From Left to Right:

1. Standard K20A(2) - 5.473" for reference

2. Custom 5.893"

3. Custom 6.250"

4. Custom 6.511"


These are the rods we'll be using in our next K-series builds. We'll be exploring for ourselves the truths and myths that empower the coveted r/s ratio theory as it applies to our beloved K engine platform. This is a classic benchracer's topic that we may be able to demystify, disprove or uphold popular and accepted practices. But that's not really the priority for these rods, we just want to make more power. Of course, we know displacement is king but we wanna have fun because we can.

And now for the introductions:

A "perfect" 2100cc, 2:1 r/s ratio - AKA our "RPM" motor

A "lousy" 2672cc, 1.42:1 r/s ratio - this is the slugger.

It's like pitting sugar ray vs. tyson.

It wasn't possible to isolate identical displacement for the two motors and meet my requirements for power. And finally, I have a 3rd combo that in my opinion has the best of both worlds:

2415cc 1.67:1 r/s ratio

It has a very good amount of stroke, but will be easy on the side-loading because I don't intend on rebuilding this motor frequently.

I think this last combo will be akin to Muhammad Ali.


-Ron

 

****** baller

 

My money is on the "lousy" motor

 

Your posts are always informative, insightful, and actually make a real contribution to HT

But back to keepin' it real....Dat **** iz sick son!!!
Can't wait to see how these motors compare, I got my money on Tyson, that motor should be just like him....CRAZY (btw he's fighting this weekend)

 

stroke and bore are also relevant. ~2:1 r/s ratio will have less sideloading than 1.4/1 r/s engine with the same stroke and bore, but if the stroke of the former is much greater than that of the latter, more mass is located farther from the crank centerline, which will make for more harmonics- even without the rods/pistons attached, the larger crank will bend and twist more when spinning at the same rpm as the smaller (bare) crank. so, while the piston acceleration rate may seem reasonable to make the bigger engine breath well, the lower end might shake apart before it can see enough rpm.

also, piston speed is determined by the stroke, so you could have an engine with a higher r/s ratio and a longer stroke which still can't breath as well at higher rpm as one with a shorter stroke and r/s ratio if the head can't support it.

as for sideloading, an F1-type engine with relatively small bore and stroke, but which is oversquare (bore exceeeds stroke) will likely have less sideloading and piston speed at a higher rpm than, say, the more 'square' b17a at ~1/2 the rpm. the bore, as well as the stroke and r/s ratio will affect sideloading and friction; larger bore = more surface contact area and > angularity from crank pins to OD of the piston.

hopefully this makes sense; excuse me if it's not so articulate.

 

i got my money on the 2:1 motor
ahh who am i kidding ...i want it to win but if its a strret motor i wont ..
as long as theres cams and compression to match it up ....oh i cant wait for the sound ....


what are you doing for cranks ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by machine4321 &raquo;</TD></TR><TR><TD CLASS="quote">what are you doing for cranks ?</TD></TR></TABLE>



https://honda-tech.com/zerothread?id=1195734

That pic and thread describes the very same process, but it's an 88mm crank the Castillo's did for us last month. Joe and Rudy should be finishing up the 105mm and the 95mm cranks for the 2672cc and 2415cc motors this week.

-Ron

 

OMG

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote">stroke and bore are also relevant. ~2:1 r/s ratio will have less sideloading than 1.4/1 r/s engine with the same stroke and bore, but if the stroke of the former is much greater than that of the latter, more mass is located farther from the crank centerline, which will make for more harmonics- even without the rods/pistons attached, the larger crank will bend and twist more when spinning at the same rpm as the smaller (bare) crank. so, while the piston acceleration rate may seem reasonable to make the bigger engine breath well, the lower end might shake apart before it can see enough rpm.

also, piston speed is determined by the stroke, so you could have an engine with a higher r/s ratio and a longer stroke which still can't breath as well at higher rpm as one with a shorter stroke and r/s ratio if the head can't support it.

