Hey guy I'm currently working on my first k24 swap and wanted to know what all is needed to make it rev more 7500 RPM and how much more power is made by changeing the VTC gear
k24a2 Rev Limit
Jdmlif3
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So how do you judge this statement:
This may bring out the "uninformed" with lots of speculation, but here it goes....
Had a discussion a few days ago with someone who insisted that a K24 at 8000rpm is way more dangerous than a K20 at 9000rpms. I have been seeing this statement all over the forums and its funny what people believe without any math.
There are certain things rod length and stroke do to the forces acting on a piston.
Increasing rod lenght= lowers piston acceleration. Decreases rod angularity, lowers piston forcces to cylinder wall. Lowers piston speed. Longer time at TDC.
Increasing stroke = does the exact oposite of the above.
Now, here is the misconseption that the misenformed tend to adhere to.. "piston speeds determines engines rpm limits". This is NOT true. Although higher piston speeds MAY follow an engines limits it is NOT the limiting factor.
The two most important factors are 1) Piston NEGATIVE acceleration and 2) Rod bearing lateral forces.
The K20 has a shorter rod (this increases piston acceleration and speed) and the K24 has a longer stroke (having the same effect) Now the one factor that cancels this out is rod length. Now we know the K24 has a longer rod, but does this cancel out the forces? Lets see....
K24 @ 8000 has a piston speed above the K20 @ 9000rpm. There are a few calculators online to prove this just search. Now piston speed does not limit an engines rpm capabilities it is G's on the NEGATIVE acceleration cycle which is higher than at TDC (P(t) = R cos(2pUt) + (L2 - R2 sin (2pUt )2) 1/2) Gotta love physics.
k20@9000 = 5126 G/s of negative acceleration
k24@8000 = 4720 G/s of negative acceleration
Rods fail on what we call the down stroke which accordging to physics is nearely double the forces at TDC. So the K20 at 9000rpms has a significant amount more force than the K24 at 8000rpms YET has a slower piston speed. So, if you want to figure out the limits of an angines RPM redline, you need to know more factors than piston speed....as a matter of fact, you do NOT need to know pistons speed at all since this is not the limiting factor. You WILL need to know
Piston+rod weight
negative acceleration
rod compression strength
bearing load limits
To summarize, increasing stroke of an engine does not lower its RPM limits IF you increase the rod length. Piston speed does not effect RPM limits. The only two things (mathmatically) that effects the limits of an engine (in reference to stroke) is the rod strength and bearing load limits. Both I believe are higher on the K24 with lower G's of force.
So, revving a K24 to 8000rpms is not a problem if revving a K20 to 9000rpms is not problem. Of course this is only my opinion, but as far as piston speeds being the issue, tell those preaching it to stop repeating what the read... do the math.
Two reasons I say this, the K24 has less negative acceleration (G's). Has heavier pistons + rods, but also has stronger rods. Rod journal size is also larger allowing heavier bearing loads. So without knowing Rod strenght and bearing load limits, no one can state what the K24 limits are (or the K20s for that matter), but according to physics, the K24's stresses are nearly the same as the K20s at the same RPMs.
This may bring out the "uninformed" with lots of speculation, but here it goes....
Had a discussion a few days ago with someone who insisted that a K24 at 8000rpm is way more dangerous than a K20 at 9000rpms. I have been seeing this statement all over the forums and its funny what people believe without any math.
There are certain things rod length and stroke do to the forces acting on a piston.
Increasing rod lenght= lowers piston acceleration. Decreases rod angularity, lowers piston forcces to cylinder wall. Lowers piston speed. Longer time at TDC.
Increasing stroke = does the exact oposite of the above.
Now, here is the misconseption that the misenformed tend to adhere to.. "piston speeds determines engines rpm limits". This is NOT true. Although higher piston speeds MAY follow an engines limits it is NOT the limiting factor.
The two most important factors are 1) Piston NEGATIVE acceleration and 2) Rod bearing lateral forces.
The K20 has a shorter rod (this increases piston acceleration and speed) and the K24 has a longer stroke (having the same effect) Now the one factor that cancels this out is rod length. Now we know the K24 has a longer rod, but does this cancel out the forces? Lets see....
