I remember a conversation I had with my father-in-law many years ago about SFI ratings. The topic came up because I was putting a 7lb flywheel in my car, and happened to notice the sticker strongly affixed to the flywheel and the corresponding clutch stating the parts were SFI certified. I wasn’t very familiar with what that meant at the time, and the explanation was that it is a rating and standardization body that supports the automotive industry, and a company who pays particular attention to racing parts.
The story I got was : “Back in the old days, flywheel explosions were common and fire suits and other safety gear were not. The SFI came along and changed all that by inspecting manufacturing processes and materials used to produce performance parts and safety clothing. In other words, the sticker is a good thing.”
As I got more involved in vehicle performance, I became acutely aware of SFI ratings on certain parts, but one thing still stuck in the back of my mind: “Flywheel explosion?! that must be a hell of a sight.”
I have never experienced a flywheel explosion before, but what I found on Honda-Tech.com the other day changed all that. Here is the video:
The following is what is left after a flywheel explodes in a 1991 Honda CRX, in pictures:
As you can see from the wreckage, this is a spectacular display of the potential energy stored in a flywheel. The bell housing of the transmission is totally gone, as is the flywheel housing on the engine side. Motor mounts were broken in half, and the radiator, intercooler, clutch pressure plate and clutch disc are completely destroyed.
Some speculation about the flywheel that was used is still going on at honda-tech.com, but my opinion on the matter is that it looks like the flywheel being used was a modified stock(!) flywheel. You can see in the “CRX Flywheel explosion 3” picture that the leftovers of the flywheel appear pretty dark, just like the stock flywheel. Were it an aluminum flywheel, there would be a much brighter silver color where the aluminum sheared apart, much like what you see where the aluminum engine and transmission were blown apart.
Anyway, I think I will be spending my $100 summit racing giftcard toward a scatter shield..