greatest rotary thing I have yet seen on this board! /applause!

 

Thanks, but I stole all of it from guys like Max Cooper, Rob Robinette, etc.

Back to the topic: you can buy the Mitsu TiAl HIP turbos for under $1000. Whether that matches the 13B-REW well I don't know. Interestingly, Mitsu is now using "titanium-magnesium", whatever that is. That's my next research subject.

Dave

 

If you go back and read the first page both the mitsubishi TiAL turbo and dodge titanium turbos were mentioned.

I must say I am very disapointed in some of the people on this forum right now.

A simple question was asked. A discusion was started then people started flaming. People with very high post counts as well as a mod.

If every time some one post's a new idea the mods and senior members flame him. People will stop coming up with new ideas.

And it seems like every time some one says "hey this might work" a few people how have posted on this thead say "Oh yeah prove it"

I think every one needs to just take a pill and grow up.

 

Feel free to point out where anyone besides the OP flamed anyone. I guess you consider us questioning his OPINIONS, which were scientifically wrong or ignorant, as flaming? Give me a freaking break.

 

The orginal poster started the flaming. Yes, I agree that HE should "just take a pill and grow up". This guy comes on like he is the ******' Internet by-God expert on ****, then whimpers and whines when no one just kow-tows to him but rather points out some well documented information. And then he starts insulting everyone, which at that point he gets what he deserves, which is the loss of any real discussion on the topic. Too bad, too...it bore some merit.

 

I wanted to know more and was disapointed that it turned into another flame thread.

 

Again, besides the OP's posts, who's flaming anyone? Lots of info has been provided here by people that actually work with materials....

 

How were his OPINONS wrong and what makes your RIGHT. Opinons are like ******* everyone has one and they all stink. Have you built a titanium turbo?

He was stating a theory there are no facts at that point, if you know the sientific method. I never read him flaming anyone in this thread, but I probobly just missed it.

 

Remember im a noob so flame all you want...

PLEASE show me scientific proof disproving the 30% faster spool theory...I just want to see your scientific backing to support such a harsh reply/flame

 

Back to the thread....I am currently spec'ing a titanium turbo for a for a very high horse power project and so I will share some of the considerations....

Material strength: This is important.....specifically mean fatigue strength. This is the amount of times you can stress a material before it fails at a certain stress level. In steel, there are levels of reduced stress that you can run at for an infinitely long time. In aluminum, it is not a question of if it will fail, but when. Materials are characterized by the strength curve. As the stress levels go up, life goes down.

Manufacture: Depending on the alloy, composition, manufacture, and treatment, the parts made from materials will be stronger or weaker, which equates basically to life to failure. Turbine wheels, when finished machined from castings are not so strong. The wheel will have minor inclusions. These castings are ususally centrifiugally cast, so the impurities are spun to the outside of the casting. Then they are machined off. This makes the wheel stronger and less likely to develop a fatigue flaw. Another and stronger method is to machine the wheel from solid stock. This makes a stronger wheel, but are most costly to manufacture. CNC time is not so cheap. We have been able to make nearly identical efficiency wheels from both methods.

Turbo life is effected most directly the accelerations that occur during spooling. The speed changes are what add to the fatigue damage of the turbine wheel. This means that starts, stops, turns, passing, any behavior that changes boost level will add damage to the wheel, be it ever so small. The life of the wheel is the cumulative damage limit. Interestingly, steady state operation does not add much to the damage total, even if you are near rated power. Maybe someone can give us a tutorial on Minor's rule....

Ok, so titanium is more expensive than aluminum and moderately more expensive than machined from solid stock. But it can live through more cycles and at higher rotor speeds. Volume for volume, titanium is stronger than aluminum, meaning greater fatigue strength.

Where does temp come into play? Generally the higher the operating temp, the lower the Young's modulas of the material. This means less strength the hotter you go. Makes sense. It is different for different materials, and I can't tell you how they all behave. Obviously ceramics retain stength at high temps better than others materials for example.

Now, if your turbo wheel has less expansion for a given temp range (material difference), then the internal tolerances can be reduced, meaning increased efficiency (in a nut shell - leaving design and all that stuff aside). A couple of % reduction in rotor speed is a lifetime in reliability. So, the perfect solution is a material with higher mean fatigue strength, that doesn't loose strength at temp, and doesn't expand (which reduces rotor speed). This baby would live forever at high boost levels.

Titanium is a good match for these requirements. It lives a long time. But it is rare and thus more costly....

I don't think making an identical part from titanium buys you power as much as it buys you reliability. But then, when are these things apples to apples?

 

Aw hey now, I missed that post when I replied. That would explain why I was off-base with addressing metallic titanium alloys. Gotta quit posting early in the morning.

