**** w/poor results: Please comment on your lightweight flywheel.

[PhoenixGTS]

It seems from my searching that folks who have lightened flywheels (mostly Fidanza) love them, but there are lots of arm-chair folks who do not have them that think they are not a good idea. Anyone have a light flywheel and think it was a waste of money (I now that is a relative term in the Viper world).

 

[Russ M]

Loosing weight of a car is always a good idea. They are relativly inexpensive considering they are a Viper product.

 

[Mike Adams]

In my opinion if you are doing the clutch or pulling the tranny anyway I would do it but other than than I wouldn't bother taking the tranny out just for doing the fly wheel

 

[Tom F&L GoR]

In addition to carrying the weight of your flywheel, the engine has to work to accelerate the rotational speed. The extra work is a function of RPM^2, so it's not like one can put a single number on the benefit.

However, this is bench racing, so we'll do it anyway. This article by a little race shop in the UK has a straightforward story to explain that the weight reduction at the flywheel is worth about 17 times the weight reduction of something not rotating (in first gear.) That jives with a rule of thumb in a Herb Adams book that said 15 times. So a 15 pound weight reduction at the flywheel should be similar to a 225 pound reduction in static weight, or perhaps the difference between with and without passenger.

I approximated:
G = 2.66 * 3.07
r = 6.5
R = 13

I'll wait for someone else to comment on what 225 pounds means in quarter mile, and then whether the money spent on the flywheel could be spent elsewhere to get the same performance improvement. But that's only forward direction; less weight is inherently good for lateral acceleration and deceleration also.

I had a light flywheel in a 340-powered kit Cobra and it made a significant difference. One was already in my '94 when I bought it, so can't compare.

 

[REDSLED]

I think the issue for you is that you've heard both sides regarding a lighter flywheel and now you are trying to justify the additional $450 to get it done as you think you are saving a ton as the install is basically free as your tranny is coming out anyway. Personally, I've had a lightened flywheel in both of my Viper race cars and I really didn't notice any difference. I'm sure the lighter weight of the Fidanza helped the motor spool up faster which I'm sure it did to some degree, but I was unable to feel the difference. Since you already have the tranny out I would spend the extra money and put the Fidanza flywheel in as you having piece of mind whether it will make your Viper better than before is worth the extra $450. You will not feel a difference but you will know that you took one step further up the pyramid of mods (which never ends) to make your Viper theoretically lighter/faster. The same can be said of the underdrive pulley that you list in your current mods. I too have had them on my race cars and I (along with the dyno) didn't notice any difference but it was one more thing to check off the list of mods. If you don't put the Fidanza in then you will just second guess yourself once the tranny is put back in and you will most likely not pull a new tranny just to put a lightened flywheel in. Good luck.

 

[PhoenixGTS]

Redsled your psychological perpsective is greatly appreciated. Hearing that you did not notice a difference and seeing comments in the archives that it "might have helped" remind that it is a low-return mod. Sound like I will be fixing my tranny and that is all.

 

[DEVILDOG]

As far as my experience I felt a significant increase in engine speed acceleration.

 

[1TONY1]

My aluminum flywheel is now sitting in the floor. Stocker is back in. If you have any drivability issues (cam lope) it may make it worse.

 

[MadMaxx]

Lightened flywheels have their best place on the track. For street use, the loss in rotating weight will make stalling a much more likely event. RPMs will drop a BUNCH between shifts. Not so much a problem when you're in the upper RPM band on a track, but bigtime issue when trying to navigate slow traffic.

Your call. I do not run ligthened flywheels on anything. Especially a big V10 who's torque and powerband is below 5500RRM. Who needs to rev quickly?

 

[MadMaxx]

PS. 70mm TB's are probably hurting you more than helping.

 

[Jim Hodel]

I'm one of the can't tell much difference crowd. I put a lightweight FW on along with a new clutch and it feels mostly like stock too me. Maybe the engine revs a little quicker, but it's not a big difference. Also, I don't see any big difference in driveability - no problems stalling here.

Jim

 

[joe117]

I use an aluminum flywheel on a Ford 4cyl stock car that I raced for a couple of years.

Stock wheel was 24lb the aluminum was 8lb.
The rules called for stock flywheel. It took that as more of a suggestion since most of the cars I raced against in that class cheated in one way or another.

On the track, my rpm range was 5k to 8k. There was a big difference in acceleration and deceleration.

For that car in that situation there is no question in my mind that the aluminum flywheel mad a big difference.

Remember, I went from 24lb to 8lb. I don't know if the difference percentage would be so much for a Viper.

Eventually, I did get caught with the illegal flywheel. When I went back to the stock, it made a noticeable difference.
When letting off and braking the first time with the old wheel back on, the car seemed like the throttle was stuck.

It was only the heavy wheel pulling me along.

