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Discussion Starter · #1 ·
I am kind of un educated right now as of the tolerances of the K-series motors but I keep imagining in my head the possibility of using a K24 block with low dome pistons with the piston pin almost protruding the oil ring (custom pistons) along with a thicker headgasket and maybe having enough room from the following modifications to be able to run a long rod in the K24, keep the torque from the 99mm stroke while being able to cut down on piston to side wall load (increasing revving capabilities)....my question is: does anybody see this as being a possible combination or is there just not enough room,does anybody know how far in the hole or out of the hole that the K24 throws it's pistons??
 

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Discussion Starter · #2 ·
Nobody??........what about the thought of using the K24 block with a K20 crank and using noticably longer rods netting a higher revving capability seeing how the K20a dyno's I've seen, the peak power always seems to be climbing still and would benefit greatly from being able to rev higher more reliably.

these are the more important issues I'm trying to get information on before I start purchasing parts and end up regreting later....any opinions would be apprieciated.....even if they are negative, if this type of thinking seems useless to anybody let me know your insight

anybody.
 

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lemonhead said:
Nobody??........what about the thought of using the K24 block with a K20 crank and using noticably longer rods netting a higher revving capability seeing how the K20a dyno's I've seen, the peak power always seems to be climbing still and would benefit greatly from being able to rev higher more reliably.

these are the more important issues I'm trying to get information on before I start purchasing parts and end up regreting later....any opinions would be apprieciated.....even if they are negative, if this type of thinking seems useless to anybody let me know your insight

anybody.
i think your going to have better look getting good responses in the daytime! as this is above me.. but i'll keep reading in hopes that i'll learn a thing or two 8)
 

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Discussion Starter · #4 ·
well I now have the specs and measurment differences between the 2.0 and the 2.4 I just need to learn how to calculate if there is room for a longer rod in the K24 or if buying the K24 block and using a K20 crank with extremely long rods would yeild a better outcome I'm leaning towards having .4 more displacment in the end, because you know we all know what they say about displacment

K20X
bore/stroke 86mm
rod 139mm
r/s : 1.616

K24XX
19.7mm increase in deckheight
bore/stroke 87mm/99mm
rod 152mm
r/s : 1.535

does anybody know what the K24 could handle to be revved to if the internals were built.....I have heard many opinions to 7500RPM but that seems to be an estimate using a stock internaled block for the example thanks for any replies in advance
 

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Well given the lack of information out there concerning built K24s - mostly due to the fact that very few people are running them at this time - any estimate would be pretty worthless. 7500 - maybe... anything higher - you're taking chances... you may really have to figure it out yourself.

As far as the K20 crank in k24 block idea - I'm assuming you have read most of the available information on rod/stroke ratio and it's effect on the durability of the motor as well as power characteristics. That being said, you have to decide what you are looking for from your motor. Compare available dyno sheets from K24s and K20s. With the K20 crank in a K24 block (using custom longer rods) you should see a powerband fairly similar to a standard K20 but you may see slightly more breathing ability in the upper rpm, and the sideloads would certainly be less than a k20 at the same rpm. The standard K24 will obviously make more power but how high can you really rev it?? and of course durability will become more of an issue the higher you rev it.

You have to consider that rev limits are always an estimate and most people estimate conservatively. Usually when you build a honda motor you make an estimate as to how high the motor could safely rev, and set the rev limiter in that area. If you dyno and your power curve is still climbing at the rev limiter, then so be it. The only other way is to throw it on the dyno and rev it till the power curve drops off or it blows up. That's an expensive gamble. So I can tell you for sure that a K24 w/long rods and K20 crank will place less load on the rods, pistons, sleeves and crank than a standard K20 would at the same RPM. Does that mean one motor will reliably rev to higher rpm than the other? I don't know. You'd have to try it and find out.

OK I'll stop rambling now. Hopefully someone can answer your question about longer rods in a standard K24 - I've never pulled one apart so I don't know.
 

