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Mazda Miata lightened flywheel points?


dwspen01
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I would like to lighten the flywheel in my 1991 Mazda Miata but can't find any reference to flywheel modifications in the rules, other than no changes/parts are free.  I am looking to use a steel flywheel that has been lightened.  How can I find out the points value?

 

Thanks,
David

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18 minutes ago, dwspen01 said:

I would like to lighten the flywheel in my 1991 Mazda Miata but can't find any reference to flywheel modifications in the rules, other than no changes/parts are free.  I am looking to use a steel flywheel that has been lightened.  How can I find out the points value?

 

Thanks,
David

The way it was explained to me was: all drivetrain components must remain stock. If it's not listed in the fixed point values, such as Cam's, valve train, carb/F.I. - then it's supposed to be left stock. 

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There is no 2x listed in the rules for a flywheel.

Check with tech, but like I said, engine/trans internals were explained to me as 'keep it stock' in my conversation with mike chisek.

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David, i am going to take a lashing for this i am sure, but here we go....

 

No one has ever pulled a trans or engine for tech in the history of champcar (that i ever heard of). Short of doing a coast down test in the vaccum of space, or trying to estimate engine coast down speed and bearing loss, there is no way to test for this. I think everyone is worrying about it too much. 

 

Now from a performance standpoint, it is debatable if there is benefit to it. Yes you will have less engine inertia to accelerate, which compared to the cars inertia could maybe actually be measurable. You will have less stored energy during shifts, and your acceleration right after a shift will suffer, which on a low power engine with a stick might be worst. The major benefit in my eyes is just the vehicle weight reduction, not rotational inertia.

 

Being a realist, it is hard to find guys to turn flywheels anymore and i would buy a decent quality flywheel of some kind and move on. If you cut it (Not on the clutch wear surface) make sure you have a smooth finish and dress any marks well with light sandpaper or a flap wheel. Only turn down the "ring" most flywheels have to add inertia. I would not thin the entire disk to get weight out. You will also reduce the thermal mass of the part, which will make clutch cooling capacity lower. More of an issue for drag racing, but still might show its head if you clutch is weak or small for the application and slips a little (then gets hot and slips alot).

Edited by Black Magic
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I never thought about it, but I'm surprised lightened flywheels do not have a point value.  Or at least a line in the rules that says "Use stock only".   Seems like something that would have come up at some point. 

 

I can see it now "Our European OEM flywheel costs 10 kilobucks so it makes racing cheaper if we use this aftermarket ultra light titanium flywheel with diamond crusted starter teeth and kung-fu grip.  It only costs 1 kilobucks and we get an extra discount when buying lexan, oil coolers, and poly bushings at the same time" :D 

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13 hours ago, Black Magic said:

Yes you will have less engine inertia to accelerate, which compared to the cars inertia could maybe actually be measurable. You will have less stored energy during shifts, and your acceleration right after a shift will suffer

 

Ugh. The flywheel weight rabbit hole... 

 

I was always under the impression that acceleration will never suffer. You are talking about momentum (inertia). In theory the motor could lose less rpm's between shifts with a heavier flywheel (inertia), but will always be harder to accelerate with a heavier flywheel. 

 

Unless you mean that by using a lighter flywheel you might have more engine speed that needs to be recovered after a shift, thus the possible disadvantage. But if acceleration is improved at every other point, is it really a disadvantage? In theory engine braking should be improved with the lighter flywheel as well. 

 

 

Edited by pintodave
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27 minutes ago, pintodave said:

 

Ugh. The flywheel weight rabbit hole... 

 

I was always under the impression that acceleration will never suffer. You are talking about momentum (inertia). In theory the motor could lose less rpm's between shifts with a heavier flywheel (inertia), but will always be harder to accelerate with a heavier flywheel. 

 

Unless you mean that by using a lighter flywheel you might have more engine speed that needs to be recovered after a shift, thus the possible disadvantage. But if acceleration is improved at every other point, is it really a disadvantage? In theory engine braking should be improved with the lighter flywheel as well. 

 

 

 

Theory or practically speaking? Practically i would consider it all pretty insensitive for speed. Wear on parts maybe....

 

 

Theory, A heavier flywheel may reduce your rpm drop when shifting by a hundred to a few hundred rpm. Depends on your shift speed, rotational inertia of engine, clutch and vehicle weight. Like having tighter gearing, this will increase your average power over the whole lap by keeping min rpm higher. Depends on your gear splits and power curve. 

 

 

 

 

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I got where you are coming from... makes sense. Like a restrictor plate car - you want to keep it wound up as much as possible. I was just making sure you weren't claiming that a heavier flywheel "accelerates" faster. I've heard that in the past and had some good debates about it. 

 

Same reason old school drag guys like the heavier flywheel, to "hit" the tires. Using the inertia to overcome some big arse tires at the launch.

