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

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Posts: 21-30 of 47
2013-07-17 14:02:48
#21
Originally Posted by BenFenner
Longer stroke typically means slower engine movement which gives more time for forced cylinder filling. Another thing to think about.


What do you mean, slower movement? Increasing stroke will always increase piston speed at any given rpm.
2013-07-17 14:18:12
#22
Originally Posted by cory
With the larger studs and step deck head there should be absolutely no sealing issues. Not to mention the fact that with the extra bore you'll be making more power with lower boost pressures ......


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??
Last edited by Boostlee on 2013-07-17 at 14-24-33.
2013-07-17 14:23:57
#23
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.
2013-07-17 14:26:22
#24
Originally Posted by boostednx
I think that nobody on here has reached the limits of a 2.0 setup so why move on and spend the extra money on a strokes setup when you can make 1000hp on a 2.0.


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.
2013-07-17 15:24:31
#25
Originally Posted by cory
Originally Posted by BenFenner
Longer stroke typically means slower engine movement which gives more time for forced cylinder filling. Another thing to think about.


What do you mean, slower movement? Increasing stroke will always increase piston speed at any given rpm.
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.
2013-07-17 15:34:43
#26
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.
2013-07-17 15:42:29
#27
Originally Posted by BenFenner
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
2013-07-17 16:52:12
#28
Originally Posted by BenFenner
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.

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.
2013-07-17 17:30:56
#29
w00t w00t, super stroker is a go!
2013-07-17 18:25:34
#30
Originally Posted by cory
All the NA SR strokers are using STD rod length.
Interesting.
For some reason that just blows my mind.
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