phwhite101

Thanks for the list! I'm going print this out and put it on my shop whiteboard and slowly work my way down it prioritizing the performance mods to start.

XuTVJet

I know I'm probably in the minority here, but I find it hard to believe that the lightened flywheel doesn't negatively impact daily driveability in these cars. I also question the "power" improvement as well. My personnel experience over the past 30 years of modding cars is that lightened flywheels on street cars rarely is good and I have to two friends with turbo NB Miatas with lightened flywheels that would agree too. The reason for a street cars flywheel's mass is to create rotational inertia to make it easier for a car to leave the line smoothly. Without that inertia, the car is more prone to stalling and you need to feed it more gas to get going. Regarding power improvement, I'm not seeing it either. The flywheels on these cars are pretty small in diameter and are connected directly to the engine. If the flywheel were 2 feet in diameter, it would be more difficult to spin up. But the flywheel is only like 12" in diameter. I've installed 14lb lighter wheel/tire combos (37lb combo vs 51lb combo) on prior car and tested them on the same drag strip, same overall tire diameter, same day, same launch style, same 60', etc. Even though the car certainly felt more lively and more responsive with 58lbs of unsprung rotational mass removed, the car wasn't even 0.1 seconds and less than 1mph quicker through the 1/4 mile on average. It was eye-opening. I'm in the process now of helping my two Miata friends reinstall their OEM 6-8lb heavier flywheels because their cars are more difficult to drive on the street with lightened flywheels (specifically 1st and 2nd gears). Lightweight flywheels are great from road racing because they help with rev matching on downshifts and drivetrain loading into turns. They really aren't intended to improve acceleration. The motor certainly revs quicker in neutral and may feel more responsive in the lower gears, but I do question any measurable performance gains. I can say for certain that a car with a lightened flywheel will much harder to launch off the line if that's you're thing.

And perhaps I heard it wrong, but the stock, non-sprung clutch is being used? With no springs and no dual mass flywheel, engagement can be harsher and the drivetrain noise will certainly be more audible.

I get that the OP is excited in the new characteristics of his car, but I caution interested parties to really research in depth the advantages and disadvantages of running a lightened flywheel before proceeding. I've made the mistake many many times of blindly following one person's glowing review of a mod to only find out the compromises/negatives were under reported. I've wasted thousands over the years on the wrong mods for a street car. I learned that race cars parts rarely improve things on a street car.

KrisA

and yet pretty much every reviewer is stating the new 911 S/T is the greatest sports car ever made, with much of credit going to the lightweight single mass flywheel and lightweight clutch.

DasCayman

I've had no negative impacts, as you saw in the video. It was my raw reaction. I have no stock in AASCO and nothing to personally gain from a misleading review. Only thing I noticed was that you need to be slightly quicker on shifts and I needed 2k rpm rather than 1.5k rpm when coming off a stop and start on a hill.

If anyone is a bad manual driver, a lightweight flywheel will make them a worse manual driver. But if you're a good manual driver, then it takes your brain 3 minutes to adjust to the new lunch and you don't really stress it again. I haven't stalled my car once or come close to stalling since the install. I even pointed out in the video that I was worried about letting my friends drive the car to experience the flywheel since I know not everyone is proficient in manual driving. But after having it on my car I have no additional worries of letting other people drive the car. If they stall it, it's because they can't operate a clutch, not because of the flywheel.

Both the dual mass and AASCO flywheel share the same diameter since the clutch needs to engage on the same footprint of the flywheel and the starter gear / starter is in the same stock location. If you wanted a smaller diameter flywheel, you'd need to move the starter and get a new clutch and pressure plate. As a result you get the performance gain of less rotational mass. It's not that the engine makes more power, it's that you rob it of less power. Imagine I ask you to pick up a 45lb plate off the floor and raise it above your head vs. a 4lb plate of same dimension. You didn't get any stronger between the tests, but the effort to lift the 4lb plate above your head is quicker and easier.


I don't really launch my car but the acceleration from 1st gear when I start at 4500rpm / ~20 mph up to the top of 3rd gear is very noticeable.

