GTR intake plenum on RB25

[browny]

doh, SK beat me to it

[lukevl]

Okay I think I need to see one. Off hunting I go...

[txtc]

Have a guess who has the fastest GTRs in WA?

Oh i think a good contender would have to be the JUN spec R34 GTR

http://private.carsales.com.au/photos/386294.jpg

ps. Was built by speedworks

[N I B]

Oh i think a good contender would have to be the JUN spec R34 GTR

http://private.carsales.com.au/photos/386294.jpg

ps. Was built by speedworks

It is 3rd fastest but had a major engine blowup on the drag strip.

ND4SPD is first Jade fisher is second 34 shares 3rd with the 33 from bunbury.

[mokompri]

Long intake runners are a definite advantage for low end and mid range torque

i think this is debatable... since you havent got any data to back this up, i'll refer to what others have already bought up.. the rb20 article in zoom that compared the long runner inlet manifold to the short runner gtr manifold. the graph clearly showed that the short runner manifold had more power down low but lost it up top, where as the long runner manifold was the exact opposite.. in fact from what i remember approx half way through the rev range the graphs crossed, at rpms over that crossover the long runner manifold was up in power and below that crossover the short runner manifold was clearly ahead in power

[mokompri]

also something to consider, its commonly known that the greddy manifold for sr20det's gives SFA difference to the stock ones for 99% of cars out there... so what im saying is, and this is my opinion, that the stock ones are damn good at what they do, which doesnt leave much room for the aftermarket to improve on... not until airflow figures go waay past the stock parameters they were first designed for anyways

[proengines]

Interesting reading guys. If everyone had the same opinions about what is best we would all still be driving around in model T Fords.

I don't know if this should be a new thread or not but I have an engine here for my own car and one for a customer, both are RB30 block, RB26 head, neither have any intake manifolding at all. Both will be single turbo, t55'ish. Aiming for around the 700hp or so mark, mine will be auto, mostly for drag use.

So, starting with nothing, what would the people who know use? I'm not so interested in what someone read in a magazine but more some real world knowledge. I have a flowbench here and can test myself but I'd like a starting point which will save quite a few dollars.

[lukevl]

Standard 26 inlet including throttle bodies.

[Sydneykid]

Standard 26 inlet including throttle bodies.

Here! Here! A good choice:cheers:

[JNR24]

Hey guys,

Heres some pics of my RB30/25 with a RB26 plenum on a 25 intake manifold.

It took around 6 hours, and cost me $300.

Any questions PM me i will be glad to help out.

[sweetr33]

looks nice, i cant see an adaptor plate in there did u just weld the runners the plenum? Did The place u took it too have any dramas doing it?

[JNR24]

It was made on that engine stand by myself dude.

Yep, just bought a 1 foot peice of aluminium tubing offcut and then cut and welded 6 pieces in between the intake & plenum.

No problems, eveything lines up perfectly.

[discopotato03]

Mine was no probs either , bolted up like it was factory - because it is . No offence but that system will suffer reversion problems particularly with big cams . Manufacturers go to a lot of trouble to get performance from sporty cam profiles hence V tech or in Nissans case at the time single throttle per cylinder and slightly more agressive cams . There is virtually no communication between the ports on closed throttle . Single throttle plenum EFI manifolds to a degree join up all the inlet ports and are mild mannered with mild cams only . With that scenario and short overlap cams the trapping efficiency is good . With racier profiles most inlet ports and valves flow surprisingly well in the wrong direction . When there's a physical barrier like a throttle plate blocking the reverse pressure wave its got nowhere to go but back in . If any of you have ever tried to live with the racy cam and single throttle set up it gets very tiresome with your daily driver in metropolitan traffic situations . The GTR Skyline and GTIR Pulsar both use the same style of inlet system , both were homologation specials developed at some considerable cost to Nissan . I think the extreme drag teams go with the big single throttle because for very high revs and airflow its the cheap simple way to go . I've no doubt it could be done just as well with six throttles and an ample plenum . Some claim that manifold absolute pressure load sensing ECU's get better signal from the "Big Log" , SK has examples of more than adequate power levels from Mass Air Sensing ECU's . Its beyond me why people spend more than the cost of a GTR head and inlet trying to re-invent the wheel , not cost effective .

[JNR24]

Hey Discopotato,

No offence taken, but just for the record 2 of my freinds both running the same intake setup as myself & massive cams have no problems at all. To be perfectly honest with you i dont realy understand what you have said above, what i do understand is "It works, & works very well" (Very streetable cars, there daily drivers), and also is very cost effective. (My head set me back $500.00, +300.00 for RB26 plenum) please PM me a phone number if you can find me a RB26 head & intake for under 1K. You will find alot of people do this because they dont have the $$ for a RB26 head & intake setup, After all if we all had the $$ im sure not to many of us, including myself would bother fabricating RB26plenum to a RB25Manifold.

Trev

[GTRgeoff]

No offence but that system will suffer reversion problems particularly with big cams.

Has anyone calculated the ideal runner lengths to counter inversion pressure waves at the various rev ranges (frequencies) for low middle and high end torque for use with the GTR plenum volume and a range of cam lifts and overlaps? I'd be inclined to consider that plenum as an infinite chamber for ease of calculation initially if you use a single throttle body. Maybe one day I'll get of the fat blurter to make an excel based tool.

Also has anyone considered the benefits of a twin throttle setup a'la the Zoom Excel that responded very dramatically some years ago? Is the throttle body a large enough restriction? My thoughts are to put 2 RB25 throttle bodies on a RB25 plenum equidistant from the centreline.

My personal interest is in a forward facing plenum so I can fit a GTR strut brace, as it won't fit with the current plenum.

[Roy]

Give me the $20,000 software and ill model it:) Problem is even with the right software, the model is only as accurate as the assumptions you have made in modelling it. You can use motion analysis software with functioning valves....or use soem rule of thumb calcs for runner length and diam, which are meant to be a good ball park starting point.

LOL...before all my RB20 probs i was going to extrude hone the std plenum and weld up another throttle body. (To see if with the cams and bigger turbo the plenum/throttle was a restriction?!?!?!0

Had the cables etc all sussed, but then lost interest in thinkering when it became a major drama to get the car back on the road. People say it wont make jack difference, but id still like to try. Notice that the NA RB25 NEO has a single throttle body but is connected to the inlet manifold in two places, ie throttle body is above exhaust cam not inlet cam, and over the rocker cover the airflow splits in two?!?!?!?!?!?!

Id love to be unemployed and try these things out Mon-Fri...cant wait to win Powerball.

[sweetr33]

definately alot of research on air flow characteristics and pressures etc.

[GTRgeoff]

Give me the $20,000 software and ill model it:) .

I don't think I'd give you a stale fish to slap yourself with mate (just trying to maintain some contention in the forums) Actually just get an employer who will let you get away with buying this sort of product. I almost did but instead we put an armoured vehicle in a wind tunnel with greater than 1/3 blockage ratio. Only cost 200+K when the software would be a lot cheaper.

Id love to be unemployed and try these things out Mon-Fri...cant wait to win Powerball.

As I said, the right employer. Maybe time for a job change.

[N I B]

Anyone from WA can check out our Single throttle body GTR and make up their own mind.

[GTRgeoff]

I'd love to but Perth is a long way on a scooter since the car is undergoing maintenance.....