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Discussion Starter · #6 ·
thanks for you reply and I agree that using a K24 block with a K20 crank and longer rods, along with all of the products that are available would be nearly unstoppable in the upper RPM range especially becuase it would be able to handle them so easily and so often

on the other side of the grass you have a K24 and by using the 99mm stroke the torque throughout the powerband might outweigh the difference that you are gaining by unleashing all of the power in the upper RPM's with the K20........

and a compromise between the 2 would be if you were able to use a longer rod in the standard K24 properly built keeping the torque and maybe extending the powerband up to say 8500RPM you would have one beast of a machine
 

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If you are looking for a compromise look at the 92mm stroke crankshaft from the new 2.2liter S2000s... I have seen it used in a K20 block it should be doable in K24 as well...

EDIT: Sorry it's 90.7mm
 

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Discussion Starter · #9 ·
Correct me if I'm wrong but from rumours I have heard (most the time never true) they are saying that using that cranks other than actual K-series calls for modification to the crank itself and can reduce reliability down the road

I'm not trying to cut all my options short, I'm just looking for cold hard facts about what different variations there are available for the K-series as long as they are feasable and practical,

do you know what the R/S ratio is if somebody were to opt for that crank if it is in fact a reliable option?....any R/S calculators out there?
 

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I found this calculator from searching yahoo
http://www.actionimport.com/Tech_Files/rod_ratio_calculator.htm

another here
http://www.dunegoon.org/rod_ratio.html

I tried to research this several months ago...after seeing a frankenstein build up in SS by skunk2. after they mated the K20a2 & K24 block they got 215whp & close to 175 lb ft...then it (project car) dropped of the face of the earth...i HEARD the motor did NOT last :?

since then I just bought a jdm K20a swap...maybe some day I will do a built TSX block (down the road) the 180 lb/ft to the wheels that hotwheelz got with I/H/E K-pro is VERY tempting.

there should be more info on built frankensteins in the near future - I know of 2 that are nearing completion
 

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very good topic! im looking into something similar myself, im not a big fan of forced induction, so i was looking for some comprimises with the K24 block and K20 head combo. thanks guys! i already like this site.
 

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u could always add a deckplate and get custom sleeves to make up for the difference. but the only really problem i would see is the timing chain. if u got the money then go for it..

u might wanna look into ERL Superdeck II.
 

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This is an old thread, but still interesting. I understand the whole cylinder sideload issue. However the worst rod/cylinder wall angle in the k20 is 18deg, and the worst in the k24 is 19deg. So I don't think that the extra 1deg is going to make/break the setup. Even though the k24 has a significantly larger stroke, it also has a significantly longer rod from the factory.

A lightweight piston/rod combo would probably be a better avenue than getting a piston package that may have issues on the street (moving the oiling ring into the wristpin area).
 

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john from hytech told me that piston speed would be too slow to put a 86mm k20a crank into a k24 block, that the dwell time at bottom dead center would possibly cause detonation. also it wouldn't fill the cylinders as well.
i was going to do this but doing the f22c crank instead to improve the rod stroke ratio. Also john said that the 1.85 rod stroke ratio of the 86 stroke crank in the k24 block was too high, that the motor would be ineficient.
just some insight
Steve
 

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Wow, this is an oldie. That is some good info Slociviccoupe, I recall John saying in the past that they were going to to some intersting motor combos, but I don't remember hearing the outcome.
Wouldn't advancing the timing and retarding the spark help mitigate the pressure with the extended time at TDC? Piston speed would be an issue if the runners were not shortened and ports closed a bit, that should be an easy fix though...custom cams would probably be needed too...
 

