Titanium rotors now running
 

I'm not sure if this is the right place for this but this is a project I have been working on.
Billet Titanium rotors.
Hope you like the pictures.
The engine is now running and I have just completed 70 miles on it so far so it is early days yet.
They are running in an FD RX7 13B engine with major extend port and GT35r turbo at the moment.
Regards
Carl

Very nice! Now you are going to start getting tons of questions asking you when you will sell them to people for half the price of standard rotors so just be prepared for it.

This is still very much in the expermimental stage but at least they are running!

I'm more interested in the performance gain and resistances to detonation/higher boost levels etc... Would be nice to be able to run 22-25 lbs and rev out till 9500 without worrying...

Very nice. Hope all goes well. These would revolutionize alot of things in rotary performance.

Thanks for sharing this. Beautiful work.

How much do they weigh?

NOW lets see titanium rotor housings. :icon_tup:

How about titanium sleeves for old housings? Worn stock friction surface could be milled out and a replacement sleeve pressed in.

I see some holes underneath the rotor gear but I still have to ask, "Are you letting oil inside the rotor for cooling"? Also, is the oil jetting in from the center of the engine like a standard rotor or did you just say screw it? Why did you machine from the gear side?

this is awesome. cant wait for the results and the advantages weight etc.....

+1

Have done over 100 miles now on these with no major issues, still running in.
Have a slight fueling problem to deal with but that should be sorted soon.

First off, good job! I have been waiting for someone to start producing Ti rotors, and looks like you are well on the way!

Question: how are they cooled? Looks like you do not have interior oil bath like stock rotors. Any plans to measure temperatures at/near the apex seals?

RE: rotor housing comments: Titanium is a terrible material for rotor housings. It has a low thermal conductivity, so it will be harder to cool. More importantly, titanium is not a good friction material, as it tends to gall with any metal to metal contact.
Also, there is little weight savings possible as rotor housing strength is not a major issue, and the stock aluminum is quite light. Obviously there is also the cost issue as well.

Rotors, on the other hand, have a lot of room for improvement. Additionally, lightening rotors not only reduces overall weight, it reduces load on the eshaft, increasing power potential. Low TC is actually good in this case, as it removes less heat from the charge, increasing thermal efficiency. There is a design concern with the low TC, though, that it could created high metal temperatures at the apex/corner seal areas, resulting in failed parts. This is why I am surprised that this rotor seems to be designed to eliminate much of the stock oil cooling. The friction issue is also a concern with Ti rotors in that seals may become stuck in the grooves.

If these issues prove to be overcome with this design then I will buy a set!

looks to me like the milled passages on the side of the rotor may be used for charge cooling
... maybe on a methanol engine this is the intended rotor cooling ?

Bravo!

This charge cooling phase would be interesting to compare to the standard blank side rotor flow.

And probably this design would not play well with the side exhaust ports.

I'm In,
Barry

Lovely work!

many kudos on your accomplishments.

Which compression ratio do these have?

Nice job! Subscribed this topic. Can you please tell us any specs?

Charge cooling would require significant other modification to the engine to create a flowpath for the air to flow through the rotor.

Also AFAIK, charge cooling severely limits MEP levels compared to oil cooling, and since I assume the point of this is to provide an increase in power, that doesn't seem like a good plan.

As stated, I really want this to work, but I was hoping for some explanation of the design...

Pat

yep, charge flow cooling won't work in this case so i'm in with everyone else who wants to see how the rotor tips will fare without cooling.

You could possibly figure out a way to insert a tooled steel insert that will house the apex seals to eliminate the question of the firction/heat issue altogether.

Any updates?

The difficulty here is the corner seal. It would be impossible to incorporate the corner seal bore in the insert with the close proximity it already has to the face of the rotor. Maybe hold it short of the bore? then we have other issues like how to actually make the insert and not have it fall out.

Ultimately, a hardened steel or otherwise insert for the apex seal is quite the challenge.

Not sure if they are tooled steel inserts or not but here is someones solution.

https://www.rx7club.com/attachment.p...1&d=1346784170

Nice. Thanks for the pic.

https://www.facebook.com/media/set/?...4719107&type=3

Mazda trix is doing this too if you are not aware...check out the pic's in the link.

Seal friction may not be a big issue. Small scale friction isnt a big deal with Ti like most people think, it just requires a surface oxide layer to get more hardness. As far as heat transfer, a steel insert will be worse than Ti, titanium has about double the heat transfer rate of steel.

I was always told that Ti has very poor thermal transfer, which is why it feels warm when you hold it. It's not warm, it's just not transferring heat from your body as quickly as other metals, so your brain says it's warm.

Then again, I never looked into it other than "Huh, that's interesting".

^You are right, I mistyped. Ti has half the heat transfer coefficient of steel, not double. Sorry.

any updates?

Updates?

Waiting for updates +1

But liked also the MAZDATRIX model, did they installed it on a car or not yet?

Did you resolve the FUEL issue you had?

Subscribed!

I thought titanium has a tendency to warp or change form under high heat or extreme use?

We did a project with an LS1, used titanium valve springs and they compressed and would not re-expand. We came to the conclusion that it was the titanium.

maybe i'm wrong though?

Jumping on

Lot's of companies sell Ti springs and retainers, so it may have been a bad set? And, I know it's no where near the heat of a rotary, but the NSX came with Ti Con-rods, and those are subjected to bending forces, ,right? I know Ti is very hard to bend, that's why when piping is made with it, half the time is with pie cuts welded together rather than bending it.

My wonder is if expansion rate is a concern? I don't know the heat properties of titanium and when I looked it up, it had me trying to do math (boo...).

If these work, I wonder how much they weigh (maybe 13-15 lbs would be my guess), and how high they would be able to rev. I've seen 12K rotaries before, but not very reliable. Usually a seal failed. Would these be able to sustain that high rev? it would be awesome to see!

Jose

Any updates?

Jeff has tested it on an RX8 and is still 6 months out from anything. He works on these on the side along with other stuff he is doing.

updates?

Interesting.

Stock rotors itself are almost bullet proof when well taken cared of. So Id say the titanium is a very good upgrade

Bump, updates?

Wow

sub.

No updates= fail
Don't you guys think Mazda and many other companies have tried other metals for rotors, housings, etc? There's nothing wrong with the stock rotors. The rotary engines power is limited by e shaft flex and engine twist and seal warpage/breakage-not the rotors.

obviously if the rotor would weigh 2 kg vs 4 kg, the shaft would worry alot less spinning over 10k as it does now with 4 kg rotors.

I think there should be nothing wrong with Ti rotors if care is taken for the right clearance. but the 2 piece design is probaly the main source for trouble. ideally one would just use a mazda die and cast it with Ti instead of steel. then the rotor would weigh already 40% less, then edm the seal grooves and machine to correct clearances.

That doesn't account for the penny pinching aspects of a company though. Im sure the rotors were made out of the most cost effective material that met the criteria.

Mazda successfully tested aluminum rotors (in a three rotor prototype), and there were many benefits. The biggest drawback (which is what prevented they're production) was cost.