Are these for sale anywhere? I'm considering a titanium DP (if available) and titanium exhaust (still undecided on which to go with) while using the stock mid-pipe. Any suggestions or first hand comments would be much appreciated...Thanks!

 

Whats the point of titanium exhaust? A lot more money and a couple ounces less weight?

 

they dont make a titanium downpipe...

 

I dont think there is a titanium dp available, and honestly, there is no point in having one besides saying that its titanium. A regular downpipe will be just fine. As for exhaust, might i suggest the greddy racing exhaust. Its about 600, which is half the price of the other titanium exhuasts, and it still performs just as good.

And since when did FD's come with stock midpipes?

 

it is not just a couple of ounces you will save, you will save some good lbs...titanium exhaust with titanium midpipe wieghs about 15 lbs versus regular exhaust and regular midpipe about 35 to 45 lbs, thats about 20 lbs savings...

 

How much does your power steering and air conditioning weigh, and I bet you still have them?

 

dont know how much they weigh, but my whole A/C system is off the car....

 

OOPs. ok then, still got your sunvisors?

 

thats gone too...since it dont work with my Broadway ricer rear view mirror

 

I always heard titanium has a pretty high fatigue rate when it comes to constant heat bombardment (such as that from a rotary engine), thats why they do not make tons of titanium downpipes. I am aware that the spaceshuttle and aircraft use titanium, but they use them in their frames, no titanium is exposed to the atmosphere where it would encounter friction IIRC.

With that said, I have seen many titanium compsite manifolds for our FD's. at least 10 from different tuners thus far. . . . but they cost an arm and a leg, and haven't seen them actually installed on any cars.

 

You would save several lbs (not ounces) but the problem is titanium can not handle the heat. It's possible heat coating may save it but it would be a very expensive experiment. The diameter needed is not readily available, which brings the cost up drmataically for a custom peice. The flanges have to be welded in a clean room or the welds will fail. The material is brittle and not a good choice for heat cycling. I've heard of titanium headers for the NSX, so again maybe it would be possible on a rotary it it was 2k heat coated but without a racing budget/sponsors I don't think it's money well spent. I did look into it along time ago and made a thread for a group buy but no one was interested. Rotaryextreme now has a Ti' midpipe, so you can inquire with them. But without proper clean welds and heat coating, it will not last long.

 

You guys couldn't be farther from the truth about the material properties of titanium. You do know that the airframe of the SR-71 is almost completely titanium don't you?

First of all, titanium has a low coefficient of thermal expansion, making it ideal for components subjected to heat cycling. Also, it has a very high endurance limit, like steels, which means that if the stresses are below that limit it does not fatigue, unlike aluminum and magnesium alloys which constantly fatigue and harden over time. The TiO2 film that forms on titanium alloys provides excellent corrosion resistance.

In the case of the SR-71 airframe, it could fly with an indefinite service life due to the continual annealing it experienced due to the heat cycling.

 

What is the melting point of Ti?

 

What does an airframe have to do with heat cycling? ...nothing. What does an airframe have to do with exhaust? ...nothing.

Titanium is brittle, not good for heat expansion.

http://www.burnsstainless.com/Titani...aniumtube.html

 

Let me rephrase the above since it sidetracked from me previous reply.

Rotary exhaust is too hot for titanium. Hence, the extreme heat cycling will cause stress cracks. (That was my point. no mention of frames).

http://www.titanium.com/titanium/aerospac.cfm

 

More info on titanium downpipes / titanium rotary exhaust manifolds:
https://www.rx7club.com/showthread.p...8&page=1&pp=15

https://www.rx7club.com/showthread.p...4&page=1&pp=15

-s-

 

GoRacer is correct. Titanium WILL NOT STAND THE HEAT!

We cannot even use Titanium on my Formula Continental racecar primary pipes - we see EGT's around 1550F.

 

Rotary Extreme makes a Ti downpipe.
http://www.rotaryextreme.com/tiex.html

 

GoRacer, an aircraft airframe does have to do with heat cycling, especially when flying at Mach 3. *think massive air friction* However, this will prove your point on Titanium.

Titanium does NOT have a low coefficient of thermal expansion.

The SR-71 had no internal fuel bladders to save weight as well as cost and relied on the frame to keep the JP-7 fuel inside the plane. Take a look at any description of how every A-12/SR-71 took off...It had to be refueled within 4 minutes of takeoff. Why? Due to the titanium airframe and skin. The planes were built with 2-5" gaps between the panels. When refueled on the ground, 70% of the fuel put in would leak out all over the ******* place. So by the time they got to the runway and airborne, they were damn near out of fuel and needed a tanker already airborne to refuel them and keep em in the air. These gaps were designed in due to titaniums coefficient of expansion. Once the friction of the air takes over, the titanium heats up, expands and seals all the gaps. Had they built the airplanes without the gaps, the titanium would expand and bulge the frame and skin out, causing major issues.

So the moral of this story, titanium definitely isnt the best for high-heat applications. Inconel is the **** your looking for.

 

Dude, you suck!! I was just about to type about the takeoff with only 150-200 lbs of fuel, then the refueling due to gaps in the fuselage. . . . you beat me to the punch!! but the exterior skin was not made of 100% titanium, it was a composite of like 12 other metals and what not. I forget the exact metals.

 

Actually, that's Chucks midpipe

 

I don't know to much about but its not that titanium is brittle by it self. when heated it tents to work harden (like when machined wrong) making it brittle. which I assume would be the problem with using it as a dp

 

I use inconel for my header assembly, eventhough it's what you'd call bulletproof it's not lighter than other materials. I think that was the idea behind Ti use. I'd also agree it's not a good material choice for a downpipe, midpipe might be okay because of the cooler temps.

Kevin T. Wyum

 

My PFS exhaust and downpipe are only about 25 lbs together.

 

Titanium DOES have a low CTE relative to the steels that are normally used in exhaust systems. Go look at matweb.com if you don't believe me.

Also, technically speaking, "massive air friction" is not the primary source of heat (although still significant) in such a compressible flow. It's the thermodynamic heating.

I'll agree with you on the inconel though, but not all of us can afford those parts like Kevin. I don't see any reason not to stick with stainless.