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Very old thread, but worth to inhale some breathing :D.

john from hytech told me that piston speed would be too slow to put a 86mm k20a crank into a k24 block, that the dwell time at bottom dead center would possibly cause detonation. also it wouldn't fill the cylinders as well.
The piston speed is indeed lower, significantly from around 45° ATDC, before insignificantly. Why because the acceleration is indeed higher from TDC on, but e.g. at 5° ATDC only 2.7 %. This is pretty insignificant, if the engine get's compared at only 100 rpm lower, both have roughly the same acceleration curves where VE get's relevant. This is an application topic. The engine speed redline, seen from equal rod bolt forces, is around +150 rpm for the long rod.

But what is really different is the mechanical engine efficiency, especially at higher engine speeds. This makes not only more endurable it compensates some of the weight disadvantages. Of course a lower rod stroke ratio helps to increase VE, NASCAR racing series proved that for long as well as the K-series drag scene, where rod/stroke-ratios down to 1.41 where successfully run. Maximal rod angle is over 20°. Those engines generate a really huuuuuuge VE, a bit above the DAMPFHAMMER 😜, because of there up 30 % higher piston acceleration and speed. You can increase ports greatly and you still will see great VE. On a long rod K20 the head port must adapt the bit lower velocity of the piston to create the same impulse and therefore the mass inhaled can be a bit lower if not adapted. So if you change nothing on the engine setup, yes there will be a disadvantage in VE, which can be easily compensated by bigger revving capacity and other stuff.

To give you guys an example. Joe did several race engines, the one for Hondata's Bonneville racer had a 90x78.5 engine the other an 86.5x86 engine. That would give as a R/S-ratio of 1.82 vs 1.62, which is really significant regarding acceleration, velocity and side load. The 1st was easily revved to 11,000 rpm with no issues on the 5-Mile-zone, the other is an all day race engine. Both made a bit below 300 hp and around 195 ftlb of peak torque on Shawn Church's dyno. The engine setup of both where quite different, but this doesn't play the role here as I said, when adapted, you won't see any differences in VE capability, but a difference in durability and forgivingness on mis-shifts.

I build all of Hondata's Bonneville engines as well as endurance road racing K20A's, and here's the story on the legal 2 liter N/A engine that we ran in the CRX last season. Top speed at the end of 4 miles was 190.6 MPH
Darton MID sleeved to 86mm, stock head gasket
stock 86mm crank, journals widened to .949" for F20C bearings and Nitrided
12.7:1 CP pistons, with stock depth [.200" and .140"] valve reliefs
Cunningham rods, 5.472" long, .938" wide, with 7/16" A1 rod bolts
Stock K20A oil pump with radiused discharge port and 100 psi spring
K2 cams [no sponsorship], .006" intake lash, .007" exhaust lash, 35 degree VTC mechanism, Eibach springs, Ti retainers.
'06 TSX head, 36mm intake, 30mm exhaust, mildly ported [317 cfm @ .500"]
Kinsler 2 3/8" [60.325mm] ITB's with custom built 60 degree turn down velocity stacks, custom built filtered airbox, RDX injectors 8" away from port flange. All this fits under the stock hood.
Stock Honda belt tensioner, alternator, and water pump.
I won't say anything about the header other than it was built by someone else, and my specs were not adhered to, not even close.
At sea level this setup made 292.8 HP and 194 lb ft of torque running on Bonneville legal ERC gasoline and NEO oil, and because of the Kinsler ITB's the HP curve was still rising at 9,700 rpm. The rev limiter was set at 9,900, but it saw a little over 10,000 a few times on the salt.
As is normal with Hondata all tuning was done at Shawn Church's shop.
If the header had been done correctly this engine would've made over 300 HP.
I built another [endurance road racing] engine 86.5 x 86 [2,021cc] that made 297 HP and 197 lb ft of torque using weenie 52mm ITB's and a totally stock head. On that one I built the header.
Both of these engines could easily be used in a street car for years because they were built to endurance racing specs.
Engine assembly takes 52 Hours if done correctly.
Joe
When you do a race engine you have always to decide which mix of compromises you follow: durability, cost, performance. Every application mixes up this into a new game, therefore engine design is quite challenging and exciting. Anyway, it is quite indifferent to sate the engine efficiency sucks on a long stroke engine generally. There is a tendency for sure, but each mouse find it's hole, so there are applications where a short rod engine isn't the way to go. Performance-wise guys try for sure the go with lower R/S-ratios and compensate this with a lot of engineering in the field of balancing inertia caused stuff. I4 engines with an 1-3-4-2 firing order have 2nd order forces, which need to be adressed. The shorter the race, the shorter the R/S-ratio ;).

