Good morning. On big Type4 engines that are going to be used on the street, it appears that keeping a stock flywheel is a plus for drivability but I’m also wondering if the bigger engines have enough torque that they can handle it lighter flywheel for a bit more zing of an experience.

The one that was on this 2.7 L motor I’m sorting out was shaved down to 12.3 pounds which seems a bit to light for street use.

EDIT - did some researching it appears that too light of a flywheel will make the car a pain on the highway, so maybe just stick with stock weight?

We have run a lightened flywheel for years. It is not a detriment on the highway, and it makes the initial launch from a stop better.

The downside is you have to use more RPMs and more slipping of the clutch to get it to take off from a stop, which will make the life of the clutch shorter.


I have not found any reason that would keep me from running a lightened flywheel.


Clay

Correct they are also known for when the engine spins down at a stop light the motor might die and you have to restart it. I remember that from my bug days with lightened flywheels.
I thought the highway issue was hills. Its easier to keep a heavier flywheel spinning on a hill or grade.
The advantage of a lightened flywheel is they spin up faster.

I've had a lightened flywheel on my '71 2.0 carbed car for years and love the throttle response. Have no issues on the highway and clutch take up doesn't seem that much different.
Putting a lightened flywheel Patrick Motorsports did for me on the '73 2.0 I'm putting back together.

2100 lbs car. So i guess it does need a lightened flywheel



Its totally not nessacary . i mean you cant abuse 1st gear anyways so

The only caveat is if you go too light, at 12lbs your fine. Id surface & use that FW

Gordon Murray would not agree with you, his newest T.50 which is about 2100lbs has a super lite flywheel. But what does he or Cosworth know ?

Quicker throttle response but higher RPMs needed before you dump the clutch. Si of one half a dozen of the other? Where does the zing come in, driving at higher revs? Not criticizing that, btw, just curious what the end goal is.

Generally, light car, light flywheel. Heavy car, heavy flywheel. IMO a very well-balanced motor is much more important no matter if the flywheel is light or heavy (within reason, as you can go too light for a street car).

Cars with lightened flywheels have a more on/off feel when hitting the accelerator. Some like that, some don't.

A lightened flywheel will allow your motor to spin up faster, but also spin down faster too. This can be and usually is much harder on the motor's thrust bearings. But, who's gonna let that stop them?

BTW, torque not an issue here. Normally, a larger motor has more torque. And a lighter flywheel needs less torque to spin it. So maybe the question is how would you like the motor to behave? Me? I like a light flywheel.

When you can access 1st gear for anything more then a crawl

Then you need it

Not that i personally dont love the charm and character of the dog leg . rockcrawler gear.... Not many sports cars have that

Good morning gentlemen. I ended up sourcing a factory weight flywheel for the car – while I drove this thing with a lightend flywheel there were so many other things going on that I couldn’t really get a sense of if the flywheel was contributing to that driving experience.

I think erroring on the side of having it have easy to live with manners is probably the right choice for now, I still have the lighter flywheel and an 11.5 pound one that I can throw on in the future if I have some burning need to change the driving experience.

Thank you for the discussion and thoughts on this. I very much appreciate the feedback.

Coming back to the OP's original question, i.e. the use of a lightened flywheel on a stroker engine...

Yes, a lightened flywheel will give you quicker rev and require more RPM at the start for obvious reasons.

But, the stroker cranks also have added rotational mass with the counterweight and the engine has a lot more torque due to its longer stroke.

So the question could be, does the cranks added mass could compensate for a flywheel mass reduction?

What have people experienced with stroker engines?

Funny thing is have you ever felt how heavy a 930 clutch and fly is?
If you like I can weigh a 996 clutch and dual mass fly, I'm guessing 30-35 lbs. Raby won't build a 996 engine with a lightened fly, LN will void any support, as well IIRC Jake doesn't build T4's with lightened flys except maybe for some special projects .

Balancing is way more important. Even if you're sticking on a balanced fly that's not a full assembly balance, in fact it can make the balance worse. First spin on a balance machine you might get 500rpm, after balancing it will almost instantly spin at 1000.
Balancing is especially important for stroked engines, as you're moving a lot of weight further out from the center. I have and will never build a stroker engine without a full assembly balance. Factory balance is for a stock engine period, even then I try to talk peeps into a full balance on their engine.

Interest and consideration on what the net loss in mass is, the Pistons are pretty light so my guess is that there’s not much mass added back from making it a stroker. interest and consideration on what the net a loss in mass is, the Pistons are pretty white so my guess is that there’s not much mass added back from making it a stroker?

The flywheel is going to a machine shop to get checked out, thanks for stressing the importance of that.

My lightened flywheel experience isn't from a Porsche, but a Corvair Turbo.
I drove the car with the stock flywheel for a year or so and then swapped to the lightweight one only because it became available cheap and I had to replace the throw out bearing anyway.
Initial feeling was the car responded to the gas pedal faster.. Accelerated somewhat quicker and when you let off the gas, you didn't always need to tap the brake to slow down in some situations. It "felt" more responsive I guess you would call it.
Also the Corvair and most early Turbo Cars had terrible turbo lag and the flywheel being lighter "seemed" to let the engine spool up faster and lessen the lag to a point.

This was all subjective.. I personally liked the feel ... but maybe not for everyone.

I wish I could have put one on my 77 930.. But I was too cheap to buy one for what they were asking.