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Discussion Starter · #1 ·
Question about the increasing stroke on the K20A2. There is a lot about bore already, but not too much about stroke. What's the maximum stroke length for the K20A2 block?

My next plan is to sleeve, increase bore and stroke along with lower compression to go along with the turbo. Right now i'm thinking 88 X 88 mm, but there is not enough decussion about stroke yet, anyone know anything useful?
 

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Lokie said:
Question about the increasing stroke on the K20A2. There is a lot about bore already, but not too much about stroke. What's the maximum stroke length for the K20A2 block?

My next plan is to sleeve, increase bore and stroke along with lower compression to go along with the turbo. Right now i'm thinking 88 X 88 mm, but there is not enough decussion about stroke yet, anyone know anything useful?
If you are going to turbocharge, don't worry about the stroke. Torque won't be a problem.

Unless you have another reason for wanting to increase the stroke.
 

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Lokie said:
Question about the increasing stroke on the K20A2. There is a lot about bore already, but not too much about stroke. What's the maximum stroke length for the K20A2 block?

My next plan is to sleeve, increase bore and stroke along with lower compression to go along with the turbo. Right now i'm thinking 88 X 88 mm, but there is not enough decussion about stroke yet, anyone know anything useful?
You could the 90.7mm crank out of the new s2k's.
 

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Yes, I believe the 90.7mm crank from the new s2k's will drop right in except I believe you have to have the snout(cant think of a better term) machined to accept the K-series crank pulley. With an 88mm bore that would give you right around 2.2L off the top of my head. That is a nice increase in displacement, enough to spool a significantly larger turbo.
 

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yes but using the s2000 crank in the k20a2 block would mean your rods would have to be shorter - 136.652mm roughly giving you a rod/stroke ratio of 1.51 which would mean you would need a lower redline with that setup!!

the stock k24 has a r/s of 1.53 just to give you an idea
 

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rod stroke is not that big of a deal. plus since you'll have to get custom rods and pistons for the stroker, it wouldn't be a problem to run a longer rod than 136mm if you're that worried about the r/s.
 

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if you use the longer stroke crank of the s2000 it pretty much uses up any space you have for longer rods unless you get really creative with your piston setup.

edit: and rod/stroke is a big deal when it comes to rod angularity - and the industry accepeted max for rod angles in degree's is 18 - anything more and you will have excessive wear to the piston major thrust area and opposing cylinder wall..

with the above mentioned setup your rod angles would be 19.496 degree's = asking for trouble!!
 

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arctic-k20 said:
if you use the longer stroke crank of the s2000 it pretty much uses up any space you have for longer rods unless you get really creative with your piston setup.
You can run a smaller compression height on the piston if you want to run longer rods.


arctic-k20 said:
edit: and rod/stroke is a big deal when it comes to rod angularity - and the industry accepeted max for rod angles in degree's is 18 - anything more and you will have excessive wear to the piston major thrust area and opposing cylinder wall..

with the above mentioned setup your rod angles would be 19.496 degree's = asking for trouble!!
Do you know how many ls/vtec or b20vtec setups there are that run fine with their oh so terrible r/s of 1.5?
 

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im sure there are a lot - all i am saying is that it is a topic of concern...

r/s isn't the be all end all but there are finite limits a setup can handle in relation to pisont speed...the g forces the rods experience are exponential to the rpms and crank length...

its not by chance that F1 engines have a r/s of 2.0 and higher
 

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arctic-k20 said:
its not by chance that F1 engines have a r/s of 2.0 and higher
very true. but how many rpm do those things turn? 17-18k?

point is, on a street motor, I am yet to see r/s make a difference in power or engine longevity.
 

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they are over 19k this year now (crazy)

i would say it all boils down to over all build quality - that will dictate your power/reliability more so than any of the other factors!

:thumbsup: jt - nice discussion - the board needs more of this!!!!!!!!!!!
 

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arctic-k20 said:
they are over 19k this year now (crazy)

i would say it all boils down to over all build quality - that will dictate your power/reliability more so than any of the other factors!

:thumbsup: jt - nice discussion - the board needs more of this!!!!!!!!!!!
heck yeah man, it's nice to be able to 'discuss' something and not start a flame war :thumbsup:
 

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oops, I didnt read carefully enough and assumed we were talking about a K24 block. But yes in a k20 block with its ~19mm(i think,not sure off the top of my head) shorter deck the r/s ratio does become a concern. Still it not as important as the absolute piston speeds, but yes a poor r/s can cause problems with increased wear on cylinder walls due to the wierd angle that are created between where the piston and rod and the rod an crank meet. While you proably wont throw a rod bolt or snap a rod like you would with to long of a stroke at too high an rpm, you will decrease the life of the engine in the long run.
 

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Discussion Starter · #14 ·
This is a nice discussion.

The rod angle is really a big issue with increasing stroke on such a 'short' block. Destroking a K24 is a lot easier. But I don't want to throw away the 'possibility' just yet. This will be a winter project anyways, so still some time to think it thoroughly.
 
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