Rb 25 Inlet Manifolds. When Do They Cause A Restriction

[SLIMVLT]

as the title says.

when does the rb25de or det inlet manifold start to hinder power development, not when it stops the car making power but when does it start to become a restriction or hindrance. so if you replaced it with a aftermarket 1 at the same power figure would u get a noticeable gain in power or torque or would u just make more power with the sacrifice of low down torque.

ive hurd of plenty or rb engines doing remarkable things with standard parts and have nothing against the ppl who are doing it but are there gains to be had by changing them

also what plenum capacity are the g-reddy plenums to suit rb25det's. are they more suited to track/ street duties or are they ok for drag applications. im in the process of building a rb25/30 hybrid with cams t04z forged bottom end ect, (and im not dreaming of doing it like some ppl do, this is happening as i have the parts)

and am undecided on the plenum to put on the thing. there are alot of good plenums around and alot are advertised on Calais turbo giving good results on paper, but i dont wanna risk leaning out a cylinder or 2 by using a plenum that isnt correct. 1 of brescianis customer r33 skylines with what i believe its 1 of there custom plenums on it is running 10's so there plenum obviously works on the strip...

u get the drift anyway

choices choices.

any feedback advice will be great and hopefully steer me in the correct direction.

Edited August 30, 2006 by SLIMVLT

[SLIMVLT]

so no 1 knows?

thanks guy's

[race_snooze]

standard intake plenum from what i have seen is a bit over the 300rwkw mark. I am sure someone will come one and correct this.

[Color_Of_Green]

If you're running a T04z then you'll definately want an aftermarket plenum. The Greddy plenums are good for large power setups but tend to make less power than stock for small power setups which I found strange but I think its because the runners are very short.

Plazmaman make nice plenums. They flow really nicely, with less flow differential between cylinders and uses the stock runners so makes excellent power for both small or large power applications. They look great too and you can get them with whatever TB flange you want.

Hope this helps.

Cheers

[2BNVS]

i should have done a before and after with my stock v's new plenum, i was just gettin everything done at once so it was a waste of time to do really... but very noticible on the street since it was a hell of a lot more responsive,( shorter piping, and flows better than the greddy items according to the flow tests) uses the stock runners and there is bugger all difference between all 6 cylinders, i also got an 80mm billet throttle body...

i got mine made by Ariel @CPC Plenums in Wollongong

goes by ISL-33P on these forums

very good value for money and look tough

ben...

Edited August 31, 2006 by 2BNVS

[R31Nismoid]

I used the stock one

369rwkw @ 24psi (sunoco 104)

Worked for me.

And i've seen other RB25's crack 300rwkw on PULP using the stock item.

Depends on your budget i guess.

And Ben, you cant say the plenum was the reason for better response etc if you changed everything at once.

That is very misleading

[infected flow]

I used the stock one

369rwkw @ 24psi (sunoco 104)

Worked for me.

And i've seen other RB25's crack 300rwkw on PULP using the stock item.

Depends on your budget i guess.

And Ben, you cant say the plenum was the reason for better response etc if you changed everything at once.

That is very misleading

lol u crack me up..hahahaha

who hasnt seen a standard inlet take over 330rwkw...but the question is will u gain anything if u change ...?

its all about flow!..

okay some choices.

1. Greddy

2. Plazmaman

3. Hypertune

4. micks metalcraft

with a to4z u should change to an aftermarket jobbie otherwise your robbing yourself of power....

Edited August 31, 2006 by infected flow

[2BNVS]

r31: yeh true i spose but i more meant it as in for the application i have, it helped alot, and its no where near as laggy as most people would have thought, but i didnt really mention that alot of friends have identical set ups just with stock plenums, and ariel who made the plenum was actually surprised how responsive it was for such modifications....

ben...

Edited August 31, 2006 by 2BNVS

[Craved]

lol u crack me up..hahahaha

who hasnt seen a standard inlet take over 330rwkw...but the question is will u gain anything if u change ...?

its all about flow!..

here is sounds like you dont know if it will get you more power with a change

with a to4z u should change to an aftermarket jobbie otherwise your robbing yourself of power....

then here you state that you will get more power with it changed ...

