Honda / Acura K20a K24a Engine Forum banner

41 - 60 of 90 Posts

·
Registered
Joined
·
21,788 Posts
lol, jdm4lyf works here at AFH. He's a tech.

he was posting from his phone, hence the horrid grammar and spelling.

he's been talking to ryan, rich, and myself about his motor build and is conflicted by what he wants to do. Were trying to explain and show him the way. I Had no clue of these posts til he just asked me some q's and telling me about this thread.

he's learning
 

·
Registered
Joined
·
188 Posts
Ok so let's get back to it shall we :)
Can we talk about difference between cams with large lift VS long duration and what the gain is? I'm under the impression that high rev, short stroke motors use long duration in order to "inertial supercharge" NA motors?
Large lift with shorter duration used to gain torque in the midrange but sacrifice peak HP at rev limit?
And then there is the Really Big profiles that I can only imagine are for large displacement high rev motors??
Any info appreciated :up:
 

·
Premium Member
Joined
·
19,965 Posts
Ok so let's get back to it shall we :)
Can we talk about difference between cams with large lift VS long duration and what the gain is? I'm under the impression that high rev, short stroke motors use long duration in order to "inertial supercharge" NA motors?
Large lift with shorter duration used to gain torque in the midrange but sacrifice peak HP at rev limit?
And then there is the Really Big profiles that I can only imagine are for large displacement high rev motors??
Any info appreciated :up:
if what I remember niko saying..short stroke engines don't allow for as long of a duration as long stroke engines do. High revving engine do make better use of valve overlap though IIRC.
 

·
Registered
Joined
·
12 Posts
hi guys, is there a performance difference with installing cams inland vs installing cams down at the coast?
for guys that live inland above sea level is it beneficial to install cams?
 

·
Premium Member
Joined
·
19,965 Posts
hi guys, is there a performance difference with installing cams inland vs installing cams down at the coast?
for guys that live inland above sea level is it beneficial to install cams?
it's beneficial everywhere.
 

·
Registered
Joined
·
4,294,967,295 Posts

·
Registered
Joined
·
182 Posts
if what I remember niko saying..short stroke engines don't allow for as long of a duration as long stroke engines do. High revving engine do make better use of valve overlap though IIRC.
I've got a set of cams here which i initially bought to go into a std K20a2 block (with springs/seals/adj.gear) but i'll be keeping them aside for a built 2.0. Plans at the moment are to run a 78.5mm crank and 90mm bore with +1mm inlet valves/de-shrouding as i'm restricted by class to keep it at around 2000cc.

Spec of the cams i have are just under 250 duration at 1mm with around 14mm lift on the intake and just over 240 deg duration at 1mm with around 13mm on the exhaust. From looking around at other specs the only cams close to these are the likes of DC 3.2's although the new Kelford B2's seem to be designed along similar lines. I'd need to check what my primaries are.

Am i right in thinking these would be spot on for a SS motor then with the relatively short duration and high lift? What would be the effect changing to a longer duration whilst retaining similar lift? Will these help what will be my midrange even though my power band and TQ will move to the right?
 

·
Registered
Joined
·
15,818 Posts
My 212.4 is 0.550.inches.but significantly longer duration.by a lot.

Heres when we documented our R25 design aka 212.4 Intake lobe 0.550 zero Lash

Its more than.just specs but its great to see someone is at least trying . That is great. Thank you Kelford

View attachment 32960
 

·
Registered
Joined
·
15,818 Posts
Doug yes spunds like a good combo.for k24 not peaky . I have a graph from a .550 will post it later
 

·
Registered
Joined
·
182 Posts
Cheers Nikos although it's for a short stroke K20 built for hill climbs. Unfortunately i need to stick to a 2000cc class or i wouldn't give a K24 a second thought.

So with retaining the same lift what effect would increasing the duration have on the overall output of the engine? i.e, peak hp, peak, tq, where it comes in, spread etc?
 

·
Registered
Joined
·
15,818 Posts
Doug, here's the graph

https://lh6.googleusercontent.com/-RxUZ4DS_-nM/UL9ShM5cZzI/AAAAAAAACWw/WnKVxPtdaRU/s1423/k24+with+212.4.JPG

thats the car

https://lh3.googleusercontent.com/-evSxzdJkj-c/UKARLzSvKTI/AAAAAAAABis/9owIynY3jIg/s720/212.jpg

Mods

12.5 compression
CP Piston 87.5mm
CP Carrillo I Beam rods
Mirco Polish Crank
APR Main Stud
Upgrade K20a Oil Pump
Jtune Baffle Sump
Full Block debur
K Tuned Water Pump and Powersteer Pump Deleted


Cylinder Head Spec: (ie. Cams, porting etc…)
Drag Cartel Prep Head USA
CNC Port by Portflow USA
SVM 212.4 Camshalfs
Racing Oversize Valve
Racing Valve Springs
Titanium Retainer
Adjustable Cam Gear
ARP Headstud
OEM Headgasket
Toda Chain Tensioner
Toda Timing Chain


For 2 liter, we have something else, 212 that would be a good match against these. I am anxious for someone to test these. thank you for letting us know
 

·
Registered
Joined
·
15,818 Posts
valves staying open longer would mean more potential for more energy but you are asking about duration as it is not related to lift and valve motion.

So for a given lift and head flow characteristics like an OEM honda head, under the valve motion model to keep jerk as low as possible and everything working great, duration is what it has to be.

We also do not split duration and intake and exhaust together is what makes the whole thing work.

Porsche Gt3, porsche cup engines, M3 racing engines etc etc use close to 290 duration and we only go that high on lifts beyond 600 if the valve motion can handle it.

One of the reasons behind this is harmonics but from a frequency point of view.

The truth is that you can put anything on these lobes and the engine might run and might even make some power but doing it the right way and saving tensioners on the way and not breaking chains or cam cores or engines or heads, or rollers, means that you have to follow all rules and design with honda oem valve motion is mind which is based on the geometry and nothing else.. The cams do not know what head you are using, or fuel or compression, only they tell the valves is how to open and close and the rest is HP somehow.


Let's assume at 6000 RPM, you are using a spring with 27000 cycle per minute natural frequency its around the 9th harmonic.. as RPM goes up, harmonic order goes down. At 9000 RPM, if you do not have control of these things, specs do not matter.

That is why there is a great aftermarket tensioner market because noone in their right mind will take the time to expain why to an audience full of doubters, haters and for the most part not serious about performance.

Email me at svmcams.com if you want to talk about this more, not because I want to sell you a set of cams, but to help you understand when I have time to reply.

As long as RPM is kept under 7000 rpm on normal cars, bad design habits will not show themselves as much... the higher the RPM the greater the need for precise opening and closing of the valve with velocities and accelerations all working the same way on each cylinder and minimum deflection at high rpm, all these things make a difference, a huge difference.
 

·
Registered
Joined
·
4,294,967,295 Posts
Welcome to the site. Please see the DIY|FAQ list, link is in my signature. Many threads there that pertain to common questions and good threads from the users here.
Also, check the sticky'd threads in the different sections. Most of the engine specific threads are in the Engine Building section. The thread you are looking for is there.
http://www.k20a.org/forum/showthread.php?t=10907
 
41 - 60 of 90 Posts
Top