Boring out RBC intake manifold

[Nuci]

Hey all,

Looking into buying an RBC intake manifold for my DC5R to replace the shitty PRB manifold. My options are:

1. Buy RBC and pair it up with stock throttle body using adapter
2. Buy RBC and get it ported to 70mm (ish) and buy 70mm throttle body

Question is, is it worth boring the manifold out to 70mm and pairing it with a 70mm throttle body? Or am I going to see the same power gains regardless of whcih option I choose? Mods are Kpro, intake, exhaust (135kw atw at the moment). Is it worth doing at all?

Any advice much appreciated.
Cheers, Nuci.

[DakDak]

K series love to breath, as do all engines really. You will definitely see results with just the RBC however it'd be even better with the 70mm throttlebody and the manifold port matched to it.

Its a must to port match the manifold to the throttlebody, because you are going with the 70mm throttlebody to let more air in right? Well having a big space then a small space or reverse, creates turbulence which is pretty much a sudden change in the atmosphere. This phenomenon will interrupt air flow which you do not want. So to let more air in only to have it hindered by turbulence is kind basically going 2 steps forward the one backwards

Either way you will definitely see results but my 2c from a tuner's perspective on a budget, do it once and do it right. So you save $$$ on retuning.

[Nuci]

So 70mm isn't considered overkill? Considering my current mods? And what types of places can bore the manifold? And is it just the inlet hole or the runners as well that need to be ported?

Cheers, Nuci.

[DakDak]

From what I see with BYP not at all my friend! Their customer cars with I/H/E RBC with 70mm throttlebody are achieving very nice gains. Im not with BYP or anything, Ive bought from them a couple times and asked about stuff. They offer a port matching service with intake manifold to throttlebody. Im not sure about other port jobs they didnt mention.

If you just want a nice street car and without big bucks, just get the inlet hole.
If your planning to build something special go all out.

[Nuci]

Ok cool cheers man. And is there much difference between brands of throttle bodies? Or are they all the same? Coz there's quite a difference in prices between spoon, J's racing, skunk2, obx etc etc.

[Benson]

RBC and 70mm will make a nice addition to the overall engine performance. Port matching the entry is very important to make it efficient. Remember you'll need a retune to get the most out of the entire set-up

RBC, 70mm T/B and port matching service all available. PM me if your interested

[Nuci]

The rbc and t/b I will be able to source no problem, it's more the port matching that's the issue. I'd rather try find someone locally (I'm in Brisbane) who can do it first before I start posting parts interstate. Is it a complex job or is it just a matter of boring the inside diameter of the inlet hole out to 70mm?

[DakDak]

Ok cool cheers man. And is there much difference between brands of throttle bodies? Or are they all the same? Coz there's quite a difference in prices between spoon, J's racing, skunk2, obx etc etc.

I'd like to know this myself lol.

[EG5]

The rbc and t/b I will be able to source no problem, it's more the port matching that's the issue. I'd rather try find someone locally (I'm in Brisbane) who can do it first before I start posting parts interstate. Is it a complex job or is it just a matter of boring the inside diameter of the inlet hole out to 70mm?

Match porting is pretty simple to do . Your local machining job will be able to do it.

[45SET]

Nuci,

I've put a RBC and a 70mm Skunk2 throttle body on my K24. The throttle body it's self looked to be a really good unit, and I've only heard good things about them (Timmy from ClubITR has been running one for a while, no problems).

As for the port matching, I had 101 do mine. I think the inlet on the manifold is 64mm, so it was bored and honed to 70mm to accommodate the bigger throttle body. All up this cost me $50, and it was a good job.

[Nuci]

If i need the Karcepts adapter for the rbc manifold, does it need to be bored out to 70mm as well? And im using the mugen intake box which utilises the stock rubber intake hose. Will that fit properly over the entry of the throttle body?

[45SET]

You can buy the Karcepts adapter with a 70mm bore. When I had mine bored out, the adapter was bolted to the manifold, and bored and honed from that.

You can by silicon induction pipes which should fit. The OEM pipe is a very tight squeeze.

[Nuci]

oh ok so you can bore the normal 63mm (or whatever it is) adapter out as well?

[45SET]

oh ok so you can bore the normal 63mm (or whatever it is) adapter out as well?

Well... yeah I guess... but why not just buy the 70mm adaptor in the first place?

If you are going to buy everything for Karcepts (Which I did) you'll need to buy the following:
- RBC Manifold
- Manifold-T/B gasket
- T/B adaptor
- 70mm Throttle body

You then need to get the RBC bored and honed to the 70mm adaptor.

[Nuci]

Well there's a place in the US which sells a kit containing all the stuff you mentioned above for a very good price, except its only with the normal sized 63mm t/b adapter. So if its possible I was going to buy that kit and just bore the adapter to 70mm along with the manifold (know someone who can bore it for me for next to nothing), instead of having to source a 70mm adapter separately.

[45SET]

Do you have a link to the kit?

I've just found the invoice from when I bought my parts from Karcepts (All parts in USD)
- Hondata Intake Manifold Gasket - $50
- RBC Intake Manifold - $205
- RBC Throttle body gasket - $9
- Karcepts 70mm Throttle Body to RBC Adapter - $46
- Skunk2 70mm Throttle Body - $350
- Shipping - $135
TOTAL = USD$795

I then paid 101 Motorsports (Underwood) $50 to bore and hone the RBC to 70mm.