K24 @ 8000 has a piston speed above the K20 @ 9000rpm. There are a few calculators online to prove this just search. Now piston speed does not limit an engines rpm capabilities it is G's on the NEGATIVE acceleration cycle which is higher than at TDC (P(t) = R cos(2pUt) + (L2 - R2 sin (2pUt )2) 1/2) Gotta love physics.
k20@9000 = 5126 G/s of negative acceleration
k24@8000 = 4720 G/s of negative acceleration
Rods fail on what we call the down stroke which accordging to physics is nearely double the forces at TDC. So the K20 at 9000rpms has a significant amount more force than the K24 at 8000rpms YET has a slower piston speed. So, if you want to figure out the limits of an angines RPM redline, you need to know more factors than piston speed....as a matter of fact, you do NOT need to know pistons speed at all since this is not the limiting factor. You WILL need to know
Piston+rod weight
negative acceleration
rod compression strength
bearing load limits
To summarize, increasing stroke of an engine does not lower its RPM limits IF you increase the rod length. Piston speed does not effect RPM limits. The only two things (mathmatically) that effects the limits of an engine (in reference to stroke) is the rod strength and bearing load limits. Both I believe are higher on the K24 with lower G's of force.
So, revving a K24 to 8000rpms is not a problem if revving a K20 to 9000rpms is not problem. Of course this is only my opinion, but as far as piston speeds being the issue, tell those preaching it to stop repeating what the read... do the math.
Two reasons I say this, the K24 has less negative acceleration (G's). Has heavier pistons + rods, but also has stronger rods. Rod journal size is also larger allowing heavier bearing loads. So without knowing Rod strenght and bearing load limits, no one can state what the K24 limits are (or the K20s for that matter), but according to physics, the K24's stresses are nearly the same as the K20s at the same RPMs.
Thanks for the physics lesson.
Bearing load limits are NOT higher on a k24, they're identical in size and function to a k20. The only k series with smaller bearing surfaces are the k20a3/a4/a5. The F22/f20c in the s2000 has more bearing loading surface than the k series do.
For running some physics formulas for us it's kind of funny how you just assumed the k24 has a different setup like that.
Either way, something in the way the k24 is setup isn't as favorable for revving high, as it's definitely more like to to go down in flames revving high.
the rod to stroke ratio is great, better than the k20, but i'm assuming the rod angles associated tend to fuck shit up more? I dunno, why don't you tell us
anyways, here's a graph of piston motion; velocity, acceleration and position:
Do you think you're capable of making a graph similar to this and showing us a k20 at 9000 rpms vs a k24 @ 9000 rpms?
k20 Rod length = 13.9cm (5.472 inches)
k24 rod length - 15.2cm (5.984 inches)
k20 stroke = 8.6cm (3.385 inches)
k24 stroke = 9.9cm (3.897 inches)
k20 crank radius: 4.3cm (1.692 inches)
k24 crank radius: 4.95cm (1.948 inches)
that's all you need right?
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101 Posts
All this butt hurt about u cant rev that high!!! have u done it!!! i did to 8800rpm for a few months and still runing strong. im planing on changing a few things and see how it does on the dyno cause if it carry power all the way to 9k rpm guess what is gonna be put to the test!! and if it doesn't blow up im gonna prove yall wrong. which it hasn't at 8800rpm. and all u saying it should blow up.. only way to find out is testing it! and i will! (baller status lol)
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88 Posts
you bet.
revving k24 stock rods to 9k does not neccessarily mean it'll blow right away. it just means you're shortening your engine lifetime drastically.
simple as that. remember, this is simple mechanics and metal properties, nothing complicated.
in the end, this is your time and your money - why not?
do it the way you like.Sorry, i should have stated it's a quote from a different forum. I know it isn't as simple as that, one thing that post thought me though is it isn't as simple as comparing piston speeds!
Yes, it does function as a simple guideline but saying the k24 is hammered the same as a k20 at the same piston speed is nonsense.
One fact is given though, the higher the piston speed the higher the wear will be, hence why Honda decided to limit the k24 lower, they have to guarantee 150k miles. Something the most of us probably don't care about, well, atleast not to that extent....
Yes, it does function as a simple guideline but saying the k24 is hammered the same as a k20 at the same piston speed is nonsense.
One fact is given though, the higher the piston speed the higher the wear will be, hence why Honda decided to limit the k24 lower, they have to guarantee 150k miles. Something the most of us probably don't care about, well, atleast not to that extent....
