First post here at AZ, but long time 1st gen RDX owner. Itching to make our first few performance mods along with general 100k maintenance item. At any rate, I noticed that the OEM cooling circuit passes through the turbo exhaust manifold; from what I've read on the K23 RDX engine overview, this purpose of this design is to " keep the exhaust components (manifold and turbo) at the optimum temperature." Can someone comment on the benefits of passing coolant through the manifold?

My initial guess is that the exhaust manifold appears to be cast aluminum, and therefore, needs to be cooled in some method to avoid thermal damage. My other thought is to bring engine operating temp up faster with rejected heat from the exhaust.

Main purpose is to maintain the optimal temp for turbo and to keep this temp down.
That's why we dont need a turbo timer )

think with an upgraded turbo and cams it would be beneficial to get the housing ported/extrude honed? or maybe coated in something to help it retain thermal energy? and potentially reduce under hood temps?

yes extrude honed!!! always made Lisa Kubo and her worlds fastest B16 have ridiculous top end back in the daY...

^really I was unaware she had it done. I was talking to Justin at detective coating he does powder coating and has a few applications for us. so maybe do it all? if so inside and out or what?

I'm aware of some cases with cracked exhaust manifolds on RDX. They were stock. So, I'm not sure about porting.

Funny you should mention thermal coating, and I mean "true" thermal coating. I had very good results (as many have before me) using SwainTech Coatings out in Scottsville, NY on my cast iron OEM exhaust manifold, turbine housing, and downpipe for my SR20DET powered '96 240SX. The thick ceramic coating is applied and permanently bonded at the molecular level and can be expected to last the life of the part. Not only do you get a noticeable reduction in ambient temps from exhaust parts, but you are also retaining greater heat inside the parts in hopes of better exhaust gas velocity.

http://swaintech.com/race-coatings/

Note the outcome of the parts I mentioned earlier. I confirmed with the technical support folks at SwainTech that their coatings can be top-coated, so I also used VHT Flameproof high-temp paint and high-temp clear to preserve the finish as the naturally white finish of the ceramic coating stains very easily with fluids, fingerprints, etc.





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that looks great!