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davitt 10-06-04 09:39

New custom PLENUMS for sale!!!

These plenums will be on sale soon.
New intake runners, ported, matched, machined and polished to suit intake manifold.

Has been flow tested and no leaning out of cyclinders occured.
Has 25% more flow over standard manifold.
Bolts straight upto head with all fittings supplied.
Has excellent flow with no restriction, no U bends

Was just seeing if anyone would be interested in these plenums?

vlt-dreamer 10-06-04 10:17

price will determine any interest mate....:)

looks good though!

scary 10-06-04 11:11

what vlt-dreamer said

flames looks wikked but id prob prefer mine without if i were to buy one...
hopefully cuts costs ;-)

darkstar 10-06-04 12:19

Not too bad, but your market will be limited to high performance applications with aftermarket computerse, as you have no provision for the standard idle control and accessories.

I suggest that you put bellmouths on each runner as well or at worst, a small half donut. Bellmouths are proven to increase flow by upto 33% due to the nature of drawing in air form a wider angle and in a more laminar way.

Also looks like you need to run a custom fuel rail and a custom top radiator hose fitting for the head. Will these be included in the kit, or are they extra etc?

If you can provide REAL flow statistics from a flow bench and compare it to other plenums that would be good for the customer so they can see where your plenum ranks.

The real test is getting a car with a stock plenum dynoed, then installing your plenum to see any torque or power improvements. As a rule of thumb, longer runners, such as the NA Manifold increase bottomend torque, but can hamper top end power. Your plenum is a classic example of a drag plenum with short runners tuned for topend poewr.


stockvlt 10-06-04 12:34

Darkstar makes some good points

If u have answers to these i would be interested depending on price

vL_hElL! 10-06-04 15:00

Likewise to what stockvlt said!!

p.s. the flames are a nice touch.

Sinister 10-06-04 15:54

im no professional, but shouldnt the volume be equal everywhere, and not get smaller as it does towards the rear???
Also how come u guys dont go longer on your runners? or is that a good length ?

StockyMcStock 10-06-04 16:11

was checking that tapering out too, i think it might be to add a bit of compression as the air gets towards to rear cylinders, to prevent them receiving less air than the front ones. not sure though, seems weird.....

davitt 10-06-04 16:27

As the above photo's are of an unfinished plenum, these plenums come with full custom rail and water outlet. These photo's are unfinished product only. I will post some more pictures up next week. Also i'll show before and after dyno's- with plenum. I know some of you may think flames seem a bit lame but it was thrown in as something different. They can be purchased without flames.... I will also have prices on these babies soon, may be a little bit dearer than JD's because of the full custom manifold (lower runners). I have be told that this plenum has had bell mouth openings fitted. I should have taken step by step photo's.

darklord 10-06-04 16:38

Does that cash filled plastic bag (and contents) come free with eadh purchase ;)

X-RB3-747 10-06-04 17:34

hey Davitt there is also another user selling similar (the whole setup) for around the $700 mark. Just letting you know so that you have a price to start at

HYPED6 10-06-04 18:20

" As a rule of thumb, longer runners, such as the NA Manifold increase bottomend torque, but can hamper top end power. Your plenum is a classic example of a drag plenum with short runners tuned for topend poewr."

Sorry darkstar... but whos thumb is this a rule of??? I agree it works in old free o ate's
and the like, but I have witnessed, read about and heard about that this is not true! Longer runners promote a better top end when forced induction is introduced due to the higher air speed when the air hits the back of the valve. Thus better cylinder filling.

JET-6 10-06-04 19:22

Benno is that for your car?

Is it made local here?

davitt 10-06-04 21:00


Originally Posted by JET-6
Benno is that for your car?

Is it made local here?

Yer mate wardy's making them. He's started his business from home, got every machine you could imagine-and the brains. Makes everything from catch cans, custom inlet-exhaust manifold, awesome work!!!!!!!!!

JET-6 10-06-04 21:18

Good old Wardy, damn havnt' seen him for ages, time to say g'day i spose!

ijd 10-06-04 22:41

Longer runners give more topend while short runners give more low-mid power. Look at a V8 with tunnel ram.