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On 6/17/2018 at 3:12 PM, Eman911 said:

My interpretation has always been, if it was done with common hand tools it's free. If it's purchased or done using machine shop equipment its points as determined by Phil.

 Please Please PLEASE  no one try to modify a flywheel ever .

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26 minutes ago, Ray Franck said:

 Please Please PLEASE  no one try to modify a flywheel ever .

 

Shoot, my second VW flywheel has been fine since I turned it down 15 years ago.  We won't talk about the first I did one other than to say I found out why no one in the aftermarket sells an 8-pounder...

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I think people get hung up on this lightweight flywheel thing from the drag racing world. Maybe in a Spec class where every little bit of everything counts towards going faster, but in my mind, a lightweight flywheel is a crap ton of work and money for no noticeable gain in a series that 25% of you chance at winning is sheer darn luck. And, not to mention, when I have to put on a prosthetic leg every day because that cheap Chinese cast flywheel I turned down exploded and blew my ankles off, I won't be too happy.

 

My 2 cents.

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I race with the same basic transmission as the Miata, and they are quite fragile. The advantage of a light flywheel on these cars is to reduce some of the shock loading on the transmission and hopefully make them live a little longer. In theory if you made perfectly smooth up and downshifts every time it wouldn’t make as much difference, but over 2hr stints in endurance racing that is pretty much impossible and you will always end up with the occasional ham fisted shift.

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1 hour ago, mhr650 said:

I race with the same basic transmission as the Miata, and they are quite fragile. The advantage of a light flywheel on these cars is to reduce some of the shock loading on the transmission and hopefully make them live a little longer. In theory if you made perfectly smooth up and downshifts every time it wouldn’t make as much difference, but over 2hr stints in endurance racing that is pretty much impossible and you will always end up with the occasional ham fisted shift.

Gotcha, makes sense then. Just watch out for the hordes who are going to come after you for reliability in endurance racing=winning. That potentially free flywheel will turn into a points adder real quick.

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13 minutes ago, UglyBoost91 said:

Gotcha, makes sense then. Just watch out for the hordes who are going to come after you for reliability in endurance racing=winning. That potentially free flywheel will turn into a points adder real quick.

 

Careful now, the board was against increasing reliability for free because it will add cost (and thus needs points). 

 

Therefore you should just decrease your hours before rebuilds to adjust for the "cost savings".

Edited by Black Magic
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2 minutes ago, Black Magic said:

 

Careful now, the board was against increasing reliability for free because it will add cost (and thus needs points). 

 

Therefore you should just decrease your hours before rebuilds to adjust for the "cost savings".

Yah, I agree with you, I think I worded it poorly. I kind of want free oil coolers, haha but I also agree with reliability=winning so I'm fighting myself ; )

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43 minutes ago, UglyBoost91 said:

Yah, I agree with you, I think I worded it poorly. I kind of want free oil coolers, haha but I also agree with reliability=winning so I'm fighting myself ; )

 

Either can be managed, i prefer to not do it with rebuild intervals and oils that have higher temp limits ( $) but i can. Maybe a separate thread? 

 

 

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9 hours ago, mhr650 said:

I race with the same basic transmission as the Miata, and they are quite fragile. The advantage of a light flywheel on these cars is to reduce some of the shock loading on the transmission and hopefully make them live a little longer. In theory if you made perfectly smooth up and downshifts every time it wouldn’t make as much difference, but over 2hr stints in endurance racing that is pretty much impossible and you will always end up with the occasional ham fisted shift.

The only issue we have ever had with out trans, in our miata is syncros...  Never damaged a single gear or bearing.  Usually get about 50-75 racing hours on a trans before grabbing 3rd becomes a fight...

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On ‎6‎/‎17‎/‎2018 at 2:23 PM, dwspen01 said:

I would like to lighten the flywheel in my 1991 Mazda Miata but can't find any reference to flywheel modifications in the rules, other than no changes/parts are free.  I am looking to use a steel flywheel that has been lightened.  How can I find out the points value?

 

Thanks,
David

Ask @Mopar 63 for the real answer- never ask anyone on this forum about technical applications as we don't know anything other than stuff that will help our own cars.

 


But how can anyone verify this during tech or post race?

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As others have said, I think this is a "giggle test" part... No body wants to pull a trans post race but I know a lot of vehicles you can remove the dust shield and or some other easy access cover and use a flashlight (I'm sure now that I've said that there are a few applications that might be totally sealed up where you can't see squat...)

 

Is it cast iron (or whatever material is OEM for your application)? Giggle test verified

 

Is it shiny, pretty, machined, or otherwise non-OEM looking material? Giggle test failed, further questioning might be in order

 

 

 Pull a T56 out of an F-body after a multi-hour race? Bahahaha. I'd rather attempt a Carl Edwards backflip off of the door sill and put myself in the hospital than pull a T56 at midnight out of an F-body...

Edited by pintodave
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