SlowCar

iTrader: (4)

uh oh..........this exhaust BS again

Frenchy4g63

No, not this exhaust BS again, I would call someone out no matter what part they were promoting when they have NO evidence what so ever to back up their claims.

Just saying one part is better than another, isn't proof to me.

Dus10

The SR-71 used Ti because of it's resistance to heat; it was the only metal at the time that could handle the high temps; so where did this "Ti getting to hot to be used as a DP" idea come from? Race bikes use full Ti headers and pipes and they have no problems with the temps. It's more of a shape/ bend issue , hence the multi segmented pipes used in racing applications. Then some of you are saying that Ti doesn't hold it's heat enough and that stainless steel is better for performance; the last exhaust shoot-out test that one of the magazines did with the Evo VIII had the full Ti Maganflow system making the most horsepower and it weighed 12 or 13 lbs! The weight reduction alone is worth the money. But of course there's always those that can't afford the latest in trickery so they down play it to save their egos. If you can afford it, get it, a 12-15 lb catback system? Sick!

240Z TwinTurbo

iTrader: (25)

The use of the term "high temp" is relative to the application. A turbo downpipe may see in excess of 1600F, whereas the SR71 Blackbird may have seen temps in the 1000F range. Quite a big difference and Ti's ability to withstand heat is dependent on the alloy. To mandrel bend the Ti it is my understanding that a softer grade must be selected. This grade used for automotive exhaust may have reduced strength at temperature properties.

Dus10

You are correct, SR temps on leading edges and engine mount surfaces were in the 1000F range.

Titanium used in exhaust manufacture is an alloy which has even higher heat properties than straight Ti. Straight Titanium has a high melting point of 3135°F (1725°C). This melting point is approximately 400°F above the melting point of steel and approximately 2000°F above that of aluminum.


Linear Coefficient of Expansion. Heating a metal to temperatures below its melting point causes it to expand or increase in length. If a bar or rod is uniformly heated along its length, every unit of length of the bar increases. This increase per unit length per degree rise in temperature is called the coefficient of linear expansion. Where a metal will be alternately subjected to beating and cooling cycles and must maintain a certain tolerance of dimensions, a low coefficient of thermal expansion is desirable. When in contact with a metal of a different coefficient, this consideration assumes greater importance. Titanium has a low coefficient of linear expansion which is equal to 5.0x10-6 inch per inch/°F, whereas that of stainless steel is 7.8x10-6, copper 16.5x10-6, and aluminum 12.9x10-6.

The reason they don't use normal Ti in pre-cat exhaust is due to it's tendancy to oxidize at high temps. So they use Ti alloys which work great and have better corrosion resistance than stainless steel.
In the US, the environmental agencies now require guaranteed corrosion resistance on exhaust systems to upwards of 100,000 miles. Titanium easily achieves this requirement and surpasses the stainless steel (409) systems currently in place. A typical expansion box and tail pipe in 409 steel weighed 10kg. A redesign with titanium reduced this to 3.2 kg! The Corvette Z06 has Ti exhaust from the factory.

Vigo

Good post Dus10! I just learned something today! Will this certain titanium alloy that's more resistant than stainless steel 409 be insanely expensive to manufacture? What would be a better option, this titanium alloy or inconel, in terms of cost of effectivenss?

Dus10

Ti prices are def comming down; and the alloys used in the auto industry are becoming more abundant thanks to auto manufacturers looking to switch over to Ti exhaust systems and other components due to the weight saving benefit which helps put their autos in a different CAFE bracket. Pressure of legislation, typically the US Corporate Average Fuel Efficiency (CAFE), adds to market competition and growing customer demand, forcing design and materials changes. As demands increase for more fuel-efficient and environmentally friendly cars, the gap between affordability and cost is narrowing and more improvements are being incorporated into engines, suspension and bodywork. Increases in the cost of fuel serve to hasten this process, while enabling more to be spent on corrosion resistance, weight and fuel saving. Mazda is looking into using Ti for the exhaust on their mini vans due to the CAFE requirments.

Inconel is def not cost effective at this time.
Oh yeah, here's the link to that magazine test with the Magnaflow Ti system.

http://www.turbomagazine.com/tech/04...ution_exhaust/

Vigo

Awesome, thanks for the answer and link! I guess I'm going to go titanium for my exhaust system. I'm so wrong about what I just said earlier! Whoops! From what I understand from what you posted, it would make sense that future vehicles will be lighter also. Is that correct?

Vigo

To sum this debate up. Pure titanium is bad for an exhaust system and certain titanium alloys are good and better than stainless steel.

SlowCar

iTrader: (4)

To sum up, Ti is the wrong metal to be used for temperature above red heat >~650C

tvbf1

iTrader: (1)

I don't get it why people would say that Ti is good for exhaust part or it can't stand the heat.

If it's that bad, then how come the F1 uses Ti Headers? Why would they spend 1000 men hours to make the Ti headers, if Stainless steel is better?

If you guys ever to the Wynn cosino and Hotel in Las Vegas you can see the Ferrari F1 Ti headers. You'll be amaze by how thin the Ti is and yet it can with stand the heat.

Plus the TME with the Ti Shaft and wheel out performs our stock turbo. Why make Ti rods, valves, retainers and etc... if they're not good with heat.

Ti is known for it's strengths, light weight and resistance to heat.

SlowCar

iTrader: (4)

Ti headers.....hmmm.....
rods, valves, retainer dont see more than 250C

tvbf1

iTrader: (1)

True about the Rods and stuff, how about the Turbo.

Here's a link to Vid clip on the F1 engine start up for McLaren Mercedez Team. You can see bright the headers glow. If this doesn't prove that Ti is capable of handling heat, I don't what else then. (This might be the Arrows team. Some place says it's the McLaren and some says it's the Arrows.)

http://www.youtube.com/watch?v=uRRcpkJxqCw

Here's another one for Renault F1. (I think the Renault are being conservative by not reving up to 18,000 rpm.)

http://www.youtube.com/watch?v=Eo-9Io41bt8

Vigo

Did you even read the thread tvbf1? The answer is clear.

SlowCar

iTrader: (4)

turbo = titanium aluminide = brittle intermetallic = shatters like glass
the aluminum in the binary intermetallic will oxidise to form an oxygen barrier to prevent further oxidation of the base material

i believe those are inconel headers..........?