rods

[Ducmarc]

anybody how much titanium rods grow I know steel rods only grow  a couple of thousandths and aluminum's grow about .020 but what does titanium do .

[GSXR RACER MIKE]

....but what does titanium do .

Get really expensive really fast!  8)

[Ducmarc]

man that's a short answer for you mike .just want to bump up my compression some but don'twant to bump the heads. figured one of our jr. rocket scientists might have an answer

[cardzilla]

Well, a lot goes into Ti rods... namely the surface treatment on the big end sides to keep it from galling the crank.  For the same reason the small end needs an insert and depending on that material your accumulated stretch will be different... of course, that's nitpicking because I'd guess it's still very close to steel although I've never used Ti rods.  The MOI is more important than weight anyway and steel carrillo's are bulletproof as well as1/3-1/4 of the cost of Ti.  Just my opinion, but I really can't think of an application that is worth the cost... unless you really just want everything trick to the nth degree.

[Ducmarc]

thanks for the help my good motor has carrillo's which work great this was a project motor that i came across. it made it through daytona without comming apart but noticed when i pulled the front head it was cleaning the carbon off the side of the dome  at. 015 deck height so added an .008 base gasket and will try again  yes i should have clayed the chamber and i did check the rod bearings . just i've heard the military having issues with expansion on   the sr 71 but thats like 1000 degress of course .having run aluminum rods in my drag car and they grow like crazy.it set my mind to wondering. and your right i'd never buy these things new. but i had them so why not.

[SV88]

Not being a metalurgist (chem. eng.) I cannot be afirmative however we are dealing with three phenomenas here:  thermal expansion,  material elasticity and lash of the system (clearances of the wrist pin in particular and design of the piston - assuming the lash on the crankshaft end is minimal) due to the fact that you are accelerating a mass and essentially stopping it cold (rotating crankshaft).  Calculating the amount of linear growth requires finite element analysis and should probably not be calculated manually.  Several engine builders have stated that Squish needs to be at least 0.025" - less than this and you are cleaning the heads of carbon (not a bad thing) or removing material (not a good thing).

[Chad Wolfe]

  Ti rods usually stretch about .003-.005 less than steel rods. Carrillo rods are stronger. But the main reason for Ti rods is to reduce the rod big end weight, therefore crankshaft weight. Other than rod material and shape, piston weight and speed are huge factors in rod stretch.

[erock768]

Calculating the amount of linear growth requires finite element analysis and should probably not be calculated manually. 

Have no worries........we have the technology and a copy of NASTRAN on the computer! I figured the engineers here well get it.