What is an inverted triangle piston skirt?

Question

The recently launched Suzuki GSXR150 boasts an inverted triangle piston skirt. From what I have been told, it seems to be MotoGP technology which has been stripped down to suit a 150cc bike. Kindly explain.

Answer 1

I am very skeptical of the claim that the GSXR150 is leveraging MotoGP technology, even the top of the line sport bikes from Honda, Suzuki and Yamaha do not leverage much of that tech other than frame and swingarm. The new Honda RC213V-S is $184,000. How much did that 150cc bike cost?

My point is, the inverted triangle piston skirt is not that fancy. It's simply a piston that has a reduced circumference face against the cylinder walls. As others have stated, the skirt drops down enough to prevent the piston from 'rocking' on the wrist pin and knocking back and forth in the cylinder bore.

Inverted triangle piston skirts have been around for quite a bit, Renault used one in the '70's in formula 1. Yamaha used one in the '70's in a later generation of it's two stroke TZ750 dirt tracker and grand prix bikes.

As @Mauro stated in theory it could be more like a slipper piston, it basically is a slipper piston it's just not that aggressive in terms of removal of material from the skirt and surrounding area of the wrist pin, or as the islanders like to say, grudgeon pin.

I suppose it is race technology but at the end of the day it's '70's era race technology. Most of the GSXR line has been running a similar piston configuration for well over a decade and a half, as has Yamaha, Kawasaki, Honda, Aprilia and Ducati.

Keep in mind they are calling the bike a GSXR but there are no other GSXR models that have rocker arms. They all use under the bucket shims where the cam lob essentially rides right on the bucket over the valve stem.

What Suzuki has done with that bike is attempt to make it the most efficient it can be without spending a large investment. They are in a friction reduction phase with the model to make it compete with all the other 150cc bikes out there, this will force the competition to, in turn, spend money to get their fuel efficiency up and in so doing perhaps create a higher cost vehicle. Suzuki works that way as do many other manufacturers but in the end, it still has rocker arms.

Hope this sufficient, cheers.

Answer 2

Given the piston skirt is the bit of the piston under the gudgeon pin on the piston/conrod, it seems this is a way of reducing drag and wear on the cylinder (i.e. less contact patch) and therefore making it more efficient.

A similar principle is used in slipper pistons

A slipper piston is a piston for a petrol engine, that has been reduced in size and weight as much as possible. In the extreme case, they are reduced to the piston crown, support for the piston rings, and just enough piston skirt remaining to leave two lands so as to stop the piston rocking in the bore.

Answer 3

Engines with a single cylinder can be arranged at any angle but typically upright or inverted.

In Gixxer they says, "An inverted triangle shaped piston skirt has also been utilized to increase bottom end torque, smaller and lightweight rocker arms and a reduced angle of the valves have all helped better combustion, aided by the good looking dual type exhaust."

That means that they have found a new angle to deliver the above features.
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