------

im not debating that they can help or not, hell i even have a plazmaman plenum myself ..

but when you bag someone, try not to contradict yourself

as far as i have seen there is always merit in going for a larger capacity plenum.

nismo version of the rb26 plenum is almost identical just larger, and the slight change near cyl 6.

for rb25/30 ... change it so you wont have to affect the geometry of the drive train to get it under the bonnet..

[shonen]

hahah leave mario alone chris.....he is still running his engine in

[infected flow]

here is sounds like you dont know if it will get you more power with a change

then here you state that you will get more power with it changed ...

------

im not debating that they can help or not, hell i even have a plazmaman plenum myself ..

but when you bag someone, try not to contradict yourself

as far as i have seen there is always merit in going for a larger capacity plenum.

nismo version of the rb26 plenum is almost identical just larger, and the slight change near cyl 6.

for rb25/30 ... change it so you wont have to affect the geometry of the drive train to get it under the bonnet..

lol you got to be kidding me...right mmm increased flow and also better direction in flow also runners are shorter but the capacity is larger and your telling me i dont know what im saying right..hahaha u make me laugh...im not contradicting myself ..hahaaha i was laughing because he= was stating he got 369rwkw and it worked, i was simply saying that changing the standard inlet you will be surprised!.....that's all..

ahahha shonen all words buddy all words....

[Craved]

increased flow and also better direction in flow also runners are shorter but the capacity is larger and your telling me i dont know what im saying right.

hence my reason for going for the plazmaman plenum, runnners are te same length as before - better for producing torque and lower rpm ..

.hahaha u make me laugh...im not contradicting myself ..hahaaha i was laughing because he= was stating he got 369rwkw and it worked, i was simply saying that changing the standard inlet you will be surprised!.....that's all..

just suprised at the amount of laughing at what others have done, coming from someone who likes to write from experience is all

problem is that many people do what ben did and change it all at once, i know i did.. and it makes it hard to guage what kind of benefits you will get from this.

either way, he will need to choose one to get the engine under the bonnet, all of them have been used on high powered cars, stick with a name brand that has been used and the rest is about which one you like the look of better .

[R31Nismoid]

increased volume is not a friend in some cases. How can you say it is unless its restrivtive to begin with?

Go do some reasearch and R&D

I doubt i would be surprised by a change to be honest.

I certainly couldnt justify $1000+ on a plenum.

And i was clearly advised that it would be a waste of money. From what i have seen and done, i would believe this to be so.

There are many doubters that the stock RB25 head/intake was good enough for good power.

The car speaks for itself really and is all the proof i needed at the time.

Consider this.

I've seen RB25's with similar/same turbos achive similar response vs power when compared with mine.

Given a few smaller differences... both made very similar power, both made very similar response.

You cant compare the two totally, and i totally understand that as all motors are different.

But for an extra $1000+ on my setup, it was totally unjustified. I made the power, i had the response.

You are almost stating you must change for more power... Based on what?

I've told you my real life R&D expiriance based on comparison of two similar motors... where a poofteenth of RPM to me really doesnt justify $1000+ in a streeter. Fair enough if i was chasing 100th of a second at a circuit, but alas, im not

Where are your results mate? Care to post them for us?

Have you got results?

Can you clearly say there is a gain?

cheers.

EDIT:

ps. Chris - totally agree with your sensibility as usual

-ash

[202.3rwkw]

i did the plazmaman swap about 3 months ago from a basic mods 33 (pfc front mount exhaust and 12psi) making 202.3rwkw to 220rwkw with the plenum. i put it on at this stage to save time and money later. didnt think id get that much out of it but hey it was a nice surprise.

glenn

[gtst25]

I take it that you've all read that zoom article a few years back where that installed a rb20 into a commodore.

They had an aftermarket (greddy I think) inlet manifold and couldn't make the required power. After lots of head scratcing etc they finally decided to put the stocko one back on and found the 20rwkw they were looking for with more torque/responce than before.

If I was going past the 400rwkw mark though I would look into an aftermarket plenum - have you guys seen the greddy copies in the group buys?? They're looking like getting cheap enough to take the gamble.

