RBC IM Upgrade

[Mudgey]

Hi Guys,

I am contemplating a few choice upgrades for the DC5, the car was remapped with KPro, a CAI prior to purchase and orignally had a 2.5" BC exhaust, now back to OEM. I need to hook up my AF Gauge to see what change the OEM exhaust has made to the AF ratios'.

The previous owners dyno shows 200whp, and a flywheel power of 239, make of that what you will. The butt dyno does show a big improvement to the mid range compared with my previous DC5 and it does feel reasonably good, however due to the big surge in torque in the midrange it does feel like the torque drops off to abruptly at high RPM's and the dyno print out does show this. I am looking for a bit more top end power. I am considering an RBC and possibly a new header with decat (but with the option of fitting a CAT for MOT purposes).

Does anybody have any experience with before and after with the RBC and did you notice the difference? I have seen some dyno's where it made a 5hp difference up top and others with 18hp difference, both Kpro'd before and after to ensure the difference was just the manifold change.

What are peoples experiences with the RBC? Did it make the engine carry more torque up top?

Cheers!

 

[Matt-DC5]

Hi mate,
When I changed to RBC I also fitted a 70mm tb at the same time. Before mapping it definitely made the car feel stronger throughout rev range, but once mapped due to a restrictive exhaust, vtec was set at 3600rpm so it doesn't feel anywhere near as aggressive. Because of this ive decided to upgrade the full system and will be going for a tweek.
From my experience having the RBC is all good and well, however if you cant get the air out as quick as its coming in there isnt much point

 

[kyle'87]

I 100% noticed a difference after I fitted my RBC manifold and for the price and OEM'ness of the install I would recommend it. However, after having it mapped and the endless desire for those extra few horses I find myself looking into getting it ported and polished to 72mm and fitting the newly released K-tuned 72mm TB.

Looking back I'm thinking I should have invested in the Skunk2 manifolds with a bit more R&D put into them than just an OEM upgrade. If you just want something that is reliable and OEM fit then the RBC is a great choice.

In regards to torque top end, I've found the Spoon 4-2 and 2-1 section are superb but you do sacrifice the mid-range. if I keep mine in the power band 5000rpm or more then it is savage and eats up what is in front of me.

 

[MilanoChris]

RBC is a great mod, its gains have been known about for years.

 

[Mudgey]

Stuff

Damn, that Torque after 5k looks superb, must feel great at about 5.5k when it just climbs 30ft/lbs in just 500rpm! What other mods have you made to emphasize top end power?

With my old supercharged K20a2 prelude, the rev limiter was set at 8800rpm by the mapper (by the previous owner before I got the engine combo), is this not commonly done with remapped K20a engines?

I think the RBC is definitely on the cars and possibly a new header too.

 

[MilanoChris]

After 8800 you get valve float and oil cavitation. Personally for the sake of 200 rpm 8600 is more than enough, you're really going to struggle making power after that anyway.

 

[C&S Evo7]

the rbc is a great mod, and porting can help but i dont think you will get any gains from a bigger TB

 

[carl hammond]

This has made for an interesting morning read as the RBC is one thing I have been told to do to my car that I have not yet done / considered, I have seen many variations advertised all over the place, RBC PBC or similar, what's the difference and how can you tell the difference as they all look the same to me?

Also are these easy to install yourself pre getting a remap?

 

[Indi]

This has made for an interesting morning read as the RBC is one thing I have been told to do to my car that I have not yet done / considered, I have seen many variations advertised all over the place, RBC PBC or similar, what's the difference and how can you tell the difference as they all look the same to me?

Also are these easy to install yourself pre getting a remap?

RBC inlet looks a lot bigger and different shaped to PRB (Stock DC5 Inlet) if you look at a side by side picture. Also they all have a stamp on the top stating whether it's 'RBC' or 'PRC'

It's fairly easy to change, can be done in an hour and half

 

[Mudgey]

Is it worth getting a 70mm TB and a port matched RBC at the same time, might be cheaper in the long run over an RBC + stock TB only to upgrade later, especially if cams and other internal mods could potentially be on the table.

I'll be fitting a 3" CAI and a 4-2-1 long tube header with de-cat at the same time.

 

[spooke]

Is it worth getting a 70mm TB and a port matched RBC at the same time, might be cheaper in the long run over an RBC + stock TB only to upgrade later, especially if cams and other internal mods could potentially be on the table.

I'll be fitting a 3" CAI and a 4-2-1 long tube header with de-cat at the same time.

From what I've read, larger TB is not worth the money.. perhaps on a forced induction build? You could always get the OEM one ported for a lot less I'd imagine, which is what the Spoon/J's are?

 

[MilanoChris]

The RBC give good gains all over the graph, TB upgrade would see maybe 2 bhp or so. I don't think it's worth it but that's NA tuning for you.

It has been covered plenty of times on here and other forums.

