My Single TB Conversion - The Saga nears the end....

[Allan74]

January 10, 2009
...Back to the Drawing Board....lol



With my less-than-addequate Photoshop skills, I was able to come up with the following:

http://www.gtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwr.com/downloads/pics/plenum_compare.jpg

In my mind, Plenum C represents an every-day, run-of-the-mill Plenum from any of the big namebrands. Jun, Hypertune, knock-offs.....you name it.

Plenum E represents a similar design, but smaller volume....and is imaginary, as in, it doesn't exist. It can best be compared to a Nismo RB26 ITB Plenum, but for Single Throttle Body.

The design I want, is Plenum F......and was the reason I did this comparison to help better explain what I wanted.

To me, this design represents everything I want in a Plenum. Lower Volume, requiring less to 'fill it' (approx OEM ITB tank Volume). Longer/Extended Runners for increased response and TB angle better inline with stock IC plumbing. This could best be compared to an RB25 Greddy Plenum. Long Runners, Low Volume Tank. Short of buying a Greddy RB25 Plenum, cutting the flange/injector mounts off and welding on an RB26 flange, this will be the Plenum that you will see on my car when completed.

80mm Throttle Body ? If the quickest BNR32 in the World can run an 80mm TB, then there isn't any reason why I can't. Yes, the Heat Treatments GTR runs an 80mm Throttle Body from Jun, as stated in the Video of the HT car I posted in the Media section (GTRVISION: Heat Treatments GTR, behind the scenes).

Let's hear what you guys think.
Allan.

[mcfly]

yes a 80mm throttle body will do enough, I agree with you there. Guys are making 2500 hp on 100mm throttle bodies.

Im not going to go choosing a runner design for you though. I do not know enough about intake reversion and plenum frequency tuning to figure that one out. I can however give you this :p

http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=471

I would use a billet tb made for a LS1 or something. Unless you prefer using the ugly q45 tb. I supposed you may save some money.

[Skym]

Interesting link.

A person on SAU has been playing with trumpet length on NA RB engine and has found shorter to be better for rallying.

Also angle of air entering intake plenum via throttle body is important.

I've heard R.I.P.S intake plenums cause problems with air flow around 6th cylinder. If you have individual cylinder fuel trim, should be able to fix it.

Shape of intake plenum around 5th, 6th should be similar to this -

http://img.auctiva.com/imgdata/9/0/9/3/4/5/webimg/183095959_tp.jpg

[Allan74]

Edited, as it makes no sense after changing the OP......lol

[mcfly]

You should be one that knows, price does not dictate function.

With that in mind who is to say the thai built knock offs wont outperform a rips plenum or jun. I find it hard to believe any intake plenum for a rb26 isn't going to cause a leaner environment for the rear cylinders.

[Skym]

Allan74, it's from a customer on SDU forum that bought a intake plenum and had it flow tested on a flowbench. Nothing against said person, just making you aware the problem exists before dropping alot of money, then having to have intake plenum around 6th modified to fix the problem, which I think that customer had done after flowbench result's.

Search under I think was "R.I.P.S intake plenum", should find the thread.

If your buying a intake plenum, ask to look at flowbench data from each cylinder. That's one of the most important parts and should never be over looked when designing or buying a intake plenum.

Even this Top Secret engine has it shaped correctly around 6th cylinder -

http://img514.imageshack.us/i/rb26completesk9.jpg/

Mcfly, I agree.

I hear it's the opposite with said intake plenum, runs richer on 6th (less air flow). I guess that shape around 6th was his solution to the problem. If you have individual cylinder fuel trim on say Motec or Link ECU (like said person uses with said intake plenum), doesn't matter so much, as it can be tuned out.

There was an article on designing Honda? intake plenum in the USA that talked about angle of throttle body from front to rear of engine that controls which cylinders the air goes to the most inside intake plenum, etc. I wish I could find that article again, as it explains alot about what to look at when designing a intake plenum. :(

[Allan74]

The problem either way, is, finding a way to monitor/test all 6 cyls for fine tuning.

I thought about an Aircraft 6 Channel EGT, but without Datalogging capabilities, it could be difficult to watch everything to get it right.

I am considering 4 EGT ports (if I get stuck using my AEM) and taping Cyls 1, 3, 5, 6.

Cyls 1-3 should give me a good reference, to help tune the rears out.

If you only had 4 ports for EGT, which Cyls would you do ?

[Allan74]

Skym, you are right about the drop off in Cyl#6 with that basic design......

Here is where I initially stole my starting pic, before I resized and reconfigured the shape etc.

This guy actually did modelling.....pressure, flow etc.

Check it out (2JZ though, same shit as RB26, just upside down)....

http://img385.imageshack.us/img385/24/pressurepc8.png

http://img68.imageshack.us/img68/7941/velocitycw7.png

http://img175.imageshack.us/img175/4272/spreadsheet1bk5.png

2JZGE Intake Manifold - HybridZ

[Skym]

Good example.

Can see on flow test data, that where the entry to intake plenum is aimed (where throttle body goes), those cylinders get the most air.

If intake plenum is designed properly, flow tested to work, individual cylinder fuel trim shouldn't matter too much when tuning engine. ECU tuning (individual cylinder fuel trim) or placement of higher flowing injector in 5th, 6th, makes up for a fault with the design of intake plenum.

On stock ECU you tend to run engine slightly richer to compensate for those cylinders that run lean with stock RB26 intake plenum.

[TougeJunkie]

That 2jz manifold is just about bang on, the Thai unit is looking more apealing with its design and shape, but for that kind of money $1000+ for either unit, making your own makes the most sense to me

Ive been kicking the idea around of having a V shaped manifold with the throttle body in the center facing downward, but figuring out if there is enough room for is another question

[Skym]

Interesting.

But you have to have the head (cams, bigger ports, etc) to match the intake plenum. Cam manufacturers ask for intake, exhaust manifold dimensions, turbo size, etc when designing cams, porting head, etc. It's alot of maths involved.

Alot easier if you have this program that can simulate everything (intercooler size, turbo's, cams, porting, etc) before doing anything -

http://www.kelford.co.nz/computer-software/

Worth the $$$.

Car manufacturers use similar programs for engine, chassis design (including design of rollcages for sports department), etc.

I think that Thai intake plenum was used on a 10sec RB20DET without problems. His forum name is RB20DETHybridnut on GTRC and here's info on his car, engine -

http://www.cardomain.com/ride/630659

[Allan74]

I personally know of 1 person who just finished fitting and tuning with one of the Thai Plenums and achieved GREAT results. He also used the Thai 80mm Billet (Blue) TB.

He did however take the time to square the flanges, clean things up a bit and if I recall, went through some monkeying around with the TPS, but everything worked out and it was a HUGE savings for him. The motor was an RB20.

[rb-racer]

I would like to go single throttle body and remove the rats nest under the intake manifold. i think i need a throttle body that has idle control built in

[Allan74]

Stupid question...

What mounts here on the bottom of the plenum ?

http://www.gtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwr.com/downloads/pics/plenum_x.jpg

Also, I noticed that alot of these style plenums do not have the IAT bung in them. Do guys mount them elsewhere ?

[mcfly]

thats for the oem aac valve

[Zacho]

Mcfly is correct. I am mounting my IAT sensor just before the t/b on the I/C piping.