The flaming began when the original poster begin with an accusation that another was "talking out of his ***". Any discussion that wasn't factual spun off of that - if you're disappointed, sorry, I expect better from someone asking questions.

Hey, if I had a dollar for every time someone asked about some impractical 'upgrade' using titanium, or replacing a plastic part with carbon fiber, I would be on the Ferrari club. Fact is, the question posed in the first post and the rest of the discussion (melting point) was at that level. Unfortunately I am human and I missed the second post, which has some compelling info, and had I read that I would have noticed he wasn't actually asking about "titanium". So all of *my* discussion will read skewed by that oversight. I won't apologize, since aside from the context I made no erroneous statements.

As for applying it to FDs, it could work quite nicely. The power range is similar, so the compressor/turbo maps should fit pretty well. But the question I'd want to resolve first is EGTs - compare the lifespan of that turbo at the EGTs of an Evo engine to the EGTs seen coming from the rotary. It might cook it without some mechanism to keep the EGTs down. But if you're good at welding manfolds so the cost is nearly just the price of the turbo, it would make for a compelling streetable single setup.

Dave

 

There is neither proof nor disproof for that. Especially because "spool" is not a technical term, and the measurement of it is not agreed upon.

I can say this:
Reducing mass has a linear relationship on rotational inertia if the turbos are of the exact same size and shape, and rotational inertia is what causes a turbo to take time to spool. Some users measure the 'speed' of a turbo spooling by the time it takes to generate X psi in Y seconds. But, the Mitsu turbo was compared to a smaller turbo, so the question become ill posed.

 

thanks to all the "newbs" for their support, and to the older mods here is an olive branch. im sorry but when i said "talk out his ***" i simply just wanted you guys to read my earlier posts about the earlier evos and how mitsu has already done a titanium turbo wheel, and somebody comes on here and tells me that it cant be done. but anyways i wasnt talking about making a turbo out of titanium just mearly exchanging wheels to a titanium one, and if im not mistaken the supra guys are using aluminum wheels. check out sport compact car mag. about the 1000hp club. but who knows the mag. could have been wrong. we all have a loved one in common on these boards, so that makes us brothers....ok group hug! hahaha

 

dave, how much hotter are the egt's compared to a 2.0 piston engine? could you run a co2 spray to keep the wheel cooler? just wondering if cryo treating would work also?

 

oh and i meant TiAl sorry its been a while since chemistry class.

 

oh and now that i have read this that olive branch wasnt for you. and i wasnt pretending to be an internet god expert on ****. i was cutting and pasting what mitsu. has already done with their turbochargers, and no i dont wimper whine. ive have been through alot worse in the last 5 years than to wimper and whine over what some hick from kansas has to say. oh and i see that you edited your post from **** off to shush. like i said know who your talking to. i dont pretend to know your job, nor do i think im a chemist.

 

Thanks for the info. Since it's a project, I assume you're limited in what you can say about it. But I am curious - does it require thousands of miles of lifespan, and what kind of EGTs are you assuming?

As for the mention of Miner's rule, it's conceptually very simple. Think of it like a FPS video game where you're getting hit by all different kinds of enemy fire. Some weapons take big hits on your 'life' when they hit you, others take just a little but come in greater numbers. Materials in fatigue basically live by similar rules: so the designer estimates how often a particular load takes place and how large it is. Miner's rule allows you to add them all up and see how long the material will last in total. So in turbos you might estimate all the spooling events, shifts, straightaway, coast-downs, etc.

Dave

 

dave i see your from harrisburg. i spent some time in carlisle

 

Are you in the service? Carlisle is a nice town.

 

roger that. but i was a dependent at that time, i believe 94-95 time frame.

 

I for one am glad some misunderstandings have been cleared up.

I don't the EGTs, but someone else here surely would. When I have a little more time I'll see if I can generate some by searches. That's the big thing in rotaries that will kill catalytic converters, crack manifolds, etc where piston engines are more tame. And I agree - using water injection or CO2 spray makes sense, but I don't have experience with those either.

Mitsu doesn't appear to be talking out their *** - if you read the paper I linked (it's a little deep) it does mention more detail about the turbo. It's neat stuff and well grounded. Basically, they were able to go with a larger turbo and not lose spool performance - so the improved turbo isn't quicker, but it has better flow and efficiency. The only thing that's not clear to me is what happens at extra-high EGTs, variable loads, and longer life requirements. 600H is not a long life for any street car either, and seeing the erosion on the non-HIP turbine is scary too. So I would personally try to get a handle on those things before applying to any car of mine. To work as an aftermarket product it has to be very reliable, robust technology since end-users are really abusive of the gear, and word-of-mouth spreads too fast.

I suspect a lot of racers have been deep into this material for several years - but they aren't giving much away about it.

Dave

 

Haha, in 94-95 I was running track meets and cross-country meets over at Carlisle high school.

Later, Dave