i was going to do this but doing the f22c crank instead to improve the rod stroke ratio. Also john said that the 1.85 rod stroke ratio of the 86 stroke crank in the k24 block was too high, that the motor would be ineficient.
The R/S-ratio would be 1.84 on a 30 mm compression height of the piston. With the 90.7 mm stroke crankshaft it would be 1.72. That's still a significant difference to the 1.62 of the K20 OEM stuff.
 

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Very old thread, but worth to inhale some breathing :D.

The piston speed is indeed lower, significantly from around 45° ATDC, before insignificantly. Why because the acceleration is indeed higher from TDC on, but e.g. at 5° ATDC only 2.7 %. This is pretty insignificant, if the engine get's compared at only 100 rpm lower, both have roughly the same acceleration curves where VE get's relevant. This is an application topic. The engine speed redline, seen from equal rod bolt forces, is around +150 rpm for the long rod.

But what is really different is the mechanical engine efficiency, especially at higher engine speeds. This makes not only more endurable it compensates some of the weight disadvantages. Of course a lower rod stroke ratio helps to increase VE, NASCAR racing series proved that for long as well as the K-series drag scene, where rod/stroke-ratios down to 1.41 where successfully run. Maximal rod angle is over 20°. Those engines generate a really huuuuuuge VE, a bit above the DAMPFHAMMER 😜, because of there up 30 % higher piston acceleration and speed. You can increase ports greatly and you still will see great VE. On a long rod K20, the head port must adapt the bit lower velocity of the piston to create the same impulse and therefore the mass inhaled can be a bit lower if not adapted. So if you change nothing on the engine setup, yes there will be a disadvantage in VE, which can be easily compensated by bigger revving capacity and other stuff.

To give you guys an example. Joe did several race engines, the one for Hondata's Bonneville racer had a 90x78.5 engine the other an 86.5x86 engine. That would give as a R/S-ratio of 1.82 vs 1.62, which is really significant regarding acceleration, velocity and side load. The 1st was easily revved to 11,000 rpm with no issues on the 5-Mile-zone, the other is an all day race engine. Both made a bit below 300 hp and around 195 ftlb of peak torque on Shawn Church's dyno. The engine setup of both where quite different, but this doesn't play the role here as I said, when adapted, you won't see any differences in VE capability, but a difference in durability and forgiveness on miss-shifts.



When you do a race engine you have always to decide which mix of compromises you follow: durability, cost, performance. Every application mixes up this into a new game, therefore engine design is quite challenging and exciting. Anyway, it is quite indifferent to state the engine efficiency sucks on a long stroke engine generally. There is a tendency for sure, but each mouse find it's hole, so there are applications where a short rod engine isn't the way to go. Performance-wise guys try for sure the go with lower R/S-ratios and compensate this with a lot of engineering in the field of balancing inertia caused stuff. I4 engines with an 1-3-4-2 firing order have 2nd order forces, which need to be addressed. The shorter the race, the shorter the R/S-ratio ;).

The R/S-ratio would be 1.84 on a 30 mm compression height of the piston. With the 90.7 mm stroke crankshaft it would be 1.72. That's still a significant difference to the 1.62 of the K20 OEM stuff.
Markus your brain is intense and loaded with solid information. In your opinion if our heads allowed a larger bore or a billet head is used, how would this extend the playground here? 90x78 to 92x75mm as an example.
 
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