Light weight flywheel?

[rubydist]

maybe if you would have actually read my first post, you wouldn't be in such a tizzy.

what I said was that I have no problem with my 3.2 mtx w/ 3.0 cams and the 8 lb flywheel, possibly because of the added torque of the 3.2. that is an accurate statement and clearly has something to do with torque and the lighter flywheel.

no one but you said anything about engine torque having anything to do with how fast the engine rpm drops when the throttle plate shuts. now you are just making things up.


I'm glad you understand physics now that we have explained it to you - you did an adequate job of echoing it back.



you also stated that with the lighter flywheel, one must rev-match when shifting, which is just bs.

 

[NotSoSlowSHO]

Dude, you are so confused...

maybe if you would have actually read my first post, you wouldn't be in such a tizzy.

Uh, my first post was in no response to your first post. Had it been, I would have QUOTED it.

what I said was that I have no problem with my 3.2 mtx w/ 3.0 cams and the 8 lb flywheel, possibly because of the added torque of the 3.2. that is an accurate statement and clearly has something to do with torque and the lighter flywheel.

You assume a lot. You assume torque is the reason for your supposed "no problem" with driveability.

This quite possibly could FINALLY shed the light on the subject that YOU need to understand what Im saying here...

The 3.2 is NOT a 3.0 SHO.

Cranks are heavier, rods are heavier, and pistons are heavier.

What does that mean??.... MORE ROTATIONAL MASS.

no one but you said anything about engine torque having anything to do with how fast the engine rpm drops when the throttle plate shuts. now you are just making things up.

Oh really???

The driveability issue IS related to engine torque -

...

Yes, engine rpms drop significantly more quickly when you release the clutch (and have the throttle closed) with the lighter flywheel.

you also stated that with the lighter flywheel, one must rev-match when shifting, which is just bs.

Uh, no I didnt.


What I did say is (quoting myself again here :laugh_ti

Unless you like abusing your SHO, shifting with a light flywheel pretty much requires you to rev match shifts.

 

[NotSoSlowSHO]

And for the record, no where did I say that driveability issues were a problem.


I run a lightweight flywheel in my DD SHO.

Have been for 10 years now.

 

[rubydist]

The 3.2 is NOT a 3.0 SHO.

Cranks are heavier, rods are heavier, and pistons are heavier.

Another false statement. maybe you should just give it up.

 

[RonPorter]

Eh boy.....

BOTH arguments have merits. BUT.....for the way I've been driving a manual tranny since 1966, the torque matters.

I have always driven with the clutch spending as little time between off & on as possible.

So I will have the clutch full-out by let's say 1K rpm.

To then have the car move and not stall, it takes torque. Sure, revving higher gets the momentum up to overcome it, but I don't do that.

Well, except a dragstrip launch for an AWD LGT.....but that's a different story.

If there isn'r enough low-rpm torque to overcome the lack of momentum with a light flywheel, you will stall. BTDT before I slightly altered my technique with a lightweight flywheel in a 3520# LGT wagon with a 2.5 liter engine not on boost....

A 3.0 liter SHO in a 3500 # car can most likely handle a ~10# flywheel better than 2.5 liters with the same weigth. As the LGT guys found. The 14# was good enough, and revved easier.

 

[NotSoSlowSHO]

Another false statement. maybe you should just give it up.

Youd better check your self.

3.2 rods and pistons are larger/massive.

3.2 cranks have large counterweights to make up for it, maintaining a balanced bottom end.


If you dont want to believe that, then you are completely helpless :laugh_ti:

 

[NotSoSlowSHO]

or the way I've been driving a manual tranny since 1966, the torque matters.

Of course it matters Ron

but by no way does changing the weight of the flywheel have anything to do with available engine torque. The motor produces what it produces, regardless of flywheel (rotational mass).

Using simply factors like RPM, LOAD, and throttle position, output remains a constant.

If there isn'r enough low-rpm torque to overcome the lack of momentum with a light flywheel, you will stall.

You're still not following. Maybe Im just a bad leader

As I said, lightening a flywheel does one thing. It changes the rate at which the motor can change revs. That means when you do a clutch dump, the motor drops in revs FASTER to meet the speed of the drivetrain (probably stationary) faster.

It has nothing to do with torque!

BTDT before I slightly altered my technique with a lightweight flywheel in a 3520# LGT wagon with a 2.5 liter engine not on boost....

yep, and your throttle feathering is whats needed to make the adjustment when going to a lightweight flywheel, in order to avoid that stall.

You are not using more or less torque. Instead of letting the motor stall in a situation that would have otherwise kept running with a heavier flywheel, you are simply helping the motor (via your right foot on the go pedal) to maintain that RPM.

A 3.0 liter SHO in a 3500 # car can most likely handle a ~10# flywheel better than 2.5 liters with the same weigth. As the LGT guys found. The 14# was good enough, and revved easier.

And it makes sense. The SHO has a pretty heavy bottom end.


Take my little 1.8L EA81 Subaru motor for example.... VERY light. Factory flywheel is HEAVIER than that of a stock SHO motor.

 

[rubydist]

Youd better check your self.

3.2 rods and pistons are larger/massive.

3.2 cranks have large counterweights to make up for it, maintaining a balanced bottom end.


If you dont want to believe that, then you are completely helpless :laugh_ti:

nice try, but still false.

the crank is the same part number between 3.0 and 3.2. that means no "large counterweights to make up for it"

the rods on the 3.2 have a larger wrist pin diameter, 22 v. 21, but are within a few grams of the 3.0.

the pistons are a little heavier due to the diameter, of course.

the few ounces of weight difference in the rotating assembly of the 3.2 has nothing to offset the difference between a 16 lb flywheel and an 8 lb flywheel.


what you believe isn't important, the facts are. of course, it helps to believe the facts.

