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Plenum Internal Trumpets Are They Needed On An Rb25Det?

HR31-PASSAGE
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HR31-PASSAGE Veteran

HR31-PASSAGE

Posted
Posted

Ok guys need to go a different plenum set up to my current one, thinking of getting a greedy copy plenum but they don't have internal trumpets so the question is are they really needed on an rb25det? My mate said cylinder 6 leans out & doesn't get enough air to it if there arent trumpets is this correct?

Also what's your thoughts on the greedy copy plenums? Anyone had any dramas with them? & do they suit top or side feed injectors or both????

Cheers

89CAL Grand Master

89CAL

Posted
Posted

Ok guys need to go a different plenum set up to my current one, thinking of getting a greedy copy plenum but they don't have internal trumpets so the question is are they really needed on an rb25det? My mate said cylinder 6 leans out & doesn't get enough air to it if there arent trumpets is this correct?

Also what's your thoughts on the greedy copy plenums? Anyone had any dramas with them? & do they suit top or side feed injectors or both????

Cheers

Might want to take advice from a better mate if hes saying that...... lean means to much air... not to little

I have a Greddy copy with no problems

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

I have a Greddy copy (of course there are a number of different manufacturers of these) on my RB30/25 going well so far. I am using the stock fuel rail and fpr and also stock throttlebody (needs an adapter plate) but it will also accept a top feed rail if you want. The only problem was that it didn't leave room for my clutch m/c so I had to buy an R33 one - problem solved. Also had to move my battery and washer bottle (minor issues). If I had lots of money I would have put an RB26 head on my RB30.

GTSBoy Grand Master

GTSBoy

Posted
Posted

Trumpets have nothing to do with evenness of distribution between cylinders. Trumpets only serve one purpose, and that is to increase the flow into each runner - or more to the point, to decrease the pressure drop associated with the inlet transition to the runner. But even that is not entirely true. Because whilst it is true that (in a large enough plenum) a bellmouth trumpet that stands up from the floor** of the plenum will flow more than just a hole in the floor of the plenum, that does not mean that a bellmouth trumpet is in fact the best inlet to the runner. In fact, the best inlet to the runner is a rolled mouth trumpet that rolls back onto the floor of the plenum. ie, not really any extra length - maybe 10mm from the floor to the top of the rolled mouth. That is all that is necessary, and has been demonstrated with proper testwork to provide the highest possible flow into a manifold runner. However, if you do go to the effort to make a plenum that includes such rolled mouth inlets, then the plenum needs to be wide*** enough that there is room for the flow to enter the trumpet mouth as symmetrically as possible - ie, all around. **floor being the side wall in the case of a typical Greddy style front facing plenum on an RB engine. ***wide meaning deep in the case of a typical Greddy style front facing plenum on an RB engine.

89CAL Grand Master

89CAL

Posted
Posted

I'm not gonna say I stand buy all of the Greddy copys, there are some duds out there, but genuine Greddy's I would 100% trust and a good quality copy as well. Mine was from Autobarn I think (Got it in a trade with someone) and all the surfaces looked pretty nice, as oposed to some which are uneven or weak

89CAL Grand Master

89CAL

Posted
Posted

since when did autobarn sold fake greddy plenums? lol

they use to be trust/greddy dealers so it might eb real?

for a while.....

And I can say its definatly not real, Shiny finish like the copy's. Not rough grey finish like the real ones

Hanaldo Grand Master

Hanaldo

Posted
Posted

I'm not gonna say I stand buy all of the Greddy copys, there are some duds out there, but genuine Greddy's I would 100% trust and a good quality copy as well. Mine was from Autobarn I think (Got it in a trade with someone) and all the surfaces looked pretty nice, as oposed to some which are uneven or weak

since when did autobarn sold fake greddy plenums? lol

they use to be trust/greddy dealers so it might eb real?

That's because it's Autobahn88 not Autobarn. Autobarn is the franchise retailer, Autobahn88 is the performance store that sells the copy Greddy plenums thumbsup.gif

On topic, my mate uses an Autobahn88 Greddy copy on his 25. Was decent quality, everything fitted together fine and the build quality was decent enough. For 400-500 odd bucks, can't go wrong.

Moodles2 Grand Master

Moodles2

Posted
Posted

Autobahn888 (or 88 I can't remember.. 8 is a lucky number to asian countries) tend to copy (and do a shitty job) of every Jap aftermarket company, HKS dumps etc

dori34 Grand Master

dori34

Posted
Posted

i'm sure if you buy a copy, spend some time with a hand grinder cleaning it up and get it flow tested, it will work out cheaper and should flow just as good as the greddys. afterall, they are a copy of it.

the bloke who sells the mild steel top mount manifolds from NZ has half the plenums, you just add your own velocity stacks & flange and TB adapter, and your off, maybe something worth looking into if you're after something low budget yet decent??

89CAL Grand Master

89CAL

Posted
Posted

That's because it's Autobahn88 not Autobarn. Autobarn is the franchise retailer, Autobahn88 is the performance store that sells the copy Greddy plenums thumbsup.gif

On topic, my mate uses an Autobahn88 Greddy copy on his 25. Was decent quality, everything fitted together fine and the build quality was decent enough. For 400-500 odd bucks, can't go wrong.

No i meant autobarn the franchise...... They always have on the shelf where i live

BOOZTJUNKEY Proficient

BOOZTJUNKEY

Posted
Posted

Yeah the autobarn near me had them on the shelf but now they don't if u ask them they will order them in but to be honest

I don't like dealing with them but 999 automotive (triplenine)

Should have them or no where to get them .

They also go under the name of kls performance and power spirit .

Also eBay seller n power maybe able to get them I personally have bout a few things of n power and never had any dramas

Dajae Community Regular

Dajae

Posted
Posted

I got mine from Vulture Motorsport. Very happy. Came with everything needed to bolt on

+1

Definitely. Quality was good too. No sharp or rough edges, nice thick walls, and great fit. Plus as stated above, every hose, nut, bolt, and nipple was supplied. I even rate their throttle body highly :D

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