Loosing 37lbs from flywheel swap. Gains?

[YukonCornelius]

I have a opportunity to swap the 50 pound dual mass flywheel in my CTS-V with a 13 pound aluminum. Normally the flywheel in this engine would weigh something around 24 pounds but GM went with a heavy dual mass to make driving easier for the old guys who they expected to buy the car. Seems like a substantial deduction from the engine. I'm wondering if anyone would like to throw any mpg change guess out.

[echo-francis]

i think there is a gain for every pound lost

[GreenHornet]

I would be surprised very surprised if you see any change in fuel economy. However what you will see from that kind of weight reduction in the flywheel is in your acceleration.

An interesting discussion about replacing stock flywheels with lightweight aluminum racing units such as what you did. Here is the website link = lightened flywheels

"The are no negative effects to lightening your stock flywheel unlike replacing it with an ultra-lightweight Aluminum flywheel. Most manufacturers make the stock flywheel very heavy. This makes the engine very smooth and enables it to retain energy at part throttle cruise and up long grades for better fuel economy.

An Aluminum flywheel goes completely the other direction with almost no weight. This lets the engine rev up very quickly and allows the engine to work easier due to the reduced weight spinning around on the back of the crank. This is fine as long as you are at full throttle and wide open throttle all the time like in a Road Race or Drag Race only car. As soon as you let off the gas the engine RPM drops instantly and the car slows down. In a road car this causes surging and bucking at cruise speeds and poor driveability and clutch engagement.

A lightened stock unit on the other hand gives you the best of both worlds. It is a compromise between the overly heavy OEM unit and a Too light Racing unit. You get the benefits of both with none of the bad qualities.

Turbo cars are exceptionally critical to flywheel weight. Too light a flywheel will make the car rev faster and possibly come on boost faster but that is only half the issue. When you let off the gas to shift the car will drop off of boost just as quickly causing a poor transition when you come back on the throttle."

GH

[Frank Lee]

I always suspected that a heavier than stock flywheel would enhance short-shifting and lugging/low rpm abilities. They went through a lot of effort to provide a dual mass system and there's probably a good reason for that.

[YukonCornelius]

Originally Posted by Frank Lee

I always suspected that a heavier than stock flywheel would enhance short-shifting and lugging/low rpm abilities. They went through a lot of effort to provide a dual mass system and there's probably a good reason for that.

I'm sure it does. If I have the space I can go from 0 to 25 mph without touching the gas pedal. I attribute a lot of that to the gearing (3.73) and the power of the engine itself. One annoyance, the flywheel is so heavy that I have to delay my shifts so the rpms can drop down enough.

Practically every performance LS motored car has received a normal flywheel weighing half of what mine does. The dual mass was strictly for comfort. They come loose after a while causing a shake on shut down, which I have. GM didn't think through a lot of the decisions they made when building this low production car, most of which was corrected in the new CTS-V.

[niky]

Dual Mass is all about vibration. which isn't a big deal on a big V8 engine as compared to the four-banger diesels they stuff them on around here.

They're ridiculously expensive and complex for what they do, though... I say: Do it. Good riddance.

[Ryland]

The dual mass fly wheel is evening out the power pulses from the engine, so you end up with more usable torque because it doesn't drop off as much between cylinders firing, you will also save your transmission from potential damaged because the fly wheel is helping to even out the engines speed over the course of the rotation, it will be like going from a regular drill to a hammer drill.

[oil pan 4]

It looks like you are getting 30mpg with your caddy so I would think you are doing a lot of highway driving?
In your case I would think the lighter flywheel would lighten your wallet and consume time more than anything.
If I was going to bet on what would save more money between a light flywheel and say something like the proper use of lawn edgeing to build an air dam and side skirts, I would put my money on the the lawn edgeing.

[niky]

While evening out the power pulses matters on something like a three- or four-cylinder motor (especially if such is a diesel), the LS, as noted, comes without the big, heavy dual-mass in other applications.

And it's a "free" upgrade. When a dual-mass flywheel's balance starts to go, you have to replace it, anyway.

[alex16]

I have used lightweight flywheels in several cars I owned in the past, 1991 Honda CRX Si, 1990 Eclipse turbo (fwd), 1995 Civic DX hatchback. All of these cars being 4 cylinders, the aluminum flywheel did offer some performance gains in acceleration but I never noticed any change in mpg, if anything it may have caused a decrease on city driving. The lighter flywheels made it much easier to stall so I would let out the clutch at slightly higher rpms with a little bit more throttle than before. I noticed no vibration changes, slightly faster reving.

I think a lightweight flywheel is a nice thing to have if your used to them but I think there is tons of better places to spend the money, places where you will see things pay for itself, such as a mechanical to electric fan conversion. I am all for aluminum, its a superior material to steel with heat dissipation and reduction of rotational mass, I will likely search for a used lightweight flywheel for my civic for the manual conversion (If I can source one for less than $100) so don't think I am opposed to the swap, I just don't think it be a mod that will pay for itself in savings.