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58 Posts
This guy referred to Newton's Second Law as a "nugatory engineering equation"
:lolface:
http://forums.clubrsx.com/showthread.php?p=50857386#post50857386
:lolface:
http://forums.clubrsx.com/showthread.php?p=50857386#post50857386
Omg that thread gave me a headache when I read it. I was told to stop posting in it and they deleted all my posts lol.
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58 Posts
Haha yeah I noticed that, OP made like 3 threads asking the same shit
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107 Posts
8k rpm
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2,323 Posts
From what I have read, when concerned with reliability most take measures to aid their K24's life. DC5 oil pump, S2000 oil pump, modified DC5 oil pump, rpm suited valve springs & retainers. Normally a better rpm suited K24 cam is needed to make power past 7500 rpm, Normally... Jackson Racing Supercharger, Rotrex, K20 head, RBC, RRC, PNP RBC, build spec headers I see aiding a K24 to make useable power above 8000rpm.
Because a engine will keep spinning after the redline has been extended by Kpro does not mean the engine is in safe territory. Taking the measures to get the engine to perform past its design requires some work.
Because a engine will keep spinning after the redline has been extended by Kpro does not mean the engine is in safe territory. Taking the measures to get the engine to perform past its design requires some work.
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58 Posts
Yep, and in addition a built bottom end (stronger rods, etc.) will also help reliability when spinning past 8k RPM
Most road racers with stock bottom end runs 8K rpms with uprated valve train and different cams... some even 8200 but I'll keep it at 8K.
I am going to run stock bottom end as well with DC 3.2 cams and see how that performs.. build bottom end is on the planning so this setup is just temporary and I will see how it goes..
Input from road racers makes more sense than people that are sometimes revving the crap out of there K24 on the street for few times...
I am going to run stock bottom end as well with DC 3.2 cams and see how that performs.. build bottom end is on the planning so this setup is just temporary and I will see how it goes..
Input from road racers makes more sense than people that are sometimes revving the crap out of there K24 on the street for few times...
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30 Posts
Back when I was Complete k24a2 long block I did the z1 oil pump and 50degree vtc and have been revving to 8600 for over a year not one issue and I've abused made 242 with 203 straight 24 long block and 258 with 203 with just the change of the head to a 20 head and changing to a plm header versus the k tuned ram header
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2,323 Posts
I haven't heard much about OIL on this thread. AMSOIL turbo formulated 10-30W did wonders for my engine performance.
I Road Raced my K24. 8K was it on revving. It sounded like it was going to die while downshifting compaired to the K20 downshifting. The K20 sounds happier at 8K and above. The cylinders are filling up easier. ON the road course my JRSC K24 was better out of the turns than my buddies JRSC K20 but he was better in the sprints......
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133 Posts
Interesting thread... can't believe how high some guys are revving these stock block K24's.
I have a k24/k20 setup running drag cartel 2.2's, supertech valvetrain, PRB oil pump, with stock k24a2 sub and have been spinning her up to 7800rpm for the past 3 years without an issue doing many trackdays. When it was n/a it still wanted to rev higher but never had the balls to raise the limit.
Now I'm turbo'd with the same setup as above, I'm making 385bhp at 7800rpm and 400hp at 8200rpm and the power is still not dipping off:scared:
Going to be replacing the pistons and rods soon with some Wiseco's and Manley turbo tuff rods, hoping to rev to about 8500rpm reliably and judging what people have been putting their engines through on this thread, it hopefully will be:new_slayer:
I have a k24/k20 setup running drag cartel 2.2's, supertech valvetrain, PRB oil pump, with stock k24a2 sub and have been spinning her up to 7800rpm for the past 3 years without an issue doing many trackdays. When it was n/a it still wanted to rev higher but never had the balls to raise the limit.
Now I'm turbo'd with the same setup as above, I'm making 385bhp at 7800rpm and 400hp at 8200rpm and the power is still not dipping off:scared:
Going to be replacing the pistons and rods soon with some Wiseco's and Manley turbo tuff rods, hoping to rev to about 8500rpm reliably and judging what people have been putting their engines through on this thread, it hopefully will be:new_slayer:
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5,631 Posts
I have a rebuilt k24/k20 using 2012 si pistons(pretty much same as 09 tsx) with a built k20 head using Prayoonto stage 3 cams. i have the type s oil pump in there and my rev limit is set at 8200. now i don't see rev limit often, but i've been problem free since summer 2012........knock on wood.
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