rb26dett intake manifold and itb's on a rb20 head

[ripracer]

Sweet and putting it to work too, I like that.

I just went through all this trouble to have a single sided intercooler, but would still love to have the 26 plenum so I can see my pretty valve covers.

I just want to see what the dyno sheets look like and thats all the convincing i'll need.

[240maximus]

Sounds powerful. put me on th rb20 list man! let me know when u got a price.

[TSL]

Any actual dyno results?

[SuicidnS13]

Add me to the Rb20det list as well as my engines are still sitting on an engine stand. Put me down for +2. Email me prices if needed to [email protected]

[BSRJIRONMAN]

+1 for the rb20det kit. Please email prices to [email protected]. thanks!!!

[Chaos the Xile]

can you post some pics of the kit that you are offering plz.

[MATTs14]

Im very interested in one of these. If you dont mind could you email me the price of one for the rb20? mattamus240(at)yahoo(dot)com. Thanks!

[legit240sx]

Got a vid but no dyno.....looks sick but i would want to see it actually making more power on paper rather then a corse.... kinda late for a two month old post but kinda interested in it

[Kalypso]

excuse me, but im curious.

- where did he get the ITB's from a 26?

- and whats the benefit of ITB's over a regular intake plenum... better flow?

[MATTs14]

The itb's come stock on the 26 and are connected to the intake manifold obviously. The advantages are better flow and better throttle response. Anyone else wanna add to that? Also im wondering where the guy went. I was ready to buy one of these and then he bailed.

[BrodyGoble]

Still kickin around...

Sorry I cant get my **** together to set aside some time to make them. I have one extra that I can sell currently. Highest bid takes it, will include everything you need as a package, all new longer studs etc...

[l0nestar]

Is that for a 20 or 25 head?

[MATTs14]

very interested in this!!! email me with pics asap and i'll take it off your hands. [email protected]. THanks and i hope to be hearing from you soon so i can make this happen

[Darius]

For clarification, ITBs do not "improve" flow since they are an obstacle and create additional pressure loss. However, in a longitudinal plenum like the Greddy or RB26, the ITBs act as a flow equalizer to better balance the air distribution between the cylinders. Plus, the RB26 manifold has a pressure balance bar to further help distribute pressure equally across all cylinders.

[DriftingisLame]

Darius, do you have any thoughts on how the RB26 intake plenum would flow with a single throttle body instead of the 6?

I have one of these with RB20 lower runners, and I believe a few members here do as well. I'm just curious as we do not have many options for intake manifolds that are affordable.

[l0nestar]

DriftingisLame,You would not have as crisp throttle-response with a single throttle-body, as with individual throttle-bodies. But knowing the level of precision around here, it should not make that much of a difference. (We do not posses our own flow-benches and engine dynos, that would make the differences quantifiably distinct. )

If you are considering mating a 26 intake (sans ITB's) to the 20 lower manifold, you will need to consider the larger diameter runners of the 26 and transitioning them as to not impede flow / turbulence.

[Cjmartz2k]

I spent the better part of a weekend port matching and smoothly transitioning me the runners into my RB25 head. It takes a good bit of work.

[DriftingisLame]

Yeah, I realized that part. I decided to keep the factory manifold on this setup of mine due to simplicity, and to keep low end on the little RB20.

I dont know if that much work will ever be worth it to me... Just for a more convenient, better looking engine bay, with less torque and 20 or so more top end HP.

[Coolwhip]

what is the determining factor in the RB20 guys going for this setup?

1) Having a forward facing manifold?2) Having ITB's?3) Increasing torque?etc?

Want to know the thoughts of you guys

[Darius]

l0nestar hit the nail on the head. The ITBs will give better throttle response than a single TB at the front of the manifold. With them also being close to the intake valve, the added turbulence should improve combustion efficiency.

[Coolwhip]

l0nestar hit the nail on the head. The ITBs will give better throttle response than a single TB at the front of the manifold. With them also being close to the intake valve, the added turbulence should improve combustion efficiency.

The same thought has been implemented in the design of the RB25 manifold I'm working on however, it seems to me that a long runner design of the RB20 lower manifold implements is the contributing factor for better torque characteristics. So to have both worlds, long runners (torque) and ITB's (response)...