Cheers

Edited August 31, 2006 by gtst25

[infected flow]

increased volume is not a friend in some cases. How can you say it is unless its restrivtive to begin with?

Go do some reasearch and R&D

I doubt i would be surprised by a change to be honest.

I certainly couldnt justify $1000+ on a plenum.

And i was clearly advised that it would be a waste of money. From what i have seen and done, i would believe this to be so.

There are many doubters that the stock RB25 head/intake was good enough for good power.

The car speaks for itself really and is all the proof i needed at the time.

Consider this.

I've seen RB25's with similar/same turbos achive similar response vs power when compared with mine.

Given a few smaller differences... both made very similar power, both made very similar response.

You cant compare the two totally, and i totally understand that as all motors are different.

But for an extra $1000+ on my setup, it was totally unjustified. I made the power, i had the response.

You are almost stating you must change for more power... Based on what?

I've told you my real life R&D expiriance based on comparison of two similar motors... where a poofteenth of RPM to me really doesnt justify $1000+ in a streeter. Fair enough if i was chasing 100th of a second at a circuit, but alas, im not

Where are your results mate? Care to post them for us?

Have you got results?

Can you clearly say there is a gain?

cheers.

EDIT:

ps. Chris - totally agree with your sensibility as usual

-ash

aaaahh and it begins

1. okay if u dont want to spend the money or u dont think it's justified than thats fine!

2. now to flow such a big turbo to4z we are talking about your saying there no gain in changing the manifold...is that right..? so therefor will flow be an issue will the engine flow without struggling...

3. u want r&d no probs ill be posting up graphs in 2weeks standard and aftermarket inlet. engine is in parts at the moment.. has been proven but didnt save graph..

4. so tell me why they offer aftermarket inlet manifolds ..why do such big companies go into so much r&d to produce a product if there is no need or nothing to be had with it...mmmm intresting dont u think..?

[SLIMVLT]

thanks for the replys guys.

yea i relised that replacing the manifold could net gains but its a cost v's gain thing that is the problem.

if its going to produce a good gain, or help with the way the thing drives then i will do it, but if its all about wank factor and looks then im not sure it will be worth it. its $1000+ that i can put into something else.

r31 nismod thats great power with the std inlet. so do u beleive that your setup could realy gain from a aftermarket inlet even though your against it, would it help.

and ive been looking around at the cpc plenums and am verry impressed with how they look, but the question still is will it work as good if not beter than the std 1. like if ppl can get huge power out of the std item is it realy worth it. say for 15 kw up top and a los down low then in my opinion its not worth me spending the money.

but if it makes 15 kw and more tourque in the midrange and looses 10 up top or more up top then in my opinion thats a great option....

im still not sure.

[Color_Of_Green]

I take it that you've all read that zoom article a few years back where that installed a rb20 into a commodore.

They had an aftermarket (greddy I think) inlet manifold and couldn't make the required power. After lots of head scratcing etc they finally decided to put the stocko one back on and found the 20rwkw they were looking for with more torque/responce than before.

If I was going past the 400rwkw mark though I would look into an aftermarket plenum - have you guys seen the greddy copies in the group buys?? They're looking like getting cheap enough to take the gamble.

Cheers

Unfortunately, Greddy plenums reduce power for the average application. Only when you go huge you get some benfits.

[Color_Of_Green]

The plazmaman is well worth the money. A lot of R&D went into it and its well proven like all their products.

When my GTST was at its first stage ( 3" exhuast, FMIC, Plenum, 12psi) I was getting around 221rwkw while all the other GTST's with same mods without plenum were experiencing between 200-208rwkw, on the same dyno. (@UAS). We put it down to the Plazmaman gear (FMIC + Plenum).

I certainly couldnt justify $1000+ on a plenum.

And i was clearly advised that it would be a waste of money. From what i have seen and done, i would believe this to be so.

$1000 is peanuts. If you havent got a spare $1000 to throw around from time to time then you shouldnt bother doing up your car...

[Turbo Tits]

so tell me why they offer aftermarket inlet manifolds?

because there is money to be made.

some companies sell plenums, some sell wheels. you can buy aftermarket wheels and make your car look worse... but the company still made money didnt they?