Toda K series 2.2L stroker kit
Thursday, November 27th, 2008I recently had a long time customer drop by the shop to have me spec out a set of custom pistons for his engine. He had purchased a used stroker kit that stroked up the K20A engine to a stroke of 90.7mm and was unhappy with it. Toda probably used the same OE crank that came out of the Honda S2000 AP2. That is a 2.2 litre with a bore of 87mm and stroke of 90.7mm. and since the distance between the main journals were the same as measured previously across the Honda H / F / K series engines, we can safely say that the cranks were interchangeable and will just need to provide for the ancillaries that was connected to the crankshaft to work in unison.
As with all stroker kits, the crankshaft features a longer stroke and required to be placed into the factory block with stock deck height. It will require either a shorter rod or a piston with the gudgeon pin moved to a higher position; i.e. shorter compression height, or a combination of both. This is simple engineering that is required so that your pistons are not going to sit out of the bore of the block deck. The kit that Toda Racing engineered was no different. In this, they used a rod that was slightly shorter, and a forged piston that had a slightly smaller compression height.
Here is a picture of the piston. It is a really nice looking piston with a decent forging that will hold up to a lot of abuse.
In this picture, the piston looks like it has gone to Ping Heaven and back…. and barely managed to survive without cracking its ring lands. The piston runs a total of 2 compression rings and an oil ring; perfect for a daily driver with no oil control issues as with their B16A stroker kits. I remembered those single compression rings pistons as consuming a lot of engine oil as they had to move the gudgeon pin up really high and did not have any provision to allow a 2nd compression ring.
What really caught my attention in this kit was the rod that came with it. Here is a picture of it (the one on the right), a really beefy looking cast rod.
When I held it, I can instantly feel the mass. It was way heavier than any of the stock K20 or K24 rods I have seen/weigh.
Here is a picture of the weight from a sample of an economical, china-made rod for the K20 weighs. I use these rods in 500hp Honda 4 cylinder motors and never had any problems with them. They feature ARP rod bolts and are very reasonably priced.
I was aghast at the weight of the rods that came with the stroker kit, to say the least. After I did some measurements, the rods seem to point to being of another OE manufacturer’s specification. The dimensions that I measured came up almost identical to those of Toyota 3S-GTE motors, with the exception of the Big End width, which was probably machined down to match the journals of the F22C crankshaft.
Look at the weight of the rods!
I guess perhaps it was purely a business decision to use an easily available rod and cost-effective solution to match up a kit that will work. In this case, only a custom piston needed to be made out. However, since most of these parts are going into NA motors, I really do not understand the rational of having a rod so heavy that will ultimately rob some performance out of the stroker kit.
I have tested and proven to many skeptical customers and critics that a good lightweight combination of rods and pistons will make more power, ceteris paribus. The heavier the rod and piston combination, the more force is required to have them change direction. In a high revving Honda engine, much of the wasted energy can be translated into more power gains, better fuel economy and lesser stress on internal components.
It is beyond me why anyone would want to purchase a kit that is more expensive than others, less well engineered than others and the worse part is, certain parts in the equation are worse off than stock! I have seen the stock K20 rods (and bolts) work well to about 400hp. I guess aggressive marketing really works when it comes to selling parts. It could also probably be that this is what the market wants. Since not all car owners can afford the most exotic of parts but would like to rely on a big brand name, this would have to suffice.
