26 Jan S2000 K Swap
S2000 K Swap: Blasphemy or the Next Big Thing?
By Brian Gillespie
Photos by Loi Song
Video by Aaron Gaghagen
When Honda dropped the AP1 S2000 on us back at the turn of the century, it was the baddest Honda you could buy. Yes, there was the Integra Type R and the NSX, but the Type R felt familiar and the NSX was a bit long in the tooth. The S2000 was new and a departure from what Honda was doing at the time. It was the buffed-out convertible that looked as good as it went. As good as the Mazda Miata (yuck-AG) handled, it was always kind of a rag top punchline for most people. That wasn’t the case with the S2000. It was a rear-wheel-drive, front-engine driver’s car. The manual transmission that it was only available with shifted with razor-like precision. Honda didn’t water the S2000 down with an automatic transmission like other manufacturers would do. No, this was the car for people who “got it.”
Even in stock form the S2000 is a thing of beauty. The amount of smart, efficient engineering that went in to it was unrivaled in it's time. (Photo courtesy of American Honda)
Then there was the engine; the S2000’s 2.0L F20C1 had the highest specific horsepower output of any naturally aspirated mass-production engine ever. It begged to be revved to the high heavens like all great VTEC powerplants. And then with the AP2 S2000 displacement was bumped to 2.2L, giving it more torque and making it a bit more forgiving for drivers who didn’t want to keep it at 9,000 RPM all the time. And people loved it.
So, if the F20C1 and F22C1 are such great engines, then why would anyone in their right mind ever think about swapping in a K-series engine? First, K-series engines are cheaper than F-series engines. Honda and Acura put Ks in millions of vehicles over a wide range of models whereas the Fs (not including older F-series that were in Accords and Preludes) were only put in S2000s. Second, there are more tuning options for the K-series. From headers to intakes to cams to pistons to rods to you name it, it’s all available for the K from many different sources.
The S2000 here is Loi Song’s from Sportcar Motion. His F22C1 blew while racing and he decided it was time to take the road less traveled by S2000 owners by going with a K24A2 using the Hasport Performance APK2 kit. He can make more horsepower with the K-series and with a bunch more torque. Hell, even if the F-series was in perfect shape, a K swap could be the smart move for racers. You could take out the more expensive engine, race with the K swap, and save the wear and tear on your F-series.
Prepping the engine
The swap starts with this. This is a F2K transmission adapter plate. Its made by Ballade Sports. Without it, you can't mount the engine to the transmission. Get yours at http://www.balladesports.com
Along with the adapter plate a key part of the swap is a Clutchmasters K to F flywheel. The clutch plate contact ring is spaced a half inch to compensate for the half inch thick adapter plate for the transmission. You can't just put a half inch spacer behind the stock flywheel. That would move the ring gear away from the starter and it would no longer be able to engage it.
Here is the engine with the adapter plate bolted on as well. It just needs the clutch and the tranny now.
The starter bolted in place.
JSP Fab makes the intake manifold adapter so you can bolt the F20 intake manifolds on the K-series engine. The intake manifold adapter is designed to be used with the K20 head found on the RSX. If you have a TSX style head you'll also need this adapter for the thermostat water bypass hose. This one is made by K-Tuned.
The reason for the adapter plate is the stock K24 manifold won't work since it would place the throttle body pointing at the firewall. Another big plus for using the stock manifold is no changes need to be made to the fuel system and throttle control.
Glamor shot with mood lighting. Bolt the clutch on next and time for the transmission.
The two studs sticking from the the side of the head are where the upper radiator hose outlet is connected. The stock one would stick out straight towards the firewall.
JSP Fab to the rescue again. They make this adapter plate that changes the outlet to a friendlier angle. But it's still tight.
The old and the new. Don't get me wrong, the F20 is a marvelous engine. Truthfully though, the K24 makes more torque, has more aftermarket support and is less expensive to modify.
Part of the belt routing on the K-series includes the idler pulley. Unfortunately it interferes with the throttle position sensor on the F20 throttle body.
A saw, a die grinder and a few minutes later the clearance issue if fixed. Not pretty, but effective. I see a future product here.
