What is a stroker kit

[thexav]

I hear people talking about stroker kits.

What is a stroker kit? What does it contain and what does a stroker kit actually do?

 

[TCJBOLDIE]

Had one in my last car and the capacity increased from 1995 to 2323cc's
It involved sorceing the crank from a 2 .4litre motor and using it in a 2 litre block that I had overbored to max factory recommendations and using forged stock length rods and forged stroker pistons with the pin height 1/2 of the stroke increase higher /closer to the crown due to the different deck height between the 2 & 2.4 litre blocks.

As a general rule a stroker crank increases the capacity so torque and HP will rise and the car will pull better at low revs BUT the longer stroke means higher piston speeds so the redline will or should be a bit lower for longevity.

The longer stroke will place more pressure on the piston skirts at BDC due to the rod angle being closer to 90 degrees.

 

[Lunchmoney]

Stroker kits are popular in Imprezas. This is one of the most popular ones (according to my mechs when discussing options with them)

® - The Official Roger Clark Motorsport Website

® - The Official Roger Clark Motorsport Website

rogerclarkmotorsport.co.uk

In short it ups the cylinder capacity to 2.1 litres by increasing the stroke length. Pros and cons as noted by TCJB

 

[obi_waynne]

It's nothing to do with cats or kittens!

Stroke is the distance a piston moves inside the cylinder.

A shorter piston on a longer rod will travel to the top of the cylinder wall (it can't go beyond that for obvious reasons) but the compression ratio of the engine will be altered as it starts at a lower position due to it being shorter and it compresses more air for the same amount of travel.

We usually think of it increasing the stroke but actually you may want to decrease the stroke for example if you are adding forced induction etc...

 

[thexav]

What an awesome knowledge base we have on here to tap into!

Thanks chaps. More mysteries solved.

 

[Lunchmoney]

It's nothing to do with cats or kittens!

I'm stunned I missed such an obvious opportunity for a cat pic!

 

[TCJBOLDIE]

That looks like great fun, thanks for sharing.

Wheres the Snow and Ice, it looks really sunny

It's nothing to do with cats or kittens!

Stroke is the distance a piston moves inside the cylinder.

A shorter piston on a longer rod will travel to the top of the cylinder wall (it can't go beyond that for obvious reasons) but the compression ratio of the engine will be altered as it starts at a lower position due to it being shorter and it compresses more air for the same amount of travel.

We usually think of it increasing the stroke but actually you may want to decrease the stroke for example if you are adding forced induction etc...

Obi I don't think you have thought that out properly.

A shorter piston pin height on a longer rod can't compress more air IF the stroke and engine capacity remains the same regardless of the rod length and piston pin height combination.
The reason one might use a longer rod is to get a better rod ratio so there is less side trust on the piston skirt at BDC

 

[obi_waynne]

I assumed a longer rod, with shorter piston! Thanks for pointing that out, I'm not trying to confuse anyone but succeeding nonetheless.

 

[TCJBOLDIE]

Just to be totally clear when "shorter pistons " are mentioned it actually refers to the gudgeon pin height or the distance from the top or crown of the piston to the centre line of the pin in the piston.

For example if you decide to use a 6mm longer rod then the pin height will need to be 6mm closer to the top of the piston otherwise the top of the piston or will protrude 6mm above the top of the block .

That is exactly what I had to do when the stroke in my last car went from 88mm to 100mm and the capacity rose from 1995 to 2323cc's with a 1mm oversize bore.