Aluminum Flywheels: The Good, the bad, and the ugly

And after that long-winded diatribe, I still say JVL's original point is basically correct. The cost/benefit of a flywheel is not as good as cams, etc., but he's underestimating the value of flywheel weight by equating it with all those other rotating things.

-Dave

eyesoreracing Wrote:
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> And after that long-winded diatribe, I still say
> JVL's original point is basically correct. The
> cost/benefit of a flywheel is not as good as cams,
> etc., but he's underestimating the value of
> flywheel weight by equating it with all those
> other rotating things.
>
> -Dave


Thanks dave!!

my main point is the poor cost/benefit in low powered cars---which implies that one solution is MORE POWER.
The other is just the normal "Battle of Assumptions".

Things like zero to whatever.
well we don't run the engine at zero. And only occasionally--in terms of duration--start from zero mph----we run the engine 3000 to whatever and drive the car 25 mph to whatever....

I sympathize a lot with Ben and all the other guys saddled with BIG HEAVY cars with pokey little motors cause both solutions, power and weight ---cost a lot of effort and or money to deal with.
and the power one brings with it a cascade of other costly downstream things needed for reliablity.

That's why I push the few cars I push---the solutions are easy and cheap.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Actually, for rotation, the greek letters arent too bad, they dont get repeated as much. It's the normal alphabet you hqave to watch for,

k=kelvin, pv=nkt constant,

Q= rate of flow, specific heat, heat added to a system,


I think there were one or two more for each, but those were all in ONE unit this quarter.It wasnt recycled at a later time, it was variable recycling at the SAME time.


The nice thing about rotational motion equations though, is they are really similar to the regular motion ones.

---

Welcome to the cult of JVL drink the koolaid or be banned.

As Dave said the effect is most noticeable in the lower gears: 1st, 2nd, 3rd. I have ran light flywheels in probably 10 applications and have never had any problems.

The only thing not to do with a flywheel is to machine down your stock cast iron one. At the 1999 Ramada Rally there was a car with a homemade cut-down stock flywheel. Guess what happened? It EXPLODED! The shrapnel basically just about cut the front end of the car off like a huge radial saw! The good thing was the car was a Saab with the flywheel on the front of the engine so only the headlights, front facia, bumper and radiator were basically just about disconnected from the rest of the car. I remember the crew describing the explosion,followed by them closing their eyes and wondering if they are dead or alive. It made me laugh a little as I had just stuffed my brand new RX7 into a bunch of trees...

George

---

Civic Rally Car

Hah! I remember that Saab! Josh and I were chasing the sweep car when we came across this Saab sitting in the middle of a long, soft straight looking like it had just crashed into a tree. Only there were no trees around...

I've seen some scary stuff on cut-down cast Mitsubishi flywheels. Big voids in the castings that were uncovered by the machining. Yikes..

-Dave

Depending on the powerplant, there are usually more pros than cons to lightened flywheels.

The biggest pro, they add HP and get the engine to rev/decel quicker. Helps with throttle response. This is true of both boosted and NA applications. Lots of dyno sheets to back that fact. As far as a cost/gain, usually worth it. Especially if the stock part is close in cost, or more than a lightened version. Just don't get one too light. By that, much less than 50% of the stock weight, Ideally, you don't want to run a 9lb flywheel in a car that came stock with a 23lb part. Something in the 12-14lb range is a good weight range, and will give good mid/high rpm gains without losing too much low end torque.

The biggest con, loss of low end torque. A bad thing if the car has a lack of torque to start with. Smaller displacement, lower compression engines will suffer most. However, with larger displacement, higher c/r, or boosted applications, less noticeable as the quicker revs get the car to the "happy" part of the powerband quicker. Especially true in variable or bigger cam apps. On a dyno chart, the lightened flywheel will typically build equal or less torque than stock, with more rpms needed, at the same time gaining hp and response. As Jay mentioned, the standing uphill start being the biggest issue to speak of. Once you get it spinning, they stay in the power well. On stage, how often are you running less than 2500 rpm?

I've run them on various powerplants, all with good results and no catastrophic failures or reliability issues. The failure George listed is the type of thing legends are made of. Also, the stories people hear when they worry about running one..

Coupled with the cams, the flywheel should work well on your Focus.

B-

---

Build the car, race the car, crash the car, fix the car..Repeat

B- Wrote:
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> The biggest pro, they add HP and get the engine to
> rev/decel quicker.

technically don't add hp, they just kinda free up the hp...

---

-Mark
www.nocoastmotorsports.net

Mark Wrote:
-------------------------------------------------------
> B- Wrote:
> --------------------------------------------------
> -----
>
> > The biggest pro, they add HP and get the
> engine to
> > rev/decel quicker.
>
> technically don't add hp, they just kinda free up
> the hp...
>
> -Mark
> www.nocoastmotorsports.net
> www.coloradorallycup.org


Look at what Dave posted above..^^^ 7lbs off the Honda flywheel is = to 200 + lbs out of the car. Going to start finding some dyno sheets.

