I believe the OEM companies using titanium rods use a powdered metal version where aftermarket companies use a billet version. Not as strong as a billet, but better fatigue life.

I could be wrong though and would have to look into it more.

As with all high strength materials, as the material gets a higher strength/density ratio, the fracture toughness almost always drops. Yes, it will hold up in the short term to very high stresses better, it is more likely to fail over the long term from just the cycles it sees.

Saying a steel or titanium component will not fail in fatigue because there is a theoretical fatigue limit and your design is below that stress/strain level is COMPLETE BULL**** though...

 

I've seen this rumor floated about, but it appears to be untrue (say those who have seen the parts).


What we've clarified is that the Ti parts are viewed as the equivalent of steel where life expectancy is concerned.

 

YES.

There is a guy on EvoTech who has them in his 4G63 eclipse/talon race car. I forget his screen name however. I think he's running the Crower rods.

I would offer up more info on 4G63 Ti internals, but I can't/won't until later this month

 

This is kinda funny worried about the cost of an EVO on a thread about titanium parts.Cost concern and titanium are like oil and water they just don't go together . It would be interesting to see a hand built full zoot EVO X. Obviously not for everyone but neither is LS7 vette but hand assembled engines do not need to only be in $60,000 rides the Ford Cobra has a hand assembled engine with some very stout internals for not much more than a fully loaded EVO X MR. It would be cool to see a WRC edition EVO X with some hi tech parts on it. I'm not saying make all EVOs $45,000 to $55,000 but a real limited edition Evo would be nice .

 

I'm personally VERY interested in this thread for my own Evo further down the road... and not to be a d***, but I have no interest in Evo X stuff here in the Evo I-IX forums. UNLESS someone has already done it, and we can garner some of that knowledge for us 4G63 owners here in the Evo I-IX forums

 

Erik... I've spent no time there (that I can recall). However, am a sponge looking to soak up info.

 

His name is Jake and he has the baddest 2G widebody I think I have ever seen. He is currently adding a dry sump to the mix.

 

Well get Manley 300m. I have a set waiting to go in

 

Jake is a friend of mine here in the Denver area. His 2G racecar is a work of art. Lots of design in that car, and a little cash, too.

He's also a pretty well known AEM tuner Tuned my RED 2.0L to 482HP/460TQ on a Superflow at 5300 feet elevation with a wide safety margin

He and Magnus worked together to design the dry sump, and Magnus is offering it for sale now... That's a beautiful part, too...

 

link to pics of said 2g racecar or ban.

 

Why don't we try balsa wood, its super light and can be very strong. I feel with the right coating we wouldn't have any of the issues that metals do oxidation etc etc that all of you are so worried about. Plus it would be really cheap to make.

 

^ That's pretty worthless in one theread that has at least a tiny bit of technical merit.

But they aren't, that's my point. Titanium has NOWHERE near the life expectance of steel.

Titanium has a lot of undesireable material properties if you are interested in long term durability at low temperatures.

It's awesome at 1000C in a jet engine though...provided you inspect it at regular intervals and put a fixed service life on it...

 

I'm not trying to target you TedB, so please don't take it that way. Just addressing some things brought up

True, GM has decided it's worth using a coating that takes 12 hours to apply to make using titanium rods feasible in a production car. I'm sure that wasn't cheap, especially considering it's a vapor disposition process. The coating alone probably cost more then what you'd pay for 1 or 2 sets of aluminum rods.

How many aftermarket companies making titanium rods use a similar coating though?

This is only assumed true in a "safe-life" design paradigm. In a damage tolerant or systems based design methodology, this certainly is not considered to be true. Many other affects come into play that will have a dramatic affect on component service life. Corrosion, manufacturing flaws, design flaws, service damage, FO damage, etc. all come into play in the real world and something that works for ever in a safe-life design paradigm may fail in a very short period of time in application.


This is contrary to how I'd see it. I see where you are coming from saying the company is basically designing for failure. However, I don't think that's the case here. The company mentioned makes various types of rods. If they are saying, "Yeah, we have some expensive *** titanium rods that are incredibly strong and work great in limited use race engines. However, we also sell a rod that will hold up well to your application and will cost CONSIDERABLY LESS, I would recommend it over the titanium rod." I think I would take there word over a company saying "these rods will never fail. Just $2500 for your last set of rods you'll ever buy."

 

The 6AL-4V used for connecting rods is an alloy specifically intended for low temp (<400C) usage, FWIW.

As for what happens in the real world, there seems to be neither a pattern nor a concern of rod failure in Acura NSX, Ferrari 355, Z06, Porsche, etc. Ti rods are now used in more OE applications than ever. I see that as the ultimate defining factor, all else being academic. With many of these OE engines seeing far more mileage (e.g. 100k++) between rebuilds than what is typical here, I find nothing to suggest fatigue cycle concerns. If one calls Crower, Oliver, etc., they'll tell you simply to 'treat as steel'. I don't interpret that as 'it lasts forever and ever'.

As for the CrN plasma coating, AFAIK, that is standard for any Ti rod to prevent galling. You'll find that Crower, Oliver, etc., all use it. It seems to be more of a necessity than a luxury.

 

If they are coating them from the aftermarket, then you are likely right and they probably are sufficient for use in a motor that does not see routine inspections. I'll never use a rod of that cost, so I've never looked into what is available. Hence the form of the question above on the weither or not the aftermarket is using these coatings.

Titanium rods wouldn’t even be possible without the research done by academia though, so I think your comment is unwarranted. Saying "all else is academic" is a back-handed slap to valid questions.

Corrosion/environmentally assisted cracking is the biggest issue with titanium. To ignore its affect by referring to a safe-life design method is…foolish.