K24a2(rbb) vs. k20a(rsp) head

allmotor98 · Sep 26, 2012

I thought i would start a new thread for searching purposes and for any future builds out there.

This is my build thread with the k24a2 head http://www.k20a.org/forum/showthread.php?t=75424

Well after the setup was dyno tuned it became apparent that something was not right as the motor was not putting down the expected power and the vtc was all over the board and wanting 40deg. Vtc all the way to redline. Which is how this thread started http://www.k20a.org/forum/showthread.php?t=77640. After some trouble shooting and coming up empty handed. There was only one thing left to do. Swap the head!

I was able to pickup an rsp head from morgan at synapseturbo.com. Threw in some supertech valves as the head was new and i didnt want to use the orginal tsx valves that came in the longblock.

Well i installed it last week and morgan was able to get me in for a retune. Needless to say i very happy with the out come. The motor picked up 20+hp and is ready to be pushed further as my rev limit is only set to 8000. I plan to swap out some minor bolt ons and tune on e85 as i am running 93 oct.

Here is the motor with k24a2 head

BlackNDecker · Sep 26, 2012

It would be awesome if you could show the two curves overlaid on the same graph:up:

Nice results though!

6spd_EK · Sep 26, 2012

Unfortunately the graphs are on to separate dynapack harddrives so there are only 2 separate graphs. I'll see if I can photoshop one onto the other of/when I get a chance

Vaikis_ · Sep 26, 2012

seems that k24a2 head not very good for CR 12.5:1, but it's strange for me. Here one guy in TSX club made good power with this K24a2 head:
http://www.tsxclub.com/forums/1st-gen-engine/54146-project-special-k-has-begun.html

allmotor98 · Sep 26, 2012

Is there a dyno graph of this car? The numbers weren't my only concern. The way the the power just flat lines at 6500 is what wasnt making any sense. Once the new graph is posted it will be very apparent. This head change the game on what this motor is capable of. Mind you it's an OEM stock port(untouched) head!

allmotor98 · Sep 26, 2012

And to add to the above if im not mistaken the blueprints are a bigger cam. I could have dropped bigger cams in my setup and probably make more power, but i dont think it would change the curve. It would probably just move it up. By swapping the head i unlocked power that was already there. That guy might benefit the same.

6spd_EK · Sep 26, 2012

I plotted points every 500 rpm here is the MSpaint overlay LOL

NABeastRR · Sep 26, 2012

Which year k24 head is this?

allmotor98 · Sep 27, 2012

'05

DRAG said:
The RBB should have never been made LOL. Good thing their mistake is easily fixed

The power gain should not surprise anyone at all. The RSP is in a class of its own compared to the RBB. In the flow areas that matter, the RSP is 20-35 cfm better...so 20hp is realistic. CFM aside, it has a better port shape all around. Though recently I saw suggestions here that we need to start flowing heads below .150 lift :blur: Here is a good first example...maybe I could have a few hundred customers share their examples. '04of that theory being put to rest.

i wouldn'te say i was surprised, more glad to figure out what was causing the poor readings on the dyno.

signalpuke said:
Are they around 500ish?

the head cost 1100. And the last i checked which was a few months ago there was only one in the u.s.

CJM · Sep 26, 2012

I recall larry of endyn saying performance wise, Honda got it backwards.

the RBB head shouldve been on the 2.0's and the RBC/RRC/PRB etc shouldve been on the 2.4's

DRAG · Sep 26, 2012

The RBB should have never been made LOL. Good thing their mistake is easily fixed

The power gain should not surprise anyone at all. The RSP is in a class of its own compared to the RBB. In the flow areas that matter, the RSP is 20-35 cfm better...so 20hp is realistic. CFM aside, it has a better port shape all around. Though recently I saw suggestions here that we need to start flowing heads below .150 lift :blur: Here is a good first example...maybe I could have a few hundred customers share their examples of that theory being put to rest.

BlackNDecker · Sep 27, 2012

DRAG said:
Though recently I saw suggestions here that we need to start flowing heads below .150 lift :blur: Here is a good first example...maybe I could have a few hundred customers share their examples of that theory being put to rest.

When Joe McCarthy posted that I immediately thought of you and how you might respond....care to elaborate further? Any thoughts on where in the RPM range < 0.150 lift is happening?

CJM · Sep 26, 2012

bare RSP heads are available brand new from Honda. . . . not as much as you may think

signalpuke · Sep 26, 2012

Are they around 500ish?

DRAG · Sep 26, 2012

About the same $ as port work that gets you another 30-70 cfm on top of the RSP even.

CJM · Sep 27, 2012

theres 3 available right now

head, guides, cam towers, tower bolts.

no rocker shafts

allmotor98 · Sep 27, 2012

Yep thats sounds right. 3 huh. Well it was a few month since i last checked.

