Injected
15+ Year Contributor
- 704
- 16
- Apr 29, 2004
-
Houston,
Texas
In my quest for knowledge I have run into a dilemma. I have been researching the affects of changing reciprocating weight for quite some time and have run into people who will say that you can't go too light for street use, and others who will say that you can. Obviously the application matters, and I am talking about street use. When launching the car with a lighter rotating assembly (RA) it is necessary to rev to a higher RPM because the lesser force of the rotating mass (RM) will be offset at lower RPMs to overcome the force necessary to accelerate the mass of the car (physics people and engineers nod if your with me). If the rotating mass is "too light", then presumably the work (actual term relating to force) to accelerate the car at a specific rate will bog if the RPMs if launched too low.
A lighter RA is seemingly accepted by the general population as a good thing for street use as you see light weight pulleys, gears, knife edging cranks, etc. Is there a tolerance level or threshold associated with lightening the RA for street use? Is there anyone out there with a rotating assembly that is too light and they can't easily drive it on the street? Or is the culprit the clutch necessary to launch at such high RPMs without bogging?
RRE's site says "Which one do you want? Aluminum, XACT or lightened stocker? They are all good. Get the lightest one that you are comfortable with and that your budget allows," and I believe that when they sold the Fidanza flywheels they had a little excerpt about those not being too light. That may be tolerable if that is all you do to lighted the RA, but there are many other things that you can do.
FFWD Connection, who is making quite a name for themselves, sells their almost-world-famous "butcherized" cranks, about which they say "As if that was not enough, and feeling a little sassy, we lighten the crank by 7 pounds which results in even quicker revs and increased horsepower by eliminating that extra rotating weight. Now, I know what you're thinking but don't sweat it...our lightening procedure does NOT hinder its reliability nor its function. In other words, GO POUND ON IT! Couple that with an aluminum flywheel and rods, and you're talking about a motor that will rev as quickly as a crotch rocket."
Can someone shed some light or open up discussion about this subject?
Oh, and to throw numbers at it, using the formula for changes in effective mass by reducing RM given by Dave Coleman, using a ligthweight flywheel (9 pounds lighter than stock) and the "butcherized" crank (7 pound reduction), a 2G GSX would accelerate as if you had removed about 250 pounds from the chasis in first gear. Add some lightweight pulleys, lighter pistons and rods, and cam gears and your probably looking at closer to 325 pounds.
Thanks in advance to anyone who will help. I'll throw some rep points to anyone with good information/experience.
A lighter RA is seemingly accepted by the general population as a good thing for street use as you see light weight pulleys, gears, knife edging cranks, etc. Is there a tolerance level or threshold associated with lightening the RA for street use? Is there anyone out there with a rotating assembly that is too light and they can't easily drive it on the street? Or is the culprit the clutch necessary to launch at such high RPMs without bogging?
RRE's site says "Which one do you want? Aluminum, XACT or lightened stocker? They are all good. Get the lightest one that you are comfortable with and that your budget allows," and I believe that when they sold the Fidanza flywheels they had a little excerpt about those not being too light. That may be tolerable if that is all you do to lighted the RA, but there are many other things that you can do.
FFWD Connection, who is making quite a name for themselves, sells their almost-world-famous "butcherized" cranks, about which they say "As if that was not enough, and feeling a little sassy, we lighten the crank by 7 pounds which results in even quicker revs and increased horsepower by eliminating that extra rotating weight. Now, I know what you're thinking but don't sweat it...our lightening procedure does NOT hinder its reliability nor its function. In other words, GO POUND ON IT! Couple that with an aluminum flywheel and rods, and you're talking about a motor that will rev as quickly as a crotch rocket."
Can someone shed some light or open up discussion about this subject?
Oh, and to throw numbers at it, using the formula for changes in effective mass by reducing RM given by Dave Coleman, using a ligthweight flywheel (9 pounds lighter than stock) and the "butcherized" crank (7 pound reduction), a 2G GSX would accelerate as if you had removed about 250 pounds from the chasis in first gear. Add some lightweight pulleys, lighter pistons and rods, and cam gears and your probably looking at closer to 325 pounds.
Thanks in advance to anyone who will help. I'll throw some rep points to anyone with good information/experience.
. This won't really be a problem if you don't DD the car but for discussions sake we'll just assume that you do daily the car. During traffic driving you must keep the car above 2k rpm or be moving at a decent speed if you ar to keep it under 2k. 