 

[Linus27]

I 100% noticed a difference after I fitted my RBC manifold and for the price and OEM'ness of the install I would recommend it. However, after having it mapped and the endless desire for those extra few horses I find myself looking into getting it ported and polished to 72mm and fitting the newly released K-tuned 72mm TB.

Looking back I'm thinking I should have invested in the Skunk2 manifolds with a bit more R&D put into them than just an OEM upgrade. If you just want something that is reliable and OEM fit then the RBC is a great choice.

In regards to torque top end, I've found the Spoon 4-2 and 2-1 section are superb but you do sacrifice the mid-range. if I keep mine in the power band 5000rpm or more then it is savage and eats up what is in front of me.

Very interesting read. I have the Spoon 2-1 and my car really lacks torque. I have been considering getting an RBC and a 4-2-1 system but did wonder if a Spoon 4-2 would be worth getting to go with my Spoon 2-1 and Spoon B-Pipe. The area I am really struggling is getting power coming out of corners, some of this is my map which needs adjusting as VTEC is kicking in around 5800 but not sure if a Spoon 4-2 is worth it now if I will lose mid range torque.

 

[kyle'87]

Very interesting read. I have the Spoon 2-1 and my car really lacks torque. I have been considering getting an RBC and a 4-2-1 system but did wonder if a Spoon 4-2 would be worth getting to go with my Spoon 2-1 and Spoon B-Pipe. The area I am really struggling is getting power coming out of corners, some of this is my map which needs adjusting as VTEC is kicking in around 5800 but not sure if a Spoon 4-2 is worth it now if I will lose mid range torque.

From what I have read it isn't the 4-2 section that causes the torque "drop" in the mid range but rather the 2-1 section, I have no conclusive proof other than my own map and tuner diagnostics. Hearsay is that the 2-1 section moves the torque curve up in the power band. What my tuner was seeing at the start of the mapping runs was around 30lb/s of torque drop/lost in the mid range. He managed to smooth this out to around 10lb/s so it is not so noticeable until I hit 5500 when the car takes off.

Another user who used the same turner with my exact setup had the same characteristics, he then changed to a Buddyclub Racing header and gained all of that lost 30lb/s. Obviously that removed the 4-2 and 2-1 section so take that how you will lol.

My VTEC crossover is at 3800 at WOT and 3800-5000ish at part throttle.

 

[Linus27]

From what I have read it isn't the 4-2 section that causes the torque "drop" in the mid range but rather the 2-1 section, I have no conclusive proof other than my own map and tuner diagnostics. Hearsay is that the 2-1 section moves the torque curve up in the power band. What my tuner was seeing at the start of the mapping runs was around 30lb/s of torque drop/lost in the mid range. He managed to smooth this out to around 10lb/s so it is not so noticeable until I hit 5500 when the car takes off.

Another user who used the same turner with my exact setup had the same characteristics, he then changed to a Buddyclub Racing header and gained all of that lost 30lb/s. Obviously that removed the 4-2 and 2-1 section so take that how you will lol.

My VTEC crossover is at 3800 at WOT and 3800-5000ish at part throttle.

Thanks Kyle, thats really interesting reading. Adds to the fact that I have the Spoon 2-1 and noticed a drop in torque. Looks like a 4-2-1 system is incoming. Difficult bit is which one. Probably a DC Sports as good value for money and feedback.

 

[kyle'87]

Thanks Kyle, thats really interesting reading. Adds to the fact that I have the Spoon 2-1 and noticed a drop in torque. Looks like a 4-2-1 system is incoming. Difficult bit is which one. Probably a DC Sports as good value for money and feedback.

It is a real shame because it is a great exhaust system, what it takes away from the mid range torque gives back from 5000rpm onwards. I say I am looking at the buddy club, but I also have my sights on a Solid Fab with removable cat. From what I've read in the dyno charts thread the DC mani gives good results so I don't think you will be going wrong with that one.

 

[MilanoChris]

Thanks Kyle, thats really interesting reading. Adds to the fact that I have the Spoon 2-1 and noticed a drop in torque. Looks like a 4-2-1 system is incoming. Difficult bit is which one. Probably a DC Sports as good value for money and feedback.

DC on mine mate, no issues but you do (as per most aftermarket systems) need stiffer engine mounts such as ESMM.

If I didn't have the DC or if it breaks I've be going for another or perhaps Solid Fabs.

 

[Linus27]

DC on mine mate, no issues but you do (as per most aftermarket systems) need stiffer engine mounts such as ESMM.

If I didn't have the DC or if it breaks I've be going for another or perhaps Solid Fabs.

Cheers Chris, I have ESMM fitted anyway so all good to go. Why Solid Fabs out of interest? Do you have good feedback on their system?

 

[MilanoChris]

Because I am not paying for a knock off copy of the Toda, the Toda is too expensive and as far as I understand it, the Solid fabs manifolds flow well and make good figures.

 

[Linus27]

Because I am not paying for a knock off copy of the Toda, the Toda is too expensive and as far as I understand it, the Solid fabs manifolds flow well and make good figures.

Makes sense to me and my thoughts also.