RB26 Intake Manifold/Plenum Options

[Allan74]

I find this to be a bit of a sore spot for me, as I should have pulled the trigger LONG AGO and bought a new Plenum - THE NISMO ITB PLENUM....back when it was $1500 USD or so last year.

The prices seem to be rising on that unit each and every day and there really aren't other suitable options....for me anyways.

Let's look at what's available....

ITB:
-----
- OEM, of course.....
- Nismo Plenum (Response + Mix oriented) - $2,000 USD
- Greddy Plenum (Power and Mix oriented) - $800 USD

Single TB:
-----------
- Everything GOOD is over $2,000 USD (Hypertune, Jun etc, then add $ for TB)
- Knockoffs/unproven are under $700 USD (the Thai units looking more appealing/better built than the Chineese)


Considering future maintenance and overall simplicity, I WAS leaning over towards a Single TB (as a SECOND CHOICE after te Nismo ITB Plenum), but everything is just rediculously priced.

Not that the idea is original or anything, as I know it has been done before......but, unless someone talks me out of it, or tells me I am a complete IDIOT for even considering it, I am considering simply buying a GREDDY ITB Manifold and WELDING a Q45 TB flange onto it and 'gutting' my ITBs, to use as 'spacers/dummies'.........

For MAX $1200 USD, what else can I really do ? (other than stick with OEM ITB of course and rebuild it/them).....

Allan

[jimbojones]

Hi Allan

Agreed on the unreasonable cost of a new manifold; considered it myself and the price is way too expensive for the increase in performance. Everything I've ever read says single TB is for max power and not response...not sure if that's the setup you're after. OEM TB's have made 1000hp so I don't think that is a 'must get rid of' step.

You would hope that someone would have figured out a mod for the OEM manifold by now; unless you're running insane power, it should flow plenty of air (BTW - what is your HP goal?) and you should be able to modify the inside to balance the flow better. May involve having to cut the manifold in 1/2 so you could get inside to work but if cut/welded nicely, would keep costs to a minimum PLUS you can keep the TB's and you know that everything would fit.

BTW - I have seen a cut manifold before but all they did was enlarge the inlet; nice cosmetic job but I don't know if it actually helped anything re: performance and I REALLY doubt it fixed the air-stacking problem on Cyl#6. I'm leery about knock-offs...sure they'll hold air but do they fit properly and are you just going to end up having new cyl. balance issues...?

Hope you find your solution...

[Allan74]

Thanks for the words Jimbo....nice to see someone else in the same boat as me.

As far as a Goal, I don't really have one. I am limiting myself to 800cc Injectors/Single In-tank Fuel Pump/Nismo RS580 Twins for the first stage of my Build to keep things simple (so basically 500 Wheel HP I guess)....but building the block/head/motor itself for 9,500+ RPM & 1,000 HP with the best parts I can buy (within reason) and not cutting corners on the foundation. I just don't want to build the fuel system or transmission this time around, so that, I guess, is my #1 limiting factor.

To me, (FOR BOLT-ON ITEMS) the Nismo ITB Plenum 'situation' (correcting lean & flow problems) is like the Tomei Oil Pump 'situation'.

Yes, it will solve most problems (short of a Dry Sump if talking Oil Pump 'fix') and give you peace of mind - but the final cost can almost be considered ROBBERY !

The Greddy Plenum's single TB 'MOD' might seem a little 'hack-job-ish'......but really, what else is there for aftermatket options that don't cost an arm and a leg ?

Allan

[mcfly]

CRC
CPC custom plenums - **NEW RB30 Race Version available** - calaisturbo.com.au - VL NATS TICKETS ON SALE NOW! www.vlturbonationals.com.au

**Race Version plenum available $1200**

RB30 Street Version plenum $900 + delivery
RB30 Race Version plenum $1200 + delivery


Back to back testing has shown an approximate increase of 40hp at the wheels using the Street Version plenum. Proven time and time again to reduce lag and substantial increases in power and torque.

All plenums come complete with:
- bead blasted runners
- 5 seperate vacuum fittings for brake booster, fuel pressure regualtor, map sensor, boost guage etc etc more if you like on request
- throttle body plate to suit whatever throttle body you like (XF, Q45, LS1 etc) included
- studs, nuts and washers to fit throttle body of your choice
- logo engraved on all plenums

Extra's available are:
- Polished plenum from $150
- 80mm Throttle body $400, overall flow is up 20% on XF throttle body (TPS Plug to suit 80mm tb additional $30)
- XF Throttle Bodies with TPS $70 (bead blasted clean) if and when available
- Billet fuel rail $200 bolt on with any style Speedflow fitting upto Dash -10. Only available with plenum purchase

Attached is a pic of what they should look like when installed. Any questions regarding installation, please feel free to contact me.

For those who want more specific info, on average, each port flows well over 200cfm @ 25" without any power porting what so ever.

Also have all the following engines catered for:
Mitsubishi: 4G93/4G63
Nissan: RB20/25/26, CA18, SR20 (non-VVT & VVT), E15
Toyota: 1JZ/2JZ

Currently developing:
Ford: XR6 turbo (since been made and just waiting for some flow/dyno figures)
Mazda: 13B turbo
Toyota: 2JZ (flow/dyno results on a month or so away)

All work is guaranteed and fixed free of charge and postage costs paid for where applicable.

Thanks,
Ariel
pm, email, sms or call 0403 279 000

[Kras]

I don't know if its worth upgrading for you current power potential, tune #5 and #6 a touch richer and call it a day.

[Allan74]

Just sent him an email ;)

http://customplenums.com

Thanks for the heads up.

[TougeJunkie]

Heres a question, why dont Nismo / Greddy / others use velocity stacks in their manifolds ? I know the Thai unit has them. You would think a slighly bigger plenum with velocity stacks would help reduce the forced air effect on #5,6. I know they might cause a bit of turbulance but wouldnt that help even out the air distribution in the plenum?

[mcfly]

velocity stacks are not in the plenum to stop a #6 lean situation. They are in their to change the runner length and or ease the flow of air into the runner. In the case of the rb26 there is not a large enough length change to alter the tq curve noticeably. The greddy plenum has curved runner entries to do much the same job.

this is a great little picture

[TougeJunkie]

That makes sense the curved runner entries more or less act like a velocity stack, but with the raised radius type velocity stack (separate from the base of the plenum) it would increase the runner length by approx 15% and further smooth the flow stream along the runner walls. It could make for a more even distribution of air since its raised from the plenum base and would not get affected by the ram air effect as much as the greddy/nismo style. The over all shape makes a big difference as well, I wonder if they use velocity stacks in the RIPS manifolds, they are shaped very well for spreading the air flow more evenly.
http://www.ripsltd.com/images/images2/Sparks%20engine%20going%20together%20intake%20side %20002.jpg

It would be interesting to see the flow bench results between the 2 different styles of plenums