im planning on building an engine during college. an all motor 85mm bore lsvtec.

i havent decided on the brands of anything yet, but i know ill be getting forged pistons and rods. ive also seen that people get lighter than stock pistons and rods. what is the actual benifit of the light weight??? would i be correct in these two assumptions??
1. lighter rotationial mass=quicker reving
and
2. also less stress on engine bearings and other stuff. increased reliability?
are their any negative effects to lighter pistons/rods???(i dont even know if an 85mm forged piston would be less than a stock ls piston)
thanks for helping educating me.

 

those are good benefits...get a light flywheel,they make a big difference and get all your stuff balanced,then you should be good to go...

 

i know that lighter stuff is good..but im trying to figure out WHY they are better. its weird, im starting to think different than i used to. im asking why and how stuff is better, not just what is better.

 

youve got it all down basically,except 1:lighter rotating mass=more power
theres not really any negative side effects,except if the lightness makes it weaker.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fearless_dsm &raquo;</TD></TR><TR><TD CLASS="quote">except 1:lighter rotating mass=more power</TD></TR></TABLE>

Care to explain?

Thank You,

Len

 

Pistons and rods are reciprocating mass, not rotating.

With more weight on the crank, it takes more actual work to move the pistons up on the compression stroke. Its the same IDEA as lightening your crank pulley, or even lightening the crank. Just in a different motion. These often fall under the "mechanical efficiencies" department, and there are not huge gains to be seen compared to improving thermodynamic and volumetric efficiency.

 

thats makes sense. thanx. i guess it makes the engine a little more efficient w/ less weight on the crank.

and i wouldnt be shaving metal off the sides of the rods and pistons either...so it wouldnt be weaker. i still have lots of time to figure out what parts im going to buy. right now, the probe rods are looking good to me. pretty cheap and light. theyd be strong enough for me. no boost/nirtrous planned.

and whenever i hear "thermodynamic and volumetric efficiency" thats way over my head. but ill probably learn about it in the next few years in college.