porkyzilla

iTrader: (1)

ok well i have a t-56 i was shipped the wrong flywheel so i had to pull it again i was wondering 7lbs lighter than cast iron flywheel what kind of et difference would that make

also worth the extra 220 dollars out of my pocket vs 60 for a resurfaced one or 170 for brand new one

rx7speed

depends on what you plan on using it for
for drag racing your not going to have the greatest launch due ot lack of inertia on the launch
with road racing style stuff it should help out quite a bit

blacksheep-1

Lighter is almost always good. If you have a 3.0 gear it may take a little more throttle to launch it, but onc emoving it will accelerate faster. 7lbs is a big difference at the flywheel.

RB83L69

In general:

A light car with a large motor and lots of gear, will benefit from a lighter flywheel; because the engine needs to spin up faster, and the extra intertia represents a significantly greater load on the motor.

A heavier car with a smaller motor and/or grocery-cart gears will benefit from a heavier flywheel; because it will store more energy before launch and in between gears, and the motor doesn't have to increase its RPMs at as high a rate (which makes the inertia penalty less severe).

TKOPerformance

It's worth it. Don't get carried away and think that if one 7lbs. lighter is good, then one 13lbs lighter is better though. Stay away from the aluminum ones. I've got one and am less than thrilled with it. 7lbs is a huge difference at the flywheel. Rotational weight is worth as much as 2-3 times the loss of static weight, plus it will allow the engine to accelerate faster.

VILeninDM

porkyzilla, where did you find that flywheel?

porkyzilla

iTrader: (1)

its an slp part...

http://www.slponline.com/view_product.asp?P=60036

its 379 but hey dealer cast iron is 299....reman with no core is 160 so i just decided to buy it its on its way :-D

so if its 2 to 3times the weight loss than essentially that would be like 3hudreths of a second on 1/4mi

TKOPerformance

Yeah, the ET improvement doesn't look all that good from just the weight loss, but the added acceleration and the increased horsepower will make the real world difference about 1/10th of a second.

blacksheep-1

actually you're not gaining any HP. If you dyno the car before and after, it should be the same numbers. You are just re-arranging the HP numbers into a different spot.

rx7speed

EDIT oops reply to the wrong post

actually though in a way you are gaining a little horsepower and torque
lighter flywheel has less mass making it easier to accelerate up to speed.
kinda like lightweight pistons. crank, driveshaft or anything else out there that reduces drivetrain loss

TKOPerformance

You are absolutely gaining HP and torque with a lighter flywheel. Well, in truth you aren't so much gaining it as you are freeing it up. Everything that has mass requires energy to accelerate. If the energy input into the system is the same, but the mass is reduced you end up with more energy on the output side of the equation. The engine will be able to use more energy to spin the crankshaft, energy that was previously used to accelerate the additional mass of the flywheel. Any engine eats up some of the power it produces keeping itself spinning. Anything you can do to reduce this parasitic loss will improve power. It's a similar concept to using roller rockers to reduce friction. Even if you keep the ratio the same you will still gain some power just from reducing the parasitic loss of the friction in the rocker assembly. Low drag rings are the same deal.

Once in motion however, the engine will not have the same tendancy to stay in motion with a lighter flywheel, so when you let off the gas the RPMs will drop much more quickly than with a heavier flywheel.

A lighter flywheel is a tradeoff, like most improvements made to your car in the name of performance. The engine will be more responsive, and put a little more power to the ground. But, the engine won't conserve RPM as well when you lift off the gas, and if you go too light the engine won't idle well.

blacksheep-1

Once the engine is up and running the HP will be the same. It will accelerate better with a lighter wheel, but the HP numbers will be the same. In other words, if the engine is up and running at 7 grand, it doesn't care what flywheel is on it. Now if you slow it down or accelerate it then yes, the wheel will make a dif, otherwise, the numbers are (essentially) the same.

TKOPerformance

At a constant, static engine speed the power won't be different. That is true. But, accelerating up to that speed the engine will produce more power by virtue of the fact that it can accelerate more quickly. More force is applied to spinning the crankshaft instead of having to continue to accelerate the additional mass of the flywheel. This translates into more HP & torque nduring acceleration. Static power is unchanged, but dynamic power improves, and dynamic power is more important in the real world.

VILeninDM

yeah, I think we are all agreeing and saying just about the same thing. The way I look at this is that force=mass x acceleration. Since lighter flywheel accelerates faster (less inertia mass), car will accelerate faster. And if mass is kept constant, that means force that is pushing the car forward will increase. That translates into more HP.

rx7speed

I would even think at static rpm you are going to lose a little power just due to keeping the thing spinning when it is trying to slow down

granted prolly not much
but still would think so

TKOPerformance

As long as the force is applied the flywheel isn't trying to slow down, especially at staic engine speed. When you let off the gas then the flywheel decerlates rapidly, and the lighter one much more rapidly that the heavier one because it has inherently less inertia. The problem at low engine speeds is the that time between power strokes is long enough to alow the flywheel to decelerate somewhat, and that causes a lopey idle if the flywheel is too light. At a higher engine speed the time window is so small that the effect is essentially negligible.

Think about it this way: Take a 5-gallon bucket and fill it half way with water. Now try and windmill it around with your arm at maximum speed. Then dump out a gallon and see how much fatser you can accelerate it. You can do all sorts of tests using this experiment, and you will see clearly how a lighter flywheel affects an engine. When you stop actively trying to spin the bucket the lighter one will decelerate faster than the heavier one too.