 

[rubydist]

Of course it matters Ron

but by no way does changing the weight of the flywheel have anything to do with available engine torque. The motor produces what it produces, regardless of flywheel (rotational mass).

Using simply factors like RPM, LOAD, and throttle position, output remains a constant.

this was not part of my original point, but since you keep saying it, I feel compelled to point out that this is false also.

if you put in a lighter flywheel, you will see on the dyno slightly higher torque and power measurements. this is because it takes less engine energy to accelerate the lighter flywheel, which results in a correspondingly higher torque and power output of the engine.

 

[NotSoSlowSHO]

nice try, but still false.
...

the rods on the 3.2 have a larger wrist pin diameter, 22 v. 21, but are within a few grams of the 3.0.

the pistons are a little heavier due to the diameter, of course.

the few ounces of weight difference in the rotating assembly of the 3.2 has nothing to offset the difference between a 16 lb flywheel and an 8 lb flywheel.

So which is it?

Correct, that the 3.2 bottom end is HEAVIER

or false?

You have contradicted yourself in one post.

if you put in a lighter flywheel, you will see on the dyno slightly higher torque and power measurements. this is because it takes less engine energy to accelerate the lighter flywheel, which results in a correspondingly higher torque and power output of the engine.

No shit sherlock.

Thats one of the reasons my first response was in the format it was.

As I said originally,

The driveability issue with a lightened flywheel is not related to torque.

Get it yet? Lightening the flywheel does NOT increase the output of the motor. But it does make more of it USABLE.

It still has NO relation to torque.


And funny, you seem to be contradicting yourself again...

Previously you said this:

Because there is less energy stored in the rotating flywheel, more engine torque is required

I thought you just said that an engine with a lightweight flywheel will provide MORE usable power, not LESS


Round in circles you go....

 

[Dubeckyj]

Wow. I didn't know splitting hairs was considered a gladiatorial sport.

Everybody keeps referring to the intertia of the flywheel, which is the point of the mod, but you're all skipping the base explanation.

Torque is power. You turn your engine on, it starts to twist. Your flywheel is bolted to the engine, which starts to twist.

Case 1: It's heavy, and it consumes torque to get up to speed (slow), but when you close the throttle plate, the intertia keeps spinning against the pumping losses inside the engine to overcome the friction and keep everything moving. You don't need to open the throttle (which produces torque) to keep everything spinning.

Case 2: It's light, and consumes little torque to get up to speed (fast), but when you close the plate, the intertia is spent extremely fast against the friction, causing the engine RPM to plummet. You need to open the throttle (which produces torque) to keep everything spinning.



Nobody's saying you need a supercharger & WOT numbers to spin up a light wheel, just that it requires more input. More torque down low = easier control. Less torque down low = harder control.

Also, rubydist didn't contradict about the engine weight. A few % difference means nothing compared to the weight loss of the flywheel. The few ounces aren't enough to provide the same amount of inertia.

The only thing I'd like more information on is the rev-matching.

 

[rubydist]

even though the lighter flywheel allows the engine to slow quicker when you close the throttle to shift, unless you shift like grandma, the engine is still going faster than you need when you engage the new gear. therefore, rev matching is not required, and it is actually easier on the syncros than with the stock flywheel.

 

[rubydist]

The 3.2 is NOT a 3.0 SHO.

Cranks are heavier, rods are heavier, and pistons are heavier.

the above statement is still false, no matter how much you try to sugar-coat it or spin it.


do you do politics for a living???

 

[rubydist]

Get it yet? Lightening the flywheel does NOT increase the output of the motor. But it does make more of it USABLE.

yet another false statement.


if the measured torque of the motor goes up, then by definition, the torque output of the motor has increased. I would think anyone would understand that.


there is an old proverb: "Better to keep your mouth closed and be thought the fool than to open it and remove all doubt."

 

[NotSoSlowSHO]

if the measured torque of the motor goes up, then by definition, the torque output of the motor has increased.

Uh....

WHAT??

You have been talking about a chassis dyno, dude.


Saying a lightweight flywheel increases the output of a motor on a dyno is like saying running a lighter wheel and tire combo does the same.

WRONG. :wave:

A flywheel is nothing more than a driveline component.

And all you are doing is lightening the rotating mass of the drivetrain


It might make more of the given output of the motor usable, but it does not magically create MORE.

 

[NotSoSlowSHO]

the above statement is still false, no matter how much you try to sugar-coat it or spin it.

Fine, remove all of your sugar coating and answer a VERY simple question.

Its an easy, YES or NO question...


Is the bottom end of the 3.2 SHO heavier than that of a 3.0 SHO?




Im waiting....

 

[kevinspann]

Y'all mad about nothin'

 

[NotSoSlowSHO]

It would get even more fun if we started to talk about flywheel diameters, and placement of weight across the flywheel :angelnot:

 

[shobote]

Getting back to the subject, If driven in very hiily areas, where you have to stop and start going up steep hills, then just stay stock. Since the car is not a DD, or driven in heavy traffic, he should otherwise be fine with a light flywheel.

 

[SHOhopefull]

Wow, y'all must be bored. Spring's not far away guys, I promise LOL

Anyhow, Bob, My red car has a Fidanzza, and before she ate her TOB, it was a lot of fun and DD. I really didn't have any problem, other than you have to be quicker on your clutch release in order to avoid a stall. Upshifts were no problem(other than the cable shifter) and downshifting is a breeze(but then I'm a truck driver, so blipping the throttle to downshift is almost automatic).

I say go for it. And for what it's worth, the red car was the first SHO I'd ever driven, so it has colored my perceptions of the motor LOL