I don't anyone to read your post and be scared off to doing this install because of driveability concerns. I have no idea what lb flywheel was installed on your friend's NB miatas as well, maybe they were 3lb? Additionally, if your car doesn't have a lot of torque, which Miata's are not known for, you need more revs to get off the line. It's why you can start off the line in basically 3rd gear with high horsepower / torque mustangs and V8's

Cheers

fatmike

The effect is magnified (multipled) by gearing:

https://www.uucmotorwerks.com/flywhe...heel_works.htm

/

DasCayman

This is a perfect explanation. Thank you. I point out in the video that the effects will be most noticeable in gears 1-3, the lower the gear, the more the effect. It’s also why I slowed to a roll in 1st gear and chuckled to see if the rear would break loose, which it did. It’s a lot of fun for the backroads since you’re spending most of your time in 1-2-3

XuTVJet

Sure it's not just a factor of cold tires and temps? I can get my 265hp 2011 Base 6MT (stock flywheel) to light up the rear tires quite easily from a 1st gear in sub 50 degree temps.

XuTVJet

The science provided in the link is quite good. The things to keep in mind though when seeing the huge "virtual" weight losses noted in 1st gear is that you don't spend much time at all in 1st gear when road or drag racing. On a launch, you're revving to 4500-5000rpms and leaving the line around 4000rpms. Same with road racing, you're often staying above 5000rpms if you are in 1st. In either case, you're only in 1st for very minimal time when racing and in road racing and I'd it's a rarity to drop into 1st except maybe auto-x. Also, lightened flywheels will making launching far more difficult and often result in bogging. Bogging off the line has a huge impact in 0-60/100mph acceleration, if that's your thing. It's why you don't want a lightweight flywheel in a car that's launch dependent.

Then there's second gear, now that's a gear that is used a lot in racing. The theoretical gain in power is around 10-15hp with the lightened flywheel. Not bad and the car may feel more lively in 2nd; however, in the taller gears, the theoretical gain drops significantly with each gear. If faster acceleration times are your thing, a lightened flywheel shouldn't be the answer as sustained power under the curve is what makes a car accelerate faster. With the lightened flywheel, the car will be harder to launch in 1st, 2nd might be marginally quicker, and the remaining gears basically no change. In a timed 0-60 or 1/4 mile run, you're not going to see a measurable improvement in ET or trap speed. Maybe 0.05 seconds and 0.5mph in 1/4 mile ET/MPH.

Now if your thing is road racing and every fraction of a second counts and you want better chassis control and rev matching on downshifts, this is where the lightened flywheel could help. Just be prepared for some compromises in daily driving.

XuTVJet

You don't think the much deeper and appropriate gearing isn't also playing into the drivetrain's "lightless". The rev matching feature is also designed to overcome the rapidness of the rpm drop.

Lastly, the 911 S/T and other higher end 911s and Cayman/Boxsters with lightened, single mass flywheels are running sprung clutch discs to help with engagement and reduce noise. The S/T uses a sprung, twin disc setup.

XuTVJet

The stock NB flywheel is around 22lbs. They're running 12 to 14 lb flywheels. Their turbos Miata make around 200wtq (235 flywheel tq). Not bad in a 2400lbs car.

They didn't notice much in the way of drivability issues until the ECUs learned the flywheel after about a week or two and hotter ambient temps (70+) came into play. After that, the cars became a bit annoying to drive especially when motors were heat soaked and clutch had some heat in them. That's where the noise, clutch chatter, etc. started to appear.

The Duke

One more thing: you seem way too happy in that vid!

dpeete

I didn’t think that pulley works on DFI motors… all the ones I have seen state that in the description… including that one:

ZuffenZeus

The problem with installing lightweight flywheels on M9X engines are the harmful harmonics. Harmonics will cause all kinds of issues, even snap a crankshaft in certain driving situations (e.g. Tracking). This is where Porsche got it right. The Geniune Porsche dual mass flywheel manufactured by LuK is dynamically balanced to the factory crankshaft and dampen out the harmful vibrations these engines can produce. Some even pair these light weight flywheels up with semi-solid engine mounts which further negates much needed dampening of harmonics. These vibrations are in turn picked up by the engine's knock sensors. You know where that goes next, right? The car's ECU will try to correct for this change, but in time bad things could happen.

Think about it like adding a new set of tires without having them properly balanced, you may be fine driving at low speeds, but once you get the car moving at higher speeds, horrible vibration, even shaking occurs. This is also a reason for speed ratings on tires. Some tires can not handle high speeds by design. Therefore, you have to spend the right money for performance tires that can handle and be balanced for top speeds, especially in track situations. During engine rebuilds, top engine builders will also check the balance of the factory crankshaft connected to the new LuK Dual Mass Flywheel and in many cases they find it's not perfect and will need additional balancing especially if the engine will be producing a major increase in power output over stock.

From another thread on the subject...







Just my thoughts. All the best!