Hi, I have a 2007 Copen 1.3 with the K3-VE engine.
I am currently working on the car and I have a new intake (manifold and filter), exhaust manifold and exhaust system; and I am thinking of also upgrading the throttle body and potentially cams (as I have read elsewhere in this forum that is a good upgrade for the stock engine).
I was wondering if anyone here knows where I could get a lightweight flywheel from, or even if they are available for these cars? If anyone has done please let me know as I would really appreciate it.
Welcome!
It’d be good to see your car and get an intro post up so we can ‘meet’ you properly.
In the meantime, to answer your question, you generally don’t go and buy a lightened flywheel off the shelf - you remove a standard one and sent it to a machine shop/engineering firm who will remove material from the stock part to get down to the target weight, while keeping the whole piece balanced.
So either remove your one, or buy a standard one (probably including engine & gearbox) and send it off for work to be done.
3 Likes
I’ve machined a heap of them to lighten. Paying someone will get it down in weight. But bear in mind as you push the weight limit the price of having it done will go up. The last grams that can come off take a lot of time. I do what I call a static balance (really just a let it roll on parallel strips that I set up with a engineer’s spirit level which is really time consuming as it’s good for 0.01mm over 1000mm). You put a precision bearing in the centre with no seal, light oil and let the thing spin or a perfectly machine ground bar as a tight press fit in the centre and let it roll. You do this drilling weight from the low spot until it settles randomly. Theoretically his gets you close there can still be some lateral imbalance not just radial. A few years ago it was $80 to have them tested. To have them corrected costs more, but I’ve never had one needing correction. And that includes ones I had tested but hadn’t balanced myself. The caveat to that was that on these I didn’t go wild removing weight. The factory drilling seems to be due to casting imperfections. So by machining only surfaces premachined and staying away from sections drilled for balance they come up within the accuracy tolerance of the dynamic balances I was getting done. One day I’ll have a go at balancing on the tire balancer at work but most will need an adapter to hang outside the big spigot. Def a mod that makes a noticeable diff in lower gears and engine braking. Power wise it’s a cheap way of making gains - https://www.gstatic.com/education/formulas2/553212783/en/power.svg
2 Likes
The most widely known lightweight flywheel that can be used for the K3 engine is often the one for the KJ-VET engine (from BoonX4), but this is sold only in Japan (I believe), and being a limited edition vehicle, it has become difficult to obtain, especially recently. Therefore, we recommend the use of the KF engine (L275mira, LA400K Copen, etc.), which is low cost, easy to obtain, and significantly lighter. This will reduce the weight by about 2 kg, 5.2 kg compared to the standard one for K3, which weighs about 7 kg. In addition, the smaller diameter has further advantages in terms of inertia weight. However, there is a major problem in that only a clutch for the KF engine can be used: the K3-VE (90 PS) has 1.5 times more power than the KF-VET (64 PS), and the stock clutch cannot handle that horsepower, so if a flywheel for the KF engine is used, a reinforced clutch for the KF engine use a reinforced clutch for KF engines. Also, in some cases, the clutch may hunch when idling. Except for this point, the installation itself is completely bolt-on, so it is a pretty good diversion.
2 Likes