Sinister 10-06-04 23:27


Originally Posted by ijd
Longer runners give more topend while short runners give more low-mid power. Look at a V8 with tunnel ram.

not really..
the stock holden v8 efi manifold has very long runners and no other manifold out there matches its low end torque

HYPED6 11-06-04 09:01

you have to factor in cam timeing as well, supercharged a vs clubsport... made power all the way to the rev limit... no good. standard manifold (power ported) advanced cam timeing 6 degrees bought the power band down to a useable level and made a heap more power. (better air velocity in the inlet manifold at certain rpm)At the end of the day, you have to set up your engine to make power at a cretain rpm band. The 10 million dollar question is when exactly do you do to set your engine up to be optimal at perticular rev band???? and one have any answers???

eg. I have read that long exhaust runners promote better topend power (turbo manifold) How ever have a look at the HKS drag R32 and its exhaust header runners are quite short???

davitt 11-06-04 11:41


Originally Posted by RB3-747
hey Davitt there is also another user selling similar (the whole setup) for around the $700 mark. Just letting you know so that you h
ave a price to start at

sounds cheap!!! does this also inclued custom made runners each tunned and ported to suit. custom fuel rail and injector bosses custom made to your injector size? who ever makes these must have there own cnc router, flow bench and other various machines yer? but sounds very cheap. maybe round about price i'm not sure.

ISL33P 11-06-04 13:01

i make the plenums mentioned by RB3-747. No, they have std non-turbo vl runners. The reason i have chose to work with these is due to the runner length being more equal, once cut compared to turbo runners. i have considered doing a setup similar to those you have but is too expensive and time consuming if i was to do it myself. the other reason is that fact that it allows for std fuel rails which have been proven to supply enough for big hp engines (once modified) and also plenty of space at the back of the plenum to mount fittings for map sensor, wastegate, boost gauge, std vl fittings and keeping them neat and out of sight, which can not be achieved with straight runners.

no i dont have a cnc router or flow bench, but easy access to them i do have.

flow bench and dyno results for mine will be available by the end of next week.

good luck.

vlt-dreamer 11-06-04 13:25

let us know how you go and what the figures are!!!

ISL33P 11-06-04 13:29

don't worry, i will. this is what people want to see.

carcrazy 11-06-04 17:00

That looks very neat, i am very interested in seeing how it all goes, keep us informed.

Loud'nLow 11-06-04 17:49

Have a look at how short the rb26dett runners are

darkstar 11-06-04 17:59

Sorry guys, i got it arsed backwards :)

For N/A Engines, Higher revving motors (undersquare, shorter stroke compared to bore, such as GTR specs 86 bore x ~73.7 ? Stroke) will tend towards shorter runners (4AGE Twincam Quad throttle etc) whilst square or oversquare lower revving motors tend to benefit from a longer runner design, (Ford Straight 6, RB30 etc).

For Turbo applications, longer runners are favorable as they give a good compromise between the above. The longer runners provide more off boost torque, thus a broader torque curve at low speeds, then at full boost there is enough air velocity to carry this all the way to redline, keeping the top end strong.

The above is for general cases.

The real deal depends on the cam shafts and valves. Having worked on Soarer Twin Turbo engines (1JZ GTE) i can assure you that the exhaust manifold is no more than 5cm long. Yet with a pair of highflows running 19psi, 440cc injectors and a piggy back/cooler/exahust etc, a car that ive been working on has made 240rwkw in manual form, 4th gear 1:1 ratio. I have seen many BIG single and custom twin turbo manifold applications fail because the exhaust manifold is tuned to the cam and the flow characteristics of the head. Having 300mm runners for a big single was a total failure, with fullboost at 5.5k (21psi) and 7.5k redline. It was so pathetic, a lightly modified soarer would have beaten it at the drags, even though it was making 340rwhp on the dyno. This was a car that i was looking at buying for a friend, but i quickly said not to buy it as it just didnt have the right package for a performance machine. High on wank factor, but low on performance. Peak power dyno figures mean NOTHING and this was a testiment to that.

To add further to this debate, the GTR uses a 6 throttle application with 10cm runner lengths, whilst the RB25 uses a plenum chamber with long runners like the rb30 with a single throttle.

SR20DET engines have a long runner and a log style plenum chamber. When Zoom magazine installed a GReddy GTR Style Plenum with short runners on the SR20, it was nothing but disappointing because it was not matched to the engine. Infact peak POWER was decreased and midrange torque was lower than the standard manifold.

In short you need to find out what works for the engine package that you are designing for. What might apply for a V6 or a straight 4, will not apply to an RB30 specifically. There may be attributes to the design philosophy, but nothing is concrete unless you make a few plenums and find what exactly works for which stage of modification.

Tapering plenum chambers reduce the flow to the rear cylidners to prevent leaning out. Even the standard GTR Plenum chamber has ~20% reduction in cross sectional flow area at cylinders 5-6. Air is fluid and as such will take the most direct path. In a log style plenum chamber, this is the rear cylinders.

If your interested in plenum and turbo applications / design of turbo systems, then buy Maximum Boost by Corky Bell. Its an insight to what works and what doesnt work, and theres quite a few general cases that could assist you in finding the right design.

If those that are designing and/or fabricating custom turbo performance parts, if you havent read this book then you shouldnt be making anything. I started my own turbo exhaust manifold then i read this book, now im starting again to get it right :)


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