Thread: Let's talk Big Bore/Short Stroke vs. Small Bore/Long Stroke Boosted

What do you mean, slower movement? Increasing stroke will always increase piston speed at any given rpm.

Although I somewhat agree with this, although you will be running lower pressures, wouldn't the decrease in bore size (and hence the subsequent removal of the all too important thermal capacity of the metal from the extra bore) lead to increased issues of temperature control and heat seepage through the cylinders (if such a thing is an issue)??

Curious and valid question as isn't one of the issues I would run into with a big bore engine on boost is for this very same reason, no??

Also, now with the increased side load of the pistons (if you are running both a longer stroke and bigger bore) also cause issues??

One of my BIGGEST scares is literally losing the ability to control heat in any high cylinder pressure application. But that's just my personal opinion and not being argumentative.

Although I agree, that's a high boost, very temperamental setup I feel, and anything to reduce engine stress (lower boost) to make the same power is something I would be prefer to look into.

Just my opinion however, nothing else.

By slower engine movement, I meant lower RPM. Typically an engine with a longer stroke does its best work at lower RPM than an engine with a shorter stroke (for various physical reasons). Because of the lower operating range (efficient RPM range) of the longer stroke engine, the average power producing stroke will have the intake valves open for a longer period of time which is a benefit for forced induction.

There aren't many benefits to longer stroke engines when it comes to producing power or working with forced induction, but there are a few. The fact that the valves stay open longer during the power band is one of the advantages.


Piston speeds, as you mention, are a different story altogether.

If the stroke increase is 6mm and you don't go with 3mm shorter rods, but instead you move the wrist pin up 3mm, won't you have to cut 9mm of material out of the piston skirt so that it doesn't crash into the crank counterweights?

I didn't think anyone stroked without getting appropriately shortened rods.

...........It's funny, but that is ALL layed out in Chuck's and Kojima's articles which I am sure many people, with exception of a few (like yourself), may have missed in the articles

Fromt what I garnered, most of the stroke is gained from both piston height increase and longer rods. No other mods (unless you use H22 rods which require simple machining) is required. Meaning: no valve relieves had to be cut as effectively, the piston height and travel distance hasn't been tampered with for the most part

However, I could be entirely wrong in how I interpreted the math

Ok now I see what you meant. Yeah you should be able to reach all previous numbers /goals at a lower rpm..

All the NA SR strokers are using STD rod lenght. You could go with the shorter option and will have some weight savings but I think depending on the revs your better off just moving the pin up, less stress on the sidewall and the higher the pin is placed the more steady it will be in the bore.

w00t w00t, super stroker is a go!

Interesting.
For some reason that just blows my mind.