Mount up!
There are only two mount kits for the K-series into S2000 chassis. Sportcar Motion opted to go with the APK2 kit from Hasport Performance with 70A urethane for a little extra engine control.
The Hasport APK2 K-series swap kit uses mounts on each side like the stock mounts. Also, it's dual height. In the higher position is identical to the stock height of the F20. The lower position the valve cover clear the hood and the head on the taller K24 stays in virtually the same position as the K20 head. Headers, intakes and turbo manifolds fit in the same position in the car regardless of which engine is used. The stock rear mount is used with the kit.
You can see in the picture of the right-hand mount, there are two mount holes for mounting the engine at different heights. The lower hole if for K20 engines and the upper hole is for the taller K24. The dual height, eliminates the need for different turbo kits for the K20 and K24 blocks. The parts fit the same regardless of the block.
The view from under. The AP1 transmission bolted to the adapter plate on the K24 block. Ground clearance is approximately the same, with th adapter plate hanging down only slightly.
The stiffener that bolts to the front subframe interferes with the new oil pan of the K-series engine.
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There is a stiffer that bolts to the subframe. In order to get the stiffener to fit, the crew at Sportcar Motion modified theirs by cutting the section of tube that touched the oil pan and welding on a new one in. Brilliant and cheap.
Which Wire Where Scare
This is the an RSX and S2000 engine harnesses. The two must become one so they can be stronger than the sum of their individual parts. Sounds kind of Zen doesn't it. The wiring is actually the hardest part of this engine swap. The RSX harness gets modified to work with the S2000 body harness and the one ECU plug that is connected to the body harness needs to be modified to work with the Hondata K-Pro ECU.
These three plugs connect the RSX engine harness to the ECU and the car's body harness. The long grey plug is the RSX's C101 plug. It's job is to interface with the car's body harness.
This is the C101 plug for the S2000's engine harness. Putting this plug on the RSX engine harness will allow it to connect to the S2000's body harness.
These are the pinouts for the two different C101 plugs. The conversion is made one wire at a time.
With the C101 connector modified we turn our attention to the harness and how it fits the engine. For the most part the RSX harness fits the K-series engine. Some wires need to be extended to work with the new S2000 intake manifold.
Along with TPS and MAP sensor plugs getting lengthened on the harness the vehicle speed sensor connector is modified. The RSX's VSS uses 12V to power the sensor, the S2000 uses a 5V powered CSS with a different connector. Then that needs to be lengthened to reach back to transmission. The electronic idle control valve and intake air temp wires need to be lengthened too.
With the connections soldered and shrink tubed, its time to wrap this thing up. If you've never done wiring before you may want to wait to wrap it up after you've fired the engine up with no MIL codes.
The engine harness has been buttoned up and the shorter serpentine belt installed since we aren't mounting AC.
Rad Man
With the engine installed you can see why you need the JSP upper radiator hose outlet. The stock outlet comes out at a 45° angle, but the JSP outlet makes a tight turn to clear the firewall.
The upper radiator hose needed to be long to reach all the way to the back of the engine. This one from Gates, part number 21707, was more than long enough. Some of the leftover was used on the lower radiator hose.
The lower radiator hose was cobbled together from two sections of hose with the right curves. This short adapter from JSP was used to join the two sections together.
You can see the two sections of hose that have been joined together
Not shown are the heater hoses. Bulk hose available at any part store where used to connect the engine's heater core. A trick little billet overflow finishes off the cooling system.
A Breath of Fresh Air
The molded rubber radiator hose cleared the stock air box nicely. Now it's time to make the connection between the throttle body and air filter.
An custom air tube was fabbed up to connect the t-body with the stock air filter. With TiG welding skills you too could whip up a nice intake air tube like this one.
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If you were to paint it black. It would look stock.
Venting
This reservoir connects to the crank case vent system.
In Conclusion…
We went with Loi to Dardan Tuning to see what his S2000’s new power plant would put down on the dyno. With some tuning this engine has the potential to do way more than what the original F22 could ever hope for with the same level of modification.
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