K-Series Intake Manifold Shootout - Super Street Magazine

If you're an enthusiast like me, you too, are a member of a web forum(s) that relates to your car and/or engine swap that provides a rich source of technical information. For me, it's the K-series engine swap, and one forum I am a member of is K20A.org. This has to be the most popular, if not most technically filled, forum on the net for K-heads since this swap blew up in 2003.

I'm also a fan of OEM Honda performance and parts. I like seeing what mixing and matching of the best OEM engine components will produce before having to go aftermarket. For the ones that know, K20s out of the box don't need much to make them fast - queue in the K-series intake manifolds!

Back at the end of July, Skunk2 finally released their K-series intake manifold to the public. I had the pleasure of being one of the first people to get my hands on one for test fitment on my K20A Type-R engine. My friend and ex-coworker from AEM (Rob Green), helped with the install and also photographed our install. The following day, I created a post on K20A.org using Robert's photos and lots of interest was generated. So much interest in fact, that it sparked the idea to dyno compare the most widely-used OEM K-series intake manifolds on the market today. That being said, these are the seven K-series intake manifolds I was able to get my paws on and dyno compare. Thanks to a couple generous K20A.org members, I was able to borrow a few manifolds I did not have access to. Some completely stock, some modified.

In addition to the shootout, I thought it would be proper to test out different sized throttle-bodies. But as it turned out, not every manifold was match-ported to 70mm. I had my stock 62mm Type-R t/b ported by Maxbore, which became 64mm tapering out to 70mm - similar to a K-series Spoon ported throttle-body. Blox Racing donated one of their new billet 70mm t/b for the shootout. Rob luckily had a ported Accord t/b which was originally 60mm, but was Maxbored to 62mm tapering out to 64mm (not shown). The Accord t/b was used on manifolds that were not match-ported to anything larger than 62mm - this included the BPR RBC and Endyne ported RBB manifolds, and were a direct bolt-on affair, no need for a throttle-body adapter plate! Excluding the stock RBC, all other manifolds were opened up to 70mm.

The shootout was performed on my own K20-R-powered '92 EG Civic at Erick's Racing Engines (ERE) in Baldwin Park, California. Internally, my engine is stock, meaning no aftermarket cams, valvetrain, pistons or headgasket - all stock Type-R internals. The mods my K20-R does have are the following: Acura RDX 410cc injectors, KPRO ECU, Rcrew 4-1 header, custom 3" exhaust with mandrel piping, AEM hybrid CAI and thermal intake gasket. With K20A-R to K20A2 (US Type-S), the only big differences are the slightly higher compression pistons (11.5 vs.11.0) and better camshaft profiles. I think this is a good base to start with and reference, especially for those K-swappers who want to leave their engine internals mostly stock.

MANIFOLD PREP

Before even heading over to ERE, I made sure all manifolds fit without issue. Some did have fitment issues and needed light modifications while others fit just fine, but then my DC5 (RSX) radiator's upper water neck and hose created clearance problems with the Throttle Position Sensor (TPS).
Before even heading over to ERE, I made sure all manifolds fit without issue. Some did hav
I wound up buying a fullsize aluminum race radiator and had it modified at Harman/A.Q. Motorsports. A.Q. moved the upper waterneck to a respectable new location which freed up the TPS clearance issue. Most K-swappers run a Civic half-sized radiator and will not run into this clearance problem. I wanted maximum cooling, hence the reason for going fullsize.
I wound up buying a fullsize aluminum race radiator and had it modified at Harman/A.Q. Mot
Then there was the upper idler pulley/oil pump assembly that needed to be shaved down some. The RAA/RBB #4 runner makes contact with upper assembly making the manifold somewhat difficult to install, hence the reason for the shaving job.
Then there was the upper idler pulley/oil pump assembly that needed to be shaved down some

The RBB and RAA manifolds needed the most modifications. Both needed a section of center webbing removed in order to feed the injector wire harness through to reach the injectors.
The RBB and RAA manifolds needed the most modifications. Both needed a section of center w
The RRC manifold needed to have an IACV port created so the IACV could work.
Luckily the modification was already performed by the owner who lent it to me. All manifolds excluding the "PRC" needed the waternecks lopped off because most of the K20A engines have a waterneck that is separate from the intake manifold.
With that taken care of, I was ready to start the shootout at ERE. The dyno testing took place on three separate days or sessions. In Session 1 we dynoed the PRC and Endyne ported RBB. Session 2 was the stock RBC and Skunk2 manifolds. Session 3 we tested the remaining BPR RBC, RAA and RRC manifolds.
ERE uses a Dynapack dynamometer that is calibrated for wheel horsepower. As a disclaimer, I would like to mention that all dyno tuners have their own preferences, calibration settings and so on with their own dyno configurations. The results I make may differ from your results.
The RRC manifold needed to have an IACV port created so the IACV could work. Luckily the