Experience with flywheel modification

[alexanderfoti]

After chopping off the cooling fins on my flywheel and replacein them with 12v cooling fans I thought I would share my experiences.

I have a digital thermostat that controls the fans based on the temperature I set. The themometer sensor is stuck inside the cylinder head air passage with epoxy.

When driving the engine quickly warms up to about 75degrees C. If the bike is in continual motion, it hovers between 75 and 85 at this time of year in the UK.

When idling it slowly creeps up to 105 degrees, when my fans kick in. 2 fans are on the intake side where the flywheel would have originally blown air through:



The other fan blows on the side of the cylinder, this fan has since been replaced with a smaller one from a yzf-r125:



With the fans running, they draw 4 amps. They cool pretty quickly at idle and click off again at 98.

Removing the fins hasnt seemed to give the engine more acceleration capability, but it does rev a bit easier at the upper rpms, as its not being limited by the fans as well.

The only time it gets hot quickly in my experience, is filtering, or high rpm on low gears up hill. As there is little air flow and lots of fuel/acceleration going on.

So far, no evidence of overheating, hopefully it also increases the fuel economy slightly.

[tappy]

Awesome - great data and information

[sbrumby]

I am not a fan of this modification. 1 you have removed very little weight in proportion to the weight of the flywheel. Adding 1 or 2 fans + sensors + wireing you are probably up to the same weight. 2 the original was designed to give even cooling to the engine, adding fans without the ducting only can give local cooling. I dont know much about the SVA but haveing exposed rotating parts i assume would be a fail.

[alexanderfoti]

The aim of the modification was to recover the up to 2hp used to cool the engine with the fins on the flywheel, rather than save the weight of the fins.

The point of the post is basically that the cylinder head temperature stays stable when moving without the fans running, implying that the stationery engines are overcooled when being used in a motorbike application.

The fans push the air through the exact same places that the flywheel did normally.

The fans in the final build are not exposed nor is the flywheel. There is ducting at the top of the engine made of aluminium that forces air into the cooling passages when travelling forward.

Like this:



But, each to their own. The engine is cheap enough that if it it does cause serious damage then it's not the end of the world. I would think twice about doing the same kind of thing to a kubota etx (if they were air cooled)

[tappy]

In terms of acceleration, 0.5Kg removed from the flywheel can be worth tens of Kg removed from the weight of the bike.
In my case going on a diet is probably as effective

[alexanderfoti]

Ditto to be be fair! It works for me, but each to their own.

[sbrumby]

To be fair I thought the pictures of the fan and flywheel was the final outcome. But I am still completely unconvinced of a 2 HP gain. and would have to be convinced with dino data.

[alexanderfoti]

To be fair I thought the pictures of the fan and flywheel was the final outcome. But I am still completely unconvinced of a 2 HP gain. and would have to be convinced with dino data.

Apologies, it was pretty obscure.

I had time to kill, so any gain is beneficial. I had a spare flywheel to put on in case I buggered it up completely.

I will keep everybody up to date on whether my engine explodes.

[pietenpol2002]

Would there be a Mrs. or significant other to update us in the event of a catastrophic failure? I might add, the flywheel's relative proximity to precious body parts might also impact (no pun intended) one's plans for fatherhood (assuming the rider's a male).

[alexanderfoti]

Would there be a Mrs. or significant other to update us in the event of a catastrophic failure? I might add, the flywheel's relative proximity to precious body parts might also impact (no pun intended) one's plans for fatherhood (assuming the rider's a male).

Heh

[alexanderfoti]

Just an update, with the cooler weather, on a consistent high speed run, my CHT is about 65 degree C, so movement on the bike is more than enough to cool the engine without the flywheel cooling.

[tappy]

Would there be a Mrs. or significant other to update us in the event of a catastrophic failure? I might add, the flywheel's relative proximity to precious body parts might also impact (no pun intended) one's plans for fatherhood (assuming the rider's a male).

Removing mass from the perimeter of the flywheel, and removing the vanes which form mass concentrations will reduce the centrifugal loads that the basic "disc" of the flywheel has to support. If it has been done carefully so as to avoid nicks, scores and other sharp features then the lightened flywheel should have LESS tendency to burst for a given speed.