 

[Steve 00RT/10]

I belong to the "could feel the difference crowd" I was aware of the faster spool up time immediately. For autocrossing it's a definite plus. I can't really tell the difference with the clutch engagement from stock. Absolutely no stalling issues. As a matter of fact, I have experimented autocrossing starting in 2nd gear. I can easily smoke the tires in second gear at 2200 RPM. No bog. I know a few guys with the older cams who have no stalling issues either. My Fidanza flywheel was $389. I would never go back to stock, but then I drag race very little and it's there that the drag race guys say you need the extra rotating mass for torque.

I now have about 13,000 miles on it. I waited till the clutch needed changing at 31K or so.

Steve

 

[Joe Dozzo]

I belong to the "could not feel any difference" group...

May be the thing that separates one from the pack with an excellent driver at the track... For street cars - not the best use of one's money in my BTDT opinion.

 

[MadMaxx]

I don't think the aluminum flywheel was a massive drop vs. the stock one was it?

 

[ViperRay]

It's only worth it if you think weight reduction is important for performance (I'm speaking of the equivalent static weight Tom refers to above).

I noticed a difference by SOTP with my RPS flywheel on the GTS at the track.

 

[Ron]

I noticed no appreciable difference except maybe a little more rev required to get going from a stop. Reverted to stock in an attempt to resolve a chatter problem. IMO better ways to spend the money.

FYI, reversion didn't help chatter.

 

[Tom F&L GoR]

http://www.web-cars.com/math/calculations.html

Drag race calculators may not be accurate predictors of "your" car, but can be used to see what the effect of a weight difference may be. I plugged in 3600 and 3400 pounds, 425 HP, and get results that were 0.23 sec different.

Stepping off the deep end in calculators, you'd have to gain 25 hp to reach the same improvement (without changing weight.)

What else gives more than 0.23 sec for the same cost?

 

[ViperRay]

The equivalent chassis weight reduction is however dependent upon the gearing with the greatest effect seen in first gear (this is because the flywheel makes more revolutions for each wheel revolution).

The difference in the equivalent chassis weight reduction between 1st and 5th gears is on the order of 10-fold so it might not be noticed in the higher gears.

The effect is therefore most noticable when taking off from a rest....I still feel it in 2nd and 3rd on the track.

 

[ViperRay]

Don't forget too that a lighter flywheel SHOULD decrease stopping distances since we also slow the mass of the flywheel in this process (assuming the clutch is engaged until downshifting).

 

[gthomas]

my post from 09/24/03:CLICK FOR THREAD

EQUIVALENT WEIGHT=0.5x(flywheelweight)x[(flywheel radius x gear x final drive ratio)/(tire radius)]squared
factory steel=over 20 pound
aluminum aftermarket=9-10 pounds
Going to the aluminum flywheel will shave off over 200 pounds in first, over 70 pounds in second, etc..
A flywheel stores energy to dampen compression and power pulses from an engine.
The aluminum flywheel will allow the engine to rev up quicker, improves throttle response across the band.
However, when cold, it will be more prone to dieing at idle(until it's warmed up).
I posted this before, I've only done the flywheel upgrade as a total package(flywheel, clutch, pressure plate, throwout bearing, and shifter).
It will improve your car.
I did not want to get into an arguement with the last person who told me it only helps on road courses, and not at the drag strip. It will help all around performance.
But, if you want total strip performance, get an automatic, with a manual valve body, even I cannot shift faster than that.
But if you want to improve your all around performance in keeping with the all around use, upgrade it.
EDIT:OOHHH YYEEEAAAHHHH....mass in motion tends to stay in motion, so a lighter flywheel will be easier to engage/disengage.

 

[PhoenixGTS]

my post from 09/24/03:CLICK FOR THREAD

Thanks for the link I have to apologize as my archive searching did not go that far back in time. That thread pretty much had everything this one does (same people even) over a year ago.

 

[cgmaster]

They are great for racing but on the street they do not do much good. The reduction of the MOI is the key if you are racing. For racing I chose a tilton unit with a 7.25" clutch. This combo is no good on the street however since it is a racing clutch.

 

[eagles]

definite improvement in SOTP in my 96gts in lower gears as the engine spools up quicker. most noticeable at lower rpm's. driving in first at low speed occasionally requires a bit more feathering of the clutch to keep from bucking. I like mine well enough to put one in my '03 as well. I used the stock pp and disk with the fidanza and am very pleased with the results.

 

[Jack B]

It will not help on a drag car - there is a fine line between bog (with slicks)and a perfect 60 ft time. The aluminum wheel will never make up what is lost in the sixty ft time.

 

[Viper X]

I'm one of the "felt the improvement" group. Engine revs quicker, car stops quicker and is generally more responsive. This is a very cheap way to gain a couple tenths in the quarter mile and will help at the track. No stalling, no negative driveability issues.

I have heard of some issues with Centerforce flywheel / clutch / pp as related to very low to the floor clutch disengagement and difficulty shifting. I haven't had any issues with my RPS light weight flywheel.

Good luck,

Dan