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Username Post: How to determine flywheel weight?
ShortyLaVen
Poster
Posts 39
04-28-19 08:42 AM - Post#2765188    

How do you guesstimate what the ideal flywheel weight is for a given application? Is there some kind of formula for TQ at launch RPM vs vehicle weight and gearing?

I understand the basic theory (i.e. heavy flywheel = more stored energy, less revs needed to get car moving; light = faster accel/decel, less inertia to help get car rolling). Is it all pretty much just guessing (or some kind of dark arts) from experience or trial and error?

The car in question has a fairly mild-ish 327, maybe in the 375ish HP range (actually I was gonna ask what you guys would guess power output might be), weighing in at about 3,500lbs. 3.70:1 rear, 2.56:1 first (M20)
grumpyvette
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts 17382
grumpyvette
04-28-19 11:09 AM - Post#2765208    

30-35 lbs is about correct for a 3500 lb car with a mild 327, less weight won,t get the car smoothly launched, and may be a P.I.T.a. on the street
flywheels less than 25 lbs are best used on cars that weight under 3000 lbs

https://www.engineersedge.com/mechanics_machines/f...

https://www.youtube.com/watch?v=uh6m-fj1r9Y

every choice you make is a compromise
heavier flywheels reduce the engines ability to accelerate the car but tend too reduce wear on the bearings and allow the car to accelerate smoothly at lower rpms, if you will almost always keep engine rpms over about 3500 rpm, a lighter 20-25 lb flywheel makes sense, if you frequently run the car in the 1200 rpm-3300 rpm range the slightly heavier flywheel makes driving easier
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!

65_Impala
Very Senior Member
Posts 4240
04-28-19 03:03 PM - Post#2765223    

If you're talking for drag racing, then lighter is almost always faster. Lighter just means launching at a higher engine rpm to compensate and then after that you put more power to the wheels while accelerating in each gear. It's stored energy, not inertia that matters. Rotational energy is proportional the inertia times the rotating speed squared. So, doubling the inertia would only double the stored energy but doubling the launch rpm would quadruple the stored energy.

On the other hand, if you want a gentle take-off on the street then a heavier flywheel (up to a point) is better since you want the energy stored at low rpm's to be higher.




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