Lightened Flywheel

[michaelj]

Has anyone done this? I have the engine out and I am going with the 9.8:1 pistons, hotter cam, bigger valves, etc... But a good friend of mine is very knowledgeable and is paranoid about a lighter flywheel. He used to own a speed shop with 7 full time mechanics so I listen close when he opens his mouth. He says I stand to lose a lot of torque and it could really mess up the cars performance as a result. I just weighed the original and its 19.5#. ITs a beast. I think I might lose a little off the line jolt but make up for it with better performance when I am "on plane" so to speak. Whatcha know? Thanks, Mike

[BEEK]

i have run fiats with lighter flywheels, and am currently building a performance engine with one. i highly recommend one. aluminum if you can afford it, if not a lightened steel one. its all about inertia, that 19.5 lbs has to be accelerated and decelerated, that is taking horsepower that could be used to power the wheels. a light flywheel will not make horsepower, it will free up already made horsepower. a light flywheel will allow the engine to rev quicker too. if there was a downside the only one i could see is, there is a little less rotational inertia to keep the crankshaft turning between strokes. this is a non factor imho

[paintdudeluke]

I can chime in on this. A sprint car has no flywheel. It can rev from idle to 8k in .2 seconds. When you let off the throttle it will drop back down to idle in .5 seconds. A sprint car is designed to race around the track ON and OFF throttle, no cruising. (like an egg beater, you stop turning it, it stops spinning) A heavy bench grinder is made to run along at a constant speed for hours. Once you get it turning, its like a steam roller, you can shut off the power and it will keep turning for a while. (think about how long a big bench grinder keeps spinning after you turn it off)
Now our application; With a light flywheel the engine will be snappier, accelerate quicker and decelerate quicker so throttle ON feels strong, throttle OFF brakes faster, but once you get up to hwy speed you will have to keep the throttle on more rather than be able to "feather" it back to a coasting engine because the weight that used to keep the crank rolling with minimal effort in not there anymore. I exaggerated the examples for effect, but I hope you can imagine the difference. If you have a highway car keep the heavier one, if you are diving into sharp hairpin turns back to back, you want a light one because you'll hardly have to touch the brakes, just let off the gas.

That was a poverty of expression, but hope I helped obviate the concept.

[fiat218]

You both make a lot of sense, as I was ask when I wanted to build a motor, How are you going to drive it

[Exit98]

I put a Miller's Mule lightened flywheel on my 1800 cc, 4-2-1 exhaust, 34ADFA Spider.

Not aluminum, that's for racing. The regular lightened steel one.

Great, great improvement. Highly recommended. Best bang for the buck yet.

Paintdude's explaination is well stated and correct. But the improvement in acceleration is significant. The reduced coasting speed, which I expected, is negligable in normal around town and highway driving. I'd never go back.

The NJ guys that drove my car before and after were amazed at the improvement.

[So Cal Mark]

aluminum flywheels are not just for racing. The 2L motors respond very well to a lighter flywheel, allowing them to rev very quickly. I have a lightweight flywheel in my 500, and that car is a blast to drive compared to a stock 500. Even though it's only a 1.4, that car cruises easily at 85-90 mph without any effort

[WYSpider]

I put a Miller's Mule lightened flywheel on my 1800 cc, 4-2-1 exhaust, 34ADFA Spider.

Not aluminum, that's for racing. The regular lightened steel one.

Great, great improvement. Highly recommended. Best bang for the buck yet.

Paintdude's explaination is well stated and correct. But the improvement in acceleration is significant. The reduced coasting speed, which I expected, is negligable in normal around town and highway driving. I'd never go back.

The NJ guys that drove my car before and after were amazed at the improvement.

Which weight did you go with?

[fiat218]

aluminum flywheels are not just for racing. The 2L motors respond very well to a lighter flywheel, allowing them to rev very quickly. I have a lightweight flywheel in my 500, and that car is a blast to drive compared to a stock 500. Even though it's only a 1.4, that car cruises easily at 85-90 mph without any effort

isnt that speeding tsk tsk, California drivers speed?

[Exit98]

Which weight did you go with?

Don't really know. I think he offers just one which is your original or one off his shelf and you send your core in exchange.

Just check with Jason. Another one of our excellent vendors.

I think Auto Ricombi and Allison Auto also offer them so you can check with them too.

Thanks for the info on the aluminum flywheel Mark. Didn't know it was good for the street.

[paintdudeluke]

All this light flywheel talk had me curious about cost. Wow, $400 is about as low as it gets. That was an 8.5lb as opposed to a 13.5 stocker. I wonder how much a shop could shave off a stock one?

[BEEK]

stock fiat 2.0l flywheel = 18.8lbs marks aluminum = 8.276

[fiat218]

stock fiat 2.0l flywheel = 18.8lbs marks aluminum = 8.276

What does the one we got at your shop weigh, not marks,the other one

[BEEK]

ill post it tomorrow

[So Cal Mark]

you have to be careful while lightening a stock flywheel. Too much removal of material will cause the flywheel to fail. And they don't usually fail at low rpm, they fly apart at high rpm and act like a giant buzzsaw. You can remove a couple of lbs

[BEEK]

i do not lighten flywheels for anyone. i install or sell flywheels made by other people. that being said. (liability) i have lightened a steel fiat flywheel 25 years ago, this flywheel, has been in street cars and in race cars and has logged well over 100k, cant tell how many miles in racing, but for at least 5 seasons. i will weigh it tomorrow as well. and give thickness specs

ps it is going in my next spider project too