B-

---

Build the car, race the car, crash the car, fix the car..Repeat

Read carefully. That's in 1st gear. 7 lbs off the flywheel, in 5th gear, is like 7 lbs...

Dyno results will only show this effect if its an inertia dyno. The faster the sweep (fast sweep on an eddy current dyno, light roller or low gear on an inertia dyno) the more gain you'll see from the flywheel.

-Dave

Mark Wrote:
-------------------------------------------------------
> B- Wrote:
> --------------------------------------------------
> -----
>
> > The biggest pro, they add HP and get the
> engine to
> > rev/decel quicker.
>
> technically don't add hp, they just kinda free up
> the hp...
>


And here I was laboring under the misapprehension that TORQUE, which is the goal of any engine builder, was somehow a function of engine volume and corrected compression ratio (corrected for intake closing ABDC)., max HP primarily a function of valve area.

And here I thought the major limitations to engine performance were first the octane fuel a motor will be fed, and combustion chamber design.

Man it's so much easier now with the Intra-webz where we can see that flywheel makes hp.





> -Mark
> www.nocoastmotorsports.net
> www.coloradorallycup.org

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I'm running a 10.3lb steel flywheel (Flyin' Miata) in my otherwise stock Mazdog Protege 4WD. The clutch went out right after I got it, so I pulled things apart to put in a new one. I decided to go with the lightweight flywheel, to sort of test it for a couple other projects I've got going, and I'm happy with how the car acts. It's faster revving for sure, and with the 103hp/111 ft-lb SOHC original engine (179k miles ago), I noticed a big difference.

Also running a lightweight, 9lb or so, steel flywheel in my 85 corolla. With that car, I ended up building an engine that was a little stouter, with slightly larger internals (2mm larger wristpins and rod journals,) than it originally had. I had the bottom end balanced of course, but I think that the lighter flywheel has added QUITE a bit of zip. As well as the 4.778:1 rear diff. Granted, this car's only seen cone squishing and some HPDEs so far, but I'm very happy with the choices I made for it so far.

With both of those cars, downshifting/rev-matching is MUCH MUCH MUCH smoother than it used to be. With the cars that still have the stock, heavier flywheel, the engine just won't decelerate fast enough, making the shifts take longer than I felt they should.

I'm sure a lot of it has to do with the driving habits I've developed.

Do I really have a point? I guess not. But, I was reading the post, and have some small experience with the topic at hand, so I thought I'd share how that experience went. Actually, since the topic was about Aluminium Flywheels, that's wrong too.

--sarge

---

---** To be in compliance with the Anarchy **---
Jorden R. Kleier
Baraboo, Wisconsin, USA
1990 Mazdog Protege 4WD
1973

My dad is bringing his aluminum fidanza flywheel down to the machine shop tomorrow to have it balanced along with the rest of the bottom end on the engine for his tr6. Saved some weight on the flywheel, sure, but the crank in that thing still weighs like 60 lbs or something ridiculous.

john vanlandingham Wrote:
-------------------------------------------------------
> Mark Wrote:
> --------------------------------------------------
> -----
> > B- Wrote:
> >
> --------------------------------------------------
>
> > -----
> >
> > > The biggest pro, they add HP and get
> the
> > engine to
> > > rev/decel quicker.
> >
> > technically don't add hp, they just kinda
> free up
> > the hp...
> >
>
>
> And here I was laboring under the misapprehension
> that TORQUE, which is the goal of any engine
> builder, was somehow a function of engine volume
> and corrected compression ratio (corrected for
> intake closing ABDC)., max HP primarily a function
> of valve area.
>
> And here I thought the major limitations to engine
> performance were first the octane fuel a motor
> will be fed, and combustion chamber design.
>
> Man it's so much easier now with the Intra-webz
> where we can see that flywheel makes hp.
>
>
>
>
>
> > -Mark
> > www.nocoastmotorsports.net
> > www.coloradorallycup.org
>
>
>
>
> John Vanlandingham
> Sleezattle, WA, USA
>
> Vive le Prole-le-ralliat
>
> www.rallyrace.net/jvab
> CALL +1 206 431-9696
> Remember! Pacific Standard Time
> is 3 hours behind Eastern Standard Time.


i can't tell if we're agreeing or not. my point was that the hp and torque generated by motor are a constant from the crank on. everything added to the car doesn't remove hp or torque from the motor just like removing stuff doesn't add. instead of using some of that energy to propel you forward, it's being used to spin stuff up.

does that make sense?

---

-Mark
www.nocoastmotorsports.net