CHILD · Feb 11, 2013

This is interesting.

Does the 06-08 RBB head flow better than the 04-05, or where the changes to the 06-08 just in the camshafts and oversized intake valves?

DRAG · Feb 11, 2013

I still love tests like this. You have a direct comparison on a simple engine...a head with a small port and high air speed VS a bigger port with better flow at higher lift and slower air.

Figment-The-Dragon · Feb 12, 2013

:like:

BlackNDecker · Mar 31, 2013

Bumping this up again. In for updates now that things are starting to thaw out...:devil:

K4NEB · May 5, 2013

Hey guys I just picked up an RSP K20Z4 head for my K24A3 (same as your K24A2)
Im guessing this was a good move?

What cams where used in this comparison?

Vaikis_ · May 5, 2013

good move.
stage 2 cams if to be more precise IPS KME camshafts.

NABeastRR · May 5, 2013

Dc 2.2

BlackNDecker · May 6, 2013

Who were you responding to? This build is using IPS KME cams as discussed here:
http://www.k20a.org/forum/showpost.php?p=1018100&postcount=1

K4NEB · May 9, 2013

K4NEB · May 10, 2013

Sorry. Thought it might have been helpfull to have another dyno sheet to look at that's all.

Bum smack received :-(

6spd_EK · Dec 4, 2013

back from the dead with another test on a different motor

2008 stock TSX (longblock) with:
RRC IM, Injen Intake, P2R TB spacer, Header & exhaust

before stock RBB head with stock valves (+1mm oem intake)

after RSP with Ferrea 6000 (std size) valves. Gained 19whp up top! fyi we were able to eliminate the tq dip from 5000-5700 with a stepped intake w/velocity stack. Getting that to fit is another story LOL

AWH · Dec 6, 2013

6spd_EK said:
after RSP with Ferrea 6000 (std size) valves. Gained 19whp up top!

Thanks for posting, Greg. Love this kind of stuff. I still refer back to the original comparison in this thread often. Helped me in the decision to buy one of Luke's heads. And now another one... :up:

fyi we were able to eliminate the tq dip from 5000-5700 with a stepped intake w/velocity stack. Getting that to fit is another story LOL

Help me on this one. Was this elimination done after these graphs, before or between? And what size/lengths did you step between? :huh:

CHILD · Dec 4, 2013

So that's basically the difference between the worst flowing head and the best, right? (excuse my noobness lol)

6spd_EK · Dec 5, 2013

CHILD said:
So that's basically the difference between the worst flowing OEM head and the best, right? (excuse my noobness lol) on a mild setup with stock compression , only rev'ing to 7400 when the head will flow to 9k

Fixed & yea that sums it up... I'll add it appears there could be a restriction in the intake track that rears its head around 6500 to redline according to the map sensor. Probably good for a few more ponies. It's not the actual intake either

BlackNDecker · Dec 5, 2013

Once again, the 20 cfm additional flow yields ~ 20 additional peak hp on both the stage 2 and stock cam motors. Thanks for sharing:up:

This latest test was with the OEM TSX header and exhaust?

6spd_EK · Dec 5, 2013

Sorry I wasn't clear, hytech header & hytech 2.5" exhaust with a catalytic converter

BlackNDecker · Dec 5, 2013

It's interesting that the stock cam'd motor made power everywhere compared with the IPS KME cam'd motor that lost hp and tq just before vtec. We're y'all ever able to tune that power dip out on the first motor?

6spd_EK · Dec 5, 2013

I mentioned earlier in the thread Larry and/or Luke alluded to the fact they've seen castings vary from bad to worse. Another friend mention he thought rbb castings got worse after 06. The built motor was running an older head. Maybe just coincidence or maybe those guys are right. On the stock motor it Could also be a combination of ferrea 6000 valves? Who knows

Power dip on the KME motor? Are you refering to the low cam? I mentioned ealier we load the dyno at a higher rpm? If so that's so the car can avoid pinging (pump gas + 12.5cr). Ignition timing and vtc is also conservative to help reduce the chances.

Same intake tested on the stock car was tested on the 2.4 kme car & did this

6spd_EK said:
here is a graph from Allmotor98's K24 (12.5 IPS KME RRC DTR header) No tuning - I bet we could have picked up some more power up top with tuning & adjusting vtc

FYI the a/f dipped real rich at 6750 (hence the same power)

Edit: You can also see here one pull the load point was 3250 and the other pull was 3500

BlackNDecker · Dec 5, 2013

Yeah, I was referring to the low cam in the third dyno graph in this thread (aka your MS paint overlay). Thanks for clarifying.

BTW, did I ever PM you about your CNC RSP v-stacks and my idea for a cnc center feed lower plenum?

K24a2(rbb) vs. k20a(rsp) head

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