Being a K-series rainman hurts my brain. Here’s a slew of trivial K-series things the average joe may or may not know…
IACV cross compatibility
IACV’s from the following engine/vehicles are cross compatible with OEM RSX Type-S K20A2/K20Z1 + aftermarket throttle body’s due to sharing the same IACV mounting flange pattern:
- 02-04 CRV (K24A1)
- 02-06 Base RSX (K20A3)
- 02-05 Civic Si (K20A3)
03-05 Accord, 03-06 Element and JDM 03-08 CL7 K20A all share the same IACV’s that are NOT cross compatible with the RSX Type-S throttlebody nor aftermarket equivalent because of their different IACV flange mounting pattern.
OEM (DBC) Throttle Body’s that are RBC/RRC/*RSP Manifold Compatible
The oem 03-05 Accord + 03-06 Element drive by cable and the semi-rare JDM CL7 K20A tb all share the same RBC throttle body flange bolt pattern. Meaning, they can all bolt up to an RBC or RRC intake manifolds without the aide of a throttle body adapter plate. The accord/element tb has a small bore of 59-60mm; CL7 tb has a 62mm normal bore size (same as K20A2/Z1 tb). The accord/element tb has a throttle pulley that supports cruise control; CL7 tb does not have cruise control throttle pulley support. Both of these throttle bodies share their own type of flanged IACV that are not compatible with any other oem K-series tb’s such as the RSX Type-S or JDM DC5/EP3 Type-R tb’s.
*The RSP manifold can support these two throttlebody’s as well but a special tb adapter plate is required in order to compensate for the RSP’s short tb flange that excludes an IACV provision.
K20A2 vs K20Z1 OEM Throttle Body Differences
The 02-04 K20A2 and 05-06 K20Z1 oem throttle body’s might look identical on the exterior but have one small but major difference: the MAP sensor vacuum source. If you take a gander on the backside of either of these tb’s, you will find the K20A2 tb’s map sensor vac source has a small recessed channel that runs parallel to the bore and then accesses the bore – this is a long running style Honda has always used with most of their tb’s (before K-series). The K20Z1 tb is an updated travesty that uses a single small vac hole that relies on the K20Z1’s PRB intake manifold’s flange to access the MAP sensor. So using a K20Z1 tb on any other manifold besides a K20Z1 PRB manifold WILL pose as an unforeseen problem. The K20Z1 tb’s MAP sensor vac feed will get choked/blocked when using it on any other manifold or if mounted to a throttle body adapter plate. You will experience engine running issues when revving up past 2500-3500rpm. The engine will stumble past 3500rpm and will be easy to misdiagnose for the unknowing. There are several fixes for this: (1) Grinding a channel from the Z1’s MAP sensor vac hole to the bore mouth (best option as this will forever fix this issue) (2) Using a K20Z1 specific thermal throttle body gasket and modifying the MAP hole by opening the hole via dremel to reach the mouth of the tb bore (3) If using an RBC/RRC/RSP manifold, use the MAP sensor provision on the manifold side instead of off the Z1 throttle body.
02-04 RSX Type-S K20A2 and 02-05 Civic Si EP3 K20A3 both share the same PRB intake manifold and throttle body.
While Honda changed up the wiring and ecu between 02-04 RSX and 05-06 RSX models, they didn’t carry that change over with the 02-05 EP3 Civic Si chassis, it stayed 02-04 wiring/ecu type into 2005.
JDM K24A RBB vs USDM K24A2 suffix number internet overhype
coming shortly.
K24 short block deck height is 19mm(1in) taller than K20 short block deck height.
The 07-09 CRV K24Z1 engine is a unique freak!
While the engine stamp ID is “K24Z1” one would assume its a typical K24Z era engine w/single exhaust port – NOPE! It’s 85% K24A and 15% K24Z. It uses an ECO K24A RAA short block/crank/rods/pistons and an ECO K24A RAA cylinder head (ie. 4-port intake & exhaust port head) + intake manifold, same eco engine you’d find in an 03-07 accord (K24A4), but it uses a K24Z’s girdle with relocated oil filter and does retain a 50 degree VTC gear just like its 02-06 K24A1 predecessor. Also the K24Z1 oil pan (PN# 11200-RZA-000) is interesting, its like an aluminum version of a K20A3 steel pan that caters to a balance shafted oil pump.
The CR-V has always seemed to be Honda’s little secret lil sandbox car.
The USDM 06-08 K24A2 TSX received updated engine components the rest of the world did not receive.
Particularly, the intake camshaft (larger profile), larger plenum RBB intake manifold, larger bore tb, 1mm larger (36mm) intake valves (altho useless/non power adders because the valve seat is still 35mm), and beefier rods at the big end. Again, there’s a lot of dumb internet hype surrounding this specific engine with the purists blowing their load over a few hp gains when comparing to the older 04-05 K24A2 variant and JDM K24A RBB variant (which is equivalent to our 04-05 K4A2).
Moving on, the 09-14 TSX K24Z7 and 12-15 Civic Si K24Z3 engines both share the same large profile intake camshaft, and its possible to use in a previous gen K24A RBB series engines if desired. The K24Z (R44) cam gear MUST BE USED as the K24Z intake camshaft is a few millimeters shorter than a K24A2/RBB intake camshaft and the R44 cam gear compensates for that. The K24Z cam lobes are narrower than the K24 RBB cam lobes but this doesn’t pose as a problem to the K24A roller rockers at all.
The K24Z VTEC lobe is a little smaller than the 06-08 K24A2 intake cam but the K24Z’s smaller primary + secondary (non-vtec) lobes have larger profiles than the 06-08 intake cams non-vtec lobes, meaning you will/should make a little more power before VTEC crossover with the K24Z cam, but the 06-08 K24A2 intake cam could make more power on the VTEC lobe due to having a slightly larger profile. Something to think about if you’re hunting for the most power with OEM parts.
Upgrading to a 50 degree VTC gear on a performance K24A engine will unlock some fatty mid range power once tuned.
…more soon