Honda K-series Inlet Manifold Information
This page is to help people learn more about the different types of inlet manifold available for the Honda K-series engine and also what inlet manifold comes on different engines as standard.
Here is a list of engine types and the inlet manifolds that come standard on them -
1. K24a / K24a3 / K24a2 - Accord Tsx CL9 - RBB inlet manifold
2. K20a Civic EP3 - PRB inlet manifold
* K20a Integra DC5 - PRC inlet manifold , it looks the same as the PRB but it slightly ported from factory and has the PRC casting stamp.
3. K20z4 - Civic FN2 - RSP inlet manifold
4. K20a Accord Euro-R - RBC inlet manifold
5. K20a Civic FD2 - RRC inlet manifold
The inlet manifolds above are listing in order of there performance abilities , the first one the RBB style is the worst performing. It has a Drive by wire flange for the throttle body and a RBB style flange connection onto the head. If your car comes standard with the RBB style inlet manifold then there are many options. The most basic upgrade is the RSP inlet manifold. This is a cheap and easy swap and gives better flow. The most common and direct fit upgrade is the RBC inlet manifold. This gives great power gains all through the rev range and also uses the RBB style throttle body flange. The RRC inlet manifold is know to make the most power of all the standard Honda inlet manifold. This manifold is alot more expensive than the RBC style so it is always a hard choice as the RBC will make 95% of the power the RRC version will.
If you are using a RBB / RBC / RSP style cylinder head but are running a non drive by wire throttle body you will need a throttle body adapter plate. This allows the non drive by wire throttle body bolt to the RBC /RSP /RRC inlet manifolds without any modifications.
If you are using a PRB style cylinder head all of the RSP / RBC / RRC inlet manifolds will need the end on the inlet manifold machined off. This a regular practice and most of the inlet manifolds are available with this machining already done.
Throttle Bodies -
For the Drive by wire models there are several Genuine Honda upgrade throttle bodies which are direct fit and give great gains. From research we would recommend staying to the 70-72mm throttle bodies for road cars as it will keep 99% of the drive-ability and smoothness of the original car. Sizes bigger than this would be more suited to track cars the on / off throttle feeling can be a little harsh or jumpy.
For the non Drive by wire models there are no Genuine Honda upgrade throttle bodies. There are lots of aftermarket versions available from lots of different brands. We would recommend for a road car using a 70-72mm throttle body as bigger than this can make the on / off throttle feeling jumpy and harsh. If you are running a track or motorsport car we would recommend stepping up to 74mm. With the testing we have done with both 80mm and 90mm throttle bodies we would only recommend these for high horsepower motorsport engines.
If you are looking to upgrade your throttle body on your Honda Accord CL7 Euro-R you will need to buy a throttle with the PRB Civic EP3 / Integra DC5 fitment. You will need an adapter plate to fit the throttle body onto the original Euro-R inlet manifold and also an idle valve and gasket from a Civic EP3 / Integra DC5.