Titanium rods...

[mike]

not sure I can afford them, but would they make a noticeable difference?
I know theoretically the engine would spin up faster because of less rotational mass but will that translate into anything I would feel?
are titanium rods strong enough? (427 small block, fuel injected)
pros/cons, discuss.
thanks

 

[Will Parker]

Titanium connecting rods are not for everyone because of their high cost. For those who want the ultimate in a racing connecting rod, however, titanium offers two outstanding advantages: It has approx 1/2 the weight of steel and twice the strength. For street machines, this won’t make much difference, but on race cars that operate above 6,000 RPM, the difference is startling. Above 8,000, the difference is even greater.

 

[mike]

Titanium connecting rods are not for everyone because of their high cost. For those who want the ultimate in a racing connecting rod, however, titanium offers two outstanding advantages: It has approx 1/2 the weight of steel and twice the strength. For street machines, this won’t make much difference, but on race cars that operate above 6,000 RPM, the difference is startling. Above 8,000, the difference is even greater.

hmmm.....i thought there might be a good diff all through the rev range.
no matter. with costs of building the gt40, i think i may have to skip the cool ti rods...

 

[Mike]

Well, not only are they stronger than steel, although I didn't think the number was TWICE as stated above, the real advantage to the lightness is not only the fast reving, but because it is nearly the same strength or better than steel and lighter, the forces applied to the rods, as well as the crank are less. Not to say that the downward force is any less from the piston, but because the mass that is going up and down and reversing motion on every rev is less, the entire assembly becomes more durable with the Ti rods. As far as I know Ti rods are much tougher than steel rods, but as far as elongation and deformation are concerned, I haven't looked at them close enough to know. There is probably a heat treat that addresses this. Does anybody actually have published numbers on, say, Scat Ti rods, or Crower Ti rods?

 

[Paul Thompson 'Hooligan']

As I understood it, per volume - Titanium does not have the tensile strength of steel, but it a LOT lighter, so the design of a component in Ti as opposed to steel will not necessarily make it twice as strong - but can make it a lot lighter. The benefit is mainly in loss of weight as opposed to increased strength. Lighter rotating/reciprocating mass is the goal and ultimately can give higher rpm and hence more power.

 

[EGLITOM]

Here some datas from the net.

Overall, a vehicle weight reduction of 1% is claimed to give a reduction in fuel consumption of some 0.7%. Weight reduction in the moving parts of the engine are however likely to be much more effective in achieving improved fuel economy than body weight reduction. Titanium alloy density is some 60% that of steel, and the elastic modulus is about half that of steel. Direct substitution of steel parts with titanium is rarely the best way to proceed, but in practice should produce an immediate weight reduction of at least 40%. The low modulus of titanium is beneficial for springs, but component redesign may be necessary in stiffness limited applications. Specific strength, and likewise specific toughness and fatigue limits of titanium compare very favourably to both steel and aluminium alloys.

<DIV align=center>Table 2. Comparison of specific strength of engineering alloys<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com

<TBODY><TR style="HEIGHT: 45.25pt"><TD style="BORDER-RIGHT: medium none; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; BACKGROUND: black; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none; HEIGHT: 45.25pt" vAlign=top width="20%">Material<o></o>

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Density kg/l<o></o>







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</TD><TD style="BORDER-RIGHT: medium none; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; BACKGROUND: black; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none; HEIGHT: 45.25pt" vAlign=top width="20%">

Youngs Modulus (GPa)<o></o>







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Yield Strength (MPa)<o></o>







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</TD><TD style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; BACKGROUND: black; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none; HEIGHT: 45.25pt" vAlign=top width="20%">

Specific Strength<o></o>​

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</TD></TR><TR><TD style="BORDER-RIGHT: medium none; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none" width="20%">CP Titanium<o></o>

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</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

4.51<o></o>







​

</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

105<o></o>







​

</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

250 – 450<o></o>







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50 - 100<o></o>​

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4.43<o></o>







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</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; BACKGROUND: #e0e0e0; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

112<o></o>







​

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900 – 1100<o></o>







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200 - 250<o></o>​

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</TD></TR><TR><TD style="BORDER-RIGHT: medium none; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none" width="20%">Ti - LCB? <o></o>

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4.79<o></o>







​

</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

110<o></o>







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</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

950 – 1400<o></o>







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200 - 290<o></o>​

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</TD></TR><TR><TD style="BORDER-RIGHT: medium none; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; BACKGROUND: #e0e0e0; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none" width="20%">Carbon Steel<o></o>

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7.8<o></o>







​

</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; BACKGROUND: #e0e0e0; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

200<o></o>







​

</TD><TD style="PADDING-RIGHT: 5.4pt; PADDING-LEFT: 5.4pt; BACKGROUND: #e0e0e0; PADDING-BOTTOM: 0cm; WIDTH: 20%; PADDING-TOP: 0cm" width="20%">

350 – 450<o></o>







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</TD><TD style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; BACKGROUND: #e0e0e0; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 20%; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none" width="20%">

45 - 60<o></o>​

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2.8<o></o>







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70<o></o>







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100 – 350<o></o>







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35 - 125​

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TOM

 

[Jack]

Mike, for the money, I'd stick with the steel rods. Ti rods are great, but unless you are spinning up 6K-7K all the time the steel rods are fine. Save some expense or put it into paint & body. Just my opinion.

 

[Sandy]

I have run 7500+ on 'Import' forged rods in one motor for a long time, ran more then that with some billet rods in the same car so no problem spinning them well into the NASCAR zone without the need For Ti. Would the lighter weight help, sure, but might not be the best spend. I think you can find a nice long thread on the subject. For the money I would spend the extra bucks on valve train and head work (which is seems to be my areas of failure), then for the Ti rods. Also some discussion on fatigue and galling came up. Mr. Mac may have had some good input but it has been a while

Sandy

 

[Doug S.]

I think you can find a nice long thread on the subject.....Also some discussion on fatigue and galling came up. Mr. Mac may have had some good input but it has been a while
Sandy

Was this the one, Sandy?

http://www.gt40s.com/forum/gt40-tec...19175-anyone-using-titanium-engine-parts.html

Cheers!

Doug

 

[fostereast]

For guys that know how to machine titanium, I'm told it's not that hard to do, however the raw material is very expensive and the cost has increased a lot lately. It does fret and can be finnicky, but once you know the parameters of machining it... I think Titanium rods on the street is not money well spent. On the track if the engine is designed and optimized for the lower mass, it is a good idea. (with the lower weight rods, you can modify the crank and other parts of the drivetrain.

Titanium is well liked because it exhibits the same failure mode as steel. Titanium, like Steel will last forever regardless of the number of stress cycles you put it through as long as you stay under some stress threshold. Keep in mind stress is just the force divided by the cross sectional area of the part, nothing fancy, and a stress cycle is an alternating load like a connecting rod would see going from tension to compression.

With aluminum that threshold does not exist, it's failure is based on the stress and number of cycles. Aluminum is lighter than Titanium, but it has no "infinite life" point on its stress strain chart.

If your trying to reduce the valvetrain mass, titanium parts can help a lot if your goal is to reduce the valvespring loads. One thing though, you need to use lighter load springs or the benefits are not realized.