What would you say about an adapter that bolted in between the lower manifold and the upper manifold (increasing the height of say 1") incorporating ITB's.

This keeps the long runners and puts ITB's in action without the similar costs of sourcing used RB26 parts (all the parts) and keeping the oem design and components which are cheaper and less parts to replace?

Very cost effective however, pretty ugly in the respect of having a cross over manifold or a plenum built off the ITB adapter to go forward looking like the Plazmaman style.

Thoughts?

[rbsileighty]

The same thought has been implemented in the design of the RB25 manifold I'm working on however, it seems to me that a long runner design of the RB20 lower manifold implements is the contributing factor for better torque characteristics. So to have both worlds, long runners (torque) and ITB's (response)...

What would you say about an adapter that bolted in between the lower manifold and the upper manifold (increasing the height of say 1") incorporating ITB's.

This keeps the long runners and puts ITB's in action without the similar costs of sourcing used RB26 parts (all the parts) and keeping the oem design and components which are cheaper and less parts to replace?

Very cost effective however, pretty ugly in the respect of having a cross over manifold or a plenum built off the ITB adapter to go forward looking like the Plazmaman style.

Thoughts?

As long as you have hood clearance this is a good idea for the 20... dyno numbers would speak the most though.

I would recommend dyno the same stock RB20 on the same dyno in the same car with a few configs to find out what's best with the least amount of fab (as to cater to the bolt-on market):

Stock mani

Current adapter w/ 26 ITB setup

RB20 lower mani w/ adapter (assuming it fits)

I have a feeling the 3rd config (the one suggested by Coolwhip) with Cams and some form of turbo upgrade would be a very solid RB20 setup (same concept as what I'm working on for fun, but more bolt-on friendly... ie. less cost involved)

As for the ITB comments above I'm not sure what I think of them... ITB's change your plenum into more of just a pressurized air source (since these are turbo cars). If you break down the system in a very basic way... your ITB's allow controlled amounts of air per cyl with better resolution and velocity than a single TB can allow due to their size being smaller but allowing similar mass flow due to their combined sectional area being similar (or more flow/larger area depending on how you size your ITB's).

The goal of making power with an intake mani is to allow as much air in as possible as fast and evenly as possible without causing a restriction in your desired power band... as for the turbulent flow... this is good for providing a more efficient engine in terms of maximizing the fuel being burned, but laminar is better for performance. Injecting under higher pressure would help this concept with an injector closer to the manifold with a short runner setup (that still produced min turbulence), but moving the injector into the cyl DI or moving the injector further away (like F1... enjoy the vid http://www.youtube.com/watch?v=y2iBbwocYZw ...I don't think the sound is matching up to the vid... but still awesome ) is best.

That's my take at least... I have some background in this stuff, but i'm no expert so feel free to disagree/make comments and corrections if you have them


Modified by rbsileighty at 12:56 PM 1/20/2009

[GTRs13]

I'm sure an update would be appreciated by most!

[Flamereka]

Hey I know this post is ancient but looking at it he only has 10 holes for the head to bolt onto where the rb20 has 14. Wouldn't this be a big problem? How about getting longer studs for ones that match up with both rb20 head and rb26 intake. Bolts into the remaining holes into the head that don't line up and then studs into rb26 intake.

[OutToWinPAHC]

I want some RB20

[godzilla_753]

I got my conversion done with finally, cars still overheating but thats another topic, Ill post up some pics, wish I had it all painted up pretty, it looks rough right now.
Did mine on a rb25 neo, no adapter plate, mated the stock intake flange to the 26 throttles via 3 seperate adapter plates. used the factory AAC valve, and TPS with a little bit of creativity. The hardest part was getting the runners to line up. I think an adapter plate woulda been much easier. Car runs strong though, really good response, I plan on adding a lightweight flywheel for some super crips revving

[LeeRoy32]

i can see this was posted quite a while ago now, but i was just wondering if i could get my hands on a adapter for the Rb26dett intake manifold to fit on my rb20det, if not do you know where i could find one..