K20/K24 build (with dyno chart)

[Richard Buckingham]

Hi all,

I've not been very active on the forums in the last year whilst I've been away from the car and the track but now I'm back as you might have seen as I'm selling lots of bits in the Marketplace Forum that are left over from my recent build.

In mid 2015 I decided to add some downforce to the car however the SRA with a K24 and only 230HP (TMI claim for power from the crank) doesn't have enough power to overcome the drag of the wings, so whilst handling and cornering is massively improved the actual lap times are not. I had already considered doing some power upgrades anyway so I decided in late 2015 to just go ahead and do a K20 head swap. My car at the time was also having some engine issues so I parked it until the engine work was complete.

Initially I was going to go alone and just source a replacement head and be done with it, however instead I worked with Mike Kojima (Motoiq.com) to come jump with a proposal for what else we could do, he could help me with some parts via some marketing and promotional work, I would get his expertise.

Build was designed as follows:

K24Z7 from my 2012 SRA.
K20Z3 head, CNC port work by Drag Cartel.
Drag Cartel cams.
Supertech Springs and Valves.
RBC Intake Manifold & Adaptor
JDX Throttle Body
RDX Injectors
JE Pistons & Rings 11.5:1 compression
K1 Rods
King Bearings
Burns Stainless custom Header & Megaphone exhaust.
ACT Spec Mini Twin Clutch
Dailey Engineering DrySump, Peterson Oil Tank
ATI Damper

Some issues to overcome:

We knew the drysump wouldn't quite fit into the Atom chassis so we had to do some cutting (took out about a 6" section) and then we added addtional bracing in 4 places to ensure strength, geometry and rigidity of the chassis was not affected.

Turns out the larger intake manifold meant we had to shave off some bits too in order to get the built engine back in place. Fortunately this was an easy job.

To tune the car you need a Hondata FlashPro from TMI, fortunately Hondata are local and between them and Jesse at TMI they hooked me up so I could pick one up direct from Hondata ($695!)

Dyno run #1.

We took the car to our local Honda genius Shawn Church at Churches Automotive Testing. He advised us to go with a conservative redline of 8,400 RPM for better long term reliability, hitting a very respectable 293whp (running on California 91 octane) Shawn said we're running out of air above 7,300 RPM and the air intake needed improving and we could probably get 10-15 more HP.

So next I took the car to Moti at Blackbird Fabworx to fabricate me a better air intake. Mike provided us with a new cone filter and velocity stack from Jim Wolf Technology and we decided to just go with a simple silicon hose going as straight as we could into the Throttle body avoiding the use of the scoop and ram air effect completely; we'll go for a more elegent solution later but this one works perfectly well as is.

Moti also added some final finishing work; heat shielding for some wires, improved bracing where we cut the chassis, some shielding of the belts to keep out debris and we decided to remove the TMI windscreen and will add a Lexan screen back later, so I have a simple custom dash right now too.

Dyno run #2.

Well Shawn might be an expert but he's not an optimist, we got an extra 19HP just from changing out the filter and air box for a simple cone filter and pipe. Hitting 312whp at 8,000 RPM and massive Torque improvements everywhere.

On the dyno equipment Shawn runs (bolt on so you don't spin wheels only axles, see pic below) he estimates a loss of 30-35 HP on my car so we're looking at 342-347HP from an NA 2.4L 4-banger. Not too shabby.

Dyno comparing runs 1 and 2:
IMG_4959.jpg

FYI: the build was also somewhat inspired by the success that Jason Payne had with his custom build described here though he saw 278whp on the dyno even accounting for the different equipment we superceded those numbers by quite a margin, probably from the header mostly, I'm still running a mechanical water pump which is about the only other component change I could do that would add more power but we decided to keep it for reliability instead. Lane also swapped out the stock intake for something of his own design which I haven't seen and also got a huge 14HP gain over factory.

Read more about the build on motoiq.com:
Part 1
Part 2
Part 3

Header:
IMG_4764.jpg

New Intake:
IMG_4964.jpg

[cvjoint]

Very nice build! Does the engine now have the best VTEC design, say comparable to the best of the K20 breed? I love the build, lots of good ideas. Good to know there is no drysump that fits the Atom. For how much G is the original pan design in the SRA good for? I was hoping on going to wider tires on my SRA.

[Richard Buckingham]

most guys put larger tires on the rear and have no problems, it depends on lots of factors of course but when I looked at my data logger I could see oil pressure dropping into the single digits on one corner at Buttonwillow and I knew that if I added more downforce I just added to the risk so I went with dry sump for that reason.

The VTEC on the car is the full K20 VTEC on intake and exhaust compared to the K24 which is intake side only.

[cvjoint]

That is so neat, I love that you brought back variable lift on the exhaust valve. I imagine you picked the 11.5 compression to run 91 octane? That $10/gallon 100 octane sure empties the wallet at the track.

I see you are in So. Cal., the turn I would watch for is the bowl at Streets of Willow. It likes to run bearings dry for extended periods of time.

Do you think running a thicker oil can add some extra protection as well? I wouldn't mind the HP loss but I suppose you also loose a bit of oil pressure since it's harder to pump.

[Richard Buckingham]

Yes 11.5 as I'm only intending to run 91 octane, the added power from going higher compression really aren't that great, similarly I could bring up the RPM but risk reliability or I could have removed the mechanical water pump too but I just don't need to push it, 312whp is plenty! I think 5w-30 is just fine in a stock SRA, I don't think the bowl at streets is that bad as its a pretty slow corner, riverside at Buttonwillow is I think the worst one for oil pressure and its sustained Gs.

[cvjoint]

Am I right in thinking the SRA oil cooler is no longer needed because of the dry sump?

[ejo]

Did the Hondata FlashPro allow you to get past the ECU lockout from TMI?

[Richard Buckingham]

Did the Hondata FlashPro allow you to get past the ECU lockout from TMI?

Yes, I mean I'm not sure if that's a TMI thing so much as a Hondata thing but to do any tuning you need to buy a FlashPro from TMI.

[cvjoint]

Ahh interesting, so even though we have a Hondata it's sealed presumably because it's an SRA spec racer.

Richard, how often do you have to adjust valves on this beast?

I was hoping you were going to make it to Sonoma for track day last time. Maybe Laguna Seca next weekend? A bit easier to get there from where you are.

[McFred]

Looks like a quality set of parts there, Richard.

Was there any significant attempts at tuning cam angle or was this a simple air/fuel/ignition remap on some canned CAM?

Thanks for sharing, I would love to hear how much lap times improved with another ±70hp!