as for sideloading, an F1-type engine with relatively small bore and stroke, but which is oversquare (bore exceeeds stroke) will likely have less sideloading and piston speed at a higher rpm than, say, the more 'square' b17a at ~1/2 the rpm. the bore, as well as the stroke and r/s ratio will affect sideloading and friction; larger bore = more surface contact area and &gt; angularity from crank pins to OD of the piston.

hopefully this makes sense; excuse me if it's not so articulate. </TD></TR></TABLE>

Yes, I forgot to mention that I am controlling bore size. It is 90mm bore common to all the combos. The cylinder head responds very well from just a valve job and minor bowl-work, without even touching the ports! We picked up 22cfm @ .500" over stock: 296cfm vs. 318cfm @ .500". Can't wait for the crazy 350-370cfm heads.

-Ron

 

props. can't wait to see how things will turn out.

 

as much as people like porting, many heads do better with material added/welded in, so the strokers might actually be better able to take advantage of more piggish stock ports.

what i've read is consistent with your findings; the valvejob is of primary importance, the bowls next, the ports/manifolding last. everything has to work around producing the fastest, most complete combustion event. bulk flow and velocity are only important insofar as the gas can be burned better.

 

i would think the smaller ports would help with the higher r/s ratio's and the the larger would benifit more by having large amounts of a/f ready in short periods of time

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote">as much as people like porting, many heads do better with material added/welded in, so the strokers might actually be better able to take advantage of more piggish stock ports. </TD></TR></TABLE>

Well, that is a topic under heavy debate among head porters. Some seem to see big results by removing a lot, others by adding.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by edo &raquo;</TD></TR><TR><TD CLASS="quote">

Yes, I forgot to mention that I am controlling bore size. It is 90mm bore common to all the combos. The cylinder head responds very well from just a valve job and minor bowl-work, without even touching the ports! We picked up 22cfm @ .500" over stock: 296cfm vs. 318cfm @ .500". Can't wait for the crazy 350-370cfm heads.

-Ron</TD></TR></TABLE>

how i envy 296cfm in stock form, thats ~ what a average ported b head flows. sigh we should all take this moment to bow down to the K.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rochesterricer &raquo;</TD></TR><TR><TD CLASS="quote">Well, that is a topic under heavy debate among head porters. Some seem to see big results by removing a lot, others by adding.</TD></TR></TABLE>

if you're after bulk flow, hog it out- but you'll likely lose velocity if everything else is =, and the faster moving air better atomizes/suspends fuel and helps it light and burn faster and more completely. all that you need is to flow the right amount of air as fast as possible. any more at the cost of speed is a waste. air doesn't burn and produce energy; fuel does.

 

Well, it is a little more complicated than that. Which is why all things are not equal. That is getting OT though.

 

Hey B19coupe off subject, You're in D-Sport this month! I was sittin at work today lookin through it on lunch , and was like, " thats b19coupe!" lol.

 

Cool
Guess I need to go find a copy.

 

PM'd

 

edo, what has happened with your engines? I saw one dyno for a 2.2l I think. Weren't you building several different ones? Any updates? Thanks..

 

I have quite a collection of very unique coffee tables:

2672cc (NA)
2415cc (NA)
2140cc (turbo)
2100cc (2:1 r/s ratio - NA)
2308cc (SC - going into a car maybe soon)

Only motor to date that's run is the 2240cc original dev combo

-Ron

 

Any reason WHY they are coffee tables? still waiting on some parts?

 

waiting on dry sumps

-Ron

 

interesting tests there ...

on the k/e prepped cranks, any more (or less) flexing from high RPMS ? or you can't tell ?

 

Well coming from a guy who runs a b17 crank with b16 rods attached to custom compression height ARIAS pistons, i'm a little biased . I'm voting for the compromise motor, cause i can relate to it. JFYI: my b-series has a 1.65 R/S ratio and a kansas flat torque curve.